key: cord-0079468-ntdq7j04
authors: nan
title: Oral Presentations
date: 2022-05-26
journal: Global Spine J
DOI: 10.1177/21925682221096074
sha: d5ab9c7ad295eec71dc1f9499a0e6d78a5d193ea
doc_id: 79468
cord_uid: ntdq7j04

nan

Introduction: Patients with osteomyelitis, metastatic disease and osteoporosis are prone to fractures with associated complex spinal deformities. Previous studies demonstrated the necessity of obtaining 360°stability in the thoracolumbar spine. Vertebral body replacements (VBRs) with expandable cages with larger endplates allow over-distraction due to their larger footprints. We analyzed the rate of segmental correction and subsidence in patients with osteoporotic and pathological fractures. Material and Methods: We performed retrospective analysis in a tertiary spine center from 02/2015 till 07/2019 of patients following a staged posterior pedicle screw instrumentation and VBR with expandable cages with large endplates. Radiological data (local sagittal angle and segmental height) as well as revision rates were analyzed. Results: We included a total of 58 patients with a median age of 68 years. 62 % were female, 38% were males. Median follow up lasted 8 months. 47% had thoracic and 53% lumbar fractures. 28% of all fractures were metastatic, 38% osteoporotic and 34% due to osteomyelitis. We achieved a significant gain in segmental height of 8 and 11 mm in the thoracic and lumbar spine, respectively and a significant segmental angle correction of 4°and 6°degrees in the lumbar and thoracic spine, respectively (p = 0.000). In spondylodiscitis cases, cage over-distraction (mean 6 mm) was associated with higher subsidence rates (mean 8 mm, p = 0.013) on follow up examinations, which resulted in revision surgery in 3 cases (5%). Conclusion: Expandable vertebral body replacements with larger endplates achieve satisfactory correction of sagittal height and angle. Over-distraction, especially in infectious cases, is associated with higher subsidence rate.

A003: A new sensitive radiographic criteria for differentiation between adult idiopathic versus degenerative lumbar scoliosis: apical pedicle diameter asymmetry Introduction: There is no reliable method to differentiate adult idiopathic scoliosis (AdIS) with the major curve present in the lumbar spine and degenerative lumbar scoliosis (DLS). Current diagnostic factors include curve apex location/direction, lateral olisthesis, Cobb levels, and the appearance of a "typical" idiopathic curve. But these become problematic to differentiate AdIS from DLS when superimposed degenerative changes occur in the lumbar spine of AdIS patients. Meanwhile, it is well known that apical pedicles in the concavity of thoracic adolescent idiopathic scoliosis (AIS) curves are smaller than the convexity. We hypothesize that adult patients with a self-reported history of AIS have apical pedicle diameter asymmetry (APDA) characterized as a difference of 1 mm or greater in the pedicle diameter between the convex and concave pedicles at the apex of a lumbar curve. Secondarily, because there is a population of adults with undiagnosed AIS, we hypothesize that not all patients with APDAwill report a history of AIS. Material and Methods: 40 operative patients with adult deformity and lumbar major curves were identified retrospectively. Chart review was performed. Radiographic measurements included lumbar Cobb angle, curve apex, and Cobb levels involved. Apical pedicle diameter at the concavity and convexity of the curve apex were measured. Results: Among 40 patients, the average Cobb angle was 48.3 degrees. Curve apex averaged at L1/2 (range L1-L3). The curves spanned 4.7 levels (range 3-7). 25 curves had the apex to the left, while 14 had apex to the right. The average pedicle diameter at the apex was 6.1 mm. 14 patients had APDA > 1 mm. 7/8 (87.5%) of patients with history of AIS had APDA > 1 mm. 6/32 (18.7%) patients without known history of AIS had APDA > 1 mm (p < 0.01). Conclusion: Apical pedicle diameter asymmetry (APDA) is a sensitive diagnostic criteria for differentiating lumbar major AdIS from DLS. The sensitivity of Introduction: Though adult spinal deformity surgeons often regard a C2-sacrum instrumented fusion as a final fusion construct that avoids junctional failure, little data exists on outcomes following C2-sacrum fusion. Material and Methods: Clinical and surgical data were collected on patients undergoing C2-sacrum fusion with four surgeons at a single center from 2015-2020. Descriptive statistics are reported. Results: Of 23 patients undergoing a C2-sacrum fusion, 6 (26%) patients required 10 subsequent operations: 3 patients had 1 reoperation, 2 patients had 2 reoperations, and 1 patient had 3 reoperations. Reoperations occurred an average of 1.5 years (range 14 days-4 years) after the initial C2-sacrum fusion. Locations of the revisions included: cervicothoracic (5) , thoracolumbar (4) , and cervical (1) . Of the 10 reoperations, 5 were for mechanical failure, 3 for wound/infection, and 2 for prominent instrumentation/spinous processes. No extension to occiput or neurologic compromise were seen. The 4 patients with mechanical failures included: 1. Upper Cspine implant pullout at 0.8 years postop; 2. Bilateral Iliac screw connector and T12 rod fractures at 0.9 years postop; 3. Unilateral lumbar/sacral screw fractures with pseudarthrosis at 1.6 years postop; 4. Bilat. T12-L2 rod fracture with progressive coronal/sagittal malalignment at 4.1 years postop. All 4 patients underwent operative revision; 1 had a 2-staged procedure. Conclusion: Complications and revisions occur in approximately 25% of patients undergoing C2-sacrum instrumented fusion. Half of those patients requiring reoperation underwent more than one revision procedure. Mechanical failure occurred at the thoracic/lumbar spine in 75% of the revised patients; one patient with failure at the cervical spine required extension to C1. Remaining etiologies included infection and prominent instrumentation/ spinous processes.

Introduction: Adult spinal deformity (ASD) is a heterogeneous spectrum of abnormalities that affect both coronal and sagittal plane of the spine in adult patients. Its prevalence is about 6% and, according the expanding portion of the global population aged older than 65 years, the disorder is of growing interest in health care. Literature suggests that in patients who do not benefit from conservative treatment, surgical outcomes are considerably favourable. The aim of our study is to evaluate clinical and radiological outcome of surgical treatment of ASD with a minimum FU of 5 years and to evaluate the predictive effect of some morphological and surgical parameters on mechanical failures. Material and Methods: We performed a retrospective review of a consecutive singlecenter registry, enrolled patients that underwent correction of ASD from January 2008 to October 2016. Patients older than 18, with a minimum of 4 levels of Posterior Instrumented fusion, a minimum FU of 5 years, with complete clinical and radiological data were included in the study. Patient with neuromuscular or reumathic disease or active tumor or infections were excluded. Demographic data and clinical data (ODI, VAS back, VAS leg and section 11 of COMI back) of the patients were collected at the last available FU. Only posterior procedure and combined approaches were collected. Pelvic Incidence (PI), Pelvic Tilt (PT), Sacral Slope (SS), Lumbar Lordosis (LL), L4-S1 Lordosis (LL4-S1), Thoracic Kyphosis (TK), Global Tilt (GT) were misused preoperatively and at each follow-up. GAP score was measured post-operatively. Data on mechanical complication and revision surgery were collected. Results: 275 patients were definitively enrolled, 47 males and 228 females, with a mean age of 60 y/o (SD 13,89) at the time of surgery. The average of FU was 8, 3 years (SD 1,7). We performed the analysis on two different databases: patient database (275) and episode database (380) including the evaluation of each surgery for the included patients. At last FU, the average of ODI was 29,7 (SD 21,7), VAS back 4,3 (DS 3,1), VAS leg 3, 9 (DS 3, 3) ; patients referred that the surgery helped a lot in 17%, helped in 46%, helped only little in 27%, did not help in 6% and made things worse in 4%. Mechanical complications were descripted in 46% (174/380), of which the 94,25% (164/174) had needed surgery. We had junctional failure in 21% (79/380) and hardware failure in 23% (89/380). The Junctional failure were occurred earlier than the hardware failure. Combined approaches, lower GAP score, PT < 20°and the achievement of ideal PT post-operatively were found as positive predictive value for mechanical failure, above all in the first 2 years of FU. Conclusion: The treatment of ASD allows good clinical outcome with a minimum of 5 years FU. 10% of patients are still unsatisfied with their clinical condition. The reintervention rate for mechanical complications is 43%. A postoperative adequate Sagittal Alignment has positive predictive value in the first 2 y. To restore ideal PT should be the goal of the corrective surgery. Introduction: When considering the surgery for deformity correction, we always evaluate spinopelvic parameters in standing position to find the ideal angular values of the spine and aim at this target during surgery. However, many studies suggest that adult patients spend most of their time in a sitting position, and in the last months a growing number of publications examined the spinal alignment in this position. To our knowledge, there is however no study that investigates the behavior of a fused spine while sitting. For this reason, we designed this prospective observational study to analyze the effect of sitting position on the sagittal alignment of thoracolumbar instrumented patients. Methods: Prospective observational study on consecutive patients that underwent corrective surgery for adult scoliosis with thoraco-lumbopelvic (both of the lower -LTLP-or the upper thoracic spine -UTLP), lumbo-pelvic (LP) or thoracolumbar (TL) fusions of 5 or more vertebrae were included in the study. Spinopelvic sagittal parameters were measured in both standing and sitting position on a full spine x-ray performed with an EOS machine. Also the Junctional Angle (JA, defined as the angle between the upper instrumented vertebra and the two first non-fused vertebrae) was measured. Results: Conversely than non-fused patients, patients that underwent a long fusion with the inclusion of the pelvis showed no significative variations of pelvic orientation from standing to sitting position. A tendency in thoracic kyphosis increasing was observed in patients with a LTLP (+3.9°, p = 0.08). In patients that underwent fusions which does not include Sacrum or Pelvis, a significant increase in Pelvic Tilt (PT) was observed from standing to sitting (+ 3.66; p < 0.05), while Sacral Slope (SS,-3.66; p < 0.05) and Lumbar Lordosis (LL, -8.67°; p < 0.05) decreased from standing to sitting. Considering JA, a slight increase (p < 0.05) has been found in LTLP and UTLP arthrodesis but not in TL (+ 0.5 p = 0.21). Discussion: Spinal alignment in sitting position is obtaining growing interest in the last period, for the implications it can have in hip-spine relationship and on the understanding of some complications as proximal junctional kyphosis (PJK). We observed a lack of pelvic retroversion in long fusions to the pelvis. Moreover, the absence of pelvic retroversion in fused patients can justify an anterior hip impingement and consequent symptoms, while the increase of JA can represent a promising element to be considered in the rising of junctional pathologies. Conclusion: Sagittal alignment of fused patients for adult scoliosis shows peculiar behaviors and adaptations in sitting position, depending on the length of fusion and on the region that underwent instrumentation. When the pelvis is not included, the patients show a behavior more similar to that of asymptomatic patients, with a pelvic retroversion and a decrease of lower lumbar lordosis. These findings can improve the knowledge on pathologies as PJK or on specific cases of anterior hip impingement.

Introduction: An understanding of outcome differences between different types of orthopedic surgeries is helpful in counseling patients about expected post-operative recovery. This study compares outcomes in patients undergoing cervical spine surgery with arthroscopic shoulder surgery using Computer-adaptive Patient Reported Outcome Information System (PROMIS) scores. We predict cervical spine surgery will yield better improvement in health-related quality of life compared to shoulder surgery, with differences evident after 3 months. Material and Methods: This study is a retrospective analysis of outcomes in cervical spine and shoulder arthroscopy patients. Patients who underwent cervical spine surgery (1-or 2-level anterior cervical discectomy & fusion, cervical disc replacement) or arthroscopic shoulder surgery (rotator cuff repair, biceps tenodesis) were grouped. PROMIS scores of physical function, pain interference, and pain intensity at Baseline (BL) and at 3-, 6-, and 12-months were determined and compared using paired t-tests. Results: Cervical spine (n = 127) and shoulder (n = 91) groups were similar in sex (25.8% vs. 41.8% female, p = 0.731) but differed in age (51.66 ± 11.62 vs. 58.60 ± 11.22, p = 0.000), operative time (148.30 ± 68.58 vs. 75.86 ± 26.94 min, p = 0.000), ASA (2.25 ± 0.61 vs. 1.99 ± 0.55, p = 0.001), and smoking status (15.7% vs. 4.4%, p = 0.008). Spine patients had worse physical function (36.48 ± 12.63 vs. 49.37 ± 8.59, p = 0.000) and greater pain interference (67.01 ± 13.58 vs. 61.67 ± 4.84, p = 0.001) at BL. Significant improvements were seen in all domains by 3 months for both groups, except for physical function after shoulder surgery. Spine patients had greater physical function improvements at all timepoints (3.33 vs. -0.43, p = 0.003; 4.81 vs. 0.08, p = 0.001; 6.5 vs. -5.24, p = 0.000). Conversely, shoulder surgery patients showed better 6-month improvement in pain intensity over spine patients (-8.86 vs. -4.46, p = 0.001), but this difference resolved by 12 months. Conclusion: Cervical spine patients had greater relative improvement in physical function, while pain interference and intensity did not significantly differ. This will help in counseling patients about relative difference in recovery and improvement between the two surgery types. 1107 A011: Clinical setting does not impact baseline patient reported outcome measures in patients undergoing anterior cervical diskectomy and fusion: a prospective study 1 Orthopaedic Surgery, David Geffen School of Medicine at UCLA, Santa Monica, USA Introduction: Racial disparities in utilization and outcomes following various orthopaedic procedures have been well documented, few studies have examined disparities following cervical spine surgerylikely a result of the high proportion of outpatient procedures. We utilized a large national database of inpatient and outpatient procedures to examine racial disparities in utilization and short-term complications of cervical disc replacement (CDR) versus anterior cervical discectomy and fusion (ACDF). Material and Methods: The ACS National Surgery Quality Improvement Program (NSQIP) database was queried from 2012-2019 to identify patients undergoing elective one or two level ACDF or CDR using CPT codes and associated diagnosis of degenerative disc disease, spondylosis or cervical stenosis. The proportion of CDR vs ACDF procedures, the proportion performed outpatient, as well as 30-day post-operative complications were analyzed by racial group (non-Hispanic white, Black, Hispanic, other, or missing). Multivariate logistic regression was used to adjust for patient factors associated with outcomes, with bootstrapping to generate model predictions and confidence intervals. Results: A total of 45,841 patients were identified over the study period, with 42,514 (92.7%) undergoing ACDF and 3,327 (7.3%) undergoing CDR. The proportion of CDR vs ACDF procedures increased from 4.1% in 2012 to 8.9% in 2019 (p < 0.001). A higher proportion of CDR procedures were performed outpatient (50.1% vs 33.3%, p < 0.001). On average, CDR patients were significantly younger, had a lower ASA, lower BMI and lower levels of specific comorbidities (smoking, hypertension, diabetes). Unadjusted 30-day complication rates were significantly higher in ACDF patients compared to CDR patients. On multivariate analysis, Black patients were significantly less likely undergo CDR vs ACDF compared to white patients (5.5% vs 4.4%, p = 0.0013). There was no difference in CDR utilization between Hispanic and white patients. Compared to white patients, Black patients had significantly higher rates of major complications (2.4% vs 1.7%, p < 0.001), return to the OR (1.6% vs 1.0%, p < 0.001), unplanned readmission (2.9% vs 2.3%, p = 0.008), VTE (0.43% vs 0.24%, p = 0.01), and non-home discharge (3.9% vs 1.8%, p < 0.001). There were no differences between Hispanic and non-Hispanic white patients regarding post-op complications other than non-home discharge which was higher in Hispanic patients (3.0 vs 1.8%, p < 0.001). The proportion of outpatient ACDF was also significantly lower in Black (29.4%) and Hispanic patients (26.3%) compared to white patients (33.3%, p < 0.001 for both). The overall rates of complication were significantly lower following CDR, and there were no differences between racial group with the exception of higher rates of non-home discharge (1.1% vs 0.13%, p < 0.001) and lower rates of outpatient surgery (37.3% vs 55.0%, p < 0.001) in Hispanic patients compared to non-Hispanic white patients. Conclusion: Black patients were less likely to undergo motion preserving surgery than white patients when adjusting for demographics and medical comorbidity. When undergoing ACDF, Black patients experienced significantly higher rates of post-operative complications, including reoperation and readmission, compared to non-Hispanic white patients. Both Black and Hispanic patients were less likely to undergo outpatient ACDF compared to non-Hispanic White patients. CDR patients experienced significantly fewer post-operative complications compared to ACDF patients, and racial disparities were substantially less pronounced.

Introduction: There is conflicting evidence whether spinal cord signal intensity influences functional outcomes in patients with Degenerative Cervical Myelopathy (DCM). The objective of this study was to assess the relationship between preoperative spinal cord signal change, postoperative signal change evolution, and functional outcome in patients undergoing surgery for DCM. Material and Methods: This prospective study investigated 104 consecutive DCM patients from 2010-2020 that underwent both preoperative and routine postoperative cervical spine MRI as part of a research protocol. Signal intensity/grade, modified Japanese Orthopaedic Association (mJOA) scores, signal resolution, and patient demographics were assessed. Results: Approximately 65% of subjects included in this study were found to have abnormal T2 signal intensity changes on their preoperative MRI. The total mean preoperative mJOA score was 13.61, increasing postoperatively to 15.98 (p < 0.001). A 1.86 point increase in postoperative mJOA was observed in those with signal resolution (p < 0.040). A near 3.7 point mJOA score increase can be observed if signal grade improves by just 1 postoperatively. Conclusion: Decreased T2-weighted signal intensity strongly correlated with increased mJOA scores, and therefore an improvement in postoperative functional outcomes in those with DCM. Surgical intervention correlated with an improvement in mJOA scores and signal intensity. Utilizing mJOA scores and MRI to identify cord signal intensity/presence to guide intervention may help improve outcomes/prognosis. 229 A015: Satisfaction with surgical treatment for degenerative cervical myelopathy is driven by improvement in MJOA, reduction in neck and arm pain and patient reported outcomes

Raphaële Charest-Morin 1 , Tamir Ailon 1 , and Nicolas Dea 1 1 Spine Division, University of British Columbia, Canada Introduction: Degenerative cervical myelopathy (DCM) is the leading cause of spinal cord dysfunction in adults. Studies have demonstrated the safety and efficacy of surgical treatment. Although the impact of surgery for DCM on patient reported outcomes (PROs) is well known, the effect on patient satisfaction has not been thoroughly evaluated. Our objective is to evaluate satisfaction following surgical treatment of DCM and determine its drivers. Material and Methods: Consecutive patients treated surgically for DCM, enrolled in The Canadian Spine Outcome Research Network (CSORN) database were evaluated 12 months postoperative. Levels of patient satisfaction were determined. Demographic, surgical, baseline and postoperative PROs were compared between satisfied and non-satisfied patients to determine putative drivers of satisfaction. Logistic regression was employed to model satisfaction as a function of predictor variables identified as significant on univariate analysis. Results: A total of 663 patients were identified: 255 (38.5%) were female, mean age was 59.8 (SD 11.8), 30.8% were working, 51.7% had a high school or greater education, 63.2% were taking pain medications and 14.8% had undergone previous cervical surgery. Baseline MJOA revealed mild (28.9%), moderate (39.6%) and severe (31.5%) degrees of myelopathy. Mean baseline neck and arm pain were both 5.5 (3.0). Baseline NDI was 40 (19.5), PCS 31.9 (10.0), MCS 43.3 (12.3) and EQ5D 0.6 (0.2). All PROs and MJOA improved significantly at 12-months postop. Satisfaction was high: 83.9% at 3-months and 80.5% at 12-months. No baseline demographic or surgical factors were significantly associated with satisfaction, nor were baseline PROs or MJOA. Conversely, all PROs and the 12-month MJOA score was significantly associated with satisfaction as were change scores in all these factors. For example, mean MJOA increased 2.3 (2.5) versus 1.2 (2.6) and NDI decreased by 15.1 (15.9) versus increased by 0.5 (16.1) in satisfied and non-satisfied patients. Binary logistic regression with backward selection revealed change in MCS, PCS and NDI as significant predictors of patient satisfaction. Conclusion: Patient satisfaction following surgical treatment for DCM was largely independent of demographics, baseline PRO and surgical details; rather improvements in MJOA, PROs and pain drove satisfaction.

can be calculated using the Patient Reported Outcome Measurement Information System Global 10 (PROMIS-10) score. Patient mental health may modulate the degree of improvement in quality of life due to surgery in patients with degenerative cervical myelopathy (DCM). We hypothesize that the preoperative PROMIS-10 mental health subscore (PROMIS-10MH) correlates with QALYs gained from surgery such that worse preoperative mental health is correlated with greater improvement in quality of life related to surgery. Material and Methods: Patient charts from January 2021 were reviewed for patients with PROMIS-10 scores collected preoperatively and 6 months postoperatively. Utility scores were calculated using previously described and validated crosswalk methods from PROMIS-10 to the EuroQoL 5 Dimension scale (EQ-5D-3L). QALYs were calculated based on utility scores. Statistical analysis including univariate and multivariate linear regression were performed in R version 4.1.0 (R Foundation for Statistical Computing). Results: A total of 94 Patients were identified as having undergone surgery for DCM with an average age of 60.88 years and average preoperative PROMIS-10MH was 12.28. Among these patients 47 (50%) underwent an anterior approach. Univariate linear regression demonstrated a statistically significant inverse relationship between preoperative mental health as measured by PROMIS-10MH and QALYs gained (p = 0.0112, Adjusted R 2 = 0.0578). This relationship remained statistically significant when controlling for age, gender, and smoking status in a multivariate model (p = 0.0090, Adjusted R 2 = 0.0577). There was no statistically significant difference between average preoperative and postoperative PROMIS-10MH scores (p = 0.8065). Conclusion: Patients with worse mental health experience greater increases in quality of life after surgery for DCM at 6 months follow up. This is not related to improvement in mental health alone. Further research is needed to further characterize this relationship, including the identification of mental health symptoms which may predict improvements quality of life. Additionally, the influence of DCM symptoms on mental health progression. Introduction: Degenerative Cervical Myelopathy (DCM) is a poorly recognised form of spinal cord injury that arises when degenerative changes in the cervical spine compress and injure the spinal cord. Timely surgical intervention is critical to preventing disability. Despite this, DCM is frequently undiagnosed, and may be misconstrued as normal aging. For a disease associated with age, and with an ageing population, we hypothesised that the elderly may represent an underdiagnosed population. This study aimed to evaluate this gap by comparing estimates of DCM prevalence based on spinal cord compression (SCC) data with hospital-diagnosed prevalence in the UK, and specifically to look at the effect of age today, and age tomorrow. Material and Methods: We queried the UK Hospital Episode Statistics (HES) database for admissions with a primary diagnosis of DCM. Age-stratified incidence rates were calculated and extrapolated to prevalence based on the assumptions of a steady state population and disease duration. We then compared this to estimates of DCM prevalence based on the published conversion rate of asymptomatic SCC to DCM. Calculated incidence rates were next applied to future population and life expectancy projections to estimate the rise in prevalence of DCM between 2018-2068. Results: The mean prevalence of DCM across all age groups was 0.203% (± 0.0165% SD), with a peak prevalence of 0.44% at age 50-54 years. This contrasts with estimates from SCC data which suggest a mean prevalence of 2.22% and a peak prevalence of 4.16% at age > 79 years. Future prevalence is projected to rise in all age groups, with an additional 43,000 to 52,000 DCM patients in the UK in 50 years. Conclusion: To our knowledge, this is the first study to estimate the age-stratified prevalence of DCM. There is a significant gap in the estimates of DCM prevalence between hospital records and spinal cord compression predictions, both in terms of mean prevalence across all ages, and age of peak prevalence. Possible explanations for this include underdiagnosis, which would therefore be a more significant problem in older age groups.

Introduction: Cervical spine degeneration causes nerve root compression (i.e., radiculopathy), pain, and disability. The role of perioperative factors in outcomes of anterior cervical discectomy and fusion (ACDF) surgery is unknown. This study aimed 1) to identify postoperative trajectories of disability, neck, and arm pain for patients undergoing ACDF; 2) to determine baseline measures that predict trajectory subgroup membership. Material and Methods: A retrospective cohort study of patients with cervical spondylotic radiculopathy undergoing ACDF. Candidate prognostic factors comprised demographic, health, clinical, and surgeryrelated variables. Study outcomes were trajectories of neck disability index scores and numeric rating scales for neck and arm pain intensity modeled with latent-class growth analysis. Associations between candidate prognostic factors and postoperative trajectory subgroups were explored using robust Poisson models and reported with risk ratios and 95% confidence intervals. Results: We modeled data from 352 patients (mean (SD)age = 50.9 (9.5) years, 43.8% female) and identified three distinct trajectories for disability (excellent = 45.3%, fair = 39.2%, poor = 15.5%), arm pain (excellent = 24.5%, good = 52.0%, poor = 23.5%), and neck pain (excellent = 13.7%, good = 63.1%, poor = 23.2%). Greater physical and mental health-related quality of life were associated with a reduced risk of poor outcome for neck pain, arm pain, and disability (per SD, range: 0. 40 were associated with a poor outcome for neck pain only. Remaining candidate prognostic factors were not associated with clinical outcome. Conclusion: A subset of patients experience poor outcomes following ACDF. Perioperative factors were shown to decrease risk of poor outcomes for pain and disability two years following ACDF. This knowledge may inform decision-making for policymakers and clinicians.

OP03: Degenerative Lumbar: Outcomes 1262 A019: Effect of in-situ fusion in lumbar spondylolisthesis on clinical outcomes and spino-pelvic sagittal balancing Ketan Khurjekar 1 , Shailesh Hadgaonkar 1 , Ajay Kothari 1 , Amogh Zawar 1 , Parag Sancheti 1 , and Ashok Shyam 1 1 Spine, Sancheti Institute of Orthopaedics and Rehabilitation, Pune, India Background: Current instrumentation systems have provided tools to correct spinal deformities. Transpedicular devices, in particular, allow firm fixation of the vertebra and improve the chances of correcting spinal deformities. Reduction of the slipped vertebra can give better alignment of the lumbosacral junction, at least in theory. Better alignment may provide better function. However, these operations involve an increased risk of neurologic complications from the screws and also the possibility of distracting neurologic elements during the corrective procedure. Fusion in situ is considered safe and has given good long-term results. Objectives: To study the effect on sagittal balancing in spine and pelvis radiographically and also, to study the clinical outcomes after surgical Insitu fusion of Lumbar Spondylolisthesis. Materials and Methods: This is a prospective study of a hundred and thirty eight patients from June 2015 to November 2016 which includes patients from age group of 20 to 80 years, excluding traumatic, pathological and cases which were treated conservatively. Clinically VAS, SF-36 and ODI scores were measured and for radiographical evaluation Lumbosacral spine AP, lateral and Flexion-extension views were taken including the femoral head, pre-operatively and then at 6 and 12 months. Posterior midline approach was taken and pedicle screws for fixation and TLIF was done in most of the cases. Results: The mean Pelvic tilt changed from a mean of 23.85 degrees to 18.25 degrees post op whereas Pelvic incidence changed from 61.58 degrees to 56.34, both of which were statistically significant. VAS score improved from a median of 8 pre operatively to 2 at 12 months post-operatively, ODI score improved from a mean of 39.07 to 7.92 and SF-36 scores showed a statistically significant improvement as well. 23 of our patients had Pseudarthrosis, 4 patients had neurological deficit whereas 4 patients had superficial infection. Conclusion: Posterior instrumented stabilisation with pedicle screws and Trans-foraminal Lumbar interbody fusion in cases of lumbar spondylolisthesis can provide significantly better clinical outcome with minimal complications and can be attributed to improved spino-pelvic sagittal balancing as evidenced on measurements of Pelvic tilt and pelvic incidence. This also suggests that the need for reduction to achieve near normal anatomical alignment, can be avoided.

Tomi Lanre-Amos 1 , Gregory Van Perrier 1 , Aonnicha Burapachaisri 1 , Constance Maglaras 1 , Michael Dinizo 1 , Themistocles Protopsaltis 1 , and Tina Raman 1 1 NYU Langone Health, Orthopedic Surgery, New York, USA Introduction: Metabolic syndrome (Met(S)), defined by the presence of obesity, hypertension (HTN), and diabetes mellitus (DM) confers an increased risk for general health related complications. An increasing number of patients who undergo lumbar spinal fusion are obese, and a subset will have Met(S). Little is known about the impact of Met(S) on perioperative complications in this population. We sought to assess the rate of perioperative complications in patients with Met(S) who undergo lumbar spinal fusion, as well as assess impact on length of stay and 90-day readmission. Material and Methods: Patients who underwent lumbar spinal fusion less than 6 levels were divided into two groups: Met(S), defined as having HTN, DM and a body mass index (BMI) greater than equal to 30 kg/m2, and no Met(S). Outcomes assessed included LOS, and 90-day reoperation and readmission. Results: A total of 3453 patients underwent lumbar spinal fusion, of which 226 met the criteria for Met(S) (Age: 63.53 ± 9.999, BMI: 35.88 ± 4.702). The Met(S) cohort was significantly older than the non-Met(S) cohort (63.53 vs 58.50 years, p < 0.001). Met(S) also had a statistically significant BMI compared to non-Met(S) (35.88 vs. 29.2, p < 0.001). Subsequently, a propensity score match (PSM) by age was performed where a total of 224 patients in each group were compared. The outcomes from the PSM showed that Met(S) patients had increased LOS (4.70 ± 3.81 vs 4.016 ± 2.42 days, p < 0.05). There was no difference in 90-day complication rates (27.6% vs 23.2%). There was no difference in 30 (2.7% vs 1.3%) or 90 day (3.1% vs 1.3%) readmission rates between Met(S) and non-Met(S) patients. Overall, there were no differences seen in complications and readmission between Met(S) and non-Met(S) in this study. Conclusion: The presence of metabolic syndrome was associated with a higher rate of LOS after lumbar spinal fusion. Given these results, efforts should be taken to optimize these comorbidities prior to surgical intervention. 585 A021: Posterolateral versus posterior interbody fusion for the management of lumbar degenerative spondylolisthesis: analysis from the Canadian Spine Outcomes and Research Network (CSORN) prospective lumbar degenerative spondylolisthesis propensity score matched study one-year. The majority of patients saw an improvement in alignment and the proportion of patients that improved was similar among surgery groups (SVA: 50%, 35%, 41%, P = 0.148; PI-LL: 64%, 66%, 56%, P = 0.617; LL: 62%, 71%, 63% P = 0.385 for D, IB and PLF respectively). LL deteriorated an average of 6.1 ± 5.7°and was similar among surgery types. Patients undergoing decompression only saw a smaller improvement in LL compared to IB (p = 0.039; D = 6.5 ± 6.0°, IB = 9.7 ± 7.6°, PLF = 9.1 ± 7.0°). SVA deteriorated an average of 14 ± 18 mm and was similar among surgery types. PLF saw the greatest improvement in SVA (48 ± 51 mm vs D, 24 ± 39 mm (p = 0.002) vs IB 18.1 ± 23 (p = 0.003)). PI-LL deteriorated an average of 7.1 ± 6.0 mm and improved an average of 11.1 ± 9.2 mm and did not differ among surgery types. Conclusion: Overall spinal alignment either remains the same or improves with the vast majority of patients undergoing surgery for DLS regardless of surgical intervention. In this large, longitudinally followed multi-centre patient cohort, more invasive surgical intervention in the form of interbody or posterolateral fusion for DLS was not associated with a statistically significant between group alignment improvement compared to decompression alone.

Introduction: We present a study on effects of socioeconomic indicators on Length Of Stay (LOS) post Transforaminal Lumbar Interbody Fusion (TLIF). Socioeconomic (SES) factors indicated are studied in terms of room index at the individual level, based on the tiered housing system in Singapore. Socioeconomic Disadvantage Index 1 (SEDI) and Socioeconomic Advantage Index 1 (SAI) were used to compare SES at the neighbourhood level. Primary outcome of this study was LOS post TLIF. Material and Methods: 201 patients that underwent TLIF procedures from August 2015 to September 2021 in our institution were included into the study. Postal codes were cross referenced with national database to derive room index (Equation for room index: Sum total [number of rooms in a flat × number of such flats per block] / total number of units in a block). SEDI and SAI indices were obtained from local studies. For individual analysis, patients were stratified based on room index (Room index less than 4 versus more than equal to 4). For neighbourhood analysis, patients were stratified based on less than/equal to versus more than median SEDI and SAI scores. These stratified populations were then propensity score matched at a 1:1 ratio based on demographics, comorbidities, previous spinal operations and surgical approach. Results: 92 (45.8%) of our total cohort were female patients and overall median LOS was 4 days (Interquartile range: [3.00, 6 .00]). When Room index values were compared, no significant differences were noted in terms of LOS, intra-operative variables and postoperative complications. There were no significant differences noted in LOS when compared based on unmatched analysis of neighborhood SES indices. Individuals from neighborhoods with higher SAI scores had a numerical trend towards shorter LOS (4.00 [3.00, 7 .00] vs 3.00 [2.00, 5 .00], p = 0.123). Numerical trends were also noted with higher rates of Hyperlipidemia (20.2% vs. 10.2%, p = 0.055) and Type 2 Diabetes Mellitus (13.5% vs. 7.1%, p = 0.152) amongst those with higher SAI. Similar nonsignificant findings with trends towards those with higher Disadvantage scores having longer LOS were noted (4.00 [3.00, 6 .50] vs 3.00 [2.00, 5 .50], p = 0.087). Most notably, after matching this population based on SEDI scores (n = 72:72), there was a significant difference with those with higher SEDI scores having longer LOS (4.00 [3.00, 6 .00] vs 3.00 [2.00, 5 .00], p = 0.017). Conclusion: Though no significant findings were found, numerical trends suggested that patients with better neighborhood SES indicators had shorter LOS even though they had higher rates of comorbidities. This is emphasised as patients with higher disadvantage indices had significantly longer LOS after matching. However, individual SES indices yielding nonsignificant indices might suggest that larger studies that incorporate patients from a national rather than institution database may be required to investigate such differences. We believe that this is a first of such a paper on TLIF and further prospective studies are required to study mortality outcomes, follow up differences as well as compliance to rehabilitative therapies. 

A025: Multicenter evaluation of the effect of surgical approach on sagittal plane alignment in one-or two-level fusions for degenerative pathology very relevant to achieving preoperatively-defined radiographic goals. In the current study we evaluate the impact of interbody graft type on spinopelvic mismatch in patients undergoing 1-2 level lumbar interbody fusions for degenerative pathology. Given evidence that transforaminal lumbar interbody fusion (TLIF) grafts do not achieve the same increases in lumbar lordosis as an anterior lumbar interbody fusion (ALIF) grafts, and that lordosis change from TLIF grafts is highly variable compared to lateral lumbar interbody fusion (LLIF) grafts, we hypothesize the following. The use of anterior or lateral grafts will have a higher likelihood of correcting or preserving spinopelvic mismatch, while the use of posteriorly-placed TLIF or posterior (P)LIF grafts would have a greater chance of leading to an under-corrected or worsened postoperative spinopelvic match. Material and Methods: This retrospective study included 474 patients from 18 centers of various practice settings across the USA. Patients were included in the study if they underwent a oneor two-level primary lumbar fusion for degenerative pathology, and obtained a standing neutral lumbar spine plain radiograph within one month prior to surgery and 6 months following surgery with visualization of both femoral heads and the entire lumbar spine (L1-S1). Patients were excluded if they had a previous lumbar fusion performed, if fusion included more than two levels, if plain radiograph quality was poor in that both femoral heads were not clearly visible and there was difficulty in assessing anatomic structures, or if surgery was performed for non-degenerative pathology (infection, tumor, trauma). Measurements of the preoperative and 6-month post-operative lumbar AP and lateral lumbar plain radiographs included: pelvic incidence (PI), pelvic tilt, lumbar lordosis from L1-S1 (LL), as well as segmental lordosis (SL) of each segment between L1-S1. Results: ALIF/LLIF resulted in significantly more segmental lordosis compared to TLIF/PLIF grafts (p < .001). Overall, ALIF/LLIF resulted in significantly more global lumbar lordotic alignment change compared to TLIF/PLIF (p = .01). Whether patients' alignment was preserved versus worsened was not significantly predicted by type of graft. Similarly, whether patients' alignment was restored versus not corrected was not significantly predicted by type of graft. Conclusion: In this large-scale multicenter study of lumbar fusion patients presenting with degenerative lumbar pathology, we report that anteriorly-placed grafts (ALIF/LLIF) led to greater improvements in alignment compared to TLIF and PLIF grafts. Posteriorly-placed TLIF or PLIF grafts tended to worsen lordosis both segmentally and globally, yet even the anterior grafts only modestly improved those two measurements. Although interbody approach indications may vary across training, geographic, and practice settings, we recommend that surgeons assess pre-operative spinopelvic parameters and strongly consider the impact of the interbody approach on sagittal alignment, both on a segmental and global lumbar level.

A026: Factors associated with nonroutine discharge after surgery for grades II and III lumbar spondylolisthesis: insights from the Quality Outcomes Database minimally invasive (MIS) interbody techniques. The NRD rate was 15.2% (N = 65): 61 patients went to post-acute/non-acute care setting, and 4 patients were transferred to another acute facility. Univariate analysis demonstrated that compared to those with RD, patients with NRD were more likely to be older (67.5 vs. 59.8 years old, p < 0.001), female (86.2%, N = 56 vs. 66.9%, N = 242, p = 0.002), have diabetes (30.8%, N = 20 vs. 12.4%, N = 45, p < 0.001); depression (33.8%, N = 22 vs. 20.2%, N = 73, p = 0.015); chronic renal disease (15.4%, N = 10 vs. 4.4%, N = 16, p < 0.001); dependent ambulation (36.9%, N = 24 vs. 11.9%, N = 43, p < 0.001); kyphosis (10.8%, N = 7 vs. 3.6%, N = 13, p,0.012); higher baseline ODI (54.5 vs. 45.7, p = 0.019); insurance through Medicare (66.2%, N = 43 vs. 36.5%, N = 132, p < 0.001); and more segments fused (2.2 vs. 1.5, p < 0.001). On multivariable logistic regression, patients in the upper tertile of age (>67 years old, OR = 11.7, p = 0.007), in the upper tertile of BMI (>31.5, OR 5.8, p = 0.01), with kyphosis (OR 10.8, p = 0.02), and with chronic renal disease (OR 14.4, p = 0.002) were found to have higher odds of NRD. MIS interbody technique with placement of interbody cage was independently associated with lower odds of NRD (OR 0.16, p = 0.005). Conclusion: This multicenter study represents the largest evaluation of patients undergoing surgery for grades II and III spondylolisthesis. Our analyses demonstrated increased age, increased BMI, kyphosis, and chronic kidney disease to be independent predictors of NRD. MIS interbody technique was found to be independently associated with lower odds of NRD. Introduction: Patients with lumbar degenerative spondylolisthesis have higher expectations of pain relief and functional well-being compared to patients with lumbar stenosis. It is unknown if these expectations vary across institutions and between types of surgery. The goal of this study was to assess variation of expectations between four major Canadian sites and between decompression and fusion. Material and Methods: An analysis was conducted on prospectively enrolled patients with degenerative spondylolisthesis between January 2015 to September 2021. Preoperatively, patients were questioned about their expected changes in leg pain, back pain, balance, paresthesias, independence, sporting activities, general physical capacity, reduced social contacts, improvement in mental well-being, prevention of worsening and their most important change expected. Results: 456 patients were included in analysis by site. Patient's expected change in independence, sporting activities, physical capacity, reduced social contacts differed by site. Patient's expected change in improved mental well-being showed a trend towards a difference by site. Patient's expectations did not differ in terms of prevention of worsening, changes in leg pain, back pain, balance, paresthesias or most important change expected. 469 patients were included in analysis by type of surgery. 131 patients underwent decompression, 338 patients underwent fusion. Most important expected change differed between decompression and fusion group with decompression expecting more commonly an improvement in leg pain (27.3%) and fusion group expecting an improvement in back pain (30.6%). A trend was observed for expected prevention of worsening (p = 0.056). No difference was observed in terms of expectations for changes in leg pain, back pain, independence, sporting activities, general physical capacity, reduced social contacts, improvement in mental well-being, balance and paresthesias. Conclusion: This first study on expectations of surgery for patients with degenerative spondylolisthesis provides very valuable insight in its variation between sites and type of surgery. Patient's expectations in changes in independence, sporting activities, physical capacity, reduced social contacts differed by site. Patients undergoing decompression expect most importantly a change in leg pain and patients undergoing fusion, change in back pain.

OP04: Trauma-Thoracolumbar 1 503 A028: Surgical management of spinal neuropathic artropathy (Charcot) in patients with spinal cord injury Vitor Viana Bonan de Aguiar 1 , Lucas Alves Aurich 1 , Ricardo de Amoreira Gepp 1 , and Asdrubal Falavigna 2 joint protection mechanisms. It is found in several clinical situations including traumatic paraplegia. The loss of the sensitive and proprioceptive pathways may lead to a progressive destruction involving an intervertebral disc and two adjacent vertebral bodies and often results in severe instability. In paraplegic patients the mechanisms underlying the occurrence of Charcot spine include: the addition of excessive loads to the spine by transfer activities, presence of impaired pain and proprioceptive sensation, iatrogenic instability due to laminectomy and concentration of loads to the lower adjacent segment fused by a previous operation. Charcot spine is relatively rare, and it should be distinguished from other progressive destructive lesions, such as spondylodiscitis and spinal tumors. The aim of this study is to describe the diagnosis, surgical treatment, outcomes and perioperative complications in five paraplegic patients with Charcot spine consecutively operated. Material and Methods: Included patients who underwent surgical treatment of Charcot spine between August 2018 and August 2019. Retrospective chart review included demographic data, initial disease, previous treatment, symptomatology, surgical treatment, clinical follow-up, radiological evaluation, and perioperative complications. Results: Male-to-female ratio was 3:2, and the mean age at Charcot spine diagnosis was 35 years old ranging from 18 to 47). All five patients had complete traumatic spinal cord injury (ASIA A) secondary to a car accident. The anatomic region of the fracture was the thoracic spine in all cases (T5, T8, T10, T9-T10, T11-T12) and the patients underwent posterior fixation at the time of the initial injury (T3-T8, T5-T10, T6-L1, T6-L1, T9-L2) . Additionally, one patient was submitted to T3-S1 posterior fixation for progressive scoliosis treatment and another patient underwent T12-L1 laminotomy for selective dorsal rhizotomy. The Charcot level was respectively at L5-S1 and L1-L2 in these patients. In the other patients Charcot occurred in L1-L2 (2) and L2-L3 (1), at the lower adjacent segment fused by a previous operation. The delay between the initial injury and first symptoms was on average 11.2 years ranging from 3 to 21 years). The most common clinical presentation was de novo deformity, loss of sitting balance, crepitus, loss of spasticity, and erectile dysfunction. All patients were screened for infection by clinical and imaging confrontation. Biopsies were done before surgery with histopathological findings of nonspecific chronic inflammation. Four patients were treated with long-segment posterior fixation and there were no associated perioperative complications. These patients had good clinical and radiological outcomes. One patient was submitted to anterior fixation because of the presence of skin complications in the lower back. Instrument failure was observed at 3 months of follow-up in this case. Conclusion: Charcot spine is a rare complication of spinal cord injury and a challenging disease. It often results in severe instability, deformity and debilitating symptomatology. Surgical stabilization with fusion and instrumentation is necessary in symptomatic patients and strict clinical and radiological studies are important for surgical planning. In this series, long segment posterior fixation yielded good initial operative and functional results. 531 A029: OF pelvis classification of osteoporotic sacral and pelvic ring fractures Bernhard Ullrich 1,2 , Klaus Schnake 3 , Ulrich Spiegl 4 , Philipp Schenk 1 , and Osterhoff Georg 4 , DGOU Deutsche Gesellschaft für Orthopädie und Unfallchirurgie e.V. 5 Introduction: Osteoporotic fractures of the sacrum and pelvis (OFP) are an increasing issue in orthopedics. It is known that MRI plays a huge role in detecting comprehensive fracture patterns. Current classification systems (CS), e.g. the "Fragility Fractures of the Pelvis"-CS (FFP) or the Alphanumeric-CS published by Krappinger et al. are CT-based, complex, and offer only moderate to substantial inter-rater reliability (in-terRR) and intra-rater reliability (intraRR). The AO Spine Sacral-CS and the Bakker-CS both are focusing on the sacrum only. Considering that sacral fractures are often a part of a pelvic ring fracture a CS should respect the entire pelvis. This study aimed to develop a simple and reliable CT-and MRIbased CS for OFP keeping in mind future use in a treatment decision score. Material and Methods: A structured iterative procedure, following the recommendations of Audigé et al., was conducted to reach a consensus among spinal and pelvic trauma experts. As a result, the proposed OF Pelvis CS was developed. To assess its reliability, 28 experienced trauma and orthopedic surgeons categorized 25 anonymized cases using X-ray, CT, and MRI scans twice via online surveys. While 13 of the raters were also involved in developing the CS (developing raters (DR)), 15 user raters (UR) were not deeply involved in the development process. Results: The OF Pelvis consists of five subgroups and three modifiers. Instability increases from subgroups 1 (OFP 1) to 5 (OFP 5) and by a given modifier. In both surveys, the interRR for subgroups was substantial: κ F = 0.764 (Survey 1) and κ F = 0.790 (Survey 2). The interRR of the DR and UR was nearly on par (κ F Survey 1/Survey 2: DR 0.776/0.813; UR 0.748/0.766). The agreement for each of the five subgroups was also strong (κ F min-max. Survey 1/Survey 2: 0.708-0.827/0.747-0.852). The existence of at least one modifier was rated with substantial agreement (κ F Survey 1/Survey 2: 0.646/0.629). The intraRR

Global Spine Journal 12(3S)

for subgroups showed almost perfect agreement (τ K = 0.894, DR: τ K = 0.901, UR: τ K = 0.889). The modifier had an intraRR of κ C = 0.684 (DR: κ C = 0.723, UR: κ C = 0.651), which is also considered substantial. Conclusion: The OF-Pelvis is a reliable tool to categorize OFP with substantial interRR and almost perfect intraRR. The OF Pelvis seems to be a resilient foundation for a treatment decision score. The similar reliabilities between experienced DRs and URs demonstrate that the training status of the user is not important.

Introduction: Traumatic TL fractures that require surgery can be treated with open fusion or percutaneous fixation. Percutaneous instrumentation has the added advantage of allowing for a subsequent removal of spine hardware. The aim of the current study is to compare the direct operative and postoperative outcomes between open fusion and percutaneous fixation in patients with traumatic single-level thoracolumbar (TL) spine fractures. Material and Methods: In our retrospective study, all patients undergoing elective spine surgery for TL fractures at a Level 1 trauma center between 2000 and 2017 were reviewed. Patients who underwent percutaneous fixation were given the option of hardware removal after the fracture had healed. Results: A total of 185 patients were included in the study, with 109 treated with an open fusion, and 76 with percutaneous fixation. Twenty-five patients in the latter group had the instrumentation removed after the fracture had healed. None of them required reoperation. In the open fusion group 54.1% of patients required a decompressive laminectomy. Percutaneous fixation patients had a shorter operative time (98.3 min vs 214 min, p < 0.0001), shorter length of stay (9.8 days vs 13.5 days, p = 0.04), and less blood loss (68.4 cc vs 691 cc, p < 0.001). They also had a better correction of their traumatic kyphosis after surgery (p = 0.005).

Conclusion: Percutaneous fixation is a valuable option for the treatment of TL fractures in cases without evidence of neural compression and can minimize operative time and blood loss. It is still unclear whether hardware removal helps prevent adjacent segment degeneration. Percutaneous fixation could allow for better reduction of the fracture with improvement of postoperative alignment.

Rohan Gala 1 and Saumyajit Basu 1 1 Spine Surgery, Kothari Medical Centre, Kolkata, India

Introduction: There is a significant increase in vertebral burst fractures in the elderly owing to the high prevalence of osteoporosis & the increasing ageing population. Many patients present with disabling pain & neurological deficit when these fractures are neglected. Spinal stabilisation in these patients not only warrants early functional recovery but also prevents prolong recumbency and further neurological deterioration. Percutaneous fixation methods (Fenestrated Screws) are now increasingly becoming popular with various cement augmentation techniques reducing the additive morbidity caused due to implant failure. Material and Methods: All osteoporotic burst fracture patients presenting with neurological compromise (incomplete) operated by percutaneous fixation with cement augmentation procedures without any direct decompression from 2016 to 2019 by a single surgeon were included. Pre operative function, radiology and neurology were noted from the digital medical record and imaging database. Post operative assessment of function (VAS & ODI), improvement in neurology (FRANKEL) and radiological changes were noted at each followup. Complications if any were noted. Results: 12 females and 4 males patients with a mean age of 66.67 years (range 50 to 87 years) and an average lumbar spine T score of -2.9 were assessed. 15 out of the 16 patients presented with more than 1 month history of pain following the onset of neurologic symptoms. All patients had fractures at thoracolumbar junction(T10-L2) except two who had fracture at L3 & L4. Mean loss of anterior column height was 47.2%, with significant kyphosis, instability and retropulsion of fragment causing canal compromise. At presentation, 8 patients were Frankel grade D, 6 were Frankel grade C and two were Frankel B. All patients were treated operatively with percutaneous fixation with cement augmented screws. The fractured vertebra was managed either with Vertebroplasty/kyphoplasty or with cement augmented screws. 6 patients had short segment and 9 patients had long segment fixation. Mean time to follow-up was 14.60 months.

Spine Section, German Society for Orthopedics and Trauma Surgery, Berlin, Germany Introduction: Osteoporotic thoracolumbar fractures are of high relevance and the therapeutic options are controversially discussed. The aim of the EOFTT study was to collect inpatient and outcome data on osteoporotic thoracolumbar fracture treatment in order to evaluate the OF-Classification, and treatment recommendations. Material and Methods: Multicenter data were collected prospectively from 2017 to 2020 in Germany and Switzerland. Inpatients with osteoporotic thoracolumbar spine fractures were included. Exclusion criteria were spondylodiscitis, tumor disease, and multiple injuries. Age, sex, fracture classification according to OF, performed therapy, mobility in 5 level (fully mobile to bedridden) and ODI were recorded during the hospital stay and at 1 year FU. Results: Data from 492 patients (118 male, 371 female) at 17 hospitals were collected. Age ranged from 41 to 97 years (75 ± 10 years) without gender difference (p = 0.170). At admission, 42% of patients suffered from fracture type OF3. The frequency of all types was: OF1 1%, OF2 27%, OF4 25% and OF5 5%. At admission the conservative group showed higher grade of mobility (median [1.Q-3.Q]: 2 [1] [2] ) than the surgical group (2, p < 0.001). 48% of the conservative and 26% of surgical patients were fully mobile. Initially neurological deficits were found in 3% in the surgery group and 1% in the conservative (p = 0.353). Conservative therapy was applied in 35% of the patients (OF1: 2%, OF2: 40%, OF3: 42%, OF4: 17%). All of them received physiotherapy and 18% an orthosis. 65% of patients were treated surgically (OF1: 0.3%, OF2: 21%, OF3: 42%, OF4: 30%, OF5: 7%). The age (p = 0.221) and sex (p = 0.573) did not differ between these groups. In 38% standalone kypho-or vertebroplasty was performed (OF1: 1%, OF2: 41%, OF3: 44%, OF4: 15%). In 47% augmented short level posterior fixation plus kypho-or vertebroplasty of the index vertebra (hybrid stabilization) was applied (OF2: 7%, OF3: 43%, OF4: 40%, OF5: 10%). Most of the procedures (89%) were performed minimal invasively. Multiple level fixation were used in 10% (OF2: 6%, OF3: 24%, OF4: 41%, OF5: 29%) and combined anterior/posterior fixation in 5% (OF3: 29%, OF4: 47%, OF5: 24%). During FU (8 ± 7 month) fracture progression occurred in 21 cases (1% surgical, 11% conservative, p < 0.001). Switching from conservative to surgical therapy due to fracture progression was necessary in 17 (11%) of the initially conservative treated patients. The ODI improved sig. during the observation time (p < 0.001). Conservative treated patients showed lower impairments, compared to the surgical group on admission (conservative: 0.58 ± 0.20, surgical: 0.72 ± 0.19, p < 0.001) and at discharge (conservative: 0.48 ± 0.19, surgical: 0.55 ± 0.17, p < 0.001). The surgical treated patients showed stronger improvement in the ODI in comparison to the patients in the conservative group (p < 0.001). At the FU both groups showed comparable ODI scores (conservative: 0.28 ± 0.21, surgical:

Global Spine Journal 12(3S)

0.33 ± 0.22). Conclusion: Low level of mobility and higher fracture classifications were triggers for surgical treatment. The significant reduction in the ODI shows that especially the surgical therapy is clinically helpful and makes early mobilization and functional improvement possible. Fracture progression occurs in 11% of conservative treated patients. Introduction: The pancreas is an organ which is at risk to be injured if there is a thoracolumbar spinal column injury. However, as we know, there is no study that gives any data of the incidence to support this assumption. Therefore, the coincidence of pancreatic trauma in patients with spine injury is still unknown. Data of the TraumaRegister DGU ® (TR-DGU) was analyzed to estimate the clinical relevance of this correlation. Material and Methods: A retrospective investigation of cases registered in the TR-DGU between 2008 and 2017 was performed. Registered patients from participating European trauma centers with thoracic or lumbar spinal injuries and met the following criteria were included: i) Injury Severity Score (ISS) ≥ 9, ii) blunt trauma, and iii) no early transfer out. We investigated the coincidence of pancreas injury in patients with at least an Abbreviated Injury Scale (AIS) of 2 of the thoracic or lumbar spine. Therefore, we included all kind of serious injuries of the thoracolumbar spine. Results: Mean age was 51.3 ± 22.3 years, 69.8% patients were male. The most frequent mechanisms of trauma were low falls (24.2%), motor vehicle (21.5%) and motorcycle (13.0%) accidents. Mean Injury Severity Score was 21.1 ± 11.8 points and all-cause mortality rate was 12.6% (95%CI 12.5-12.8%). The overall incidence of pancreatic injury was 60.7 (0.61%; 95% CI 0.58-0.65%) per 10,000 patients. In patients with an AIS score of 0-1 points, 2 points, and ≥ 3 points, incidence was 51.8 (0.52%; 95%CI 0.48-0.56%), 99.3 (0.99%; 95%CI 0.89-1.10), and 53.4 (0.53%; 95%CI 0.39-0.71%) per 10,000 patients, respectively. Patients with severe spinal injuries (AIS ≥ 2) were more likely to present with a concomitant pancreatic injury compared to patients with no or only minor spinal injury (AIS 0-1) (OR 1.75; 95%CI 1.55-1.99). Conclusion: Concomitant pancreatic injury in patients with spinal injuries of the thoracolumbar junction is rare. However, patients with more severe spinal injuries were overall more likely (OR 1.75) to present with an accompanying pancreatic injury than those with minor thoracolumbar injuries. The rate of pancreatic injury was lower in patients with an AIS ≥ 3 compared to those with an AIS of two. Therefore, trauma surgeons treating severely injured patients must be alert not to overlook this rare concomitant injury, because it does not clearly correlate with injury severity of the spine.

Introduction: An Agreement study was carried out, with the purpose of perform an external independent inter-and intraobserver agreement evaluation of the new AOSpine OF classification for osteoporotic thoracolumbar fractures (OFc). Material and Methods: Complete imaging studies of 97 patients (X-rays, CT scans and MRI) with osteoporotic thoracolumbar fractures were selected and classified using the OFc by six spine surgeons (three senior surgeons with more than 15 years of experience and three surgeons with less than 15 years). After a 4-week interval, the same cases were presented to the same evaluators in a random sequence for a new classification assessment. The weighted kappa coefficient (wκ) was used to determine the inter-and intra-observer agreement.

Results: The inter-observer agreement was moderate with a wκ of 0.59 [0.54-0.64]. The intra-observer agreement was fair, with a wκ = 0.35 [0.29-0.40]. Inter-observer agreement slightly improved for junior staff between first and second evaluation. Better agreement was obtained by senior staff at the inter and intra-observer agreement. Conclusion: This independent assessment demonstrated that new OFc allows only moderate inter-observer agreement and fair intra-observer agreement. Further studies are necessary prior to its widespread adoption. Keywords: Agreement study; osteoporotic vertebral fractures; osteoporotic fracture classification.

A035: Acute operative management of osteoporotic vertebral compression fractures is associated with decreased morbidity

Emily Mills 1 , Andy Ton 1 , Gabriel Bouz 1 , Ram Alluri 1 , and Raymond Hah 1 1 Orthopedic Surgery, Keck School of Medicine at the University of Southern California, Los Angeles, USA Introduction: Osteoporotic vertebral compression fractures (OCFs) are common and represent a large economic and patient burden. The purpose of this study is to determine if acute percutaneous vertebral augmentation (PVA) alters morbidity compared to nonoperative management. Material and Methods: A retrospective cohort analysis was conducted using the Nationwide Inpatient Sample (NIS) from 2015-2018. Patients with nonelective admissions for OCFs were identified using ICD-10 codes. Exclusion criteria included age < 50 years, fusion and decompression procedures, and presence of neoplasms and infections. Propensity score matching was implemented to construct 2:1 matched cohorts with similar comorbidities at admission. Patients were divided into acute operative, defined as PVA within one week of admission, and nonoperative treatment groups. Univariate and multivariate regression analysis were performed to compare differences between in-hospital complication rates. Significance was set at p < 0.05. Results: Propensity matching resulted in 14,850 patients in the operative group and 29,700 patients in the nonoperative group. Upon multivariate analysis, acute operative treatment within one week was associated with significantly lower rates of pneumonia Introduction: Anterior cervical discectomy and fusion (ACDF) and cervical vertebral body replacement of (VBR) are associated with a relatively low rate of complications. Yet, C5 nerve root palsy (C5P) is a severe one, ranging from 3 to 15% of patients referring to current literature. Its pathogenesis remains unclear despite various theories and studies. Our hypothesis was that intraoperative shoulder depression contributes significantly to this severe complication. The aim of the present study was to prospectively examine the incidence and pathogenesis of postoperative C5P after anterior cervical surgery via a multicentric approach focusing on this very question. The participating centers were blinded to the main objective of the study in order not to bias their standard procedure. Material and Methods: From 2018 to 2021, 9 spine centers prospectively included 1,244 patients (58.5% men, mean ± SD age 57 ± 13 years) suffering from degenerative or traumatic diseases of the cervical spine undergoing ACDF of VBR. Standardized examination was performed preoperatively, one day postoperatively, day of discharge, and 2 months postoperatively. Results: Overall, postoperative C5P occurred in 3.94% of cases. Of those, 20 were transient and 29 permanent. Patients with C5P were significantly older (p = 0.002) while gender, body-massindex, and secondary diagnoses could not be identified as predictors. Besides significant differences in radiological measures, patients with C5P underwent surgery with longer incisionto-suture times (p < 0.0001) and more levels (p < 0.0001). The duration of shoulder depression had a significant impact on C5P (p = 0.002), without clear cut-off value in maximum tolerable time. Conclusion: The occurrence of C5P after anterior cervical surgery is 3.94%. Our hypothesis that C5P is associated with prolonged intraoperative shoulder depression was confirmed and should be avoided in order to decrease the risk of C5P. For the surgical approach, patients who underwent anterior cervical surgery had a higher incidence of complications compared with those receiving posterior cervical approach (p < 0.0001). Also, patients undergoing posterior lumbar interbody fusion (PLIF) and more than 4 segments fixation had higher incidences of neurological complications than those received transforminal lumbar interbody fusion (TLIF) and less than 4 segments fixation (p < 0.0001 and p < 0.0001). Nerve root injury (0.58%) was found to be the most common type of neurological deficits following spinal surgery (p < 0.0001).

Conclusion: Based on a large population analysis, the incidence of neurological complications after spinal surgery was 1.02%. And patients who underwent anterior cervical surgery, PLIF procedure and more than 4 segments fixation were more likely to have neurological complications.

Introduction: Thrombin-gelatin matrix (TGM) is a rapid and potent hemostatic agent but it has some drawbacks including cost and time spent in its preparation. The purpose of this study was to investigate the current trend in use of TGM and to identify the predictors for TGM usage in order to ensure its proper use and optimized resource allocation. Material and Methods: A total of 5520 patients who underwent spine surgery in the multicenter study group from April 2020 to March 2021 were included in the study. Introduction: Hybrid surgery (HS), combining adjacent anterior cervical discectomy and fusion (ACDF) and cervical disc arthroplasty (CDA), is a relatively recent treatment option for multilevel cervical degenerative disc disease (DDD). Although ACDF has been the standard of surgical care for single and multiple level cervical disc disease for many decades, over the past decade-plus, CDA has been shown to be a safe and highly effective alternative to ACDF. Yet, some patients with multilevel disease are not good candidates for CDA at one or more of the levels, so HS may be more suitable in those patients. There are minimal patient-reported cervical HS outcome measures published to date, so the effect and reliability of HS are still unclear compared to ACDF or CDA alone. Given the novelty of HS and the relative shortage of clinical data adequately evaluating the treatment option, this current study aims to assess the patientreported outcome measures, patient satisfaction, complications and reoperation rates of cervical hybrid procedures for symptomatic cervical multilevel DDD in a single institution. Material and Methods: Retrospective cohort study data was collected and analyzed from patients who received cervical HS for symptomatic cervical DDD between 06/2018 and 02/ 2020. A total of 34 patients (13 male, 21 female) with mean age of 51.7 ± 9.2 years (range 36-71), and follow-up 12-30 months are included in this report: 26 patients had 1-level CDA and 1-level ACDF (1+1); 3 patients had 2-level CDA+1-level fusion; 7 patients had 1-level CDA+2-level fusion; and 1 patient had 1-level TDA+3-level fusion. Data was collected preoperatively and postoperatively at 3, 6, 12, and 18 months, then yearly thereafter. Patient reported outcome measures included patient satisfaction, Visual Analog Score (VAS) for neck and arm pain, and Neck Disability Index (NDI). Complication, reoperation, and readmission rates, as well as operation duration, length of stay (LOS), opioids use were also assessed. Results: The most common indication for surgery was multilevel cervical spondylotic radiculopathy (70.6%), followed by axial neck pain (20.6%), and cervical spondylotic radiculomyelopathy (8.8%). Improvement of pain and disability scores were clinically significant and these improvements were sustained throughout the follow-up period. There were no reoperations. All patients stayed in the hospital 23 hours or less. Introduction: Cervical disc replacement surgery aims to preserve cervical motion in younger patients who present with symptomatic degenerative cervical disc herniation and mobile facet joints. We aimed to determine the demographics, pre-operative range of motion, operative parameters, postoperative parameters, range of motion at 2-years postoperatively, in 27 patients who presented to our unit over a 6-year period who underwent cervical total disc replacement surgery. Material and Methods: We performed a retrospective chart review of 27 patients who presented to our unit with degenerative cervical disc disease, from 01 January 2014 to 31 December 2019, who underwent cervical disc replacement surgery. The data collected included patient age; gender; mechanism of injury; clinical presentation; cervical level/s involved; description and site of the disc herniation; length of preoperative symptomatology; pre-operative cervical range of motion; length of operative procedure; volume of intra-operative blood loss; amount of immediate postoperative radiculopathy pain assessed by the visual analogue scale; complications; length of hospital stay; and cervical range of motion at 2-year follow-up. Introduction: Cervical disc arthroplasty (CDA) has become an alternative procedure for the treatment of refractory cervical degenerative disc disease with satisfactory outcomes. However, some adverse outcomes have recently emerged, such as anterior bone loss (ABL). ABL was defined as non-progressive early peri-prosthetic vertebral bone loss commencing within 6 months after surgery. The primary aim of the present study was to explore the influence factors of ABL after CDA and effects of ABL on the clinical and radiographic outcomes. Material and Methods: One hundred and fifty-five patients who underwent single-level Prestige-LP CDA between January 2008 and December 2017 were enrolled in the study. The Japanese Orthopaedic Association (JOA) score, Neck Disability Index (NDI), and the visual analogue scale (VAS) score were used for clinical outcomes evaluation. Radiographic parameters including cervical lordosis, C2-7 range of motion (ROM), disc angle, segmental ROM, and the lengths of the upper and lower endplates were assessed on the X-ray films. Device-related complications, including ABL, subsidence, radiographic adjacent segment pathology, and heterotopic ossification, were recorded. Univariate analysis and logistic regression analysis was used to screen the influence factors. Patients were grouped according to whether ABL occurred after operation, and the differences in clinical and imaging evaluation parameters were compared. Results: There were 94 cases (60.6%) in the ABL group and 61 cases (39.4%) in the non-ABL group. Multivariate analysis showed that the age and BMI were influence factors for ABL after CDA (p < 0.05). The JOA score, NDI, and VAS score significantly improved in both groups at 3 months after operation (p < 0.05), and the scores were further improved at last follow-up (p < 0.05). There was no significant difference in JOA score, NDI, and VAS score between the two groups before and after operation (p > 0.05). The preoperative cervical lordosis was significantly smaller in the ABL group than in the non-ABL group (t = -2.402, p = 0.018). At last follow-up, the segmental ROM was significantly greater in the ABL group than in the nonABL group (P < 0.05), and the lengths of the upper and lower endplates were less in the ABL group than in the non-ABL group (p < 0.05). Heterotopic ossification occurred in 67 cases (43.2%), including 32 cases in the ABL group and 35 cases in the non-ABL group; the difference between the two groups was significant (χ 2 = 8.208, p = 0.004). High-grade heterotopic ossification was detected in 26 cases (13 cases in the ABL group and 13 cases in the non-ABL group). Twenty-nine cases (18.7%) had radiographic adjacent segment pathology, including 15 cases in the ABL group and 14 cases in non-ABL group; the difference between the two groups was not significant (χ 2 = 1.190, P = 0.276). Conclusion: The incidence of ABL after CDA was relatively high, which mainly occurred within 3 months after operation, and no longer progressing with stable radiographic features after the first 12 months. Age and BMI were independent influence factors for ABL. ABL does not affect the clinical outcomes but may preserve more ROM of prostheses. Introduction: Neck Pain following Cervical Laminoplasty is one of the major concerns as well as neurological recovery. In literatures many authors recommend preservation of C7 muscle attachments. To repair the muscular structures of cervical spine may be the key of post-operative neck pain after laminoplasty. Some reports on this postoperative complication were reduced by C7 preservation or skip laminoplasty. However many cases still requires C7 laminoplasty and/or laminectomy to treat CSM in daily practice. We aimed to reduce the postoperative neck pain. We repair the muscular function to restore the cervical muscular function. We focused cervical muscular function on muscular function attached to C2 and C7 which have large spinous process. That means C2 and C7 play a major cervical motor function because morphologically C2 and C7 may have a main muscular function. In order to reduce postoperative neck pain and restore cervical motor function to report muscular restoration of C2 and C7 muscular attachment in the same anatomical direction with non-absorbable suture stitches (Cross Tightening Muscles We evaluated the cervical vertebral alignment (C1-Th1) for each patient and neck pain (VAS) at 2 ,4 and 12 weeks after surgery. Results: Cervical curvature between C1-Th1 was significantly restored in Cross Tightening Group and VAS score regarding Neck Pain was also significantly reduced at 4 and 12 weeks after surgery. VAS was 0 to 2 at 4 weeks after surgery compared with the patients (VAS 4-8), p < 0.05. Conclusion: CSM often requires C3 to C7 laminoplasty, but post-operative neck pain is the major concerns though many reports suggest us the preservation of C7 structures. Actually, conventional laminoplasty didn't show the significance of muscular function after surgery. Preparing laminoplasty we require the removal of muscle attachment from laminae. We often observe Multifidus Muscles are shortened as if they were gum bands. Besides C2 and C7 have a larger spinous process which seems to have major roles for cervical motion. We focused on the muscle function restoration in order to reduce post-operative neck pain. We report the preliminary restoration methods for cervical motor function with Cross Tightening Multifidus Muscles. This suture method may restore the muscular function in major cervical motion in the normal anatomical direction comparing with the conventional fascia suture, and may be superior to the convention suture methods in terms of post-operative neck pain and cervical anatomical curvature. Introduction: Lower rates of adjacent segment disease have been demonstrated with cervical total disc replacement (CTDR) at midterm follow-up as compared to anterior cervical discectomy and fusion. There is limited data on patients regarding preoperative sagittal alignment and the ability of CTDR to address sagittal deformity. Considering kyphosis of the cervical spine can lead to residual compression of the neural elements, we performed a radiographic analysis to compare sagittal alignment after CTDR. Methods: A retrospective review of 139 patients (mean follow-up 9.5 months) undergoing one and two level CTDR was performed. Lateral radiographs from the pre-operative visit, immediate postoperatively, and the final follow-up visit were analyzed. The Harrison posterior tangent method was used to determine the cervical sagittal alignment from C2-C7 as well as the intersegmental angles. Paired t-tests were used to analyze radiographic measurements compared to baseline and independent t-tests were used to detect between-groups differences. Statistical significance was set at p ≤ 0.05. Results: 194 cervical levels underwent CTDR with adequate follow-up data. Based on pre-operative measurements, n = 123 levels were in lordosis (5.1 ± 4.3°) and n = 71 in kyphosis (-4.1 ± 3.3°). Immediately after surgery, mean intersegmental angles (e.g., C5-6) were significantly different from pre-operative values in both the pre-operative lordosis (6.3 ± 6.5°, p = 0.02) and pre-operative kyphosis (-0.1 ± 6.8°, p < 0.001) groups. Change was greater in the pre-operative kyphosis group compared to the pre-operative lordosis group (4.0 ± 7.1°vs 1.2 ± 5.7°, p = 0.003). This corresponded with only a 49% reduction in the number of kyphotic levels in the pre-operative kyphosis group with 51% remaining in kyphosis. Additionally, there was a 17% increase in the number of kyphotic levels in the pre-operative lordosis group. At the final follow-up visit, mean intersegmental angle for the pre-operative lordosis group was 5.4 ± 7.3°(p = 0.68) and was significantly different from pre-operative values in the pre-operative kyphosis group (-0.8 ± 7.2°, p < 0.001). Interestingly, this final follow up data corresponded with only a 41% reduction in kyphotic levels in the pre-operative kyphosis group and a 21% increase in kyphotic levels in the pre-operative lordosis group. Pre-operatively C2-C7 global alignment was lordotic n = 111 (16.2 ± 9.1°) and in kyphosis n = 28 (-6.4 ± 6.0°). Immediately post-operatively in the lordotic group, 6.3% were noted to become kyphotic. Overall, the lordotic group had a mean immediate change of 1.4°± 10.2°(p = 0.15). In the kyphotic group 46% corrected into lordosis immediately post-operatively leaving 54% of patient in kyphosis with a mean correction of 9.1°± 8.6°(p < 0.001). At final follow-up, the pre-operative lordosis group had a change of 1.4°± 10.2°(p = 0.09) with 5.4% of patients becoming kyphotic. In the pre-operative kyphosis group 53% of patients continuing to have a kyphotic C2-C7 angle. However, this group demonstrated improvement of 6.9°± 6.9°(p < 0.001). Conclusion: This study represents one of the largest studies evaluating sagittal alignment after CTDR. This study demonstrates cervical kyphosis on pre-operative imaging may not be completely corrected after CTDR. This study is limited in that these radiographic findings have not been compared to clinical outcomes. Given our current knowledge of sagittal alignment of the cervical spine, surgeons should exercise caution when utilizing CTDR technology in patients with cervical spine kyphosis. Introduction: The cervical spinal cord could be dynamically compressed during cervical motion, neutral MR images may not fully reflect the dynamic spinal cord compression. Both static and dynamic factors contribute to the pathogenesis of cervical spondylotic myelopathy. A wide range of cervical motion as a poor risk factor suggests that dynamic stenosis may adversely affect the clinical course. The severity of dynamic stenosis may be a predictive factor for mild CSM progression. The application of dynamic MRI for clinical decision-making is not a preoperative routine procedure. We think that dMRI can lead to a modification of the surgical plan based on the neutral MRI and more levels should then be treated. Material and Methods: A Single centre retrospective study with IRB approval and consent was done. (June 2019-May 2021). Patients with symptoms of myelopathy/ myeloradiculopathy were included. Dynamic MRI was performed by positioning cushions under the posterior neck for extension and posterior head for flexion, as tolerated. T1-and T2weighted sagittal images and T2-weighted axial images were acquired in the neutral position, and sagittal T2-weighted images were acquired in flexion and extension positions. mJOA score and Muhle Grading was used to assess the patients and canal compression. Morphometric analysis was performed in N, F and E positions. The tightest area of the spinal canal was defined as compression level on the neutral MRI. Cervical lordosis (C2-7) Anterior and posterior cervical cord length (aLC, pLC), SC area were analysed. The length of the cervical cord (LCC) was defined as the distance between a line crossing the cord at the upper edge of the anterior (aLCC) and posterior (pLCC) arches of C1 and the line along the lower endplate of C7. Results: 100 patients, (34/F and 66/M), mean age (58.2 ± 11y) were analysed. Significant differences were found for pLC, SC area, C lordosis and cervical cord angle. mJOA score positively correlated with age (p = 0.03) and negatively with SC area (p = 0.007). pLC was 109.7 ± 9.3 mm in F, 107.3 ± 10.3 mm in N and 100.5 ± 9.7 in E. The differences in all positions were significant (F vs. N, p = 0.04; F vs. E, p < 0.001; N vs. E, p = 0.03). Significant difference was noted between SC area in E and N (61.9 ± 13.3 vs.72.2 ± 22.1 mm 2 , p < 0.001, respectively) and F and E with the difference of 8.4 ± 5.1 mm 2 , p = 0.001. Although instability was suspected in 20.6% of the cases according to ordinary xrays, instability was found in 41.3% of cases after dynamic MR examinations. 50% of patients were classified to high grades (grade 2 and 3) in Muhle scale in Extension, but only 35% in neutral. Conclusion: Dynamic MRI helps to identify significant cervical canal stenosis that are partially or completely absent on neutral MR imaging, and preoperative extension MRI can be of great value to determine the accurate number of levels to decompress surgically. Modification of the type and the extent of surgical decompression based on the results of dynamic MRI should be assessed in future prospective studies. Introduction: Lateral lumbar interbody fusion (LLIF) was initially developed to be performed in the lateral decubitus position, facilitating indirect neural decompression and interbody cage insertion while obviating the need for paraspinal musculature dissection. Nevertheless, this technique may limit segmental lordotic correction andwhen posterior instrumentation is indicatedrequires either procedure staging or placement of pedicle screws in the lateral decubitus position. To address these drawbacks, attention has recently shifted towards the prone trans-psoas technique. However, anatomical relationships between the vertebral column, psoas muscle and its contained lumbar plexus, and the retroperitoneal vasculature may be affected by prone positioning. This study sought to quantify radiographic differences in psoas morphology, great vessel anatomy, and lumbar lordosis between supine and prone positioning to optimize surgical planning and minimize the risk of neurovascular injury. Methods: This study retrospectively analyzed a consecutive single-surgeon cohort with lumbar degenerative pathologies. Any patient with intraoperative computed tomography (CT) imaging obtained using O-Arm spinal navigation while positioned extended-prone on an open Jackson table was included, regardless of procedure type. Patients were excluded if indicated for revision fusion, trauma, infection, or tumor. Measurements were made on supine preoperative magnetic resonance imaging (MRI) and prone intraoperative CT from L2 to L5 levels. These included the anteroposterior and mediolateral proximity of the psoas, aorta, inferior vena cava (IVC), and anterior iliac vessels to the vertebral body. Psoas transverse and longitudinal diameters, psoas cross-sectional area (CSA), total lumbar lordosis, and segmental lordosis were assessed. Supine and prone anatomies were compared via paired t test, while ANOVA and the Spearman correlation coefficient evaluated the relationship between lumbar level and the magnitude of translation. Results: Twenty patients were included for analysis. Prone positioning led to significant psoas anterior translation (5.14 mm prone vs. 1.5 mm supine, p < 0.001), although the magnitude of anterior translation significantly decreased at more caudal segments (ρ: -0.39, p = 0.002) and was lowest at L5 where slight posterior retraction was observed (-0.31 mm, p = 0.024). No positional differences were observed in psoas lateralization, CSA, longitudinal diameter, or transverse diameter. When prone, IVC was found to significantly migrate anteriorly (7.24 mm prone vs. 2.56 mm supine, p < 0.001), however decreased anterior displacement was demonstrated at more caudal levels (ρ: -0.38, p = 0.004). There were no significant differences in the anatomic locations of the aorta and iliac vasculature. Average segmental lordosis significantly increased when prone (14.62°prone vs. 11.39°supine, p < 0.001).

Conclusion: This study suggests that anatomical relationships between the vertebral column, psoas muscle, and great vessels may change in the prone position and differ intraoperatively from supine imaging. Relative to the vertebral body, the psoas and IVC demonstrated substantial anterior mobility when prone -particularly at more cephalad levels -thereby promoting a safer intra-operative environment. Additionally, prone position enhanced segmental lordosis and may be critical to optimizing sagittal restoration pre-discectomy. Further clinical investigations are necessary to corroborate these findings in a prone lateral cohort.

Hamid Abbasi 1 1 Neurosurgery, Inspired Spine Health, Burnsville, USA Introduction: Oblique lateral lumbar interbody fusion (OLLIF) is a recent innovation in MI spinal fusion OLLIF is performed with the patient in the prone position and employs an oblique lateral approach that enables the instrumentation to pass through Kambin's triangle, which is defined as the space between the exiting nerve, the superior border of the caudal vertebra, and the superior articulating process of the inferior facet. While it has long been shown that arthroscopic fusions through Kambin's triangle are feasible, these procedures have suffered from high complication rates due to nerve damage. To avoid these complications, we have modified the procedure by using electrophysiological monitoring and biplanar fluoroscopy to ensure a safe approach. Unlike other MI approaches to the lumbar spine, OLLIF can safely be employed from T12-S1 and does not require any ostomies. Material and Methods: This study is a retrospective case series including 303 OLLIF procedures performed by the same surgeon. Procedures were performed in five Minnesota hospitals. Institutional review board (IRB) exemption was granted by Pearl Pathways IRB on 30 January 2017 (IRB study number 17-TRIS-106). The Clinical Trial registration for this study is registered on clinicaltrials.gov as trial NCT03726190. All patients underwent a full course of conservative therapy before being considered candidates for surgery. Preoperative imaging included magnetic resonance imaging, X-ray of the lumbar spine with flexion and extension. OLLIF is indicated for severe degenerative disc disease, spondylolisthesis, spinal stenosis and disc herniation. Skin to skin surgery time, blood loss, fluoroscopy time, and hospital stay were recorded and entered into a custom database immediately after discharge. Because no suction is used in OLLIF, blood loss was measured by postoperatively weighing sponges and subtracting their dry weight. We also obtained routine CT follow-up imaging to assess fusion and hardware failure at least 300 days after surgery. Images were read by two independent radiologists. Results: Perioperative outcomes are presented are stratified by the number of surgical levels. For a single-level OLLIF, mean surgery time was 52 ± 18.9 minutes, with a blood loss of 42.2 ± 31.1 mL, 198.8 ± 87.2 seconds of fluoroscopy time and a hospital stay of 2.2 ± 1.7 days. Linear regression shows that controlling for the number of levels, there is no significant impact of BMI on surgery time (OLS coefficient 0.23, 95% CI -0.15 to 0.61) and that each additional level of surgery increases surgery time by 24.9 (95% CI 21.72 to 28.10) minutes. Conclusion: This study is the first to present outcomes in a large cohort of OLLIF patients. We demonstrate that OLLIF is a safe, efficient and efficacious technique for fusions of the lumbar spine from T12-L1 to L5-S1. In OLLIF, the spine is approached without compromising supportive connective tissue, muscles or osseous structures. This allows for faster surgeries and short hospitalization even in patients with significant disability and obesity. Based on our perioperative, clinical, and radiographic data we propose that OLLIF should be considered a preferred option for fusions of the lumbar spine. Introduction: Lateral lumbar interbody fusion (LLIF) is an innovative minimally invasive technique for various lumbar degenerative disease (LDD). The purpose of this metaanalysis was to compare the fusion quality and outcomes directly between patients who underwent standalone LLIF with and without supplemental posterior instrumentation. Material and Methods: A comprehensive literature search was performed for relevant studies using PubMed, EM-BASE, Web of Science, and Cochrane Library without time restriction. The stand-alone and instrumented LLIF were compared by the fusion rate, the radiographic parameters, the cage subsidence rate, the clinical outcomes, the complication rate, and the reoperation rate. Results: A total of 13 studies comprising 1090 patients with LDD were included. There were comparable improvement of clinical outcomes at the last follow-up and complication rates between patients who underwent stand-alone and instrumented LLIF. Nevertheless, the lower fusion rate (p = 0.006), the inferior improvement of disk height (p < 0.001) and segmental lordosis (p = 0.013), the higher cage subsidence rate (p < 0.001), and the higher reoperation rate (p = 0.045) were observed in the stand-alone group. Conclusion: Both stand-alone and instrumented LLIF were effective in improving the clinical outcomes of patients with LDD. However, the stand-alone LLIF was associated with inferior fusion quality, inferior maintenance of indirect decompression, and higher reoperation rate due to highgrade cage subsidence. For patients with risk factors of high-grade cage subsidence, the LLIF combined with posterior instrumentation may be the better choice 876 A058: Advantage of single-position oblique lumbar interbody fusion with percutaneous pedicle screw instrumentation Min-gu Jang 1 and Kyung-deuk Seo 1 1 Orthopaedic Surgery, Konyang University Hospital, Daejeon, South Korea Introduction: To evaluate the technical feasibility and advantage of single-position oblique lumbar interbody fusion (OLIF) and the subsequent clinical and radiologic outcomes Material and Methods: Among the 93 patients that underwent OLIF from January 2017 to January 2019, those that with single-level pathology and followed up for at least a year were enrolled. Deformity, stenosis due to trauma, and patients that underwent additional direct posterior decompression were excluded. Patients were divided into those that underwent the whole surgical procedure on lateral position (Group A) and those that underwent cage insertion on lateral position and subsequent percutaneous pedicle screw fixation after changing the patient to prone position (Group B). Demographics, operative and anesthesia time, clinical outcome, and postoperative complication were compared between the two groups. Results: Total of 93 patients were enrolled in this study, 36 patients in Group A and 57 patients in Group B. The mean age, and sex ratio, did not differ between the two groups (p > 0.05). However, the index levels were more in Group A, which showed a significant difference between two groups (p = 0.012). The preoperative diagnosis included degenerative and isthmic spondylolisthesis, and foraminal stenosis. The mean operative and anesthesia time were 291.1 and 402.6 minutes in Group A, and 232.9 and 297.5 minutes in Group B, respectively. Clinical outcome of VAS back and leg did not show significant difference between the two groups. No complication including pedicle screw malposition occurred in both groups. Conclusion: Single-position OLIF on lateral position is a feasible procedure that can decrease anesthesia time without complication compared to the conventional position changing method.

A059: Single-position surgery versus lateral-then-prone-position circumferential lumbar interbody fusion: a systematic literature review Neurosurgery, Hospital Regional de Concepcion, Concepcion, Chile Purpose: to compare the outcomes of single position (SP) circumferential lumbar interbody fusion in lateral decubitus versus dual position (DP) fusion. Methods: A systematic literature review was performed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines in PubMed, Web of Science and Scopus database to identify comparative studies reporting the outcomes of SP lumbar interbody fusion versus DP. For risk of bias assessment ROBINS-I (Risk of bias in non-randomized studies of interventions) tool was used. Results: Four comparative studies were included from an initial search of 3780 papers. All four studies were retrospective cohort studies comparing outcomes of singleposition versus dual-position LLIF. A total of 349 patients were operated using a SP versus 254 DP. All the studies involved reported: operating time, estimated blood loss, length of stay, change in segmental lordosis and complications. From a general perspective, baseline variables were similar in both groups in all the studies and all reported a significant decrease in operative time and length of stays with SP. Conclusion: literature comparing single-position versus lateral then prone lumbar fusion shows a tendency towards shorter operating time and hospital stays in single position lumbar fusion, while maintaining similar perioperative outcomes. Keywords: lumbar fusion, single position spine, dual position spine, flip spine, lateral lumbar interbody fusion Introduction: Surgical management of thoracic disc herniations is challenging. Specifically, efficient and safe bone removal is difficult due to the small working window, long working distance and proximity to the spinal cord. The use of cannulated reamers may palliate these difficulties that are often encountered with burrs or osteotomes. We hypothesize that the use of cannulated reamers is a safe technique that facilitates efficient bone removal when performing a thoracic discectomy via a minimally invasive lateral retropleural approach. Material and Methods: Consecutive case series analysis of a novel surgical technique. Seven consecutive patients that presented with thoracic myelopathy from a thoracic disc herniation were reviewed. A minimally invasive retropleural approach to the lateral aspect of the thoracic spine was performed. Threaded guide wires were placed in the posterior aspect of the vertebral bodies adjacent to the affected disc space and sequential cannulated reamers were passed over the guidewires to perform partial corpectomies around the affected disc space. The posterior annulus, posterior longitudinal ligament, and herniated disc material were then resected using Penfield dissectors and Kerrison rongeurs to complete the decompression. Results: Seven patients underwent surgery with this technique. The levels involved were T8-T9 (1 patient), T9-T10 (2 patients), T10-T11 (1 patient) T11-T12 (1 patients) and T12-L1 (2 patients). There were no complications related to the use of cannulated reamers and all patients had stable or improved neurologic function postoperatively during their inpatient hospital stay. One patient required a chest-tube. All patients had post-operative CT scans that showed good decompression and demonstrated the extent of bone resection. Conclusion: The use of cannulated reamers provides a simple, effective, and efficient method for safe bone removal to facilitate minimally invasive thoracic discectomy via a lateral approach. This is a reproducible technique using commonly available equipment. , and few studies have assessed factors that might predict the need for revision with direct decompression. We investigated the rate of successful indirect decompression by LLIF with the proposed patient selection criteria, and identified risk factors associated with failure. Material and Methods: Data from 191 patients with lumbar degenerative diseases undergoing LLIF were reviewed. All the following criteria must be fulfilled: 1) dynamic clinical symptoms (pain developing when standing or walking, but subsiding by > 50% when resting in a supine position), 2) presence of reducible disc height (presence of a disc height discrepancy ≥ 1 mm between supine and upright positions), 3) no profound weakness and 4) no static stenosis. The primary outcome was success rate following indirect decompression with LLIF. Secondary outcomes were clinical and radiographic outcomes after at least 1-year of follow-up. Preoperative, procedure-related and postoperative factors were assessed for their relationship with failure. Results: Of 191 patients,13 patients (6.8%) required additional direct decompression due to persistent pain, giving a criteria success rate of 93.2%. All patient-reported outcomes, including ODI, VAS of pain score following surgery in the success group showed significantly more improvement compared to the failure group at all follow-up assessments. Factors associated with failure of indirect decompression included low bone mineral density (BMD) (T-score < 2.1), low reducible disc height (<13%), low postoperative disc height (<10 mm), high-grade cage subsidence and use of plate fixation. Conclusion: We proposed patient selection criteria for indirect decompression with LLIF which had a satisfactory success rate and identified factors associated with the need for additional direct decompression. Our proposed criteria may assist selection of patients likely to achieve good results following indirect decompression with LLIF, and optimize selection based on risk factors of failure. Introduction: Degenerative disc disease (DDD) is a common cause of low back pain often involving more than one lumbar spinal level. When conservative measures fail, anterior lumbar interbody fusion with posterior pedicle screw fixation (ALIF PPF) or transforaminal lumbar interbody fusion with posterior spinal instrumentation (TLIF PSI) can be utilized. While the benefits of fusion in alleviating pain and improving clinical outcomes have been well outlined in the literature, long-term consequences between varying approaches remain controversial. Therefore, the purpose of this study was to assess the overall revision rates, complications, pelvic incidence (PI)lumbar lordosis (LL) mismatch correction, and functional clinical outcomes of AILF PPF and TLIF PSI in the treatment of two-level lumbar DDD. Material and Methods: A retrospective review was performed to identify all patients between 2013-2018 with at least 2-year follow-up who underwent two-level ALIF PPF or TLIF PSI for the treatment of spondylosis due to degenerative disc disease. Each cohort was matched for age, sex, BMI and levels operated. Revision rates, average time to revision and complications between groups were compared. PI-LL mismatch was calculated from both pre-and post-operative radiographs and degree of correction was compared. Functional outcomes were assessed with ODI, VAS-b and VAS-l measurements at follow-up visits. Standard binomial and categorical comparative analyses were performed. Results: A total of 80 patients were included in this study, 40 in the ALIF PPF cohort and 40 in the TLIF PSI cohort. Mean follow-up of the ALIF PPF and TLIF PSI groups were 39.5 and 45.6 months, respectively. The overall revision rates were 10.0% for the ALIF PPF group and 5.0% for the TLIF PSI group (p = 0.396). Mean time to revision was 323.1 ± 200.2 and 244.2 ± 178.9 days for the ALIF PPF and TLIF PSI cohorts, respectively (p = 0.067). There were 8 smokers in the ALIF PPF group, two of which had revision surgery and 10 smokers in the TLIF PSI group, one of which had a revision surgery. Two patients in the ALIF PPF group sustained injury to the common iliac vein intraoperatively. Each cohort achieved a similar proportion of PI-LL mismatch correction, 81.3% in the ALIF PPF group and 87.5% in the TLIF PSI group (p = 0.644). There were 13 females and 27 males in each cohort, successfully matched for age, sex, BMI and levels operated. Both groups experienced significant improvements in their functional outcome scores compared to their preoperative values; however, the magnitude of improvement was not statistically significant. Conclusion: Twoyear follow-up results suggest that ALIF PPF and TLIF PSI are both reasonable alternatives for the treatment of symptomatic, two-level degenerative disc disease. After long-term follow-up, there were less revision surgeries in the TLIF PSI cohort, however the difference was not significant. Both cohorts achieved a similar proportion of PI-LL mismatch correction and improvement in functional outcome scores. Introduction: Four out of five adults suffer from low back pain (LBP) at least once in their life. This translates into an enormous financial impact; LBP is responsible for annual healthcare costs of over $100B in the US. Physical therapy (PT) is one of the most common first-line nonpharmacological treatments used in the management of LBP. Digital therapeutics offer novel treatment options that are globally-accessible, high-quality, and cost-effective. Here, we compare the quality of exercise execution when using an AIbased motion correction technology (MT) application relative to live PT followed by sessions at home with printed handouts. Material and Methods: This study was a two-arm, parallel assignment, and open label randomized controlled pilot study. 40 patients with chronic LBP with an average pain intensity of > 4/10 were enrolled. Patients were randomly assigned to one of two arms: 1) live PT and handouts, or 2) the MT mobile application (Kaia app, Kaia Health), which uses the front camera of mobile devices to detect and evaluate exercise performance, while providing real-time audio-visual feedback. Participants were recorded performing 8 repetitions of 4 exercises (tabletop arm-leg raise, beginner's squat, move hip and plank), and a panel of 5 blinded PTs evaluated the recordings. The primary endpoint was non-inferiority of the MT based on the dichotomous (0 or 1) acceptability (with a threshold of 0.9 average score) of patient exercise performance. Secondary endpoints included non-inferiority of the average of the binary PT rating of the patient's overall exercise performance, as well as of specific exercise segments (on a scale of 0-3). Results: 34 patients were included in the final analysis (2 were pilot patients, and 4 were early terminations). Inter-rater reliability was good to excellent (based on exercise, ICC range:0.61-0.89). The MT was non-inferior as compared to live PT/handouts for overall exercise execution (p < 0.01, δ = -0.15), using a thresholded dichotomous measure. Furthermore, the MT was non-inferior for both overall exercise execution, as well as for each individual exercise, when using mean acceptability as a metric (p < 0.05). Finally, the MT was non-inferior overall for the individual exercise segments (p < 0.01). Conclusions: The MT is non-inferior to live PT instruction/printed handouts in ensuring LBP exercises were performed correctly. The MT is an economical and accessible alternative, and this study paves the way for further evaluation in larger clinical studies. Introduction: A ring-shaped hydrogel, designed for coimplantation with pedicle screws to provide sustained analgesia following spinal surgery is currently under development. Local anesthetic sustained release formulations encapsulate high doses of drugs to be able to provide therapeutic local concentrations for an extended period of time. To minimize risks of local anesthetic systemic toxicity, it is vital that drug is released from the formulation in a predictable manner and does not lead to toxic systemic concentrations. While initial safety data has to be obtained using animal experiments, obtaining an in vitro-in vivo correlation (IVIVC) can lead to faster development with reduced animal testing. To study the systemic pharmacokinetic properties of the current hydrogel and allow IVIVC development, multiple hydrogels were applied in a sheep model for spinal surgery. Methods: Bupivacaine-loaded hydrogels underwent in vitro release testing in a simulated physiological environment. In vitro release kinetics were fitted to mathematical models to determine the mechanism of release. Further, hydrogels were co-implanted with pedicle screws in a sheep model for spinal surgery. At predetermined intervals, sheep were sacrificed and hydrogels were explanted. Residual bupivacaine content was determined and correlated to in vitro release kinetics (IVIVC). Further, blood was sampled at set time intervals after surgery to determine serum bupivacaine levels. Pharmacokinetic analysis on serum level data including Wagner-Nelson deconvolution was performed to obtain AUC, Tmax, Cmax, absorption constants and clearance rates. Results: Hydrogel drug release displayed a first-order profile that was characterized by initial burst release. Sheep received a cumulative dose of 150 or 300 mg bupivacaine. In vivo release was highly correlated (R 2 > 0.99) to in vitro release kinetics. Hydrogels provided sustained bupivacaine serum levels up to 168 hours. The time to Cmax (Tmax) was delayed 40-fold compared to values of bupivacaine HCl infiltration reported in literature. All recorded serum levels were well below toxic thresholds. Deconvolution yielded an elimination constant equal to the absorption constant, indicating an absorption-limited systemic clearance of bupivacaine. A dose-dependent increase in AUC was observed. Conclusions: Bupivacaine-loaded, ring-shaped hydrogels provided sustained drug release for > 72 hours in a sheep model for spinal surgery. Excellent IVIVC was obtained, which may facilitate predicting in vivo effects of adjustments to the hydrogel based on in vitro data and reduce the number of animal experiments necessary. Low systemic levels of bupivacaine were obtained and Cmax was substantially delayed compared to the previously reported Tmax of clinically used bupivacaine HCl infiltration. Taken together, these results display the feasibility of the hydrogel to provide safe and sustained release of bupivacaine following spinal surgery.

Introduction: Hospital cost containment efforts are increasingly restricting operative time. As such, attempting to maximize the efficiency of limited operative time is critical. Unfortunately, scheduling is predominantly performed manually, which requires reasoning about unknowns such as case-specific length-of-surgery and variability while attempting to maximize throughput of surgical cases. This often leads to operating room (OR) overtime and sub-optimal throughput rates. In contrast, scheduling using mathematical optimization methods such as integer linear programming (ILP) can produce maximum system efficiency. These mathematical techniques have been used extensively in the operations management, engineering and business fields with great success. As such, the purpose of our study was to use ILP techniques to create an optimal surgical schedule for the spine service at a major academic hospital. A secondary goal was to compare the efficiency of this schedule to the current widely accepted system of manual scheduling. Material and Methods: OR data at our institution was collected from 2016-2021, with the scheduling, surgical duration, overtime and number of OR days extracted. The data was configured to represent the historic manual scheduling process. This was then inputted into an integer linear programming model with the goal of determining the minimum number of OR days to complete the same number of cases while not exceeding the historic overtime values. Results: All surgeons saw a median 12% (range: 10.2% to 13.1%) reduction in the number of OR days needed to complete their annual case-load compared to their historical scheduling practices. Meanwhile, the OR overtime varied by a maximum of 5%. The daily OR configurations differed from historic configurations in 67% of cases. In addition, the number of configurations per surgeon was reduced from an average of 5 to 4. Conclusion: Our results demonstrate a significant increase in OR throughput rate (12%) with no change in operative time required. This has considerable implications in terms of cost reduction, surgical wait lists and surgeon satisfaction. The results of our model are also easily interpretable as a guideline for surgeons to book elective cases to maximize utilization of their OR time. Further optimization may be achieved by taking into account factors that could predict case duration such as surgeon experience, patients characteristics, and institutional attributes via machine learning techniques. Ultimately, these mathematical models have potentially massive implications at a health care systems level, and so should be explored across all fields of medicine. Introduction: Image segmentation is important for creating representations of musculoskeletal images that lend themselves to meaningful analysis. The purpose of this study is to evaluate multiple deep learning architectures for the task of multi-class segmentation of bony structures on lateral lumbar radiographs. Methods: 816 lateral lumbar radiographs were manually annotated to create masks of bony landmarks representing thoracic vertebrae, L1 vertebra, L2-L5 vertebrae, sacrum, femoral heads, and the background. These segmentations were paired with corresponding raw radiographs to form a 6-class segmentation dataset which was utilized as ground truth to train and evaluate four deep learning algorithms: U-Net, Doubled U-Net, MultiResUNet, and Doubled MultiResUNet. To evaluate algorithm performance, dice similarity coefficients (DSC) and accuracy scores were calculated. To compare the algorithms with each other, 36 paired t-tests were performed between all model architectures across all segmentation classes. Results: U-Net, MultiResUNet, Doubled U-Net, and Doubled MultiResUNet all achieved an overall DSC of 0.943 and an accuracy of 0.991, with the exception of MultiResUNet (accuracy: 0.992). Significant differences between model architectures were found in the thoracic vertebrae, femoral heads, and background classes only for 10 separate comparisons (all p < 0.05). Conclusion: This work proposes the strongest known bony segmentation algorithms for lateral lumbar radiographs to date. These algorithms may be useful for region of interest localization, automated shape analysis of bony structures, and automated spinopelvic parameter measurement on lateral lumbar radiographs. These applications may both streamline the clinical workflow and enable studies of spinal morphology and pathology at large scale. Introduction: The estimated accuracy of freehand pedicle insertion techniques range from 93.0% to 98.5%, and errors in screw placement are associated with significant morbidity. Robotic techniques (RT) were implemented to avoid pedicle screw malposition; however, their cost-benefit is debated. Augmented reality mediated spine surgery (ARMSS) is an emerging technology in spine surgery.. ARMSS has shown non-inferior accuracy to RT. With the recent clearance of the U. S. Food and Drug Administration, ARMSS guided procedures have been adopted and accelerated. However, the impact of this technology in the perioperative outcomes has not been described related to RT. This study was performed to describe the perioperative outcomes after spine instrumentation using ARMSS or RT at a single institution Material and Methods: Retrospective analysis were performed for thirtysix consecutive patients who underwent pedicle screw placement guided by AR-HMD (n = 8) or a RT (n = 28). Differences in operative time (ORT) of the spine surgeon, blood loses, length of stay (LOS) and revisions were determined. Data was compared using independent t test. A sub analysis using a surgical invasiveness score (SII) was used to adjust for potential bias of patient level characteristics with the impact of the outcomes of the patient. Results: The mean age at time of surgery was 62.24 ± 15.3 years. Indications for spine surgery were degenerative (n = 26 [AR = 6 RT = 20]), spine deformity (n = 3, AR = 1, RT = 2), spine tumor (n = 5 [AR = 1, RT = 4]). Infection (n = 1) and trauma (n = 2) cases were present only in the RT group which were excluded in the final analysis. Patients that underwent AR-HMD assisted surgery had an average ORT of 345 ± 147 min, blood loss of 481 ± 465 mL, LOS of 6.63 ± 4.4 days. Patients that underwent RT assisted surgery had an average ORT of 345 ± 207 min, blood loss of 407 ± 592 mL, LOS of 8 ± 2.8. There were no statistically significant differences between the surgical approaches related to ORT, blood loses, LOS or number or revisions. Differences in SII did not significant impact in the perioperative outcomes of this cohort. Conclusion: This study suggest similarity in perioperative outcomes between ARMSS and RT guided spine surgery. Validation with a larger cohort of patients and controlled study designs will help to determine if the perioperative outcomes obtained with AR-HMD guided spine surgery are as effective as robotic guided approaches. Introduction: Academic meetings serve as an opportunity to present and discuss novel ideas, with manuscript publication in a peer-reviewed journal being the eventual goal of presented research. Previous studies have identified factors predictive of publication without generating predictive models. However, machine learning (ML) presents a novel tool capable of generating these models. As such, the objective of this study was to use ML models to predict subsequent publication of abstracts presented at a major spine surgery meeting. Materials and Methods: All abstracts from the North American Spine Society (NASS) annual general meetings (AGM) from 2013-2015 were reviewed. The following information was extracted: number of authors, institution, location, conference category, subject category, study type, data collection methodology, human subject research, and FDA approval. Abstracts were searched on the PubMed, Google Scholar, and Scopus databases for publication. ML models were trained to predict whether the abstract would be published or not. Quality of models was determined by using the area under the receiver operator curve (AUC). The top ten most important factors were extracted from the most successful model. Results: A total of 1119 abstracts were presented, with 553 (49%) abstracts published. During training, the model with the highest AUC and accuracy metrics was the partial least squares (AUC of 0.77 ± 0.05, accuracy of 75.5% ± 4.7%). During testing, the model with the highest AUC and accuracy was the random forest (AUC of 0.69, accuracy of 67%). The top ten features for the random forest model were (descending order): number of authors, year, conference category, subject category, human subjects research, continent, and data collection methodology. Conclusion: This was the first study attempting to use ML to predict the publication of complete articles after abstract presentation at an academic conference. Our study used ML to identify key predictive features, combining them to create a potent predictive model. This technique can be used to improve the quality of scientific meetings while demonstrating the potential for broader applications of ML in academia and healthcare. Objective: Endoscopic lumbar interbody fusion seems to be a good alternative to open or minimally invasive procedures. In the treatment of spondylodiscitis, the perioperative risk could be reduced and faster mobilization achieved. Methods: A prospective observational study of patients with spondylodiscitis was performed. Five consecutive cases were treated with simultaneous percutaneous pedicle screw instrumentation and transforaminal endoscopic interbody fusion. Clinical outcomes were assessed by visual analog scale (VAS) and Oswestry Disability Index (ODI). Secondary outcomes were operative time and intraoperative blood loss. Results: There were 4 male and one female patient. The average age was 74 (range 64-79). VAS declined from 6 before surgery to 1 at 3-month follow-up. Mean ODI decreased from 83 before surgery to 32 at last follow up. One patient developed a new neurological deficit. Intravenous antibiotics followed by oral antibiotics was given for 2 and 8 weeks, respectively. Healing of the inflammation was achieved in all cases. The average operating time was 145 minutes and the mean blood loss was 220 ml. There were no implant related complications. Conclusion: Simultaneous percutaneous pedicle screw instrumentation and endoscopic transforaminal interbody fusion seems to be a safe and effective method for the treatment of spondylodiscitis. Introduction: Instrumented spinal surgery is frequently performed yet perceived as extremely painful, likely by damaging the densely innervated periosteum. Opioids are the cornerstone of analgesic treatment following spinal interventions, but can lead to a plethora of side effects. Moreover, patients are at risk of opioid dependence or addiction. Local anesthetics such as bupivacaine have the potential to decrease opioid consumption and provide effective local postoperative pain relief but have limited applicability in spine surgery due to a short duration of action. To provide sustained analgesia, various extended-release formulations of bupivacaine are in development. However, efficacy beyond 24 hours is often limited as the active drug can freely diffuse away from the target site. This study assessed the feasibility of a robust hydrogel for sustained and stationary bupivacaine delivery, designed for co-implantation with pedicle screws, in a sheep model for spinal surgery. Methods: Gelatin-based ringshaped hydrogels were prepared and loaded with bupivacaine crystals. Surgical co-implantation of pedicle screws and hydrogel rings was performed in 15 female sheep using a posterior midline approach. Six screws and rings were implanted per sheep, yielding a total bupivacaine dose per sheep of 220 mg. After 4, 8, 24, 48 or 72 hours, animals were sacrificed, deep compartment wound fluid was sampled and hydrogel rings were explanted. Residual bupivacaine dose was determined and a cumulative release curve was constructed. Results: Hydrogel rings successfully underwent spinal implantation in all 15 sheep. Residual bupivacaine dose was detectable at 72 hours. Hydrogel rings displayed a firstorder release profile in vivo, characterized by an initial burst release. All rings stayed in place after surgery. Some rings developed a radial tear but multivariate regression analysis revealed that this did not influence release. Bupivacaine wound fluid levels exceeded serum levels by a factor 2300, and serum bupivacaine levels were detectable but well below toxic thresholds through 72 hours. One sheep displayed direct and complete postoperative paraplegia in which, during obduction, a significant medial breach by a pedicle screw into the spinal canal was confirmed. Conclusions: Ring-shaped hydrogels designed for co-implantation with pedicle screws to provide local analgesic treatment following spinal surgery were tested in a sheep model. Hydrogels provided sustained release of bupivacaine for 72 hours. High local drug concentrations combined with serum levels well below systemic toxic thresholds underline its localized mechanism of action. The present hydrogel has the potential to provide localized and sustained analgesia following instrumented spinal surgery. Introduction: Sagittal alignment is an important consideration in idiopathic scoliosis (AIS) deformity correction and is associated with patient quality of life. While posterior spinal fusion (PSF) is currently the standard for correcting IS deformity, it is associated with loss of lumbar lordosis and resultant pain and fatigue. VBT is a novel fusionless growth modulating surgical technique that has been used in surgical treatment of IS. It relies on the Hueter-Volkmann Law, leading to growth modulation of the skeletally immature spine. While VBT has been shown to have good coronal plane deformity correction, there is a paucity of research examining its effects on the sagittal plane. This retrospective single-center cohort study compares radiographic sagittal parameters between IS patients undergoing either VBT or PSF. Material and Methods: Retrospective analysis of IS correction surgeries with LIV in the lumbar spine from 2013 to 2020 with pre-and 3-month postop standing full body plain films available was performed. Patients were grouped as VBT or fusion. Outcome measures: Age, height, weight, BMI, Risser score, LIV and levels instrumented. Radiographic analysis included pre-and postop pelvic tilt (PT), pelvic incidence lumbar lordosis mismatch (PI-LL), and thoracic kyphosis (TK). Measures were compared using independent samples t-tests, with significance set at p < 0.05.PSM was completed for demographic differences. Results: 76 patients (34 VBT, 42 PSF) were included in the study. There were no significant differences in patient age, BMI, Risser or levels instrumented. VBT cases were more frequently extended to L4 (61.8% v 11.9%, p < 0.001). There were no preop differences in PT, PI-LL and TK. Both VBT and PSF demonstrated similar improvements in radiographic parameters of sagittal alignment including PT Introduction: Pre-operative mental health status is a known risk factor for worse post-operative outcomes after lumbar spine surgery. However, few studies have investigated the effect preoperative mental health has on patients after surgery for adult spinal deformity (ASD). We investigated the effects of preoperative depression, as measured by the Modified Zung Depression Index (MZDI), on post-operative Oswestry Disability Index (ODI) scores after corrective surgical treatment for ASD. Material and Methods: An institutional review board approved database consisting of a consecutive series of patients with ASD from 2014 to 2019 treated at a single academic institution was used for this study. All patients were 18 years or older, underwent long-segmental spinal fusion from the thoracic spine to the pelvis, and had at least 6 months of follow-up. MZDI scores were measured at patient's first pre-operative visit; scores ≥ 33 were categorized as depressed. ODI scores were measured at both the first pre-operative visit and final postoperative visit. Age, history of spine surgery, Charlson comorbidity index (CCI) score, alcohol consumption, tobacco consumption, history of mental health disorder, history of antidepressant use, body mass index, and pre-operative pain visual analog scale score were collected. Pre-operative cobb angle, upper instrumented vertebrae (UIV) tilt angle, thoracic kyphosis, lumbar lordosis, sagittal vertical axis, pelvic incidence, pelvic tilt, T1 sagittal tilt, and T1 pelvic angle were measured. Statistical analyses were performed using SPSS 27.0. Comparison of means was conducted using Student's t-test. Demographic and radiographic variables with a P-value less than 0.200 on univariate linear regression analysis were included in the multivariate analysis to determine the correlation between MZDI scores and patients' baseline variables and ODI scores. Statistical significance was defined as P < 0.05. Results: A total of 51 patients were included in this study. The average age was 62.2 years, 33% of patients were male, and 43% of patients were depressed. BMI and pelvic tilt were significantly less in depressed patients, but all other demographic and radiographic variables were not significantly different between groups. Average pre-operative ODI, post-operative ODI, and percent change in ODI for depressed patients was 61 ± 14, 49 ± 19, 18 ± 41; average pre-operative ODI, post-operative ODI, and percent change in ODI for depressed patients was 63 ± 15, 50 ± 19, 14 ± 52. There was no significant difference in pre-operative, postoperative, nor percent change in ODI score between groups. Univariate linear regression revealed BMI Ito be significantly associated with decreased absolute (R = -0.300; p = 0.032) and percent change in post-operative ODI (R = -0.376; p = 0.007). Amongst CCI, history of mental health disorder, history of anti-depressant use, BMI, number of instrumented vertebrae, UIV tilt, and lumbar lordosis, which were included in the multivariate analysis, only BMI was significantly associated with percent change in postoperative ODI (R = -0.023; p = 0.047). Conclusion: Our study suggests that increased BMI, not MZDI score nor depression status, is a significant risk factor for worse improvement in ODI after long-segment spinal fusion with pelvic fixation in patients with ASD. Introduction: The lumbar shape and lumbar lordosis (LL) are important for surgical optimization in adult spinal deformity (ASD) surgery and our understanding of these parameters is continuously evolving. We analyzed a large, multiethnic, asymptomatic population to determine lumbar shape variations and the relationship of lumbar shape with spinopelvic parameters and classified the population using the Roussouly system. Material and Methods: 468 healthy volunteers without spinal disorders were recruited from spine centers in 5 countries as part of the Multi-Ethnic Alignment Normative Study (MEANS). Radiographic parameters were measured via the EOS imaging system. Pearson's correlation test and linear regression were used to find correlation and relationship between LL and other spinopelvic parameters. One-way ANOVA was performed in RStudio to compare lumbar shape across three categories of pelvic incidence (PI) (low, < 45°; average, 45°-60°; high, > 60°), lumbar apex (L2, L3, L4, or Other), and Roussouly classification categories, followed by pair-wise t-test with Bonferroni correction. Significance level was set to p < 0.05. Results: The average LL was -57.44°, L1L4 (proximal LL/pLL) was -20.64°, L4S1 (distal LL/dLL) was -36.80°. The average PI was 52.01°. PI was moderately correlated with pLL (r = -0.54) and weakly correlated with dLL (r = -0.16). Mean pLL was different between all pairings of the low, average, and high PI groups, while mean dLL was different between only the low and average, low and high PI groups. Thoracic kyphosis (T4-T12) was moderately correlated with pLL (r = -0.36) and dLL (r = -0.33). dLL is linearly related with LL by the relationship dLL = 0.44556 *LL -11.20862 (R 2 = 0.41 Introduction: Spinal deformity, is a prevalent condition. Arthrodesis procedures are often indicated but are associated with significant potential postoperative complications. Various studies have identified urinary tract infection (UTI) as a post-operative complication after spine fusion. However, UTI is uncharacterized and understudied in the context of fusion for spinal deformity. The primary aim of this study was to determine the incidence of UTI after multi-level posterior fusion for spinal deformity. Secondary aim involved determining which patient factors increased the risk of UTI. Material and Methods: Patients who underwent posterior arthrodesis for spinal deformities from 2010-2019 were queried from the PearlDiver database and then separated by number of levels operated on. After propensity matching for age and gender, the three groups were analyzed for incidence of UTI within 1 week, 1 month, 2 months and 3 months. Patients that contracted UTI within 1-month following surgery were then analyzed for the presence of diabetes, obesity, rheumatoid arthritis, and coronary artery disease existent within one year prior surgery. For each group, patients with the aforementioned risk factors (the RF group) were compared to the non-risk factor group (noRF group). The two subsets were compared at each time point using the Pearson chi-2 test. Odds ratios were also calculated and reported. Results: A total of 20893 patients underwent posterior arthrodesis procedures for spinal deformities from 2010 to 2019, with 4112, 10284 and 6497 patients having < 7, 7-12 and > 12 levels fused, respectively. Post-matching, each level group had 2239 patients, with a female split of 1628 (72.7%) and a highest incidence age range among the 15-19 age group (24.6%). At 1 month, 2 months, and 3 months, the >12 subgroup showed statistically higher UTI incidence when compared to 7-12 and <7. At the final time point of three months, UTI was similar between <7 and 7-12, with 3.8% and 3.9% respectively (p = 0.41), and statistically higher in the >12 subgroup, with 4.6% (<7 versus 7-12: p = 0.005; <7 versus >12: p < 0.001). Highest UTI incidence increase occurred within the first 7 days for <7 and from 1 week to 1 month for groups 7-12 and >12. For each level subcategory, the RF subset had significantly higher UTI rates at 1 month, 2 months, and 3 month when compared to the patients with noRF. Difference between UTI incidence of RF and noRF was largest at 3 months (<7: 4.9% vs 2.6%, p < 0.001; 7-12: 6.8% vs 2.5%, p < 0.001; >12: 7.4% vs 3.3%, p < 0.001). In addition, odds ratios were consistent and significantly greater than 1 for the RF group across all time points (<7 = OR: 2.8, p < 0.001; 7-12 = OR: 2.1, p < 0.001; >12 = OR: 2.3, p < 0.001). Conclusion: The pooled risk factors were associated with an increased risk of UTI following posterior arthrodesis for spinal deformity, regardless of the number of levels. In addition, posterior fusion procedures on greater than 12 levels had the highest rate of UTI. This is the first study to analyze and compare UTI incidence following arthrodesis on different level lengths for spinal deformity. Introduction: The number of elderly patients undergoing spine surgery has increased with the advent of new techniques and more nuanced understanding of global malalignment as patients age. To our knowledge, the relationship between inpatient physical activity after ASD surgery and post-operative complications in the elderly patient (age > 65 years) has not been reported. The ability of the elderly patient to walk independently as early as possible following adult spinal deformity (ASD) surgery may decrease the perioperative complication rate. The purpose of this study was to track daily in-patient step count as a quantitative assessment of postoperative activity level for a cohort of elderly patients undergoing ASD surgery. Material and Methods: We performed a review of 185 ASD patients over 65 years of age (Age: 71.5 ± 4.7; BMI: 30.0 ± 6.1, ASA: 2.7 ± 0.5, Levels fused: 10.5 ± 3.4). We derived the number of feet walked over the first three days after surgery from physical therapy documentation and evaluated for association with 90 day perioperative complications Results: Within the cohort of 185 patients, the mean number of feet walked within 3 days of the index procedure was 165.5ft ± 243.8. The185 patients were subdivided into quartiles based on number of feet walked: 1st: > 233.51 ft, 2nd: 62.01 -233.5 ft, 3rd: 7.01 -62.00 ft, Q4th: 0 -7.00 ft. There was no significant difference in patient characteristics between the groups. The rate of overall postop complications, cardiac, pulmonary, and ileus were higher in the 3 rd and 4 th quartiles of patients that took the fewest steps. Patients that developed any postop complication (106 ft ± 172 vs 211ft ± 279, p = 0.001), ileus (26ft ± 49 vs 174 ± 248, p = 0.001), deep venous thrombosis (DVT) (23ft ± 30 vs 171ft ± 247, p = 0.001), and cardiac complications (58ft ± 94 vs 192ft ± 261) walked less than patients who did not sustain complications. Walking less than 62 feet in the inpatient setting after ASD surgery was associated with higher risk for any postoperative complication (54.3%, p = 0.05), cardiac complication (34.8%, p = 0.03), pulmonary complication (21.7%, p = 0.01), and ileus (15.2%, p = 0.03). Conclusion: Elderly patients who walked less than 62 feet in the first three days after ASD surgery have a higher rate of postoperative complications, specifically pulmonary, cardiac, DVT, and ileus than patients who walked more. Steps walked after ASD surgery may be a helpful and practical addition to the surgeon's armamentarium for monitoring the recovery of their patients. Introduction: Patients with ASD often require complex revision surgery for deformity correction, pseudarthrosis, and instrumentation failure. Patients who undergo a first revision ASD procedure are at high risk for requiring multiple revision surgeries. To date, there is little data on patients that require multiple ASD revisions surgeries. We sought to identify the rate of recurrent surgery in the revision ASD patient and the most common indications Material and Methods: 310 patients (Age: 63.9 ± 11.1; BMI: 28.9kg/m 2 ± 6.1; 65.8% Female) with ≥ 4 levels fused undergoing a revision of a previous thoracolumbar fusion were reviewed. The incidence of multiple revisions after the index revision was assessed, as well as surgical and patient risk factors. Results: Among the 310 ASD revision patients, 12.3% (38) required a second revision within 2 years postoperatively. For the 38 patients who required a second revision, the indications for the second revision were: 7% rod fracture, 47.4% recurrent pseudarthrosis, 31.6% flatback deformity, 23.7% adjacent segment disease and 18.4% proximal junctional kyphosis. Of the 38 patients, 21% went on to require a third revision surgery. Indications for the third revision were: pseudarthrosis (50%), rod fracture (25%), adjacent segment disease (12.5%), and proximal junctional kyphosis (12.5%). Risk factors for requiring multiple revision surgeries were diagnoses of iatrogenic and degenerative flatback deformity and the inclusion of pelvic fixation at the first revision. Conclusion: We report a 2.6% rate of multiple revisions surgeries at minimum 3 year follow up in patients who undergo a first revision ASD procedure. The most common indication for multiple revisions was pseudarthrosis. Factors associated with requiring multiple revision surgeries were diagnoses of iatrogenic and degenerative flatback deformity and the inclusion of pelvic fixation at the first revision. Patients with BMI ≥ 35 should be medically optimized before they undergo ASD surgery.

A079: Does upper instrumented vertebrae selection influence 2-year postoperative cervical sagittal range of motion following thoracolumbar spinal deformity surgery starting in the upper thoracic region?

Introduction: Cervical spine flexibility allows the neck to maintain a horizontal gaze. Although the cervical spine is the most mobile segment, it is unclear to what extent, if any, the upper instrumented vertebrae (UIV) after thoracolumbar (TL) deformity surgery will affect the cervical sagittal range of motion (CSROM). We aim to examine the relationship between various cephalad levels of UIV and CSROM at 2-years postoperative following adult TL deformity surgery. Material and Methods: We evaluated 44 consecutive postoperative TL deformity patients with 2-year postoperative cervical flexion and extension (F/E) x-rays from 2016-2018. No patients had a prior history of cervical fusion. UIV selection was divided into three groups: T1, T2 and T3/T4. CSROM was measured using the C1-7, C2-7 and O-C7 Cobb angles using maximum effort F/E x-rays. Baseline clinical and radiographic parameters were reported. A oneway between subjects ANOVA was conducted to compare the effect of UIV on CSROM in all three groups. Results: The breakdown of UIV in 44 TL deformity patients was: T1 (9), T2 (21), and T3/4 (14). There were no significant differences in baseline demographics, pre/postop global alignment parameters at 2 years postop. ANOVA demonstrated a significant effect on postop O-C7 flexion (F = 8.98, p = 0.0007) between UIV groups. Post hoc comparisons using the Tukey HSD test indicated that there was a significant increase in O-C7 flexion between UIV T1 and UIV T2 (Mean Difference [MD] = 18.58°,95%CI 6.3, 30.8) and UIV T1 and UIV T3/4 (MD = 21.92°,95%CI 8.2,30.8). However, no significant difference was seen in O-C7 flexion between UIV T2 and UIV T3/4 (MD = 3.35°, 95%CI -8.1, 14.8). Although there was a trend for CSROM to increase with UIV T2 and UIV T3/4 selection when compared to UIV T1, the mean CSROM change between groups did not reach significance. Conclusion: This is the first study of its kind evaluating CSROM following TL deformity surgery starting in the upper thoracic spine. At 2 years postop, cervical flexion is significantly reduced with a UIVof T1 compared to UIV T2 or UIV T3/4, but cervical extension and total CSROM are no different.

A080: The frailty phenotype predicts outcomes following surgery Shane Burch 1 1 Orthopedic Surgery, University of California San Francisco, San Francisco, USA

The Frailty Phenotype Score (FPS) is a measure of frailty based on fatigue, slowness, weight loss, weakness and energy expenditure. A score from 0-5 is assigned with scores for Robust (0) and Frail (3) (4) (5) defining each category. The purpose of the study was to determine if the FPS was predictive of outcomes following surgery. Patients with a diagnosis of spinal deformity (scoliosis, kyphosis) or degenerative spinal disorders (lumbar spinal stenosis, degenerative disc disease, etc) were evaluated pre-operatively and postoperatively. A FPS score was calculated pre-operatively and patients were assigned a Frail or Robust phenotype. Patients were followed longitudinally for more than two years using the Oswestry Disability Index. Data was collected prospectively on 177 patients with a diagnosis of spinal deformity and 248 with a degenerative spinal condition. The study group was divided into robust and frail patients. Data was collected pre-operatively, at 6 wks, 3 months, 6 months, 1 yr, 2 yr and more than 3 years. Comparison was made between pre-operative and each post-operative time point for Frail and Robust patients. The results demonstrate a significant difference between ODI scores at all time points up to one year for both degenerative (26.57 vs 42.1; p < 0.001) and deformity conditions (16.0 vs 46.0; p < 0.001). The difference was maintained at two years in the deformity population but not maintained in the degenerative group. Robust patients have better pre-operative scores and improve more than patients with a Frail Phenotype. The components of the frailty Phenotype may be important predictors of surgical outcomes. Outcome variables were classified as either discharge to home or to PACF. Predictive variables included pre-operative, operative, and inpatient factors. Following univariate and multivariate analysis, a predictive calculator using 12 selected variables was developed. The predictive model was built using 80% of the selected cohort (N = 7,093) and validated on the remaining 20% (N = 1,773). Metrics, including area under the curve (AUC), sensitivity, and specificity, were generated to assess performance. Results: Inclusion criteria were met for 8,866 patients, with 55.3% discharged home and 44.7% discharged to a PACF. Multivariate analysis demonstrated the following pre-operative factors as significant risks for nonhome discharge: increasing age > 60 years, female gender, increased CCI scores, COPD, HTN, drug abuse, osteoporosis, depression, controlled diabetes mellitus, and academic institution. Operative factors associated with increased risk of a non-home discharge were longer fusions (≥ 8 levels) involving both the thoracic and lumbar spine. Hospital LOS ≥ 6 days and post-operative inpatient complications (neurological, urological, respiratory, and infectious) were each predictors of non-home discharges. Of the models generated, logistic regression yielded the highest AUC of 0.76. Stepwise logistic regression was used to simplify the model and assess number of variables needed to reach peak AUC. The final model utilized 12 selected predictors (and had an AUC of 0.75, with a sensitivity of 78% and a specificity of 60%. An interactable calculator is accessible at https://discharge.bubbleapps.io/ version-test. Conclusion: In this analysis of 8,866 patients, a risk prediction tool was developed to generate real-time likelihood of PACF discharge in patients undergoing elective spine surgery for ASD. The predictive model had an AUC of 75% and is the first to utilize a multicenter, large cohort of ASD patients to inform development. The calculator may facilitate identification of ASD patients at risk for discharge to a PACF, which may guide better preoperative planning, facilitate management of patient and family expectations, and inform early discharge planning. Introduction: Titanium-coated Polyetheretherketone (Ti-PEEK), as interbody cage in lumbar fusion surgery, has no difference in fusion rate compared to polyetheretherketone (PEEK). However, no comparative study has been performed in minimally invasive transforaminal lumbar interbody fusion (MI-TLIF), that stability relies primarily on interbody fusion. Questions In MiTLIF, (1) Does Ti-PEEK cage reduce pain scores and improve functional outcomes? (2) Does Ti-PEEK provide better fusion rate? Material and Methods: A randomized controlled trial of 82 patients undergoing 1-2 levels MI-TLIF were conducted. Patient-reported outcomes were recorded using visual analogue scale (VAS), Oswestry Disability index (ODI), and EuroQoL-5D-5L. Postoperative radiograph and computer tomography was assessed for fusion and subsidence at 6 Introduction: Transforaminal endoscopic discectomy has been found to have equivalent outcomes to traditional discectomy techniques. Controversy exists concerning whether this should be performed under general anesthetic with neuromonitoring or can be safely performed on awake patients without neuromonitoring. Performing such procedures on awake patient's has the benefit of avoiding general anesthesia as well as the costs associated with neuromonitoring without affecting the safety profile of the procedure. The purpose of this study is to evaluate the safety and effectiveness of awake endoscopic discectomy in an ambulatory surgery center setting. Material and Methods: 100 consecutive patients with lumbar disc herniations treated with transforaminal endoscopic discectomy by a single surgeon were enrolled in the study. All procedures were performed under conscious sedation with local anesthetic. Preoperative and postoperative Visual Analog Scale were recorded and compared. Time spent in recovery prior to discharge home and complications were also recorded. All patients tolerated the procedure well and none had to be transitioned to general anesthetic. Patients were required to ambulate and void prior to discharge from PACU home. No patients required admission to the hospital. Results: Patients' average VAS score went from mean of 6.85 to 0.74 (median 7 to 0) immediately postoperatively. The average time spent in PACU prior to discharge was 56.7 minutes. Average VAS score at 2 weeks was 3.07 (median 2.5). Complications associated with these patient's include 1 CSF leak which resolved with a blood patch, 8 cases of radiculitis and 5 recurrences treated with revision discectomy within the first 90 days of the index procedure. One patient developed remote recurrence. Two patients developed adjacent segment herniations which the elected to manage with endoscopic discectomy. No post op infections were recorded. Rates of radiculitis in our cohort following transforaminal endoscopic discectomy varied by location of herniation. 2/18 patients with foraminal herniations developed radiculitis, 4/11 patients with far lateral herniations developed a radiculitis. 1/71 patients with a central/paracentral herniation developed radiculitis. This patient had a cephalad extrusion necessitating a higher positioning of the endoscope in order to reach cephalad to the disc. 1/5 patients with lateral recess herniations developed radiculitis, however, this patient had disease extending into the foramen and required decompression near the DRG. Conclusion: Endoscopic transforaminal discectomy can safely be performed under local anesthetic infiltration or local block with conscious sedation without the need for neuromonitoring. This offers multiple advantages including cost savings for avoiding neuromonitoring, issues with post general anesthesia, including urinary retention, nausea or vomiting, and delirium. Patients at our institution also had a very low time in PACU (Time to walk, void and discharge). Patients with cephalad extrusions may benefit from more aggressive bone resection, or even a trans SAP approach in order to avoid inadvertent impingement on the dorsal root ganglion. Patients with an extraforaminal herniation had a 20.6% chance of developing radiculitis in our cohort. All patient's radiculitis symptoms resolved except for one patient who developed radiculitis after a central herniation, this patient was lost to follow up 1 month after surgery. Introduction: Administration of opioids is still a standard practice in peri-operative analgesia after lumbar spine arthroplasty despite the surge in opioid-related overdose deaths and declaration of the opioid epidemic in the last decade. Aim of this study was to evaluate efficacy in reducing postoperative pain and opioid analgesia of a novel interdisciplinary strategy combining preoperative thoracolumbar interfascial plane (TLIP) block and percutaneous/endoscopic transforaminal lumbar interbody fusion surgery and to determine time to first postoperative ambulation and hospital length of stay. Material and Methods: In this prospective review with retrospective control, 42 patients who underwent elective singlelevel percutaneous/endoscopic transforaminal lumbar interbody fusion surgery between 2015 and 2021 were divided into 2 groups: TLIP group with 17 patients who underwent TLIP block and non-TLIP group with 25 patients. Both groups received the same postoperative analgesia with morphine as patient-controlled rescue medication. Visual analog scale and Oswestry Disability Index scores were evaluated. Statistical evaluation was performed with Student t test. Results: In contrast to the non-TLIP group, in the TLIP group, postoperative mean visual analog scale back score and mean Oswestry Disability Index score significantly decreased from 6.6 to 3.3 (p < 0.01) and 32.8 to 23.6 (p < 0.01), respectively, at hospital discharge. No differences were found between the groups at 1 month. Overall mean follow-up time was 29 ± 18 months (range, 3e78 months). Patients in the non-TLIP group were administered a median postoperative 24-hour morphine dose equivalent of 23 mg (range, 8-31 mg), while patients in the TLIP group did not require opioid analgesia (p < 0.01). Patients in the TLIP group started postoperative ambulation at a median of 4.1hours (range, 2.5-26 hours) with a median hospital length of stay of 24 hours (range, 20-48 hours) (p [ 0.112). Conclusion: TLIP block significantly improves patient outcome at hospital discharge after transforaminal lumbar interbody fusion surgery without postoperative administration of opioids.

A085: The use of primary sacroiliac joint fusion for lower back pain due to sacroiliac joint pathology: a systematic review and meta-analysis Introduction: Chronic low back pain (LBP) is amongst the top ten causes for decrements in disability-adjusted life years globally. Sacroiliac joint (SIJ) pathologies are well known causes of chronic low back pain, however conservative versus operative management (CM) has been a point of contention. The effects of conservative management of SIJ pain has shown to be limited, yet open SI joint fusion (SJF) is invasive and associated with extended hospital stays. Over the last decade, minimally invasive SIJF has been investigated as a new treatment for low back pain due to SI joint pathology. As such, the aim of this study was to quantify the effect of sacroiliac joint fusion (SIJF) on patient reported outcomes in patients with chronic low back pain caused by SIJ pathology. Materials and Methods: Embase, Cochrane, PubMed, and Scopus databases were searched prior to August 18th 2020 for the treatment of SIJ pathology. Primary outcome measure was the Visual Analogue Scale (VAS) for lower back pain. Secondary outcome measure was the Oswestry Disability Index (ODI). For single cohort studies, treatment outcomes were analyzed using the pooled mean VAS and ODI scores. For studies comparing SIJF to CM, treatment outcomes were analyzed using the standardized mean difference (SMD) for VAS and ODI scores. Results: A total of 558 patients and six studies were included: two randomized controlled trials and four prospective cohort studies. Five out of the six studies were industry funded. Mean pooled VAS scores at baseline was 76. 3 Study Design: Prospective comparative study. Objective: To quantify the educational benefit to surgical trainees of using a high-fidelity simulator to perform minimally invasive (MIS) unilateral laminotomy for bilateral decompression (ULBD) for lumbar stenosis. Methods: Twelve orthopedic and neurologic surgery residents performed 3 MIS ULBD procedures over 2 weeks on a simulator guided by established AO Spine metrics. Video recording of each surgery was rated by 3 blinded, independent experts using a global rating scale. The learning curve was evaluated with attention to technical skills, skipped steps, occurrence of errors, and timing. A knowledge gap analysis evaluating participants' current versus desired ability was performed after each trial. Results: From trial 1 to 3, there was a decrease in average procedural time by 31.7 minutes. The cumulative number of skipped steps and surgical errors decreased from 25 to 6 and 24 to 6, respectively. Overall surgical proficiency improved as indicated by video rating of efficiency and smoothness of surgical maneuvers, most notably with knowledge and handling of instruments. The greatest changes were noted in junior rather than senior residents. Average knowledge gap analysis significantly decreased by 30% from the first to last trial (p = 0.001), signifying trainees performed closer to their desired technical goal. Conclusion: Procedural metrics for minimally invasive ULBD in combination with a realistic surgical simulator can be used to improve the skills and confidence of trainees. Surgical simulation may offer an important educational complement to traditional methods of skill acquisition and should be explored further with other MIS techniques.

Introduction: Percutaneous cement discoplasty (PCD) was introduced as a minimally invasive surgical procedure to treat symptomatic vertical instability at the lumbar spine. Due to the low number of relevant publications the early and late clinical outcome (complications, hospital stay, reoperation rate, late effects) are not well described. The aim of present study is to summarize the perioperative and postoperative complications after PCD and to identify factors that predict the chance of cement leakage and of prolonged length of hospital stay (LOS). Methods: 344 patients were treated with PCD in the study period. 57 patients had a concomitant procedure like decompression or vertebroplasty (PCD+). Demographics, clinical features, surgical and non-surgical complications were analyzed. The effect of perioperative factors on cement leakage and on LOS were determined with logistic and linear regression. Results: In PCD group 21 (7.3%) patients had symptomatic and 76 (26.5%) had asymptomatic cement leakage, while in PCD+ group symptomatic leakage was found at 1 (1.8%) patient and asymptomatic leakage at 6 (10.5%) patients within the first 40 days. Distribution of postoperative symptoms differed significantly between patients with cement leakage (6.4%) and without cement leakage (2%). During the index hospitalization, majority of patients with postoperative symptoms were treated conservatively, the early reoperation rate for PCD was 2.8%, and 1.8% for the PCD+ group. Age, BMI, type of PMMA, surgeon's level of experience and operated levels were identified as risk factors of cement (p < 0.01, c-index = 0.807). PCD+, BMI, Charlson score, reoperation, postoperative symptoms and medical adverse events increased significantly the LOS in our cohort (p < 0.01). Conclusion: Current study shows that severe complications as well as early reoperation rate are low after PCD. Cement leakage from the intervertebral space is quite frequent, but mostly asymptomatic. The occurrence of the leakage is influenced by high age, high BMI, low viscosity PMMA, low surgical experience and multilevel procedure. Furthermore, we identified high BMI, Charlson score, reoperation due to cement leakage, concomitant surgical procedures and postoperative symptoms as risk factors of prolonged on LOS after PCD. Introduction: Hybrid-operating rooms (hybrid-OR) are used in different fields of surgery. In spine surgery the possibility of a high resolution 2D images and the possibility of 3D-scans showed promising results in minimal invasive pedicle screw placement. In combination with the possibility of 3Dnavigation even pedicle screw placement in the upper thoracic spine can be done minimal invasive. Still, the disadvantage of high cost and possible increased radiation needs to be compensated with high accuracy and safety. Material and Methods: From June 2014 till December 2019 a hybrid operating room was used for minimal invasive pedicle screw placement in a level-1-trauma center. It consists of a floorbased flat-panel robotic C-arm with 3D-scan capability (Artis Zeego, Siemens; Germany) combined with navigation (BrainLAB Curve, BrainLAB; Germany). All patients with fractures T1 to L5 were included in the study. All cases were operated through a minimally invasive incision and a Jamshidi needle was advanced through the pedicle and a K-wire was placed. If 2D image quality did not allow safe placement 3Dnavigation was used to place the K-wire. Afterwards 3D-scan was performed to control perfect position of the K-wire and pedicle screw thickness and length was planned in the 3D-scan before placement of the screws. If a K-wire needed repositioning another 3D-Scan was performed. Postoperative CTs were used to evaluate perforation of the pedicle screws. Screw perforation grade was assessed as grade I when completely within the pedicle, II < 2 mm, III 2-4 mm, and IV > 4 mm outside the pedicle. Results: Overall 354 screws were placed in the upper thoracic spine (T1-T6), 746 in the lower thoracic spine (T7-T12) and 645 in the lumbar spine. Navigation was used in 31 out of 57 upper thoracic spine cases, in 12 out of 123 lower thoracic spine cases and in 12 out of 146 lumbar spine cases. In 33 out of 327 cases at least one K-wire was changed after the 3D-Scan. Overall 1562 pedicle screws were completely within the pedicle, 167 were assessed as grade II, 16 as grade III and 0 as grade IV. So overall 99,1% of the screws showed perforation less than 2 mm. Mean radiation was 335 ± 26 mGy and significantly higher in the upper thoracic spine compared to the lumbar spine. Conclusion: Despite higher costs and radiation the hybrid-OR allows highest accuracy and therefore patient safety in minimal invasive pedicle screw placement in the thoracic and lumbar spine.

A089: Long term outcomes of the optiLIF or percutaneous lumbar interbody fusion procedure: a retrospective study Deepak Awasthi 1 , Cole Awasthi 1 , and Elizabeth Boudreaux 1 1 Neurosurgery, Thibodaux Regional Health System, Thibodaux, USA Introduction: Degenerative disc disease is a common spinal problem presenting with predominately low back pain. There is a subgroup of patients who do not improve with nonsurgical management. In these patients, interbody fusion is a reasonable surgical option that can be performed through anterior, posterior, or lateral approaches. We describe the longterm outcomes of a novel percutaneous approach called op-tiLIF which utilizes an approach through the Kambin's triangle and then insertion of an expandable OptiMesh device followed by percutaneous pedicle screws. The optiLIF procedure uses tissue dilation instead of broad dissection, a facet sparing approach and indirect decompression from in situ filling and expansion of OptiMesh to conserve bone and muscle. This OptiMesh device received FDA approval (USA) for this procedure in September 2020 after excellent results from the SCOUT (Spineology Clinical Outcomes Trial) study. Our institution has been performing this procedure since 2010. We wanted to focus on patients who underwent a single level percutaneous interbody fusion without any additional decompression or bony removal with about 3 years or more of follow-up. Material and Methods: This is a retrospective study analyzing the outcomes in patients who underwent a single level percutaneous lumbar fusion using the optiLIF technique for degenerative disc disease with or without spondylolisthesis. From 2016 to 2018, 40 patients were identified of which 26 patients were available for follow-up in June 2021. Patients with previous lumbar surgery were excluded. The preoperative and postoperative visual analogue scale (VAS) and Oswestry Disability Index (ODI) scores were analyzed with statistical analysis using the t-test. In addition, postoperative lumbar CT scans were analyzed for fusion by an independent reviewer. Results: The average age of the 26 patients was 53.1 years (range 25-74 years). There were 11 males and 15 females. The L45 level was the most common level fused (21), 5 patients underwent L34 fusion. The average follow-up period was 4 years (range: 30-64 months). The mean preoperative VAS score was 8.6 cm; mean postoperative VAS score was 2.9 cm. The mean preoperative ODI score was 58.2; mean postoperative ODI score was 19.2. Both scores were significant at p < .00001. The fusion rate was 95%. There were 3 patients with persistent neuropathic pain controlled with medications. There was one patient that required adjacent level fusion 2 years after the initial surgery. There were no complications related to the OptiMesh device. Conclusion: Our study is one of the longest follow-ups of the optiLIF technique utilizing the OptiMesh device. This retrospective study highlights the safety and efficacy of this technique and device. The OptiMesh device has an excellent fusion rate. This technique provides meaningful relief of pain and significantly improves the preoperative disability with short hospital stays and thus accelerating patient recovery.

A090: Microscope-assisted tubular discectomy has poor immediate outcomes when a preoperative transforaminal epidural steroid is given within 3 months of surgery Akash Shakya 1 and Ayush Sharma 1 1 Orthopaedics and Spine Surgery, Dr BAM Hospital, Mumbai, India

Background: Microscope-assisted tubular discectomy has improved the immediate postoperative functional outcomes following lumbar spine surgeries. With the TFESI having become a mainstay of management of pain, we are increasingly seeing patients being operated with such minimally invasive approaches after having an TFESI. The study was aimed to evaluate the effect of a preoperative transforaminal TFESI on the outcomes following microscope assisted tubular lumbar discectomy for a prolapsed intervertebral disc (PIVD). Methods: A retrospective analysis of the prospective data was done for the patients operated for a PIVD between November 2017 and April 2020 by microscope assisted tubular lumbar discectomy at a tertiary care spine centre. The patients were divided into two groups based on the history of TFESI in the past one year. Those with TFESI were further divided into 3 subgroups based on duration between TFESI and surgery.

Demographic, operative and functional outcomes were recorded at preoperative and postoperative 1 month, 3 months, 6 months and 1 year. Oswestry Disability Index (ODI) and Visual Analogue Score (VAS) for both backpain (VAS-BP) and leg pain (VAS-LP) were used for functional assessment. Result: 244 patients were enrolled of which 132 belonged to non-TFESI group and 112 to TFESI group. Of these, 47, 39 and 26 belonged to < 3 months, 3-6 months and > 6 months subgroups respectively. Preoperative data was comparable. ODI and VAS scores were comparable among the two groups at each point. However, subgroup analysis revealed that < 3 months subgroup had significantly inferior VAS and ODI scores compared to non-TFESI group. They also had longer surgery duration and blood loss. However, the scores were comparable after the first month. We did not notice any increase in the infection rates. Conclusion: Microscope-assisted tubular discectomy within 3 months of an TFESI has an inferior functional outcome up to 1 month. Blood loss and duration of surgery was also comparatively higher than those who did not have such an intervention prior to the surgery. Introduction: A number of outcome measures are available to evaluate the function and health of people with spinal cord injury (SCI), however, none of those cover the whole spectrum of functional status, secondary problems, mood and social consequences with a single scale. The AO Spine Knowledge Forum Trauma initiated a project to develop such instrument for the spine trauma population: the Patient Reported Outcome Spine Trauma (AO Spine PROST). Previous studies have shown that the AO Spine PROST is reliable and valid among people with spine trauma, with no, transient or mild neurology. Data on its applicability for use in people sustaining AISA Impairment Scale (AIS) A and B and non-traumatic cause of injury are unavailable to date. The aim of this study was to examine the applicability of the AO Spine PROST in people with motor-complete traumatic or non-traumatic SCI. Material and Methods: Semi-structured cognitive interviews were conducted with 29 adults with a motor-complete SCI (AIS A or B). Participants were asked to complete the AO Spine PROST and four additional evaluation questions rated on a 1-5 point Likert scale (5 most positive), while verbalizing their thoughts about their answers. Interviews were audio recorded and transcribed. Codes were identified and linked to a coding schema. Qualitative data were used to interpret the quantitative results. Results: Almost three-quarters of the participants (71.4%) had a traumatic SCI. Positive ratings of the measure were obtained regards comprehensibility (mean 4.0), nonoffensiveness (4.6), relevance (4.2) and completeness (3.6) . A question about the emotional impact of SCI was indicated to be missing. A recurring topic found during the cognitive interviews included the importance to weight an assistive device in the score. The use of multiple examples per item raised uncertainty, mostly solved by patients through averaging their score. Some individuals indicated that the possibility to express even better function compared to pre-trauma would be valuable. Conclusion: Overall, the AO Spine PROST appeared to be applicable in adults with a motor-complete traumatic or nontraumatic SCI. Recommendations were made for improvement in instructions, terminology and used examples in the items. Only minor changes were proposed to make the tool applicable to spinal cord injured patients as well. This study forms an important milestone for the further development of the AO Spine PROST as well as its applicability to the entire spectrum of spine trauma and SCI patients, leading to improved care and research in this specific patient population.

A092: Current practice of acute spinal cord injury management: a global survey of members from AOSpine International Nader Hejrati 1 , Christopher Ahuja 1,2 , and Michael Fehlings 1,2

Introduction: Remarkable strides have been achieved in the realm of spinal cord injury (SCI) management. As such, the field of SCI research has experienced a rapid evolution with preclinical studies elucidating key mechanisms underpinning the pathobiology of the disease. Seminal works have uncovered the importance of the secondary injury cascade, which promoted successful translation of neuroprotective interventions for patients with acute SCIs. These findings have now been adopted in guidelines such as the 2017 AOSpine guideline on SCI management. However, longstanding controversies surrounding hemodynamic management, timing of surgical decompression and the use of steroids have complicated implementation of these guidelines into clinical practice. The objective of this study was to examine knowledge, adoption, and barriers to guideline implementation. This internationally conducted survey aims to examine current practices of clinicians around key aspects of SCI management including the administration of steroids, hemodynamic management, and timing of surgical decompression. Material and Methods: A request to participate in the survey was distributed to AO Spine Members International during 2021. The questionnaire was structured into the following four sections: 1) demographic data of the respondent, preferred practices surrounding 2) steroid management, 3) hemodynamic management and 4) timing of surgical decompression. Data were analyzed in R using Chi-squared tests and ANOVA. Results: Five hundred and ninety-three international spine professionals completed the survey. With 53.8%, the majority of respondents were Orthopaedic surgeons (n = 319), followed by 35% Neurosurgeons (n = 209), 8.3% Traumatologists (n = 49) and 1.7% belonging to other disciplines (n = 10). In 40.1% (n = 238), respondents worked at a low-volume institutions (0-5 patients with acute SCIs per annum), while 32.9% worked at mid-volume institutions (6-20 per annum) and 15% (n = 91) worked in high-volume institutions (more than 20 patients per year). There was a bimodal distribution with regard to the administration of steroids with 53.6% administering steroids (n = 256) and 46.4% not administering (n = 222). Interestingly, fewer respondents in high-income countries (defined by World Bank) stated they would give steroids (40.1%) versus middle income countries (62.6%). 331 respondents (81.5%) answered that they would provide mean arterial pressure (MAP) guided treatment in the intensive care unit or an analogous monitoring setting while 75 (18.5%) stated they would not. Regarding surgical decompression, 325 responded that they would provide decompression within 24 hours (87.8%) while 45 responded that they would not (12.2%). Interestingly, despite overwhelming evidence and surgeons' responses that would offer decompression, 231 (62.4%) stated they encounter logistical barriers in their institutions. Conclusion: The heterogeneity in current practices of acute SCI management highlights the necessity for the development and knowledge transfer of high-quality guidelines. Future research efforts will need to address barriers of guideline implementation, such as logistic hurdles in the realization of early decompressive surgery. Introduction: Injury severity after traumatic spinal cord injury (SCI) in the acute setting is assessed by a standardized neurological examination that is subjective, poorly predictive of outcome and often impossible or severely confounded by pharmacological sedation, or concomitant injuries. Therefore, biomarkers that objectively characterize severity and are able to predict outcome are urgently needed for clinical decisionmaking, communication with patients and their families as well as study design. Preliminary data shows that serological values of NF-L and GFAP are interesting candidates for objective diagnostic and prognostic biomarkers. Previous studies also tried to assess magnetic resonance imaging (MRI) findings as potential surrogate markers for SCI. The following study aims to combine certain MRI findings with serum values of NF-L and GFAP as potential markers to characterize injury severity, predict outcome and eventually monitor treatment response in future clinical trials. Material and Methods: This is a retrospective analysis of prospective collected data. Patients with acute traumatic SCI were included in an observational trial in which serial serum samples were collected in the first 5 days after injury. The concentrations of NF-L as well as GFAP were analyzed using SimoaTM technology. ASIA impairment Scale (AIS) grade and motor scores were obtained according to the International Standards for Neurological Classification of Spinal Cord Injury at presentation and at 6months post-injury. As MRI parameters we assessed the Maximal Canal Compromise (MCC), Maximal Spinal Cord Compromise (MSCC), intramedullary lesion length, intramedullary hemorrhage, BASIC score and sagittal grade. We included all patients from our institution that were enrolled in the prospective trial and had preoperative MRI available.

Results: 68 patients met inclusion criteria and had a preoperative MRI available in our institution. In a multi-center trial, serological NFL-L and GFAP levels predicted AIS improvement with 75-80% accuracy and were able to discriminate between motor complete and incomplete with 90% accuracy. Conclusion: Preliminary data indicates that Nfl and GFAP levels in the serum qualify as potential biomarkers after acute human SCI. This study will evaluate the potential additional prognostic value by adding several MRI parameters. Introduction: Extracranial traumatic vertebral artery injury (eTVAI) occurs in approximately 10% of non-penetrating head and neck traumas. Most cases are initially asymptomatic with an increased risk for delayed stroke. Guidelines for the work-up and management of eTVAI are outdated and predominantly supported by Level III evidence. Furthermore, consensus is lacking regarding screening, treatment, and follow-up of asymptomatic patients with eTVAI. Given this, our objective was to investigate national practice patterns reflecting these domains. Material and Methods: An electronic, case-based survey was distributed by the Canadian Neurosurgery Resident Research Collaborative to members of the Canadian Neurological Sciences Federation and Canadian Spine Society. Case 1 involved an asymptomatic patient, low energy injury mechanism, and radiographic imaging demonstrating a non-displaced cervical lateral mass fracture extending into the foramen transversarium. Case 2 involved an asymptomatic patient, high energy injury mechanism, and radiographic imaging demonstrating a unilateral oblique C2 body and contralateral pars fracture. In both cases, screening questions were followed by angiographic findings. Case 1 angiography: stratified based on luminal diameter reduction and presence or absence of intimal flap. Case 2 angiography: traumatic pseudoaneurysm dissection. Survey responses were analysed using descriptive statistics. Results: One hundred-eight of 182 participants (59%), representing 20 academic sites, completed the survey. The majority (71%) of respondents do not use a criterion-based screening tool to diagnose eTVAI. Regarding Case 1, 78% of respondents would screen for eTVAI; of those, 97% would screen with CTA and 88% would perform screening immediately. Ninetyseven percent of respondents would initiate medical therapy; the majority would treat with aspirin (89%) for 3-6 months (46%). Most respondents would follow-up clinically (89%) or radiographically (75%), every 1-3 months, respectively. Regarding Case 2, 73% would screen for eTVAI, of which 96% would screen with CTA and 88% would screen immediately. Ninety-four percent would initiate treatment. Fifty-four percent would treat with aspirin for 3-6 months (35%) and 36% percent of respondents would utilize endovascular therapy. Most would follow-up clinically (97%) or radiographically (89%), every 1-3 months, respectively. Conclusion: This study highlights consensus in national practice patterns for the work-up and management of asymptomatic extracranial traumatic vertebral artery injury. Goel-Harms technique for AAI using were reported. Preoperatively, patients were assessed clinically using the JOA score, and radiologically with plain radiography, CT scan, and MRI of the craniocervical region. Postoperatively, all patients were followed according to our scheduled clinical and radiographic imaging protocol. The following parameters were recorded; JOA score, construct stability, fusion, and abnormal events. Results: A total of 25 patients completed one year follow-up and fulfilled our criteria were recruited for this study. The mean age was 10.68 ± 4.47 (range, 3-17) years. Fifteen patients were males and 10 were females. The final diagnosis included Down syndrome in 7 patients, type-II dens fracture in 6, os odontoideum in 3, AARF in 7, and aneurysmal bone cysts (ABC) in 2 patients. RTA was reported in 6 patients, falls in 3, and sports in 3. The mean operative time was 128.8 ± 15.78 minutes, operative blood loss was 291.2 ± 142.20 ml, mean hospital stay was 3.88 ± 1.36 days, and the mean follow up was 21.76 ± 8.22 months. The mean preoperative JOA score improved from 15.96 ± 1.46 to 16.76 ± 1.92 at the last follow up. Sound bone fusion was reported in 92% of patients. Conclusion: Our data suggest that Goel-Harms technique is safe, feasible, and effective procedure in management of paediatric reducible AAI. Special care should be offered to young patients with Down syndrome. Introduction: Traumatic spinal cord injury (SCI) is a common condition that can have a devastating impact, often affecting young people and incurring substantial disability. Despite heightened interest in research and efforts to establish evidencebased clinical practice guidelines, neurological recovery occurs in only a fraction of patients with acute SCI and is often limited. Furthermore, there exists a lack of consensus regarding optimal medical and surgical management on a number of controversial topics, reflected in ambiguous guidelines and wide variations in practice. Material and Methods: We aimed to develop an evidence-based "Code Spinal Cord Injury" treatment protocol tailored to our institution, UC Davis Medical Center, that was inspired by "Code Stroke" and previously published SCI treatment protocols. Our specific objectives were to 1) review relevant literature; 2) achieve consensus among our Neurological and Orthopedic Spine Surgeons on best-practices; 3) develop a detailed treatment protocol that streamlines care and eliminates barriers; 4) create a rapid MRI protocol ( < 10 minutes); 5) engage physicians, nurses, and managers across all relevant teams; 6) implement protocols to measure time from door-to-decompression and 1-year neurological outcomes, to provide feedback for continuous improvement; 7) create a living document that is frequently updated to reflect the latest knowledge on optimal management of SCI. A narrative review of the literature was performed and a protocol was developed by the spine surgeons and implemented as an institutional protocol, in collaboration with numerous departments throughout the hospital. Results: Evidence has recently emerged that fills several knowledge gaps in previous clinical practice guidelines. First, it has become evident that surgical decompression should be performed as early as possible (e.g. surgery within 2 hours), up to 36 hours after injury, as it increases the likelihood of neurological improvement. Second, pre-operative MRI should

Global Spine Journal 12(3S)

be performed when feasible, as it frequently produces findings that alter surgical decision-making. Third, the role of high-dose corticosteroids remains controversial, but benefits may outweigh risks in certain patients (e.g. young, healthy, cervical injury, within 8 hours) and should be considered a treatment option. Fourth, adequate decompression of the swollen spinal cord is necessary for optimal outcomes, and this can be measured with intraoperative ultrasound and post-operative MRI. Fifth, optimization of spinal cord perfusion may be helpful to improve neurological recovery, but must be balanced with the risks of vasopressor administration. We incorporated these and other current findings into a comprehensive algorithm that covers assessment, rapid imaging, pharmacological therapies, critical care management, timing of surgery, and enrolment in clinical studies. Conclusion: SCI management is complex, but protocolizing assessment and treatment has the potential to raise the standard of care and deliver enhanced outcomes. Locally, we plan to compare neurological outcomes and complications before and after implementation of the initial version of this protocol. Other centers may consider implementation of "Code Spinal Cord Injury" protocols, and future guidelines efforts will hopefully offer similar detailed guidance. Introduction: The current rate of surgical treatment for type II dens fractures is not known as most studies are of limited sample size. The goal of this study was to determine the current standard treatment for traumatic dens fractures across the USA and to identify factors that increase the likelihood of surgical management. Material and Methods: This study is a retrospective cross-sectional review of the National Trauma Data Bank (NTDB) between October 2015 and December 2016 for traumatic type II dens fractures. Patient data including age, race, gender, displacement, neurologic sequelae, abbreviated injury scale (AIS) rating, mechanism of injury (fall versus transportation-related) and surgical versus nonsurgical management was extracted and analyzed with multivariable logistic regression, conditional odds ratios, and chisquared analysis. There were 1,612,873 trauma cases logged in the NTDB during the specified timeframe. Of these, 4,737 patients were identified that met inclusion criteria. Age was confounded with all of the other effectors below and was not modeled. AIS was not significantly associated with management (p = 0.878) and was consequently removed for a better fit through a backward elimination procedure. Modeling interactions between effectors did not significantly improve the model fit over a main effects model. Ultimately, 4,423 patients were included in the main effects model once those identifying as a race other than White or Black and those with missing mechanism of injury data were removed. Results: Isolated type II dens fractures occurred at a rate of 0.3% among all trauma patients (n = 4,423). Surgical treatment was provided for 11.1% (n = 495). Parameters that increased the likelihood of surgery included posterior displacement (OR 5.59, 95% CI 4.02-7.77, p < 0.001) > neurologic damage (OR 4.32, 95% CI 3.11-6.00, p < 0.001) > anterior displacement (OR 2.82, 95% CI 2.10-3.80, p < 0.001) > black race (OR 1.63, 95% CI 1.12-2.38, p = 0.012) > male gender (OR 1.41, 95% CI 1.16-1.710, p = 0.001) > transportation-related injuries versus falls (OR 1.28, 95% CI 1.02-1.61, p = 0.031). Conditional odds ratios showed that among women, black women were almost twice as likely to receive surgery compared to white women and, among white patients, white men were more likely to receive surgery than white women. Black patients also received operative management more frequently even when neurologic damage was absent (OR 1.54, 95% CI 1.02-2.33, p < 0.001), for anteriorly displaced fractures (OR 1.90, 95% CI 1.22-2.95, p = 0.004), and when fractures resulted from falls (OR 1.88, 95% CI 1.11-3.20, p = 0.019). White women represented a disproportionate number of patients over 65 years old (55.5%; χ2 (1, n = 4,423) = 152.7, p < 0.001). Conclusion: The incidence of surgical treatment of dens fractures is low. As expected, displacement and neurologic damage most strongly predicted operative management; however, black race and male gender also increased the likelihood of surgery, raising the question of provider bias versus patient treatment preferences. Additionally, white women over 65 years old are disproportionately affected by dens fractures, paralleling osteoporosis trends and known agerelated degenerative changes.

Renate Krassnig 1 , Hohenberger Gloria Maria 2 , Viertler Elisabeth 3 , and Wildburger Renate 1 the osteoporotic fractures in the elderly. Risk of the transiliactranssacral screw positioning is that the critical area of nerve root exit has to be passed twice. For secure screw placement, without causing iatrogenic neurovascular injuries, the knowledge of distances to the narrowest areas is essential. Purpose of this anatomical study was to examine the optimal intraosseous screw placement for the first two sacral segments. Material and Methods: Images of uninjured pelves from 50 patients (64-line CT scanner) were evaluated. Then virtual transiliac-transsacral srews were positioned into the first two sacral segments. The distance from the screws' entrance points at the ilium's alar bone to the narrowest portion of the whole pedicle as well as the height and width in this area were measured. Descriptive statistics were used and gender related differences were evaluated using student T-test. Results: For the first sacral segment the distance to the narrowest zone amounted in mean 62.75 mm respectively 63.31 mm, depending on the selected way of measurement. For the second segment the mean distance to the neuroforamina was on average 50.61 mm, respectively 51.54 mm. The average height in S1 measured 25.88 mm and the average width 25.49 mm. The average height for S2 was 17.54 mm and the average width 17.61 mm. We could not find any statistically significant gender correlation for the measured distances. Conclusion: Results of this anatomical study may help in performing a safe surgical procedure. Introduction: A retrospective and prospective analysis of the surgical treatment and results of 139 patients with traumatic craniocervical, atlantoaxial lesions operated during 10-years period (2011-2020) at our department was performed. The aim of the analysis was to assess the factors affecting correction of craniocervical and high cervical instability, comparing O-Arm System procedures versus C-arm procedure. Material and Methods: The mean age of the patients was 61 years. The female to male ratio was 1:1,4. We analyzed 139 patients with traumatic lesions and we found 75 odontoid fracture II and III Type, 36 Hangman fracture and 28 combined craniocervical and atlantoaxial fracture. In 139 patients we performed 146 operations. Because of craniocervical and atlantoaxial instability we made screw fixation in all of 139 patients. In 37 patients we performed additionally decompressive laminectomy. In order to improve screw placement accuracy, we performed intraoperative O-Arm in 121 cases. Results: The operative duration was 2 h. in O-Arm operations and 4 h in Carm operation. The blot loss was 250 ml in O-Arm and 550ml in C-Arm procedures. The most common operative complications were: CSF leakin 1 case, postoperative infectionin 6 cases, screw misplacement -in 2 cases and 1 case of early operative mortality. The 24-monts follow-up showed good recovery in 105 patients, moderate disabling in 25 patients, severe disabling in 4 patients, vegetative state in 2 patients, death in 3 patients in bad general condition. Conclusion: Early correction of craniocervical and high cervical instability facilitated neurological recovery by preserving the existent neurological function. Using of O-Arm increase significant operative screw placement accuracy, and preserve intraoperative nerve and vertebral artery injury. Fusion was achieved in all patients. Recently because of the improvement of neuroimaging techniques, operative approaches, surgical techniques and neurointensive care the results of treatment of these lesions are optimal.

OP12: Deformity-Thoracolumbar (Adolescent) -Complex Cases and Issues 1362 A100: Comparable corrective and overall surgical complication rates achieved in both VCR-based versus non-VCR-based surgical corrective techniques for the treatment of severe rigid scoliosis or kyphoscoliosis patients: observations from randomized clinical studies Introduction: Vertebral column resection (VCR-based) surgery is a powerful corrective technique for correcting severe rigid spinal deformities but also, often associated with significant risk of major perioperative and neurological complications according to evidence from the spine literature. Other non-VCR-based surgical maneuvering techniques for correcting severe rigid spinal deformities to achieve satisfactory patient outcomes do exist. Combined studies that compare complication outcomes between these technical approaches can aggregately infer where the complication rates resonate more. Meta-reviews of comparative studies on complication outcomes between VCR-based and non-VCRbased corrective maneuvers for the surgical management of severe rigid scoliosis or kyphoscoliosis patients are highly lacking. Material and Methods: A comprehensive literature review with meta-analysis was performed from January 2000 to September 2021. We aimed to investigate whether VCRbased and non-VCR-based corrective surgeries show similar morbidity and surgical complication outcomes. The selection criteria included: i) comparative studies strictly and specifically comparing VCR-based versus non-VCR-based techniques ii) English-only articles with case series of ≥ 10 patients, iii) studies with defined average major curve Cobb angle of ≥ 80 o and flexibility of <30%, iv) reported complication rates, and v) a minimum of 2-year follow-up period. The assessed complications included: perioperative cardiopulmonary events, dural tear/nerve injury/significant intraoperative neuromonitoring changes, surgical site infections/ wound complications, implant/cage-related issues, immediate postoperative intensive care unit (ICU) admission, and reoperation within 2-years following primary corrective surgery. Other clinical variables included averages of operative time (OT), estimated blood loss (EBL), and hospital length of stay (HLoS). Odds ratios (ORs) and weighted-mean differences (WMDs) with their respective 95% confidence intervals (CIs) were computed by heterogeneity based on fixed or random effects models for outcomes between the two surgical approaches. Statistical significance was set at (p < 0.05). Results: A total of 4 randomized studies were observed. Of the 174 patients analyzed, 52.30% (n = 91) and 47.70% (n = 83) were VCR-based and non-VCR-based. The incidence of dural tears/nerve injuries/significant intraoperative neuromonitoring changes was significantly higher; [OR = 6.78, CI = (1.75 to 26.17), I 2 = 0%, (p = 0.006)] in the VCR-based techniques compared to the non-VCR-based techniques. The overall surgical complication incidence was higher in the VCR-based group but not statistically significant, [OR = 2.47, CI = (0.51 to 11.90), I 2 = 69%, (p = 0.26)]. There was a significant increase of EBL in the VCR-based group compared to the non-VCRbased group; [WMD = 396.70, CI = (206.90 to 586.49), I 2 = 0%, (p < 0.0001)]. No other significant findings were observed for perioperative cardiopulmonary events, surgical site infections/wound complications, implant/cage-related issues, immediate postoperative ICU admission, operative time, HLoS, reoperation, and major-curve corrective rates 2-years following primary corrective surgery between VCR-based and non-VCR-based surgical approaches, (p > 0.05). Conclusion: Our study indicates that both VCR-based and non-VCR-based surgical maneuvers showed comparable overall surgical complication outcomes while a significantly higher perioperative neurological complication incidence and averagely estimated intraoperative blood loss resonated more in the VCR-based group compared to the non-VCR-based surgical group. The VCR-based technique was associated with 6.78 times higher neurological complications compared to non-VCR-based techniques. Average correction rates were 53.4% and 52.3% in the VCR-based and non-VCR-based techniques, respectively. Approximately ≥ 50% of major curve correction rate was achievable in both surgical groups.

A101: Spinal deformity and split cord malformations type I: one-stage or two-stage treatment?

Olga Sergeenko 1 , Dmitriy Savin 1 , and Sergey Ryabykh 1 1 

Introduction: According to various sources, the incidence of split spinal cord malformation (SCM) in congenital spinal deformities ranges from 5 to 49%. SCM is a relatively rare form of a congenital neural anomaly and it can cause tethered spinal cord syndrome. The classical approach to treat SCM I is preliminary bone spur removal before spinal deformity correction. There are authors pointing to the benefits of one-stage spinal deformity and SCM treatment and even deformity correction without septum removal. The main question of this work is: which treatment strategy is more beneficial for the patient? When can a one-step treatment be preferable to a twostep treatment? Material and Methods: Analysis of the literature on the different types of combined surgical treatment of spinal deformities with SCM I was performed. We have provided our own data on 27 patients treated for congenital spinal deformity and SCM I, one of which underwent Schwab IV type osteotomy at the apex of the deformity through the bony septum and pedicles. Inclusion criteria were: presence of spinal deformity in combination with SCM 1, performed surgery to correct spinal deformity, follow-up period of at least 2 years. Results: The result of the literature review was controversial, requires additional research. The average age of patients was 8.8 ± 6.6 years old. One-stage treatment of SCM I and spinal deformity was performed in 10 patients (group I) and two-stage in 14 patients (group II). Three patients with severe myelodysplasia, SCM I and congenital kyphoscoliosis underwent correction of spinal deformity without SCM I removing (group III). The group I had the longest surgery duration (mean 289 ± 75 min) and largest blood loss (mean 560 ± 386 ml), a high percentage of deformity correction (mean 69.6%) and the highest rate of complications (60%). The most optimal was the two-stage treatment with the mean surgery duration 191 ± 137 min, mean blood loss 339 ± 436 ml, mean correction rate 63% and frequency of complications 21%. The average follow-up time was 6.0 ± 2.6 years. Conclusion: One stage surgery associated with a large surgical invasion and a large number of complications. It can be used in some cases, for example when the wide bony septum (SCM I) is localized at the apex of the congenital scoliosis or kyphosis. In all other cases, it is worth adhering to a two-stage treatment. Many new works demonstrate the relative safety and effectiveness of deformity correction without removing the SCM. In our opinion, indications for treatment of spinal deformity without SCM I removing can be: the need to perform a shortening osteotomy outside the SCM zone. The remaining cases require a thorough assessment and a balanced decision.

A102: Vertebral morphological changes in dystrophic scoliosis jeopardizing surgical safety Shanmuganathan Rajasekaran 1 , Pushpa BT 2 , Sri Vijay Anand KS 1 , Rishi Kanna 1 , and Ajoy P Shetty 1 1 Department of Spine Surgery, Coimbatore, India 2 Department of Radiology, Ganga Hospital, Coimbatore, India Introduction: Spinal deformity is the most common orthopaedic manifestation in Type1-neurofibromatosis (NF-1). As bracing is ineffective, early and aggressive surgical intervention is recommended in dystrophic curves to prevent the malignant progression of curves. Posterior alone surgeries for deformity correction are on the rise. However, spinal instrumentation in NF-1 is challenging due to its altered anatomy. We did a study to document anatomical changes jeopardizing instrumentation safety in Neurofibromatosis deformity correction surgeries. Materials & Methods: The apical and two adjacent vertebral segments above and below amounting to 50 segments in 10 NF scoliotic deformities were studied to document the changes in lamina, pedicle, vertebral body, and spinal canal that could jeopardize assessment of starting point and trajectory of pedicle screws and strength of lamina for sub-laminar wires. The extent of changes was appropriately classified. Results: Extensive anatomical changes were noted. These changes were more severe at the apex and independent of the curve severity. Both laminae were normal in only 36 (Type 1), rest had either gross asymmetry in length and shape (Type 2; 21) or also in sloping (Type 3; 13). Of the 140 pedicles, normal pedicles were found only in 48 (Type 1); while they were divergent (Type 2; 4) or abnormally elongated with only thinning (Type 3a; 26); or with sclerosis (3b; 34); or very curved and wavy (3c; 23) and even fractured or indistinct (Type 4; 5). It was notable that 92 of the 140 pedicles were unsuitable for pedicle screws. An unique phenomenon of body drift was identified in 29 segments which could jeopardize screw placement and rib dislocation into the canal was found in 18 segments. These changes were more severe at the apex and independent of the curve severity, depending more on angulation, vertebral translation, and rotation. Conclusion: Gross morphological changes jeopardizing both sublaminar wire strength, starting point, and trajectory of pedicle screws were common in NF. Therefore, detailed preoperative assessment and planning by a 3D CT are essential as these changes were not readily appreciated in radiographs or MRI. Introduction: Growth-friendly surgery (GFS) for early onset spinal deformity (EOSD) is often utilized with successful results, but in some instances, deformity progression occurs despite, and possibly as a result of the use of GFS. In these scenarios, multiplanar curve progression can occur, leading to failed growth friendly surgery (f-GFS) and significant morbidity. In patients with f-GFS, consideration of "salvage" therapy may be appropriate, involving the use of solutions including prolonged halo-gravity traction (HGT), or threecolumn osteotomies (3COs). Here, we describe our institutional experience with salvage therapy for f-GFS in EOSD patients, seeking to increase the awareness of this patient population by describing the clinical management and treatment outcomes. Methods: This was a retrospective case series of EOSD patients with f-GFS and subsequent salvage treatment at a tertiary children's hospital. Indications for intervention included curve progression and one or more of the following findings: 1. trunk imbalance, 2. neurological compromise, 3. respiratory insufficiency, and 4. wound issues and/or implant prominence. In most cases, index surgeries were performed at outside institutions, while the most recent surgical treatment was performed the senior author in the majority of cases. The study was conducted under the approval of the institutional review board. Results: 29 patients

Global Spine Journal 12(3S)

with f-GFS were identified. Mean age at first surgery was 5.3 ± 2.6 years. Mean age at most recent salvage intervention was 14.6 ± 5.6 years. Mean follow up duration after salvage intervention was 1.1 ± 1.1 years. Mean follow up from index procedures to latest evaluation was 10.9 ± 6.6 years. Patients were previously instrumented with VEPTR (7), TGRs (10), MCGRs (4), Shilla (3), or none/In-situ fusions (6) Introduction: Halopelvic traction device has been used in the past to manage severe spinal deformities but many cumbersome complications were reported. Keeping in view the halo-pelvic distraction as an effective and affordable means of treatment, which can also be modified to reduce the rate of complications, a halo-pelvic apparatus was designed using standard Ilizarov set. The constructed assembly incorporated the versatility of an Ilizarov ring fixator and was used for various types of spinal deformities Methods: Patients presented to the department with various spinal deformities from January 2021 to August 2021 were applied modified halopelvic assembly before definitive surgery of kyphoscoliosis. Modified assembly consisted of a pelvic component made from 2 Ilizarov femoral arches, connected to each other anteriorly, through a threaded rod. The posterior aspect of the assembly was kept free from any rods or arches so that patient could lie supine. The Ilizarov femoral arches were anchored to the pelvis bone with Ilizarov half pins (6 mm in adults and 5 mm in children). On each side of the pelvis, one pin was placed in the supra acetabular area and a 2 nd pin 10 to 12 cm posterior to the anterior superior iliac spine. Halo ring was anchored with the skull using 6 pins in a standard manner. Pelvic assembly and the halo ring were connected using 4 threaded rods, through which distraction was given at the rate of 2 to 3 mm per day. Distraction was continued from 4 to 8 weeks, keeping an eye on the neurology, signs of pin tract infection and pin loosening. For cervical scoliosis patient, 4 hinges were incorporated into the construct, after an osteotomy at the level of C3 vertebra, gradual distraction was done at the concave side and compression at the convex side for 6 weeks. Results: Modified assembly was applied to thirty two patients (age range 8-36 years 20 M/12 F), among them 30 presented with kyphoscoliosis (of various etiologies including 7 post caries severe kyphotic deformities with maximum Cobb angle of 168), 01 with cervical scoliosis and 01 with cervical trauma. More than 60% improvement in magnitude of deformity was noted in all cases of kyphoscoliosis with improvement of neurology in 4/5 paraplegic patients. Two patients gained grade 4 power in the 1 st week of distraction while other two gained grade 2 power. Cervical scoliosis patient had congenital fusion of C2-C5 vertebrae with severe torticollis, the deformity was corrected in 6 weeks. The cervical trauma had unstable fracture of C2 vertebra, assembly was applied to immobilize the spine and the patient was mobilized the very next day. After 8 weeks the assembly was removed with complete healing of the fracture. Conclusion: The results of this study reveal that our modified halo-pelvic Ilizarov distraction assembly is a device with unlimited potential, which can achieve good correction in various severe spinal deformities without significant risk to neurology, fewer complications and good patient compliance. ) and 17 had a severe Cobb angle (>40°). In terms of PA, 72 patients (53%) reported participation in yearly PA activity excluding physiotherapy and mandatory physical education classes, and 55 (40.7%) in weekly PA that caused sweating, increased heart rate and shortness of breath. The 80 patients that did not participate in any PA were asked to provide reasons for their lack of physical activity. 30% of patients reported "lack of time" and 16.3% reported "laziness". Other reasons include lack of interest (6.3%), the COVID pandemic (2.5%) and being unfit (5%). A Physical Activity Index (PAI) in kcal/week was calculated based on subjects' answers to flights of stairs climbed, city blocks walked and sporting activities. Patients that were unable to provide a numerical answer to such questions were excluded from the PAI calculations. Background: The natural environment at high altitude has a significant impact on the growth and development of children, The incidence of complications related to internal fixation of growing rods in the treatment of early-onset scoliosis is high.

There are no reports about the complications related to internal fixation of two or more times in the treatment of early-onset scoliosis with growth rods. Purpose: The main purpose of this study is to study the clinical characteristics of patients with EOS in high-altitude areas, as well as the clinical efficacy of traditional growth rod technology in the treatment of patients with EOS in high-altitude areas, and to analyze risk factors for complications related to internal fixation of scoliosis twice or more. Method: 59 patients with EOS who underwent growth rod surgery from September 2007 to December 2017 were retrospectively analyzed. All patients had complete clinical data. They were divided into high altitude group (A) and low altitude group (B) according to the altitude of their living areas. The clinical data, imaging data and complications of the two groups were analyzed and the risk factors of the patients with more than two internal fixationrelated complications were analyzed. Statistical analysis were conducted and p < 0.05 was considered statistically significant. Results: The average age and follow-up time of patients at the initial operation were 8.9 ± 2.4 years and 51.91 ± 25.23 months. All patients underwent 234 operations with an average operation interval of 11.4 months. The height, weight and BMI of patients in the high altitude group were lower than those in the low altitude group. Cobb angle, thoracic kyphosis angle, T1-S1 and T1-12 in the two groups were significantly improved, the thoracic kyphosis angle in group A was statistically significant greater than that in the group B. There was no significant difference in pelvic incidence angle, sacral inclination angle and pelvic inclination angle between the two groups at each time point before and after operation. The patients in group A had a total of 60 internal fixation related complications. Results showed that the number of operations in group A was >3 times, and the follow-up time was ≥ 50 months. Preoperative thoracic kyphosis angle > 50°, postoperative thoracic kyphosis angle > 50°, postoperative lumbar kyphosis angle > 50°and postoperative sagittal axial distance > 40 mm were the risk factors for two or more internal fixation related complications (p < 0.1). Results also showed that the number of operations >3times, postoperative thoracic kyphosis angle > 50°Postoperative lumbar lordosis > 50°is an independent risk factor. The risk of two or more internal fixation related complications in patients with immediate postoperative thoracic lordosis > 50°is 18.647 times higher than that in patients with immediate postoperative thoracic lordosis < 50°. Conclusion: Children with early-onset scoliosis in highaltitude areas have serious deformities, and growth rod treatment can achieve good results. The number of operations >3 times, the postoperative thoracic kyphosis angle > 50°, and the postoperative lumbar lordosis angle >50°.Risk factors for the occurrence of two or more internal fixationrelated complications. Introduction: The correction of severe Adolescent Idiopathic Scoliosis (AIS) with a curve > 90°and < 25% of correction on bending films poses a surgical challenge. In fact, these curves are characterized by peculiar anatomopathological features: extreme rotation, translation and pedicle dysplasia. These features, combined with high rigidity of the curve, make surgical correction tough: either two-stage procedures with temporary internal or external traction in order to obtain an adequate mobilization of the deformity, or one-stage techniques based on aggressive tricolumn osteotomies are frequently needed. To overcome these issues, the authors adopted a technique called Hi-PoAD (High Density Pedicle screws, Ponte osteotomies, Asymmetric rods contouring, Direct Vertebral Rotation), already described for Adult AIS. The rationale is to use high density constructs and wide posterior release (through Ponte osteotomies) to spread forces over multiple levels, achieving optimal one-stage correction. The aim of this article is to present the results of Hi-PoAD technique for the treatment of severe (main curve > 90°) stiff AIS at minimum 2 years follow-up in a cohort of 39 patients. Material and Methods: All the patients affected by AIS with a main curve > 90°Cobb and less than 25% curve correction on side bending, consecutively operated by the same surgeon (first author) using Hi-PoAD technique between 2016 and 2019, were enrolled and retrospectively evaluated. All had main thoracic major curves (Lenke 1, 2, 3), with a Coronal-Deformity Angle Ratio (C-DAR) < 15. All patients received one stage posterior spinal fusion; pedicle screws were placed at all levels with power-assisted technique, asymmetrical Ponte osteotomies were performed at the apex of the deformity and at the four periapical levels (two above and two below the apex). Then, translation manoeuver and en-bloc Direct Vertebral Rotation (DVR) were performed over two asymmetrically molded, simultaneously applied, cobalt-chrome rods. Radiographic and clinical score data were collected preoperatively, postoperatively and at last follow-up (2 years minimum), to assess deformity correction, coronal and sagittal alignment and clinical outcome. Introduction: Spinal osteotomy is a frequent surgical procedure used to achieve spinal alignment correction in both sagittal and coronal planes in severe and rigid deformities. There are multiple types of spinal osteotomy, as indications for each one. In asymmetric osteotomies, surgical approaches have traditionally been performed by a combined anterior and posterior approach, however, in the past years, the posterior-only one has become more frequent. Although spinal osteotomies usually have satisfactory outcomes, patients are at an increased risk of complications when using these techniques. We described the surgical technique of an oblique osteotomy for scoliosis correction by posterior spinal fusion. Methods: A detailed description of the surgical technique is presented, as a descriptive retrospective cohort. Patients diagnosed with congenital, syndromic, neuromuscular, and idiopathic scoliosis, taken to oblique vertebrae osteotomy by posterior approach, operated between January 2014 to June 2020 for a minimum of 1-year follow-up after scoliosis correction surgery, were included. Patients with associated spine deformities were excluded. A frequency analysis was performed. Surgical technique is described. With the patient prone and multimodal neuromonitoring, transpedicular screw fixation and identification of the osteotomy site, a partial laminectomy of the vertebrae is performed. Protecting nervous roots and dural sac, osteotomy is performed over the vertebral body initiating at the superior region of the pedicle to the inferior region of the opposite pedicle. A second osteotomy is done, initiating at the inferior edge of the pedicle to the inferior region of the opposite pedicle achieving convergence of the two osteotomies. Oblique osteotomy is completed by directing convergence or divergence depending on the sagittal balance goal, extracting the fragment. Results: A retrospective cohort of 74 patients is described. Demographic characteristics were analyzed, mean age 15 years (SD 5.6), mainly with congenital scoliosis (51%), followed by neuromuscular scoliosis (31%). Apex was located at the thoracic spine in 47.3% of the cases and thoracolumbar in 36.5%, and laterality is evenly distributed. Preoperative Cobb angle oscillated between 21°a nd 60°in 40.5% of the cases with a postoperative Cobb angle between 0°and 40°in 77% of the patients. Intraoperative bleeding between 0 to 1000 cc was presented in 54% of the patients, somatosensory evoked potential loss 2.7% with no neurological permanent impairment, and other complications in 25.6% including infection, health care associated infection, durotomy requirement, and gastrointestinal alterations. Conclusions: Oblique spine osteotomy is a modified surgical technique where an osteotomy is performed with unilateral pedicular extraction. Is an alternative for correction of rigid deformities in severe scoliosis with a minor surgical time, incidence of intraoperative bleeding and requirement of performing other types of osteotomies.

References: Introduction: The most common indication for low back surgery is sciatica caused by lumbar disc herniation, with a lifetime prevalence between 12 and 27% for sciatica. Surgery is typically offered to patients with persisting and/or intolerable leg pain with or without low back pain, or with severe limb or bowel/bladder paresis. The majority of operations are performed electively and on relative indication. Most clinical studies regarding outcome after lumbar spinal surgery tend to focus on favorable outcomes based on mean improvements or success rates according to patient-reported outcome measures (PROMs). However, an efficient strategy for improving the quality and safety of health care is to focus on unfavorable outcomes. To enhance individualized risk prediction, we have previously defined benchmark criteria for both "failure" and "worsening" one year after lumbar microdiscectomy, based on frequently used PROMs. In previously published data, 30-40% of non-successful outcomes one year after surgery have been reported, and a large proportion of these cases cannot be classified as "failure", indicating that non-success and failure are not interchangeable subjects. The aim of this study was to develop a prognostic model calculating individual risk (%) for failure and worsening after surgery for lumbar disc herniation, based on a large cohort from the Norwegian Registry for spine surgery (NORspine). Material and Methods: This multicenter cohort study included 11,081 patients operated with lumbar microdiscectomy, registered at the Norwegian Registry for Spine Surgery. Follow-up was 1 year. Uni-and multivariate logistic regression analyses were used to assess potential prognostic factors for previously defined cut-offs for failure and worsening on the Oswestry Disability Index scores 12 months after surgery. Since the cut-offs for failure and worsening are different for patients with low, moderate, and high baseline ODI scores, the multivariate analyses were run separately for these subgroups. Data were split into a training (70%) and a validation set (30%). The model was developed in the training set and tested in the validation set. A prediction (%) of an outcome was calculated for each patient in a risk matrix. Results: The prognostic model produced six risk matrices based on three baseline ODI ranges (low, medium, and high) and two outcomes (failure and worsening), each containing 7 to 11 prognostic factors. Model discrimination and calibration were acceptable. The estimated preoperative probabilities ranged from 3 to 94% for failure and from 1 to 72% for worsening in our validation cohort. Conclusion: We developed a prognostic model for failure and worsening 12 months after surgery for lumbar disc herniation. The model showed acceptable calibration and discrimination, and could be useful in assisting physicians and patients in clinical decision-making process prior to surgery. Introduction: The etiopathogenesis of Modic changes is unresolved. Two proposed theories implicate trauma and subclinical infection. Traditionally, Modic changes has been defined and studied using magnetic resonance imaging alone. Being a pathology of subchondral bone, it is only natural that CT scan will be reflective of bone changes better than MRI. With this in background we did a study to probe the pathophysiological basis of Modic change (MC) by multimodal imaging rather than by MRI alone. Materials and Methods:

The study was done in three steps. In Step 1, radiological signs found in documented mild infections and traumatic end plate fractures were identified by MRI and CT and by careful elimination, three signs unique to infection and trauma were distilled. In step 2, by ranking Z score, appropriate positive values for infection and negative for trauma was assigned and an 'Infection Probability Score' (IPS) was developed. The score's ability to differentiate infection and traumatic end plate changes (EPC) was validated in further 30 patients (15 infection and 15 trauma). In step 3. the score was applied to 80 non-specific low back pain patients (NSLBP) and the probability of EPC as a result of infection was assessed. Results: The three unique signs for infection and scores were: involvement of end plates at both sides of the disc (+3), typical CT erosion patterns of the subchondral bone associated with infection (+2) and extensive reactive sclerosis (+1). Involvement of superior EP only (-3); single vertebral body edema (-2)and none or only a rim sclerosis (-1) were the pure signs for traumatic EP changes. The confidence interval pointing towards infection was 65% for score 4; 79% for score 5 and 89% for score 6. The mean IPS score for the 80 patients with MCs was 4.5. None of the patients with a MC had a negative score thus excluding trauma as an etiology of MC. The findings also allowed the proposal of an alternate pathway of 'primary endplatitis' as a cause of MC with four possible clinico-radiological outcomes. Conclusion: Inclusion of CT in evaluating MC helped to identify signs indicating a high probability of infective process for MC. Contrary to the traditional belief that MCs are secondary inflammatory changes, the study findings indicated that blood borne primary infective endplatitis may in fact be the cause of MC. A pathway with four possible clinico-radiological outcomes which correlated with the clinical observations in NSLBP patients was proposed. Introduction: Intervertebral disc (IVD) degeneration is the central component in numerous common spinal pathologies. While this disease affects millions of people, the mechanisms driving it remain poorly understood, and treatments for it are nonspecific. Previous work has shown that elevated intracellular lactate is involved in degeneration, which was once thought to be purely mechanical. Here, we present experiments utilizing mouse models of IVD degeneration designed to elucidate the role of lactate/lactate transport in degenerative disc disease, and the underlying metabolic pathway(s). Methods: Three disc degeneration models were studied: 1) lumbar-disc poke, 2) tail-disc poke, 3) spinal instability, and a 4) sham/control group. Female mice (C57BL/6J, n = 30) were randomly assigned. In group 1, a retroperitoneal approach exposed the IVD of the lumbar spine. In group 2, the needle was inserted in the tail IVD. In group 3, lumbar instability was induced by resection of bilateral facet joints and supraspinous/interspinous ligaments. Mice were euthanized at 2, 4, and 8 weeks. IVD degeneration was evaluated using histological and immunofluorescence analysis. Disc-tissue extracted RNA was analyzed using QPCR. We performed statistical analysis using Student's t-test; p < 0.05 was considered statistically significant. The study was approved by the local governmental animal care committee and was conducted according to the national legislation on protection of animals and the NIH guidelines for the care and use of laboratory animals. Results: At 2, 4, and 8 weeks, groups 1-3 demonstrated disc degeneration characterized by loss of NP cells and the gradual increase in matrix components in the NP. Sham mice demonstrated no significant disc degeneration. In groups 1-3, the distinction between NP and AF was lost, and immunofluorescence results demonstrated the increased expression of collagenX and MMP13 in the NP. There was a gradual decrease in expression of GLUT1 (NP cell marker) and of MCT4/Slc16a3, a lactate transporter. A rarer lactate transporter, MCT3/Slc16a8, was upregulated. Hypertrophic chondrocyte markers increased. Both the NP and end plate (EP) of sham mice maintained strong expression of MCT4, while the NP and EP in injured mice had markedly reduced expression of MCT4. Expression of hexokinase 2 (HK2), a key enzyme in glycolysis, was also reduced (in group 2). Conclusion: IVD degeneration at 2, 4, and 8 weeks was characterized by loss of NP cells and the gradual increase in matrix components. Our results introduce novel evidence supporting a common molecular pathway whereby discs degenerate after direct injury or instability. Importantly, MCT4 was down regulated, while MCT3 was upregulated. We demonstrated that loss of MCT4 expression plays an important role in the degeneration of the intervertebral disc. While MCT4 is associated with lactate exportation, and its loss results in elevated intracellular lactate and disc degradation, MCT3 is rarely expressed and may act as a "rescue" lactate transporter. Our novel finding that dramatic loss of MCT4 expression occurs after disc injury suggests that this transporter may play a functional role in IVD degeneration. Decreased HK2 gene expression led to reduced glycolysis and may also contribute to disc degeneration. Introduction: i-Factor (ABM/P-15) is a commercially available bone graft enhancer which is a synthetically manufactured P-15 collagen peptide fragment, that is adsorbed on anorganic bone matrix and suspended in an inert hydrogel. The efficacy and safety of i-Factor is now well-established in cervical spinal fusion surgeries. However, the same has not been validated in the lumbar spine. The purpose of this study was to investigate the efficacy of ABM/P-15 (i-Factor) in achieving fusion in lumbar spine and comparing it to that of recombinant bone morphogenic protein (rhBMP-2) and demineralized bone matrix (DBM). Material and Methods: Institutional Review Board (IRB) approval was taken for this study. (IRB No. 2021/04/WSH/002) A retrospective analysis of prospectively collected data of 140 patients with degenerative lumbar spinal pathologies, who underwent instrumented lumbar interbody fusion surgeries in a single speciality spine centre between the years 2016 and 2020 was conducted. The indications for surgery were lumbar degenerative disorders with instability/ spondylolisthesis wherein fusion was deemed necessary. All patients with a minimum follow-up of 6 months were included. Patients with inadequate follow-ups, missed timely follow-ups, inadequate documentation of the records were excluded. Patients with concomitant posterior decompression at the index level, traumatic pathologies, infections, inflammatory or autoimmune diseases and tumours were excluded. Based on the material used for the augmentation of the bone graft at the fusion site, the patients were divided into three categories namely, i-Factor group, rhBMP-2 group, and DBM group. Various clinical and radiological parameters such as visual analogue scale (VAS) scores for back and leg pain, Oswestry disability index (ODI), spinopelvic parameters, C-reactive protein levels, presence of union, time to achieve union, complications were analysed and compared between these three groups. Results: Out of 140 patients i-Factor, rhBMP-2 and DBM were used in 46, 44, and 50 patients respectively. Patient characteristics like age, gender, smoking history, bone mineral density, and presence of diabetes mellitus were comparable amongst three groups. Average follow-up was 11.65 ± 3.57, 18.34 ± 9.87, and 26.2 ± 14.9 months respectively in i-Factor, rhBMP-2, and DBM groups. Fusion was achieved in 97.9%, 93.2%, and 98% patients in i-Factor, rhBMP-2, and DBM groups, respectively. Average time-to-union was 4.05 ± 2.01, 10 ± 4.28, and 9.44 ± 3.49 months for i-Factor, rhBMP-2, and DBM groups (p < 0.001) respectively. Average pre-operative VAS-score was 6.93 ± 2.42, 7.14 ± 1.97, 7.01 ± 2.14 (p = 0.900) respectively, which reduced to 1.02 ± 0.80, 1.21 ± 0.96, 0.54 ± 0.70 (p = 0.112) at the last follow up. Pre-operative ODI scores were 52.7 ± 18.02, 55.4 ± 16.8, 53.56 ± 19.6 (p:0.751), which postoperatively reduced to 33.77 ± 15.52, 39.42 ± 16.47, 38.3 ± 15.89 (p < 0.001) and further to 15.74 ± 8.3, 17.41 ± 10.45, 16.76 ± 9.81 (p = .002) respectively at the last follow-up. No infection was seen in rhBMP-2 and i-Factor group while 3patients in DBM group got infected. 1-patient in each rhBMP-2 and i-Factor group while 2 in DBM group suffered superficial wound complications. Cage subsidence was the most common complication and was seen in 21.7%, 30.2%, and 13.8% cases respectively in i-Factor, rh-BMP-2, and DBM group (p = 0.332). Conclusion: Bone graft augmentation using ABM/P-15 (i-Factor) appears to achieve union significantly earlier than rhBMP-2 and DBM in lumbar spinal fusion cases while maintaining comparable clinical and complication profile. Introduction: Lumbar fusion as a low back pain treatment continues to be a challenge to physicians because of the multiple techniques and materials available, all of them in the pursuit of providing patients with pain stability, restoring lordosis, and correcting deformity. Techniques include: transforaminal lumbar interbody fusion (TLIF), lateral lumbar interbody fusion (LLIF, XLIOF, OLIF) and anterior lumbar interbody fusion (ALIF). Today, successful lumbar fusion is associated to better clinical outcomes and now it is enhanced and targeted through the use of bone graft materials, for example i-FACTOR Bone Graft, osteogenic cell binding peptide P-15, bound to an anorganic bone mineral (ABM). This peptide has showed to improve bone formation when used in fixation devices in a targeted and limited way to the implant surface (Ectopic Bone Growth) by activating osteoblast precursor cells; plus the use of autologous bone marrow aspirate concentrate that increases the benefits of the bone graft, by the osteogenic, osteoinductive and osteoconductive stimuli. The main objective of this study is to standardize the lumbar fusion process in the 3 techniques and achieve a more efficient and predictable lumbar fusion, evaluating results with radiological and clinical scales. Material and Methods: 30 patients underwent lumbar fusion, divided in two groups (15 each one), one with the use of i-factor bone graft (Group A), and the other with the use of i-factor bone graft mixed with bone marrow aspirate concentrate 1:1 (Group B). Group B was subdivided into 3 groups, 5 of them went under OLIF, 5 under ALIF and 5 under TLIF. Bone marrow was harvested from the patients via puncture aspiration of the iliac bone. Radiological outcomes included fusion rates per the Lenke scale. Clinical outcomes were evaluated via the Oswestry Disability Index (ODI), Short Form Performance (SPF-36) and Visual Analog Scale (VAS and VASS) for pain and satisfaction. Results: Lateral lumbar radiographs at 6 weeks follow up was performed and analyzed between groups, differences in fusion rates between group A and group B were shown to be significantly improved with the use of p15/BMA + ABM (Group B). Clinical scales showed at ODI pre an avg of 36.5, ODI at 6 wk 875. SPF-36 pre an avg of 31.25, SPF-36 at 6 wk of 81.25, VAS pre an avg of 7.75, VAS at 6 wk of 1.75. VASS Pre an avg of 2.625, VASS at 6 wk of 8.875. Successful fusion was observed in Lenke A -12.5%, Lenke B -87.5%. Differences in fusion rates in the Group B between techniques seemed to be similar and non dependent on the technique. Conclusion: Fusion rates in this study are significantly improved by the use of mixed Ifactor and bone marrow aspirate concentrate, in short time and with better clinical outcomes than the use of i-factor alone, and non dependent on the technique and reducing general costs. Further study with long-term follow-up is required to achieve significant differences between groups and within groups. This study compared first-time spinal fusion patients who received rhBMP to a comparative group who did not receive rhBMP from 2003 to 2017 and investigated re-fusion rates and postoperative complications, including infection, seroma/hematoma, radiculitis, heterotopic ossification, and cancer. A secondary analysis was performed investigating 18 subtypes of benign and malignant neoplasms. Five longitudinal observational databases were utilized, including four insurance claims databases and one electronic medical record. Confounding was controlled for using propensity score matching and analyzed resultant covariate balance as an indicator of successful confounding control. Negative and positive controls were utilized to control for unmeasured confounding and calibrate the observed confidence intervals. Results: Across all five databases, 60,427 patients were identified with rhBMP and 349,771 patients without, totaling 161,213 and 923,822 years of patient observation, respectively. rhBMP was associated with statistically significantly fewer postoperative infections, with a hazard ratio of 0.88 (95% CI: 0.78-0.99). No significant difference was seen with the other outcomes, including benign and malignant neoplasms. Substantial control of measured confounding was demonstrated by propensity score adjustment, and negative and positive controls revealed noticeable residual bias that was controlled for through confidence interval calibration. Conclusion: In the largest longitudinal observational study to date, rhBMP was determined to be safe and effective as compared to non-BMP usage in spinal fusion, with lower rate of postoperative infections. Importantly, no increased rates of cancer were detected. Coding error and the retrospective design may be an important source of bias. Despite these limitations, the large population size and statistical design give considerable significance to the results and conclusions of this study.

A115: Intradiscal injection of autologous bone marrow aspirate concentrate improves low back pain at one year Fenil Bhatt 1 , Lindsay Orosz 2 , Alexandra Thomson 1 , Samuel Namian 2 , Niteesh Bharara 1 , Christopher Good 1 , Thomas Schuler 1 , and Colin Haines 1 1 Virginia Spine Institute, Reston, USA 2 National Spine Health Foundation, Reston, USA Introduction: Chronic low back pain is one of the leading causes of disability and poor quality of life in the US and worldwide. A common cause of chronic low back pain is degenerative disc disease. Current nonsurgical treatments for degenerative disc disease-associated low back pain are typically effective. However, for patients who fail these treatments, surgical fusion is often used as last line treatment. Surgical treatment is associated with higher healthcare expenditures and a more invasive procedure. As such, there is growing interest in the field of regenerative medicine and stem cell therapy as a less invasive treatment for low back pain. Methods: A total of 32 consecutive patients over the age of 18 years diagnosed with discogenic low back pain clinically or by discography who underwent injection of autologous intradiscal BMAC at a single multi surgeon orthopedic spine center were included in this study. Active smokers and patients who had pain generators other than purely discogenic pain were excluded. For primary analysis, patients completed baseline and 1 year post-injection ODI, VAS back, VAS leg, and EQ-5D-5L questionnaires; their scores were compared over time. Preprocedural lumbar MRIs were reviewed for Modic changes and assigned a Pfirrmann grade. 13 postprocedural MRIs were available and reviewed using the same parameters. Results: Thirty-two patients (56.3% male) with a mean age of 45.9 (range 19-65) underwent BMAC injection between 1 and 6 levels completed 1 year follow up. Mean VAS back and leg scores improved from 54.0 to 30.4 (p < 0.001) and 27.9 to 13.3 (p = 0.005), respectively. Mean ODI scores decreased from 33.5 to 21.1 (p < 0 .001), and EQ-5D-5L scores improved from 0.69 to 0.78 (p = 0.001). Using established minimum clinically important difference values, 59.4% of patients saw a clinically significant improvement in VAS back pain, 43.8% in VAS leg pain, and 56.3% in ODI scores. On preprocedural MRIs, 62.5% of patients had a Modic score of 1 or 2 and 93.8% had a Pfirrmann grade of 3 or higher. Postprocedural MRIs were available for 13 patients, and 61.5% had no measurable change in Pfirrmann grade. Three patients worsened by one Pfirrmann grade and one improved by 1 grade. Conclusion: Intradiscal injection of autologous BMAC was shown to significantly improve pain and quality of life at one year. Additionally, this study meets 88% of recently published AAOS reporting standards for studies relating to mesenchymal stem cells. The results of this study suggest that intradiscal injection of autologous BMAC has the potential to be an effective nonsurgical treatment for chronic discogenic low back pain.

A116: Retrospective evaluation of spinal fusion using a biphasic calcium phosphate bone graft with a novel submicron surface topography Katherine Sage 1 and Kornelis Poelstra 2 1 Orthopedics, Kuros, Boston, USA 2 Robotic Spine Institute of Las Vegas, Las Vegas, USA Introduction: Limited availability of autologous bone graft has led to a vast array of alternative bone graft options including allograft, demineralized bone matrices, bone morphogenic proteins, and synthetic bone grafts. In this retrospective review, a novel synthetic biphasic calcium phosphate (BCP < µm) bone graft was utilized for cervical and lumbar spinal arthrodesis. Material and Methods: Seventy-seven patients divided into two cohorts (25 cervical and 52 lumbar) underwent interbody reconstruction arthrodesis surgery, using a combination of allograft and a novel BCP < µm with a unique submicron surface topography. Fusion outcomes were assessed via flexion-extension radiographs and Computed Tomography (CT), and clinical outcomes were assessed via modified Prolo scores. Results: Successful lumbar fusion rates determined by radiographs or CT were achieved in 94 of 97 levels (96.9%), or 49 of 52 patients (94.2%). Successful cervical fusion rates were achieved in 75 of 80 levels (93.8%), or 21 of 25 patients (84%). All pseudarthroses were observed in three or more level reconstructions, with 100% fusion rates in all one-and two-level cases. Modified Prolo scores showed significant differences in 74/77 patients with 46.3% and 48.1% improvements in the lumbar and cervical cohorts, respectively. Conclusion: This novel submicron surface topography BCP < µm offers a promising bone graft substitute for reliable augmentation of cervical and lumbar arthrodesis. Introduction: A multitude of hemostatic agents exist for spinal deformity surgery that act upon the coagulation cascade, such as fibrin, gelatin, or thrombin. Floseal ® is a hemostatic agent consisting of bovine flowable gelatin matrix and human derived thrombin used in spine surgery to minimize blood loss. Several studies have been published regarding the safety of Floseal ® with no side effects or complications noted. However, recent literature has detailed life threatening allergic reactions to Floseal ® . In this case series and systematic review we present two cases of life threatening anaphylaxis to Floseal ® at our institution, and the 10 previously reported anaphylactic reactions. We analyze the risk factors, intraoperative, and postoperative management of these anaphylactic reactions. Material and Methods: The two reported cases are according to the 2013 CARE (Case report) guideline. A comprehensive literature search of publications up to September 2021 was conducted using the PubMed, World of Science, Embase, and Ovid MEDLINE databases based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The search strategy included the following keywords or MeSHterms: "floseal," "bovine flowable gelatin matrix," "gelatin human derived thrombin," "surgicel" "anaphylaxis" "spine surgery," scoliosis," "CDR," "spinal fusion," "allergic reaction". A total of 297 studies were initially identified and screened, 7 were included in the final analysis. Results: All 12 cases of anaphylaxis occurred within minutes or seconds of injection under pressure into a cannulated pedicle screw tract. The pressurized insertion is pushed directly into the vertebral venous plexus to the inferior venous cava and subsequently the heart and lungs. This can lead to a quick anaphylactic reaction due to the short time from injection to the systemic circulation in an allergic individual. It is imperative to obtain a detailed history preoperatively of reactions to vaccines as some routine childhood vaccines contain gelatin. If a history of a reaction is elicited, consultation with an allergist should be requested, and testing for the allergy should be performed by both prick skin testing and serum specific IgE for beef and pork as well as bovine and porcine. In terms of treatment, tryptase level should be drawn to confirm the allergic reaction; management should consistent of epinephrine, steroids, and inhaled albuterol for a quick recovery for these patients with life threatening anaphylaxis. Conclusion: In this case series, we present two patients with a life-threatening reaction to Floseal ® that was appropriately treated. 10 cases of a similar reaction are reported in the literature. In all cases, hypotension, tachycardia, and increased airway pressures occurred shortly after pressurized injection of bovine gelatin into a cannulated pedicle screw tract. In patients with a history of an allergic reaction to gelatincontaining foods or medications, preoperative allergy testing should be performed. In patients with bovine or porcine gelatin allergies Floseal ® should be avoided. Introduction: Despite advances in treating acute spinal cord injury (SCI), measures to mitigate permanent neurological deficits in affected patients are limited. Augmentation of mean arterial blood pressure (MAP) to promote blood flow and oxygen delivery to the injured cord is one of the only currently available treatment options to potentially improve neurological outcomes after acute spinal cord injury (SCI). However, to optimize such hemodynamic management, clinicians require a method to measure and monitor the physiological effects of these MAP alterations within the injured cord in real-time. To address this unmet clinical need, we developed a series of miniaturized optical sensors and a monitoring system based on multi-wavelength near-infrared spectroscopy (NIRS) technique for direct transdural measurement and continuous monitoring of spinal cord hemodynamics and oxygenation in real-time. We conducted a feasibility study in a porcine model of acute SCI. We also completed two separate animal studies to examine the function of the sensor and validity of collected data in an acute experiment and a seven-day post-injury survival experiment. Material and Methods: In our first animal experiment, nine Yorkshire pigs underwent a weight-drop T10 vertebral level contusion-compression injury and received episodes of ventilatory hypoxia and alterations in MAP. Spinal cord hemodynamics and oxygenation were monitored throughout by a transdural NIRS sensor prototype, as well as an invasive intraparenchymal (IP) sensor as a comparison. In a second experiment, we studied six Yucatan miniature pigs that underwent a T10 injury. Spinal cord oxygenation and hemodynamics parameters were continuously monitored by an improved NIRS sensor over a long period. Episodes of MAP alteration and hypoxia were performed acutely after injury and at two and seven days post-injury to simulate the types of hemodynamic changes patients experience after an acute SCI. All NIRS data were collected in real-time, recorded and analyzed in comparison with IP measures. Results: Noninvasive NIRS parameters of tissue oxygenation were highly correlated with invasive IP measures of tissue oxygenation in both studies. In particular, during periods of hypoxia and MAP alterations, changes of NIRS-derived spinal cord tissue oxygenation percentage were significant and corresponded well with the changes in spinal cord oxygen partial pressures measured by the IP sensors (p < 0.05). Conclusion: Our studies indicate that this novel NIRS system can monitor real-time changes in spinal cord oxygenation over the first seven days post-injury and can detect local tissue changes that are reflective of systemic hemodynamic changes. Our implantable spinal cord NIRS sensor is intended to help clinicians by providing real-time information about the effects of hemodynamic management on the injured spinal cord. Hence, our novel NIRS system has the near-term potential to impact clinical care and improve neurologic outcomes in acute SCI. To translate our studies from bench to bedside, we have developed an advanced clinical NIRS sensor that is ready to be implanted in the first cohort of acute SCI patients in 2022.

A119: Minimum two year follow-up comparison of correction of L5 tilt and fractional curve in vertebral body tethering versus fusion for idiopathic scoliosis Nathan Kim 1 , Constance Maglaras 1 , Brooke O'Connell 1 , Aonnicha Burapachaisri 1 , Kimberly Ashayeri 2 , Themistocles Protopsaltis 1 , and Juan Carlos Rodriguez-Olaverri 1 1 Orthopedic Surgery 2 Neurosurgery, NYU Langone Health, New York, USA Introduction: Untreated idiopathic scoliosis (IS) can produce worsening deformity and subsequent compensatory fractional curve and coronal L5 tilt progression. Existing research has associated improved patient outcomes with correction of the fractional curve and improvement in L5 tilt. The surgical method of choice for treating IS has been posterior spinal fusion (PSF) for decades; however, surgery is not without risks. In particular fusions run the risk of stress on adjacent segments and pseudoarthrosis. Further, the rigidity of the PSF technique limits LIV selection in the lumbar spine. Vertebral body tethering (VBT) has the potential to surgically correct IS in a motion preserving context. In the absence of a rigid fusion, lower LIVs can be indicated for surgery affording greater potential for improving thoracolumbar coronal imbalance compared to fusion procedures. VBT is a newer surgical technique being utilized to correct IS consequently the optimal candidates for VBT are still being determined. This multi-center retrospective cohort study compares fractional curve and L5 tilt correction in IS patients undergoing VBT versus fusion with LIV in the lumbar spine. Material and Methods: Retrospective analysis included IS correction surgeries with LIV in the lumbar spine from 2013 to 2020 from multiple centers with baseline and minimum 2-year postop standing full spine plain films available. Patients were grouped into VBT or fusion groups. Outcome measures included age, Risser score, LIV, and levels instrumented. Radiographic analysis included pre-and postop main, secondary, and fractional curve cobb angles, and L5 tilt. Measures were compared using independent samples t-tests, with significance set at p < 0.05. Propensity score matching (PSM) was completed for demographic differences. Results: 41 patients (21 VBT, 20 PSF) were included in the study. VBT patients ranged from 10 to 22 yearsold and tended to be younger (14.9 ± 2.8 v 15.5 ± 2.9, p = 0.511). More VBT cases extended to L4 (61.9% v 15.0%, p = 0.002) than fusions. There were differences in preop secondary curve cobb angles (49.8 ± 12.5 v 41.2 ± 12.6, p = 0.035) and L5 tilt (18.3 ± 6.7 v 12.9 ± 8.1, p = 0.026), but not in main or fractional curves. VBT patients had smaller postop fractional curves (3.6 ± 4.2 v 15.2 ± 7.2 deg, p < 0.001) and postop L5 tilt (5.8 ± 4.1 v 9.0 ± 3.9, p = 0.014) than fusions and greater improvement in L5 tilt (-17.2 ± 10.1 v -6.3 ± 6.9 deg, p < 0.001). After PSM for Lenke classification, 24 patients remained (12 VBT, 12 fusion). Differences between preop L5 tilt or main, secondary, and fractional curve cobb angles were no longer significant. VBT continued to show greater correction of L5 tilt (-16.8 ± 7.1 v -6.2 ± 5.3, p < 0.001), and had smaller postop fractional curves (4.9 ± 5.1 v 13.3 ± 8.3, p = 0.007). Conclusion: This study demonstrates that VBT allows for more caudal LIV for IS correction. After propensity score matching for Lenke classification, VBT patients achieved improved L5 tilt correction and a greater decrease in postoperative fractional curve after 2 years than fusion patients. These findings suggest there is significant potential for further exploring the role of VBT in the correction of coronal imbalance in the thoracolumbar spine of IS patients. . The average number of implanted screws for SO was 6 ± 3, and for RAS 8 ± 4 (p = 0.028). No differences in blood loss (ml) per screw SO 117 ± 54, RAS 99 ± 63 (p = 0.234) could be found. X-ray dose (cGYm2) per screw was for SO with 214 ± 135 higher as for RAS 114 ± 165 (p = 0.010). Time for pedicle screw placement per screw (min) did not differ: SO 8 ± 5, RAS 9 ± 4.Time of robotic registration: 26 ± 13 min. Specific complications for robotic surgery were all technical difficulties and occurred in 21% (n = 9): one loss of X-ray capability, one inability to plan a pedicle screw for L5 due to CT issues, one collision of the robotic arm with the fixation clamp at T 9, one necessity for a double registration, insufficient planning of ilium screw, one necessity for a double CT scan, postoperative reassessment because of pelvic pain following a pin breakout intraoperatively, and inability of robotic to identify S1 and S2.The learning curve showed significant reduction in the total time of robotic registration (p = 0.007). Discussion: During the 5-month period using RAS, the learning curve showed reduction time needed for robotic registration and reduced X-ray dose. The blood loss and the time required for screw placement seems very comparable. Nevertheless, the time required for patient positioning and incision-suture time are still slightly longer with RAS, compared to the standard open procedure. The higher the number of inserted screws the lower the time difference gets. During the learning period substantial time deviations as well as technical complications must be expected. Introduction: Recent technological advances have augmented the use of both robotic and navigated assisted spinal surgery. However, the superior strategy to facilitate screw accuracy remains unknown. Our objective was to evaluate the early experience of using robotics in spinal surgery and compare it to the use of navigation alone in spine surgery. Material and Methods: A retrospective, propensity score matched cohort study was utilized to compare pedicle screw placement in patients who underwent thoracolumbar fusion with robotic arm assistance versus navigation alone. Spine surgery cases at a quaternary care institution from 2019-2021 were queried. The Gertzbein and Robbins System was utilized to grade screw placement accuracy. Indications included deformity, degenerative thoracolumbar spondylosis, and spinal tumor. Unpaired two sample T-test was used to compare age, sex, body mass index (BMI), and type of surgical approach (i. e. minimally invasive versus open) between the two groups. T-test and Chi-square test were utilized to determine which covariates are confounding. Results: In the robotic group, a total of 129 screws were placed (121 had perioperative computed tomography (CT) for screw placement verification). In the navigated group, a total of 131 screws were placed (all had perioperative CT for screw placement verification). The pedicle screw placement inaccuracy was statistically significantly greater in the robotic group at 10.7% (13/121) compared to 3.1% (4/131) in the navigated group (p = 0.04, < 0.05). Out of the 13 misplaced screws in the robotic group, only one required revision. There were no significant differences in demographic findings between the groups, including age, sex, and BMI (p > 0.05). The main factor contributing to screw misposition was medial or lateral displacement of the robotic trocar by a hypertrophied lumbar facet and sloped transverse process. Conclusion: Early experiences with robotics in spine surgery may be correlated with higher rates of screw malposition. Future developments for robotics must include solutions to prevent drill or trocar skiving to minimize medial or lateral screw deflection. Introduction: Anterior tension band injuries are usually the result of high impact hyperextension trauma. However, these injuries can be increasingly observed in geriatric patients based on the current demographic change. Current surgical treatment includes anterior plating bearing the risk of soft tissue irritation, such as esophageal dysphagia or rupture, and degeneration of adjacent cervical segments or implant failure due to an iatrogenic spondylodesis. Tape suture constructs, reenforcing ligamental stability while permitting physiological micro mobility of the affected motion segment, are already established for ligamental injuries in ankle, knee or shoulder surgery. However, there is no data regarding the feasibility of these constructs for hyperextension injuries of the subaxial cervical spine. Consequently, this study examines the biomechanical properties of tape suture constructs for the treatment of AO type B3 injuries compared to anterior plating. Materials and Methods: Two groups, each consisting of 6 synthetic cervical segments (C5/6, Sawbone ® ), were formed and the anterior longitudinal ligaments (ALL) were dissected, simulating an AO type B3 injury. A cervical cage (DePuy Synthes ® ) was then placed between the cervical vertebrae. The corresponding segments were then either treated with an anterior 4-hole-plate (DePuy Synthes ® ) or a tape suture construct, similar to the Speed-Bridge TM (Arthrex ® ), implanted ventrally according to the anatomical course of the disrupted ALL. The specimens were then mounted onto a biomechanical testing machine in a neutral position and biomechanical forces were applied through a lever arm until a force of 6.66 N was reached in the sagittal plane, simulating extension and flexion. Then, rotational forces to both directions were applied until cervical resistance resulted in a rotational force of 1N/m. Implant failure was defined as a dislocation exceeding 25 mm for extension and 7°for rotation. For statistical analysis, the dislocation and its corresponding force of each specimen was measured and compared between the groups. Results: Preliminary results show a mean range of extension of 3.39°±

1.09°for anterior plating and 3.99°± 0.50°for the tape suture construct (p > 0.05). Mean range of rotation was 2.79°± 0.85°for anterior plating and 5.36°± 1.56°for the tape suture (p < 0.05). No specimen suffered from implant failure.

Detailed evaluation among the specimens is currently in progress. Conclusion: The tape suture construct provides sufficient biomechanical stability for the treatment of AO type B3 injuries compared to anterior plating. Regarding movement in the sagittal plane, especially cervical extension, which's limitation is crucial for ligamental healing, the tape suture shows no significant inferiority compared to the plate osteosynthesis. Yet, the rigid plate osteosynthesis highly compromises cervical rotation, a motion that is usually not affected in a hyperextension injury, while the tape suture here approaches the physiological range of motion of 9.3 ± 1.9 mm. Consequently, the tape suture construct is a promising alternative to the current gold standard of anterior plating for the treatment of AO type B3 injuries based on its excellent biomechanical results and its preservation of cervical micro mobility with a concomitant prevention of an iatrogenic spondylodesis. Introduction: The incidence of fractures in the upper cervical spine in elderly patients (> 65 years) after trauma lies between 1.26% and 3%, depending on the adopted protocols for CT scan at the emergency department. The incidence of vertebral artery injury after trauma is reported to be up to 88% in some of the series. The majority of these injuries remain however clinically silent due to cross-flow. However, the stabilization procedures could jeopardise the integrity of the vertebral artery as well. Many tumours in the craniocervical junction lay in a close proximity to the vertebral artery, making their resection limited due to the vascular anatomy. Methods and Materials: This is a small retrospective, single-institution study of three patients, who underwent a dorsal stabilization of the axial or subaxial spine, using a hybrid technique for the intraoperative visualization of the vertebral. The technique is a combination of intraoperative navigation (O-Arm, Medtronic) and application of contrast prior to the first intraoperative scan for neuronavigation. Using this technique both the bone and the vascular structures are available for navigation. Three patients are included in the study -2 with upper cervical spine fractures and one with metastatic diseases, involving the foramen of the vertebral artery on multiple levels. Results: Utilizing this technique, a total of 10 screws were surgically inserted. None of the screws showed suboptimal positioning and close proximity to the vertebral artery. The vertebral artery was visible and blood flow was preserved on the second scan (intraoperatively). Conclusions: This technique should be considered not as a golden strategy for the treatment of upper and subaxial cervical pathologies. It is an additional strategy for the complex spinal procedures, aimed to aid the surgeon in difficult cases with distorted anatomical landmarks. Introduction: Obesity is a risk factor for morbidity after lumbar spinal fusion surgery. This study aimed to analyze the sole effect of body mass index (BMI) on early morbidity in patients after SPS and FLIP lumbar spinal fusion, and unplanned return to OR within one year after the index procedure. In this regard, we compared perioperative outcomes between obese patients (BMI ≥ 35) versus non-obese patients (BMI < 35). Additionally, we compared perioperative outcomes between SPS obese (BMI ≥ 35) and FLIP obese (BMI ≥ 35) patients. SPS and FLIP surgeries in obese (BMI ≥ 35) patients will have longer operative time, higher EBL, and higher rate of unplanned return to the OR at one year follow up. Material and Methods: Included in the analysis were 454 patients who underwent primary SPS and FLIP surgeries with bilateral percutaneous pedicle screw fixation between L2-S1 with minimum 1-year follow-up from 3 separate institutions. SPS, 68 obese (age: 60.4 ± 10.5, CCI: 1.82 ± 1.47), 280 nonobese (age: 62.9 ± 11.6, CCI: 1.84 ± 1.13); Flip, 26 obese (age: 55.7 ± 9.14, CCI: 2.38 ± 1.55), 79 non-obese (age: 57.2 ± 13.4, CCI: 2.61 ± 2.21). Surgical characteristics, radiographic outcomes, and 90-day complications were assessed, including unplanned revision within one year follow-up. Statistical analyses were completed using t-tests, chi-squared tests, and Post-Hoc tests with a significance set at p < 0.05. Results:

There were no significant differences in patient characteristics between obese and non-obese patients undergoing SPS or FLIP surgery. There was a significantly higher radiation dose in SPS surgeries for obese patients versus non-obese patients (65.0 ± 49.7 mGy, 30.8 ± 28.2 mGy, p = 0.002), without a significant difference in estimated blood loss or length of stay. There was also a higher neurologic complication rate in obese patients than non-obese SPS patients (2.9% vs. 0.4%, p = 0.039); however, there was no difference in 1 year revision rates. Further, there were no significant differences in neurological deficits between obese SPS and FLIP patients. For FLIP surgeries, longer operative times was noted for obese patients compared to non-obese (372.9 ± 156.8 minutes, 292.3 ± 78.2 minutes, p = 0.017); however, there were no differences in estimated blood loss, length of stay, or perioperative complications between obese and nonobese patients. Of note, there was a significantly higher radiation dosage and operative time for FLIP obese patients than SPS obese patients (119.6 ± 149.8 mGy, 65.0 ± 49.6 mGy, p = 0.012; 372.9 ± 156.8 minutes, 104.6 ± 61.5 minutes, p = 0.000). There was a significantly increased operative time in obese (SPS and FLIP) patients versus nonobese (SPS and FLIP) patients (178.8 ± 154.5 minutes, 140.7 ± 100.4 minutes, p = 0.025). Conclusion: Obese patients undergoing SPS surgery required increased radiation exposure during the procedure, and experienced a higher rate of neurologic complications postoperatively, compared with non-obese patients. Further, there were no differences in perioperative outcomes between obese and non-obese patients undergoing FLIP procedures, despite a longer operative times. There were no significant differences in neurological deficits among all (SPS and FLIP) obese patients. However, there was a significantly increased operative time and radiation dosage for FLIP obese patients than SPS obese patients. Obese patients experienced an increased operative time compared to non-obese patients.

A125: Augmented reality-assisted spine surgery: an early experience demonstrating safety and accuracy with 218 screws Fenil Bhatt 1 , Lindsay Orosz 2 , Anant Tewari 2 , Rita Roy 2 , Christopher Good 1 , Thomas Schuler 1 , Colin Haines 1 , and Ehsan Jazini 1 1 Virginia Spine Institute, Reston, USA 2 National Spine Health Foundation, Reston, USA Introduction: In spine surgery, accurate screw guidance is critical to achieving satisfactory fixation. Augmented reality (AR) is a novel technology to assist in screw placement and has shown promising results in early studies. This study aims to provide our early experience evaluating safety and efficacy with an FDA approved head-mounted (HMD-AR) device. Materials and Methods: Consecutive adult patients undergoing AR-assisted thoracolumbar fusion between October 2020 and August 2021 with 2 week follow-up were included. Preoperative, intraoperative, and postoperative data were collected to include demographics, complications, revision surgeries, and AR performance. Intraoperative 3D imaging was used to assess screw accuracy using the Gertzbein and Robbins (G-R) grading scale. Results: 32 patients (40.6% male) were included with a total of 222 screws executed using HMD-AR. Intraoperatively, 4 (1.8%) were deemed misplaced and revised freehand. The remaining 218 (98.2%) screws were placed accurately. There were no intraoperative adverse events or complications, and AR was not abandoned in any case. Of the 208 AR-placed screws with 3D imaging confirmation, 97.1% were considered clinically accurate (91.8% Grade A, 5.3% Grade B). There were no early postoperative surgical complications or revision surgeries during the 2 week followup. Conclusions: This early experience study reports an overall G-R accuracy of 97.1% across 218 AR-guided screws with no intra or early post-operative complications. This shows that HMD-AR assisted spine surgery is a safe and accurate tool for pedicle, cortical, and pelvic fixation. Larger studies are needed to continue to support this compelling evolution in spine surgery. A model which can make in-situ nanofibers deposition composed by a polymer solved in water directly into lesion sitewithout pressure and extra surgical manipulation needs, can be a feasible tool for a surgical application as a simple and considerable low-cost option provided by solution blowspinning (SBS) technique. Taking the poly(vinyl alcohol) --PVA polymer in distilled water solution in sterile conditions and apparatus, authors applied the SBS technique for medullary compatible nanofiber formation, defining the technical fabrication parameters and considering the cytotoxicity conditions to predict their feasibility for a future translational therapeutic strategy, as novel biomaterial approach option, facing potential advantages over others -first study to test SBS technique in spinal cord injury therapeutic approach. Material and Methods: SBS fiber production and characterization was experimentally executed: aqueous PVA solutions (1À20wt%) were prepared at 90°C and 300 rpm for 3 h. PVAs with different molar masses and hydrolysis degree were tested. Nanofibers were produced from PVA solutions in a commercial airbrush at different experimental conditions: air pressure (1-7 bar), outer nozzle diameter (0.2-0.5 mm), solution feeding rate (0.3-5 mL min-1), nozzle-to-collector distance (15-90 cm), and the number of thermal blowers coupled to the SBS system (1, 2) -morphology and mean diameter of the fibers were investigated by field emission gun scanning electron microscopy and had their mean diameter calculated (100 random measurements/each sample). Having the ideal nanofibers and technical parameters, 3 cell lines -VERO, 3T3 and cultured rat resident spinal cord cells -were exposed to them by elution method (3 cm 2 samples, N = 3 per group per experiment, ISO 10993, produced from the 18wt% PVA2 solution). Cells were seeded at 3-5×10 3 cells per well in 96-well plates or 15-20×10 3 cells per well in 24-well plates, depending on the experimental protocol. All experiments were performed three times in triplicate. MTT assay, DAPI and Live/Dead controlled method analysis at 24 h, 48 h, 72 h, and 7 days were performed. An ex-vivo animal model was applied to investigate the adherence of nanofibers to spinal cord and degradability onto natural conditions. Results: PVA nanofibers were effective produced, reaching a mean fiber diameter of 247.42 ± 11.33 nm, with peak ranging 200-400 nm. All desired conditions (entanglement, no solvent bubbles) were identified in MEV images. Cellular cytotoxicity tests showed significant cellular metabolic inhibition and decrease of mitotic activity after 24 and 48 hours PVA eluate exposition, for 3 cell lines tested. On the other hand, a significant recovery and increase of metabolism and mitotic activity was pointed out for 72 hours on, being stable/getting better than control culture results. Ex-vivo model showed an instant adhesion and fast degradation of nanofibers deposited in situ on rat medulla. Conclusion: PVA nanofibers in distilled water solution could be generated in nanometric scale by SBS system, demonstrating biocompatible properties to spinal cord in situ deposition.

Global Material and Methods: SINS 7-12 metastatic spinal tumor patients were retrospectively reviewed with pre-and postoperative KPS. Follow-up ranged from 1 month to 13 years. Baseline clinical characteristics including age, sex, SINS score, Bilsky grade, neurologic function, and preoperative KPS were collected. Postoperative KPS scores were collected at first follow-up visit which averaged about 3 months post-operatively. Paired, nonparametric Wilcoxon signed-rank test to determine significance of improvement in KPS after surgery. Ordinal logistic regression was used to identify factors associated with the change in KPS. Results: Sixty six patients were evaluated. The median SINS score was 11 with a mean follow-up of 3.7 years. Postoperatively, significant improvement in KPS occurred from a median of 50 to 70 (p = 0.0003). Ordinal logistic regression showed that patients with pre-operative KPS of 70 and 80 had more improvement compared to patients with KPS at very low (20) or very high (90) ranges. This improvement in KPS was observed independent of the Bilsky grade, (grade 2, p = 0.045; grade 3, p = 0.001). However, improvement in KPS was associated with ASIA motor improvement on univariate ordinal logistic regression (OR = 1.05, CI = 1.02-1.10, p = 0.004), and this effect was maintained after controlling for Bilsky cord compression grade on multivariate models (p = 0.005). Conclusion: Potentially unstable metastatic tumor patients with SINS score 7-12 appear to have improved KPS scores with surgery. Introduction: The SORG-ML algorithms for survival in spinal metastatic disease were developed in patients who underwent surgery and have been externally validated for patients managed operatively; however, there are no external validations of these algorithms in patients managed nonoperatively. The purpose of this study was to externally validate SORG-ML algorithms for survival in spinal metastatic disease in patients managed nonoperatively with radiation alone. Material and Methods: Adult patients 18 years or older undergoing conventional external beam radiotherapy or stereotactic radiosurgery for spinal metastatic disease from 2000 to 2020 at two academic medical centers. The primary outcome was mortality at 90-days and one-year. The performance of the SORG-ML algorithms was assessed by discrimination (receiver operating curves and area under the receiver operating curve (AUC)), calibration (calibration plots), decision curve analysis, and overall performance (Brier score). Results: Overall, 2074 patients underwent radiation alone for spinal metastatic disease and 29% (n = 521) and 59% (n = 917) had ninety-day and one-year mortality, respectively. On complete case analysis (n = 415), the AUC was 0.76 (95% CI: 0.71-0.80) and 0.78 (95% CI: 0.73-0.83) for ninety-day and one-year mortality with fair calibration and positive net benefit confirmed by decision curve analysis. With multiple imputation (n = 2074), the AUC was 0.85 (95% CI: 0.83-0.87) and 0.87 (95% CI: 0.85-0.89) for ninety-day and one-year mortality with fair calibration and positive net benefit confirmed by decision curve analysis. Conclusion: The SORG-ML algorithms for survival in spinal metastatic disease generalize well to patients managed nonoperatively with radiation alone; future studies are ongoing to determine validity of these algorithms in international contexts.

A130: Sarcopenia is significantly associated with pathologic vertebral compression fractures in cancer patients undergoing tumor surgery Rafael De la Garza 1 , Joshua Benton 1 , Yaroslav Gelfand 1 , Saikiran Murthy 1 , Vijay Yanamadala 1 , and Reza Yassari 1 1 Neurosurgery, Montefiore Medical Center, New York, USA Introduction: Pathologic vertebral compression fractures (pVCF) in cancer patients are a significant cause of pain and disability. Sarcopenia is a state of diminished muscular mass and strength and has been associated with poor outcome in patients with spinal tumors. The objective of this study is to evaluate the association between sarcopenia and pVCF in patients undergoing surgery for spinal metastases. Material and Methods: A total of 104 patients with complete preoperative computed tomography imaging who underwent oncological spine surgery at our institution between 2013 and 2021 were identified. Patients with pVCF were compared to patients without pVCF (controls) and assessed for the presence of sarcopenia. This was defined as a cross-sectional area of the psoas muscle at the L4 pedicle level less than 10.5 cm 2 for men and less than 7.2 cm 2 for women. A multivariable analysis was conducted with pVCF as the dependent variable.

Results: One-hundred and four patients were examined with an average age of 62 years and 58.7% male prevalence. The prevalence of pVCF was 49%; 55.8% for women and 44.3% for men (p = 0.246). Sarcopenia was diagnosed in 38.5% of patients; 46.5% of women and 33.8% of men (p = 0.157). The prevalence of sarcopenia was 54.9% for patients with pVCF compared to 22.6% in controls. On multivariable analysis controlling for patient age, sex, body mass index, and tumor growth rate, sarcopenia was significantly associated with pVCF (OR 4.5; 95% CI, 1.73 -11.6; p = 0.002). Evaluated as a continuous variable, increasing psoas size was significantly associated with lower odds of vertebral pathologic fracture (OR 0.72; 95% CI, 0.60-0.88; p = 0.002), corresponding to a decrease in risk of 27% per every 1 cm 2 increase in psoas size. The mortality rate was significantly higher for patients who experienced a pVCF compared to controls (58.7% vs. 38.2%, p = 0.019). Conclusion: Cancer patients with pVCF were significantly more likely to have sarcopenia compared to patients without pVCF in this study independent of age, sex, body mass index, and tumor growth rate. This association warrants further investigation given sarcopenia is a potentially treatable risk factor.

Introduction: The objective of this analysis was to compare sociodemographic characteristics and outcomes between cohorts of patients receiving separation surgery for spinal metastases at two neighboring institutions, one private and one public, affiliated with a major academic medical center in a large metropolitan area. Material and Methods: Patients who received separation surgery for spinal metastases between 2013 and 2021 were included in this analysis. Sociodemographic factors, treatment characteristics, and outcomes were compared between those treated at a private hospital and those treated at a neighboring public hospital using Rao-Scott chi square tests. Results: Compared to those treated at our private hospital, patients treated at our public hospital were more often younger (p = 0.005), of Black or Hispanic race (70% vs. 14.9%, p < 0.001), and insured via Medicaid or Emergency Medicaid (48.6% vs. 3.2%, p < 0.001). They more frequently presented with ESCC grade 3 compression (81.6% vs. 49.2%), potentially unstable or unstable lesions as denoted by SINS > 7 (64.1% vs. 37.7%), and increased neurologic impairment as denoted by ASIA Impairment Scale scores of A, B, or C (35% vs. 7.9%). Local progression was less frequently observed in patients treated at our public hospital (28.2% vs. 54.7%, p = 0.001), although this is likely due to poorer clinical and radiographic follow-up amongst this cohort. Median survival was significantly lower in patients treated at our public hospital (Median [Range]: 81 [11-1,873] days vs. 264 [0-3,092] days, p < 0.001), although this is also likely confounded by lower rates of follow-up. Conclusion: This study highlights substantial disparities amongst patients treated for spinal metastases at neighboring institutions affiliated with a major academic medical center. Further work is needed to identify reasons for these disparities and create avenues by which to mitigate them. Introduction: Patients with acute metastatic spinal cord compression (MSCC) may experience long-term functional impairment. It has been established that surgical decompression improves neurological outcomes, but the effect of early surgery remains uncertain. Our objective was to evaluate the impact of early versus late decompressive surgery with or without instrumentation for acute MSCC due to spinal metastases (SM). Material and Methods: We retrospectively reviewed a consecutive cohort of all patients undergoing surgery for SMs (decompression, instrumentation, or both) at our institution. We determined the prevalence of acute MSCC; the time between onset of symptoms as well as between acute neurological deterioration and surgery; and neurological impairment graded by the ASIA scale upon presentation and discharge. Results: 693 patients were screened (mean age: 66 years; 30% female). Most common locations of the SM were the thoracic (43.5%) and lumbar (23.3%) spine. 140 patients (21.7%) presented with acute MSCC, defined as neurological impairment corresponding to ASIA grade D or lower acquired within up to 72 hours before admission. All these patients underwent surgical decompression (81.1% had additional instrumentation; 75.0% from posterior only and 6.1% with additional vertebral body replacement). The median time from admission to surgical intervention was 16±14 hours in patients with acute MSCC, compared to 148 ± 274 hours in the non-acute group (301 patients) that also underwent decompression but had a symptom onset between 72 hours to 28 days before admission (p < .001). Within the group of patients with acute MSCC, those who underwent early surgical intervention (i.e., before the median 16 hours) had a significantly higher rate of ASIA improvement by at least one grade at discharge (26.5%) compared to those who had surgery after 16 hours (10.1%; p = .024). There was no difference in the surgical revision rate between the late and early surgery subgroups (13.0 vs. 15.7%, p = .654). Conclusion: Timely surgical intervention is pivotal for patients presenting with acute MSCC, substantially improving functional outcomes. While it is difficult to determine a clear time cut-off, the treatment strategy should entail the earliest possible surgical intervention. Introduction: Multiple Myeloma (MM) is a plasma cell tumor causing anemia, renal failure, and distinct bone destruction. In advanced stage, 70% of MM patients suffer from vertebral column lesions. Indications for surgery are made with restraint because of an allegedly high complication rate including hardware failure and surgical site infections. However, structured data assessing indications and different types of spine surgery in MM patients is lacking. The aim of this study is to present such clinical data of a large cohort of MM patients suffering from vertebral column lesions. Material and Methods: Patients with vertebral column lesions due to MM were enrolled in this study at two academic oncological centers between 2005-2020. Data sets were retrospectively assessed regarding epidemiological, clinical, oncological, treatment and outcome data. Surgical data included surgical technique, duration of surgery and complications. The spinal instability neoplastic score (SINS) of every vertebral lesion was assessed. Ethical approval (EA4/063/20) was granted. Results: 450 patients were enrolled in this study, suffering from 3621 vertebral column lesions. Median age at admission was 67 years. 89% suffered from vertebral pain and 17% from neurological deficits. 68% (n = 308) of the patients received surgery, of whom 35% (n = 108) received kypho-or vertebroplasty ± decompression, and 65% (n = 200) instrumented spine surgery. Of these, 60% (n = 119) received posterior decompression + fusion (47% percutaneous), 6% (n = 13) anterior fusion + corpectomy, and 34% (n = 68) posterior or 360°fusion + corpectomy. Surgical complications occurred in 1% (kyphoplasty) and 10% (instrumented surgery). In 26% surgery was performed at a median 3 years following the diagnosis of the vertebral lesion. The leading indications for surgery were pain (73%) and instability according to SINS (68%). Patients treated surgically had significantly more potentially instable or instable lesions according to SINS. Conclusion: With this study, we report on a large cohort of 450 MM patients of which the majority (68%) received spine surgery. Vertebral pain and spinal instability according to SINS were the leading causes for surgery. With respect to spinal metastases of other entities, we see a comparatively low complication rate in patients treated with kyphoplasty or with reconstructive surgery, but prolonged time from initial diagnosis of symptomatic spinal lesion to surgical management. Further prospective cohort studies are needed to generate robust data on optimal timing and technique of surgical intervention in MM patients. Introduction: Spinal metastases are often diagnosed, referred and treated in a late stage. Optimizing referral patterns may potentially accelerate and improve this process, however can also potentially lead to increased health-care costs. The costsaving aspects of timely treated patients with spinal metastases have however not been assessed in detail. This study aims to analyze the difference in costs between patients who were surgically treated in a timely or delayed fashion for metastatic spinal disease. Materials and Methods: The mean medical costs of 204 timely treated patients were compared to the mean medical costs of 93 delayed patients. The costs were divided into pre-clinical costs (medical consultation, diagnostics, pre-surgical admission), clinical costs (surgery, hospital admission, complications) and rehabilitation costs up until three months postoperatively. Results: Mean treatment costs for a timely patient were € 23.324 and for a delayed patient € 31.227. There were no significant differences in mean pre-clinical costs (€ 3.229 vs € 2.528), the mean clinical costs were higher in the timely treated group (€ 16.298 vs €15.571) but the mean rehabilitation costs were significantly higher in the delayed group. (€ 3.803 vs € 13.022). This large difference was mainly due to high costs associated with clinical rehabilitation or geriatric rehabilitation in the delayed treatment group. Conclusion: Delayed surgical treatment of patients with spinal metastases is associated with significantly higher costs than timely surgical treatment. This difference is primarily caused by the large differences in rehabilitation costs between the two groups. Potentially, the differences in mean costs between the two groups may be even larger beyond three months postoperatively due to more expensive follow-up care, the inability to work and the necessity of home modifications and informal care. These findings should be included in future debate on the costs of optimizing referral patterns for patients with metastatic spinal disease. Background: Posterior hemivertebra resection and pedicle screw fixation is one of the effective surgical methods for the treatment of congenital scoliosis caused by hemivertebra. Postoperative adding-on phenomenon is an important postoperative complication. The incidence and risk factors of adding-on phenomena are still controversial. At present, there are no studies on the risk factors for additional phenomena after posterior hemivertebra resection with pedicle screw fixation. Objective: The aim of this study is to evaluate the clinical efficacy of posterior hemivertebra resection with pedicle screw fixation in patients with congenital scoliosis, and to analyze the incidence of postoperative distal adding-on phenomenon and its risk factors. Method: A retrospective study was performed in patients with congenital scoliosis who were treated with posterior hemivertebra resection with pedicle screw fixation. The patients were followed up for 5 years after operation to evaluate its clinical efficacy, count the incidence of distal adding-on phenomenon. The risk factors for distal adding-on phenomenon after posterior hemivertebra resection and pedicle screw fixation were further analyzed. Univariate analysis was first performed for various factors, and multivariate regression analysis was performed for statistically different factors to identify independent risk factors for the occurrence of distal adding-on phenomenon.

Results: The retrospective study included 27 consecutive patients with congenital scoliosis who underwent posterior thoracolumbar hemivertebra resection and short-segment fusion and were followed for more than 5 years. The correction rate of segmental scoliosis deformity was 65.9%, total scoliosis was 60.2%, compensatory caudal curve was 69.2%, compensatory cranial curve was 30.3%, and segmental kyphosis was 61.9%. There were five cases of proximal junc- Introduction: The apical deformation in thoracic adolescent idiopathic scoliosis (AIS) is a combination of rotation, coronal deviation and anterior lengthening of the spine. Surgical correction can be performed anteriorly or posteriorly, but regardless of the approach both the concavity and convexity can be shortened or lengthened. However, the magnitude of the convex-concave and anterior-posterior length discrepancies in thoracic AIS, and how this needs to be modified to restore optimal spinal harmony, is unknown. Therefore, the purpose of this study is to determine the convex-concave and anterior-posterior spinal length discrepancies in main thoracic AIS curves and the same segment in non-scoliotic, sex and age matched controls. Materials and Methods: From existing CT-databases, 80 pre-operative AIS patients with right-sided primary thoracic curves were sex-and age-matched to 80 healthy controls. For each patient, the main thoracic curve was measured from Cobb-end to Cobb-end vertebra, and the exact same segment in the straight spine of the corresponding matched control. Vertebral body endplates and posterior elements were semi-automatically segmented to retrieve the length of the left and right side of the anterior column and along the posterior pedicle screw entry points, accounting for 3D-orientation of each individual vertebra. Four spinal length parameters: anterior-left, anterior-right, posterior-left and posterior-right of the main thoracic curves were compared to corresponding levels in controls. Since this study is performed on only right-sided primary thoracic curves, the left side is always the concavity and the right side is always convexity.

Results: The main thoracic curves showed anterior lengthening with a mean anterior-posterior length discrepancy of +3.0 ± 6.0%, compared to a standard thoracic kyphosis with -5.6 ± 3.4% in controls (p < 0.001). The mean right-left length discrepancy was +20.4 ± 7.3% in AIS compared to +0.3 ± 1.1% in controls (p < 0.001). While the posterior concavity was -21.6 mm shorter, the posterior convexity was +7.8 mm longer in AIS compared to controls. For the anterior side, this was -7.0 mm concave and +20.8 mm convex. The length discrepancies anterior-concave, anterior-convex and posteriorconcave were more pronounced in more severe curves (p ≤ 0.013), but not for posterior-convex. Specifically for surgical correction with a posterior approach this has implications: In the least severe curves (45°-60°) the posterior discrepancy was -19.0 mm concave and +8.7 mm convex, which implies a lengthening of the concavity 2.2 times the shortening of the convexity. While in the most severe curves (over 80°), this was -24.7 mm and +7.3 mm, which would mean a concavity lengthening of 3.4 times the convexity shortening. Conclusion: This study confirms anterior lengthening in thoracic AIS. However, when the spine is measured over four sides, it was observed that this lengthening moment is more oblique, present as an anterior-convex spinal lengthening. To restore optimal spinal harmony during posterior surgery, the posterior concavity should be distracted together with a smaller shortening on the convexity. Furthermore, in more severe curves the ratio between concave distraction and convex shortening is greater. While in anterior surgery mainly the convexity needs shortening while allowing a slight lengthening of the concavity. . Main location of stenoses (median Naganawa-Score: 3; mean AP-spinal-canal-diameter: 7.7 ± 2.2 mm) were the C3-to C6-level. 31% of the patients were assigned for a laminotomy procedure, 20% for a hemilaminectomy and 49% for a laminectomy/laminoplasty. There were no significant differences of patients´characteristics, blood loss, operation time and in-patient stay between the three groups. Independed from the mode of surgery, the spinal canal was significantly widened (median Naganawa-Score: 0; mean AP-diameter: 11.4 ± 3.6 mm) and myelopathy (mJOA-Score) improved (each p < 0.001); a higher BMI was significantly correlated with a worse mJOA-improvement (r = 0.293; p = 0.003). Quality-of-life (Short-Form-36v2 ® -Health-Survey/Neck-Disability-Index) and reduction of neck-pain level were similar in the three groups at last follow-up (mean: 28 months). Conclusion: Individual tailoring of the surgical approach according to the underlying compressive pathology is feasible in CSM to achieve the minimal patients' periprocedural burden.

A148: Can C5 radiculopathy be a risk factor for "neurogenic" frozen shoulder? An MRI-based case-control study Salvatore Russo 1 , Robert Vardanyan 1 , Santhosh Thavarajasingam 1 , and Hadie Adams 1 1 Neurosurgery, Imperial College, London, United Kingdom Introduction: Considering that the innervation of the shoulder girdle comes mainly from the cervical nerve roots, it seems plausible that cervical spine disorders can be associated with shoulder pathologies. While limited in their number and scope, previously published studies have investigated this hypothesis and found a high incidence of upper limb musculoskeletal disorders in patients undergoing assessment for cervical spine disorders. However, of all the shoulder pathologies, no published studies have investigated the association between cervical radiculopathy and glenohumeral adhesive capsulitis (or frozen shoulder [FS] ). The present study aims to explore the relationship between these two conditions. Method: We conducted a single centre retrospective study of patients treated for FS between January 2004 and December 2018. We included 292 patients with a clinical diagnosis of FS who underwent glenohumeral hydrodistension and had a confirmatory ultrasound demonstrating anterosuperior capsular thickening. 32 patients also had MRI of the cervical spine for cervical spine disorders. We performed an image-based case-controls study to assess the association of cervical foraminal stenosis with FS. Two independent fellowship-trained spine surgeons assessed the foramen at C3/4, C4/5, C5/6 and C6/7 on MRI. We compare the presence or absence of foraminal stenosis on the same side of the frozen shoulder with the presence or absence of stenosis on the contralateral side. The results were analysed with the McNemar exact test. Results: The mean age of the patients was 54.8 (SD 10.7). 25 patients (78%) had neck pain on the ipsilateral side to the FS. 14 patients (44%) had evident radicular pain, and 6 patients (24%) had wasting of the deltoid and/or rotator cuff muscles ipsilateral to the FS. 21 patients (84%) had at least 1 consultation with a spine surgeon regarding their neck symptoms. 12 patients (57%) had a spinal procedure targeting the C5 cervical radiculopathy: 7 had a CT guided steroid injection of the C5 nerve root, and 5 patients underwent a C4/5 anterior cervical discectomy and fusion. The MRI based case-control study to assess the association between foraminal stenosis and FS demonstrated a statistically significant correlation of the side of the FS and ipsilateral stenosis of the C5 nerve (P-value < 0.001). 18 patients had foraminal stenosis on the ipsilateral side of the FS (56.3%), 9 patients had bilateral foraminal stenosis (28.1%), 4 patients had no C5 foraminal stenosis (12.5%), and 1 patient had C5 foraminal stenosis on the contralateral side to the FS (3.1%). No significant correlation was found at C3/4, C5/6 and C6/7. Conclusion: We found an association between FS patients receiving glenohumeral distention and ipsilateral C5 foraminal stenosis, and we hypothesise that C5 radiculopathy can be a risk factor for secondary "neurogenic" adhesive capsulitis. The retrospective nature and potential selection bias are the 2 main limitations of this study that preclude our ability to draw conclusions on any causative mechanism. Prolonged immobilisation secondary to painful C5 radiculopathy, shoulder girdle muscles denervation or a neuroinflammatory process mediated by C5 nerve innervating the anterior glenohumeral capsule are all plausible hypotheses that need investigating with prospective studies. titanium coating (ProTi) with nano, micro, and macro features 1 have been FDA cleared for use. Preclinical research has demonstrated significantly accelerated bony deposition on ProTi devices compared to titanium or PEEK alone 1 . However, clinical research has not previously been performed on these devices. The objective of this research is to examine the clinical outcomes of patients undergoing cervical fusion with ProTi interbody fusion devices to evaluate safety and performance. Material and Methods: Institutional Review Board approval was obtained to perform a retrospective and prospective registry to gather healing outcomes data on patients treated with the ProTi interbody fusion devices. Retrospective patients who underwent cervical fusion with the ProTi interbody fusion devices, a cellular bone matrix and supplemental plating were evaluated for radiographic bone fusion and clinical outcomes at 12 months. Results: Patients treated with the ProTi interbody fusion devices demonstrated osteo-integration with the vertebral endplates at early timepoints and bridging bone across the interbody space at final follow-up (12 months). Flexion and extension radiographs demonstrated stabilization at the fusion site with no movement. Clinical outcomes supported the radiographic findings with pain improvement and/or resolution, alleviation of extremity motor, sensory and reflex deficits, and a return to normal activity. Conclusion: This early analysis in an ongoing study was the first to evaluate the clinical outcomes of next generation interbody fusion devices with ProTi technology for cervical fusion applications. Study results demonstrated osteo-integration with the vertebral endplates, bone bridging across the interbody space and successful clinical outcomes with return to motor functionality, pain improvement and/or resolution and return to normal activity. While additional research is required to fully evaluate these ProTi interbody fusion devices, early evidence demonstrates the ability of these devices to obtain solid cervical fusion. Conclusion: In our model, age, CAD, and COPD are significantly associated with increased LOS following ACDF. Patients with DM also had a significantly longer LOS, but this loses significance in the multivariate model when controlling for age and the other medical comorbidities. This suggests that while DM is associated with other factors which may increase LOS but is not related to increased LOS itself. Further research is needed to characterize the relationship between LOS and medical comorbidities.

Jason Garber 1 1 Neurosurgery, Las Vegas Neurosurgical Institute, Las Vegas, USA Introduction: Although extremely effective at a single level, anterior cervical discectomy and fusion (ACDF) with an anterior cervical plate (ACP) for a multilevel construct can be associated with a number of peri-and postoperative complications. Such complications include esophageal dysphagia, loss of sagittal balance secondary to plate installation, and technical difficulties with the placement of anterior cervical plate over a multiple fusion levels. As an alternative, and quite possibly superior to cervical plating, individual cervical integrated interbody fusions with subsequent compressive/lag fixation, has emerged as a promising alternative. This has the potential to allow for smaller exposure, zero anterior profile, and individual, but multilevel specific sagittal realignment. Objectives: The purpose of the study was to retrospectively evaluate patients treated from single to multiple levels with integrated interbody fusion. Material and Methods: A total of 203 patients consecutive patients with symptomatic cervical degenerative disc disease with radiculopathy and/or myelopathy were surgically treated with a cervical integrated interbody fusion device with compressive fixation between the C3-C7 levels. Patients were assessed pre-and post-operatively at 6 weeks, 3, 6, 12, 24 months. Patients were evaluated for patient-derived outcome measures, and radiographic parameters (effect on device-level lordosis, overall cervical sagittal alignment, and fusion status), and device-related complications. Results: The average age at time of surgery was 53.4 ± 10.7 years. All had failed conservative treatment. 74 patients underwent the procedure at single level, 68 patients at 2-levels, 39 patients at 3-levels, and 17 patients at 4-levels, 4 patients at 5-levels, and 1 patient at 6-levels. Blood loss was minimal and no intraoperative complications were recorded. Hospital stay was minimal with 92% of patients being released the following day. Radiographic results showed lordosis was maintained in the global spine and bone formation was present in the inner column of the device. Overall fusion rate was 92%. The revision surgery patients showed better alignment than pre-operatively with static plates. There were no signs of heterotopic ossification of the ligaments or vertebral bodies. At 6 months, none of the patients reported chronic dysphagia. There were no device failures out to last follow-up. 86% of patients were able to return to the same level of work as prior to surgery. Conclusion: For patients undergoing single and multi-level cervical fusion, integrated interbody fusion with compressive/lag fixation appears to be a viable alternative. Previously, studies with static integrated interbody fixation devices have not reported as well as ACP with regards to fusion and clinical outcomes. The benefit of a lag design to provide better fixation and more accurate maintenance of the lordotic curve of the cervical spine was seen in our series. Patients reported they were well satisfied with their results and experienced significant pain relief. The opportunity to either revise a previous ACDF with ACP or add to a pre-existing ACDF offers greater flexibility to treat the pathology at the index level rather than approach as a global construct. Introduction: Cervical myelopathy, caused by spinal cord compression, is characterized by symptoms including gait dysfunction, balance and dexterity derangement, and potentially but not universally complaints of neck and arm pain. A positive Hoffmann's sign on physical examination is classically regarded as virtually pathognomonic of cervical myelopathy. In clinical practice, patients seen for conditions unrelated to the cervical spine, and without other signs or symptoms of myelopathy, are occasionally observed to have a positive Hoffmann's sign on examination. The purpose of this study was to assess the prevalence of significant cervical spine pathology in patients with a positive Hoffmann's sign but no clinical complaints referable to the cervical spine, and thereby assess the implications of a positive Hoffmann's sign in an otherwise asymptomatic individual Material and Methods: Over the course of two years, among patients treated for lumbar spine-related complaints (low back and/ or leg pain) without any cervical complaints (neck and/or upper extremity complaints) and without any gait, balance, or dexterity derangement, 20 consecutive patients were identified who had incidental findings of positive Hoffmann's signs (unilateral or bilateral). No other findings of myelopathy were present. All 20 patients underwent cervical spine MRI examination to assess for spinal cord compression, and the results were analyzed. The degree of spinal stenosis was graded as none, mild, moderate, or severe; the presence or absence of myelomalacia was noted; and the ultimate pursuit of cervical spine surgery was noted. Results: All 20 patients had findings of spondylosis; 14 had mild or moderate stenosis; 6 had severe stenosis; 3 had findings of myelomalacia. Surgery was recommended in 5 patients, and pursued in 4. Bilateral Hoffmann's signs were noted in 4 of 6 patients with severe stenosis, 3 of 3 with myelomalacia, and 4 of 5 for whom surgery was recommended/pursued. Only 2 of 14 patients with mild or moderate stenosis had a bilateral positive Hoffmann's sign; all other patients with mild or moderate stenosis had positive Hoffmann's signs identified unilaterally. One of 5 patients for whom surgery was recommended had a positive Hoffmann's sign noted unilaterally. Conclusion: Patients with incidental findings of positive Hoffmann's signs frequently have significant occult cervical spine derangement. In those otherwise asymptomatic patients with an incidental identification of a positive Hoffmann's sign, the spinal cord compression was sufficiently severe as to demand surgical recommendation in 25%; 15% had radiographic findings of spinal cord damage (myelomalacia). Bilaterally positive Hoffmann's signs correlated most reliably with significant pathology, but the presence of a unilateral Hoffmann's sign did not exclude the possibility of significant abnormality. Consideration should be given for cervical spine MRI evaluation when encountering a positive Hoffmann's sign, even in the setting of an otherwise asymptomatic patient. Introduction: In multilevel posterior cervical instrumented fusions, extending the fusion across the cervico-thoracic junction (CTJ) has been associated with decreased rate of re-operation and pseudarthrosis but with longer surgical time and increased blood loss. However, the impact on patient reported outcomes remains unclear. The primary objective was to determine whether extending the fusion through the CTJ influenced patient reported outcomes (PROs) at 3 and 12 months after surgery. Secondary objectives were to compare the number of patients reaching the minimally clinically important difference (MCID) for the PROs and mJOA, operative time duration, intraoperative blood loss (IOBL), length of stay (LOS), discharge disposition, adverse events (AEs), re-operation within 12 months of the surgery, and patient satisfaction. Material and Methods: This is a retrospective analysis of prospectively collected data from an on-going multicenter observational cohort study of patients with degenerative cervical myelopathy. Patients who underwent a posterior instrumented fusion of 4 levels or greater (between C2-T2) between January 2015 and October 2020 with 12 months follow-up were included. PROs (NDI, EQ5D, SF-12 PCS and MCS, NRS arm and neck pain) and mJOA were compared using ANCOVA, adjusted for baseline differences. Patient demographics, comorbidities, and surgical details were abstracted. Percentage of patient reaching MCID for these outcomes was compared using chi-square tests. Operative duration, IOBL, AEs, re-operation, discharge disposition, LOS and satisfaction was compared using chi-square test for categorical variables and independent samples t-tests for continuous variables. Results: A total of 206 patients were included in this study (105 patients not crossing the CTJ and 101 crossing the CTJ). Patients who underwent a construct extending through the CTJ were more likely to be female and had worse baseline EQ5D and NDI scores (p > 0.05). When adjusted for baseline difference, there was no statistically significant difference between the two groups for the PROs and mJOA at 3 and 12 months. Surgical duration was longer (p < 0.001) and IOBL was higher in the group extending to the upper thoracic spine (p = 0.013). There was no significant difference between the groups for AEs (p > 0.05). Satisfaction with the surgery was high in both groups but significantly different at 12 months (80% versus 72%, p = 0.042 for the group not crossing the CTJ and the group crossing the CTJ, respectively). The percentage of patients reaching MCID for the NDI score was 55% in the non-crossing group versus 69% in the group extending through the CTJ (p = 0.06). Conclusion: In this observational cohort study, up to 12 months after the surgery, there was no statistically significant differences in PROs between posterior construct extended to or not extended to the upper thoracic spine. The adverse event profile did not differ significantly, but longer surgical time and blood loss were associated with construct extending across the CTJ. Introduction: Lumbar Total Disc Replacement (TDR) is a treatment option with 30 years experience and extensive publications on clinical results. However, there are few publications on mid-and long-term mobility. There is also sparse literature on the quality of mobility or the difference between L4-S1 2-level TDR vs TDR/ALIF Hybrid constructs. The purpose of the study was to measure mobility parameters in flexion-extension for two groups (L4-S1 TDR vs Hybrid); compare motion at L4-L5; participation of pelvis mobility; global lumbar motion; and flexion-extension effectiveness by measuring L1 Race. Besides determining the difference of mobility between TDR and Hybrid, we discussed potential compensations above and below L5-S1 fusion/L4-L5 TDR, as compared to two-level TDR. Material/Methods: 235patients, operated between 2003-2013, were included in the study: 170 patients received 2-level TDR (TDR group) and 65 received L4-L5 TDR and L5-S1 ALIF (Hybrid group). Hybrid patients had 2-level indications equivalent to the TDR group, but only received 1-level TDR due to insurance reimbursement constraints. Both groups were equivalent in age, body habitus, and preoperative clinical parameters (ODI, VAS). Patients' selection for evaluation was based on presence of clinical success criteria and pre-and postoperative sagittal X-rays and dynamic flexion-extension films at minimum 24 months follow-up. Pelvic parameters (Incidence, Pelvic Tilt, Sacral Slope) were measured. L4-L5 and L5-S1 flexion-extension range of motion (ROM) was measured pre-and postoperatively. Pelvic motion was determined by measuring sacral slope in flexion-extension. The influence on lumbar lordosis (L1-S1) was also analyzed. To show the effect the lumbopelvic complex has on global motion, we measured L1 Race (flexion-extension L1 ROM). Results: The absolute motion and relative gain of 2-level TDR shows its superiority over Hybrid constructs in all measured parameters. When L5-S1 is fused, there is no compensation from pelvic motion to overcome the loss of mobility. TDR group shows a pelvifemoral ROM gain of 16.77o, vs a gain of only 6.11o in the Hybrid group. L5-S1 fusion also reduces L4-L5 TDR mobility in Hybrid group, compared to 2-level TDR, and decreases flexion compared to baseline. There is a mean reduction in ROM of 1.53°in Hybrid group vs 20.02°gain in TDR group. L1 Race also reflects the superiority of 2level TDR vs hybrid with a gain of 32.58°in TDR vs 4.68°i n Hybrid, demonstrating that reduced global motion is principally due to loss of L5-S1 motion. Conclusion: This comparison between 2-level TDR and Hybrid demonstrates a lack of compensation through lumbar mobility and pelvic motion when L5-S1 is fused, and debunks these preconceived ideas. Although clinical measures of activity (ODI) and pain (VAS back and leg pain) are equivalent between the groups, functional superiority of 2-level TDR is confirmed. Two new ROM parameters introduced here-Pelvic motion and L1 Race must be integrated in all ROM studies as they quantify pelvic participation in mobility and the functional effectiveness of motion preservation. In this first long-term comparison of mobility between 2-level TDR vs L4-S1 Hybrid,2-level TDR demonstrates overall superiority. Consequently, 2-level TDR must be systematically indicated whenever TDR is indicated for both levels, and accepted as the "gold standard "for reimbursement purposes. Introduction: Multiple studies have shown that lumbar Total Disc Arthroplasty (TDA) is not only safe and effective in treating chronic lumbar DDD, but also provides a better surgical alternative to fusion with respect to patient-reported results, restoring motion, and reducing reoperation rates and severity of adjacent level degeneration. Published evidence is limited for follow-up past 5-7 years after TDA. In this study, we expand the evidence favoring TDA with results up to 21 years, of a large patient cohort treated with semi-constrained ball-and-socket lumbar TDA. We compare the results for one-level vs. twolevel patients, and evaluate whether or not prior surgery at these levels has an effect on clinical outcomes. Methods: A total of 1,187 chronic lumbar DDD patients (622 male, 565 female, mean age 43 ± 9.81 years, range 17-86 years), underwent lumbar TDA in 1999-2013. 772 patients had one-level and 415 patients had two-level procedures. 373 out of 1,187 patients (31.5%) had prior index-level surgery (recurrent disc herniation or post-discectomy syndrome). Patients were evaluated preoperatively, then followed postoperatively at 3, 6, 12, and 18 months, then yearly thereafter. Patient follow-up ranged between 7 and 21 years (mean 11 years, 8 months). Data collected included radiographic, neurological/physical assessment, self-evaluation using the Oswestry Disability Index (ODI) and Visual Analog back and leg pain Scores (VAS). Complication, reoperation/revision rates, and perioperative data points were also assessed. Patients were stratified into one-(1L) and two-level (2L) procedure groups, then divided into prior (PS) or no-prior surgery (NPS) at the index level for data comparison. Patient demographics (age and gender) were comparable for all groups. Results: All groups showed dramatic and statistically significant ODI reduction by 3 months post-surgery (p < 0.001) and then maintained scores over time. ODI improvement was mean 26 points for groups 1, 2 and 3, while group 4 (2L/PS) had mean 24 points ODI improvement. Although patients with prior surgery took longer to reach final VAS pain levels (6 vs. 3 months), there was no statistical difference between groups in pain reduction at 24 months. Although not statistically significant, the group with highest average preoperative VAS pain (group 2) had the greatest reduction in pain. Improvement of ODI and VAS pain is summarized in Table 2 (baseline-24 months follow-up). 49 of 1,187 patients (4.12%) required new or revision surgery. Revisions were classified into four groups: posterior release/laminectomy at same level; TDA revision; scar/hematoma; and Adjacent Level Surgery (ALS). Rates were too low in all groups to compare them statistically. Total TDA revision and ALS rates over 7-21 years were very low: 0.67% and 1.85%, respectively. Conclusions: In one of the largest groups of TDA patients evaluated, this study demonstrates the robust long-term clinical success of one-and two-level lumbar TDA, as assessed at 7-21 years postoperatively. Patients had significant and maintained reduction in disability and pain scores over time, and low rates of index revision/ reoperation or ALS, when compared to long-term published fusion data. Also, both 1-and 2-level lumbar TDA patients improved and patients with prior surgery at the index level had outcomes equivalent to patients with no prior surgery. Introduction: Indirect decompression technique may be limited in that it does not include direct removal of the offending intervertebral disc or osteophyte protruding into the canal. We sought to evaluate resolution of radiculopathy, as well as perioperative complications in lumbar fusion with indirect or direct decompression techniques. Material and Methods: Patients ≥ 18 years of age diagnosed with preoperative radiculopathy undergoing single-level lumbar fusion with minimum 1-year follow-up were included. Patients were grouped by indirect and direct decompression. Direct decompression (DD) group included TLIF with or without direct decompression procedure as well as ALIF and LLIF with direct decompression procedure. Indirect decompression group included ALIF and LLIF without DD procedure. Outcome measures assessed were visual analog scale (VAS) scores at baseline, 3, 6, and 12 months post-op, resolution of radiculopathy at 3, 6, and 12 months post-op, and perioperative complications. Results: Propensity score matching performed for age resulted in a total of 116 patients in this analysis: direct decompression (N = 58; 67.2% female, age 53.9 ± 12.9, BMI 30.3 ± 5.9) and indirect decompression (N = 58; 61.4% female, age 54.6 ± 12.6, BMI 30.0 ± 6.3). There was significantly greater estimated blood loss in the DD group versus indirect group (242.4 ± 128.5 v 171.79 ± 143.9 mL, p = .007). Significantly more patients in the DD group had full resolution of radiculopathy at 3 months post-op relative to the indirect decompression group (53.1% v 13.73%, p = .002). Patients in the DD group also demonstrated a significantly larger reduction in VAS score 6 months post-op (indirect: -.897 ± 4.3 v direct: -2.889 ± 2.3, p = .044). Conclusion: Patients who underwent direct decompression experienced significantly greater resolution of preoperative lower extremity radiculopathy at 3 months compared with those who underwent indirect decompression alone. At 6 and 12 months, no differences were noted between the two groups. There was no difference in complications rates. In a particularly debilitated patient, these findings may influence the surgeon to perform a direct decompression to achieve more rapid resolution of radiculopathy symptoms.

A157: Propensity-matched outcomes comparing lumbar interbody fusion and total disk arthroplasty: a Canadian spine outcomes research network (CSORN) Study

Introduction: There is a paucity of published and generalizable literature investigating patient-reported outcomes following lumbar disc arthroplasty (LDA) for symptomatic degenerative spondylosis. The objective of this study was to quantify long term reported outcomes following lumbar disc arthroplasty performed as a stand-alone procedure as compared to a propensity-matched lumbar spine fusion cohort. Material and Methods: National multicenter review of prospectively collected data on patients enrolled by the Canadian Spine Outcomes Research Network (CSORN) who underwent one or two-level LDA for symptomatic lumbar spondylosis. Arthroplasty patients were propensity score matched to fusion patients. Patients had a primary diagnosis of degenerative lumbar spondylosis and a chief complaint of back pain. Patient reported outcome scores and satisfaction were assessed longitudinally. Results: Propensity-matched cohorts of 61 LDA and 55 fusion patients were collected with at least one year follow-up. Cohorts were matched on age, gender, BMI, smoking status, and number of surgical levels. No differences were found between patient education, symptom duration, medications, and work status. Perioperatively, no differences were found in operative time (LDA -122.5min, Fusion -146 min, p = 0.224). Statistical differences were found in length of hospital stay (LDA -1.44 days, Fusion -1.93 days, p < 0.05), and intraoperative blood loss (LDA -292cc, Fusion -160cc, p < 0.001). A trend was found toward higher perioperative adverse events in the fusion cohort (p = 0.05). Adjusted for baseline pain scores, there was a trend towards greater improvement in leg pain amongst the fusion group (LDA --1.754, Fusion --2.597, p = 0.079). No difference was found in the improvement of back pain scores (LDA --3.722, Fusion --4.408, p = 0.148). At one year follow up, no differences were found for Oswestry Disability Index scores (LDA --21.905, Fusion --26.311, p = 0.220). In similar fashion no statistical differences were noted between groups for EQ5D, Physical and Mental Component Summary scores. Conclusion: Our national outcomes demonstrate comparable results to international literature and confirm the generalizability of the current published data. For both LDA and fusion, comparable improvements in all outcome scores were observed at one year. There was a trend towards greater leg pain improvement and higher perioperative adverse events amongst the fusion cohort. . Patients from 5 different centers were included (France, Japan, Singapore, Tunisia, and the United States). Volunteers were divided into 3 main groups depending on PI values: PI<45°; 45°60°. 3D measurements were performed using a commercially available 2D/3D modelling software. ANOVA and Tukey's HSD for post-hoc analysis were used to determine the differences between groups. Results: Distribution of Lumbar lordosis (LL) showed significant difference between the three PI groups (p < 0.001). The average value of LL is increasing with PI value. The PI-LL and PT also showed significant differences in their distributions according to PI groups. Linear regression analysis allowed to defined a closed correlation between PI and LL as follow: LL = 0.5635 x PI + 27.989 and between PI and PI-LL with the following equation PI-LL = 0.4365xPI -27.989. The means (SD) of PI-LL were -9.86°(9.46) for PI < 45°, -5.95°(9.74) for 45°< PI < 60°, and 2.23°(10.61) for PI > 60°, respectively. Conclusion: PI showed significant correlation with PT, LL and PI-LL. The normal value of PI-LL considering PI and the linear regression equation in this study could help to evaluate the sagittal alignment and provide reference value for planning to establish the target restoration of sagittal curve in corrective surgery.

A159: New method to adapt the lumbar aligment of supine CT-based virtual 3D lumbar spine models to standing X-rays Peter E. Eltes 1 , Benjamin Hajnal 1 , Máté Turbucz 1 , Agoston Jakab Pokorni 1 , Ferenc Bereczki 1 , Jennifer Fayad 1 , and Aron Lazary 1 1 In Silico Biomechanics Laboratory, National Center for Spinal Disorders, Budapest, Hungary Introduction: Standing radiographs serve an important role in determining the lumbar lordosis of the spine, which plays a central role in surgical planning. Yet, there is no widely accessible method to adapt the lumbar alignment of supine CTbased virtual 3D lumbar spine models to standing X-rays. The lumbar lordosis influences the behavior of the patient-specific lumbar spine finite element models. The aim of the presented method was to develop a new method to adapt the lumbar alignment of supine CT-based virtual 3D lumbar spine models to standing X-rays to improve the accuracy of the in silico clinical investigations. Material and Methods: In a cohort of 50 patients with monosegmental degeneration of the spine, segmentation and registration of the lumbar vertebrae and sacrum was carried out by two independent investigators. Segmentations were compared using the Dice similarity index, which was >0.9 in all cases. Retrospective imaging data was used for our study, consisting of CT scans and biplanar (frontal, sagittal) standing spine radiographs. Intersegmental and lumbar lordosis (LL) angles were measured in both cases, which showed an average difference of 2-4°between corresponding segments, and 5.4°between LLs. Registration of the vertebrae was carried out using the X-ray module of the Materialise Mimics ® software, with the resulting spine geometries exported as STLs. Virtual X-rays were made from the mid-plane sections of the registered 3D lumbar spine geometries, which were used to evaluate the accuracy of the registration by comparing intersegmental and LL angles with the corresponding standing radiographs by two independent observers. Results: The segmentation accuracy of the geometries had a higher Dice Similarity Index than 0.92. The average difference for each segment and LL was < 1°. Intraclass correlation was calculated for each measured angle, which yielded > 0.8 in every case, designating excellent inter-rater reliability. The 3D accuracy was evaluated with the Hausdorff Distance and in 98% the geometrical difference was lower than 1 mm over the vertebral geometries. Conclusion: We propose an accessible, accurate and reproducible method for the creation of patientspecific 3D lumbar spine geometries that represent the standing alignment of the spine. The method can facilitate future research, clinical applications, and has potential for automation in the future. The method has the potential to increase the accuracy of the in silico clinical trials for spinal implants.

A160: Midline sparing bilateral laminotomies prevents disc collapse compared to traditional laminectomy -A biomechanical finite element analysis Hossein Elgafy 1 , Vijay Goel 2 , Ali Kiapour 2 , and Nabil Ebraheim 1 1 Orthopedic, University of Toledo Medical Center, Toledo, USA 2 Departments of Bioengineering, University of Toledo, Toledo, USA Introduction: Traditional laminectomy is the long-standing surgical gold standard for relief of pain induced to spinal stenosis. However, loss of the posterior tension band due to this technique may result into settling of the motion segment leading to neural foraminal stenosis and recurrence of the symptoms. An alternative technique, which conserves the posterior tension band through the midline sparing bilateral laminotomies, may provide good long-term outcomes. The objective of the study was to biomechanically compare two competing surgical techniques for alleviating spinal stenosis. Material and Methods: An experimentally validated finite element model of the intact L3/S1 segment was used to simulate the laminectomy and bilateral laminotomies across the L4/L5 level. Segmental Motion, intra-discal pressure (IDP), facet load and foramina opening were compared between the intact and surgical models in response to 400N of axial compression and 10Nm moments. Results: Segmental motion and IDP after L4 laminectomy increased in flexion, especially at L4/L5 disc level. The laminotomy model had biomechanics close to the intact model, especially in flexion. The distance of L4/L5 foramina in both surgical models decreased in extension, lateral bending and axial rotation compared with the intact model. However, in flexion the distance in foramina opening increased in laminectomy model. Facet loads at L4/L5 after both procedures decreased in extension, lateral bending, and axial rotation. Conclusion: The midline laminotomy surgery induced much less alterations in biomechanics of spine compared to traditional laminectomy. The increase in IDP and motion for laminectomy model means that the load on the disc is higher as compared to the midline sparing which may lead to longterm disc degeneration. The findings of the current study show that midline sparing laminotomies may prevent disc collapse due to reduced disc loading without sacrificing the opening of formina, as compared to the traditional laminectomy. Introduction: It remains unclear how the use of telemedicine, with the limited opportunity to perform a detailed physical examination, affects the ability to formulate a surgical plan for spine patients. The objective of this study was to compare the accuracy of surgical plans generated from in-person and telemedicine evaluations. Materials and Methods: Consecutive new patients who were evaluated by the orthopaedic spine division between 2019 and 2020 were identified. Patients were included if they were indicated for elective spine surgery at their first appointment, had documented definitive surgical plans, and received surgery within 3 months. Patients were divided into two cohorts based on initial appointment type: telemedicine (N = 39) and in-person appointment (N = 92). The primary outcome was change in surgical plan from the initial appointment to the actual preformed procedure, defined as either a change in number of operated levels (e.g., adding additional level), change in the surgical approach (e.g., change from anterior to posterior cervical fusion), change in the performed procedures (e.g., adding fusion to decompression), or change in region of surgery (e.g., change from lumbar to cervical surgery). Statistical analysis included Student's T-test or Wilcoxon's rank-sum test for continuous variables and Chisquare analysis for categorical variables. Secondary analysis compared the length of stay, hospital complication rate, and readmission/reoperation rate between patients who had changes to the surgical plan and those who didn't. Results: There was no significant difference in the accuracy of initial surgical plans between the telemedicine and in-person cohorts (79.5% versus 82.6%, p = 0.673). The most common modification in the surgical plan (79%) was change in the number of operated levels, of which all but one of the 19 patients received one more operated level. Less common reasons were change in approach (13%) and change in procedure (8%). Patients with changes to their surgical plan experienced longer length of stay (3.1 versus 2.0 days, p = 0.027) than patients with consistent surgical plans. Conclusion: Telemedicine and in-person evaluations generated similarly accurate surgical plans. Initial surgical plans most often change for adding operated levels. Our findings show that telemedicine visits are an acceptable option for preoperative assessment to generate surgical plans, however further research is needed. Lumbosacral transitional vertebrae (LSTV) are congenital spinal anomalies, in which an elongated transverse process of the last lumbar vertebra fuses with varying degree to the "first" sacral segment. The presence of an LSTV disrupts normal spine biomechanics and anatomy. The sacrum, lying at the base of the vertebral column, optimizes the dissipation of the weight of the upper body toward the sacroiliac (SI) joint by working as a fused mass of boney elements. The sacrum's ability to dissipate load depends on its size and its surface area with the SI joint. Low back pain in the presence of an LSTV was originally noted by Mario Bertolotti in 1917 and termed "Bertolotti's Syndrome". According to Quinlan et al., the prevalence of Bertolotti's syndrome is 4.6% in the general population and 11.4% in patients under the age of 30. We analyzed 90 cases in which the presence of the lumbosacral transition vertebra (Bertolotti's syndrome) was related to important axial and radicular symptoms, associated or not with deformities and degenerative diseases. This review focuses in to review the literature and report our experience with 90 cases. This literature review involved clinical case reports, randomized controlled trials, a series of cases describing Lumbosacral transitional vertebrae and bertolotti's syndrome. The research was performed using the Pubmed database targeting all English language publications available involving Lumbosacral transitional vertebrae. This review was organized applying the MeSH terms "Lumbosacral transitional vertebrae and pain", "Lumbosacral transitional vertebrae and surgery, Lumbosacral transitional vertebrae and surgery and lumbar", "Bertolotti's syndrome and pain", Bertolotti's syndrome and pain and surgery", "Bertolotti's syndrome and Lumbosacral transitional vertebrae The Pubmed / Medline search on lumbosacral transitional vertebrae retrieved 1,068 articles. After that, 24 papers were recovered. After analyzing the titles of the articles, they were selected for a summary review, considering the relevance and relationship with this article. All relevant data were collected and tabulated in a Microsoft Excel © spreadsheet. All eligible articles for this study were case reports and literature reviews. Here, we describe the results, results of the surgery and our experience with lumbosacral transitional vertebrae. Ninety cases were analyzed in which the presence of lumbosacral transition vertebra (Bertolotti's syndrome) was related to important axial and radicular symptoms, associated or not with deformities and degenerative diseases. Of the 90 cases, 72 patients underwent diagnostic and therapeutic blocks with anesthetics and steroids.35 patients with pain sustained after the blocks underwent radiofrequency denervation of the abnormal joint area, with improvement in 70% of cases. Of the 90 cases, 22 cases received direct treatment with partial or total transverse resection, with excellent results in 90% of cases. Bertolotti syndrome is a pathology that gives rise to specific symptoms, usually associated with deformities and degenerative diseases, is underdiagnosed, underestimated, undertreated and probably plays a very important biomechanical role in the development of deformities and degenerative diseases. it is part of a specific group of pathologies that can be associated with poor results and complications in the treatment of degenerative diseases. Introduction: Post-operative pain at the surgical site is a distressing event for the patients as well as treating doctors. The post-operative pain after spine surgery is usually higher than most other surgeries. Pain management after spine surgery is particularly essential as it directly affects some of the most important decisions which include patient's postoperative mobilization & physiotherapy, the doses of opioid as well as non opioid analgesics, lengths of the hospital stay, functional outcomes and overall patient satisfaction with surgery. The literature suggests that the use of analgesic cocktails containing various drugs such as opioid and/or non-opioid analgesics, local anaesthetics and epinephrine, which are infiltrated locally at the surgical site have a definite role in reducing postoperative pain and early rehabilitation in patients who undergo total hip and total knee replacement surgeries. Thus, this study was performed to investigate the utility of intra-operative local infiltration of analgesic cocktail in patients undergoing lumbar spinal decompression surgery. Material and Methods: After obtaining the institutional review board approval (2018-08-WSH-004), a prospective double-blinded randomized controlled clinical trial was conducted in a single specialist spine hospital. The trial was registered in the Korean clinical trials registry (registration number: KCT0004222). A total of 81 patients (41 cases and 40 controls) between the age of 18-75 years, with isolated diagnosis of symptomatic one/two-level lumbar central/foraminal stenosis, planned for elective one/two-level uni/bi-lateral open lumbar laminectomy with or without discectomy were included in the study. The cases group received paraspinal infiltration of a cocktail containing morphine ropivacaine, ketorolac and epinephrine at the end of the surgery. The control group did not receive any paraspinal infiltration. Results: The average age of the population was 55.29 years (56.51 in case group and 54.07 in control group). There were 55% males in cases group and 70% in control group. The average preoperative VAS score was 5.4 ± 2.65 and 4.45 ± 2.67 in the cases and control group respectively. At 3 hours post-surgery, this became 4.75 ± 1.99 and 5.77 ± 2.05 respectively. . The ERAS bundle contained elements which included prehabilitation, patient education, perioperative multimodal analgesia including preoperative acetaminophen and gabapentin, Erector Spinae block/ Thoracolumbar Interfascial Plane (TLIP) block, postoperative analgesia regimen to reduce strong opioid intake and early mobilization. Data collection with regards to compliance with protocol, length of stay, strong opioid use postoperatively and postoperative outcome scores were done. We compared the data with the cohort of patients who had lumbar fusion surgery 1-2 levels without the ERAS protocol. Results: A total of 29 patients who underwent lumbar fusion surgery 1-2 levels with ERAS protocol from November 2020 to December 2021 were studied. This cohort were compared with 25 patients who underwent Lumbar fusion surgery 1-2 levels without eras protocol (non-ERAS). For patients with ERAS protocol programme, the compliance with preoperative (93.1%) and postoperative (86.2%) medications were relatively good. Compliance with post-operative elements such as early physiotherapy and mobilization, early removal of urinary catheter (by POD 2 -89.6% POD 3 -100%) and drain were also excellent (POD 2 -75% POD 3 -100%). Patients who underwent the ERAS protocol required significantly smaller number of strong opioids (32% drop when compared with non-ERAS) and length of stay on an average (ALOS) in the acute hospital was 2.96 days when compared with non-ERAS cohort with ALOS of 4.6 days. The compliance with preoperative education (37.9%) and preoperative physiotherapy (79.31%) was relatively poor. Conclusion: Implementing the ERAS protocol for lumbar fusion for 1-3 level had significant decrease in use of postoperative opioids and had significant effect on length of stay. There was improved collaboration and communication between spine surgeons, anesthetists, and physiotherapists with improved patient care in mind. Even though the compliance to the programme was relatively poor in the preoperative phase of ERAS, the outcomes were promising. We aim to further improve the pre-and post-operative compliance to the programme and further improve patient outcome. Introduction: The objective of this publication is to investigate the totality of published literature surrounding spinal stenosis surgery in patients with Achondroplasia. We hypothesize that there are a variety of spinal surgery techniques to address spinal stenosis in achondroplasia and that these surgical techniques result in satisfactory outcomes for spinal stenosis. Our publication meets the new 2020 PRISMA updated standards/protocols. Materials & Methods: PubMed database search was conducted on November 24, 2021, using the following Boolean search algorithm: (achondroplasia OR Achondroplastic) AND (steno* OR lami* OR decompr* OR Sacr* OR lumb* OR thorac* OR cervic* OR spin* OR fusion OR fuse OR instrum* OR crani* OR spondy* OR vert* OR neuro* OR kypho*). The search was then limited to "Full Text" and "English" language. 3 reviewers narrowed the search to include only articles related to surgery involving the spine in achondroplasia. This resulted in 126 articles, and 74 of these studies were excluded as they were not specific to spinal stenosis surgery. This resulted in 51 spinal stenosis surgical articles for our review. Results: Of the 126 records identified, 51 were eligible and contained data relevant to spinal stenosis surgery in achondroplasia spanning from the years 1952 to 2021. The overall risk of bias in these articles was low to moderate. Surgical intervention for spinal stenosis in achondroplasia ranged from single or multilevel decompression to total craniospinal decompression, decompression and fusion, and full deformity correction and fusion after decompression. Various surgical techniques were employed ranging from novel instruments for decompression, to specialized approaches for interbody fusion. Conclusion: The limitations of this study include multiple case reports and series prior to the year 2000. Study level of evidence ranged from level V (expert opinion) to Level III (meta-analysis). Surgical intervention resulted in improved outcomes for spinal stenosis in achondroplasia. Delayed time to diagnosis and delay to surgical intervention resulted in worse neurologic outcomes. Complications included transient neurologic changes, permanent neurologic deficits, infection, recurrence of symptoms from adjacent level stenosis, and injury to anterior structures from anterior vertebral body pedicle screw penetration. Introduction: Chronic low back pain after spine surgery is a diagnostic as well as a therapeutic challenge to a spine surgeon. Lumbar spinal fusion can result in changes the spinopelvic profile of the patient thereby placing undue stresses on the surrounding structures such as SI joint to maintain the cone of balance. Only a few studies have studied the incidence of new onset SI joint pain following lumbar spine fusion surgery. We aimed to explore the association between new onset SI joint pain following Transforaminal Lumbar Interbody Fusion (TLIF) for degenerative spine disorders and changes in spinopelvic parameters. Material and Methods: A retrospective analysis of hospital records and imaging database of a tertiary care institute was performed for patients who underwent TLIF from October 2018 to October 2019. The 354 patients who satisfied the eligibility criteria were divided into two groups based on the presence of new-onset sacroiliac joint pain postoperatively (Group A, SI joint group n = 34) and Group B, normal controls, n = 320). Clinical and radiological spinopelvic parameters were compared between the two groups Results: The patients in Group A had a greater postoperative pelvic tilt (PT) compared to Group B (p < 0.001). Patients with postoperative SI joint pain (Group A) had a significantly lesser preoperative and postoperative lumbar lordosis (p < 0.001) compared to the other group. Patients with postoperative SI joint pain had a predominant cephalad migration of the apex postoperatively (30/34 patients) whereas the other group had predominant caudal migration (44/320 patients) or no migration of the lumbar apex (272/320 patients) postoperatively. Conclusion: New onset SI joint pain is a common cause of morbidity after TLIF surgery with an incidence of 9.6%. The preoperative and postoperative lumbar lordosis are significantly lesser and the postoperative pelvic tilt is significantly higher in patients with new onset postoperative SI joint pain compared to those who do not have postoperative SI joint pain. The cephalad migration of the lumbar apex is significantly associated with new onset postoperative SI joint pain. Introduction: Osteoporotic compression fractures (OCFs) place a large burden on the healthcare system. The purpose of this study was to determine 1) does percutaneous vertebral augmentation (PVA) increase the rate of refracture following osteoporotic compression fracture? And 2) do antiosteoporotic medications alter the rate of refracture following percutaneous vertebral Material and Methods: The PearlDiver Humana database was queried for all patients with a diagnosis of an OCF from 2015-2019. We then divided these patients into those who underwent either vertebroplasty or kyphoplasty within 3 months following initial OCF and those who did not undergo PVA. We then further subdivided the PVA group into those who received anti-osteoporotic medications within 1 year following OCF and those who did not. We compared the refracture rate of those who underwent PVA versus those who underwent nonoperative management, as well as the refracture rate of patients who underwent PVA and received anti-osteoporotic medications compared to those who underwent PVA and did not receive anti-osteoporotic medications. Results: A total of 20,495 patients suffered an osteoporotic vertebral compression fracture during the study period. Of those, 14,770 (72.1%) underwent nonoperative management, and 5,725 (27.9%) underwent PVA. Of those who underwent nonoperative management, 20.2% suffered a refracture following initial OCF, compared to 17.2% in the operative cohort. This was not significant in univariate or multivariate analysis (OR 1.01, CI 0.94-1.09, p = 0.816; aOR 1.01, CI 0.94-1.09, p = 0.774). Of those who underwent operative treatment, 412 (7.2%) received anti-osteoporotic medications and 5,313 (92.8%) did not. Patients who received medications had a refracture rate of 6.5% compared to a refracture rate of 18.0% in those who did not receive medications, which was significant on both univariate and multivariate analysis (OR 1.24, CI 1.08-1.43, p = 0.003; aOR 1.20, CI 1.04-1.39, p = 0.012). Only 7.3% of patients received a prescription for anti-osteoporotic medications following initial osteoporotic vertebral compression fracture. Conclusion: PVA does not alter the rate of refracture, whereas antiosteoporotic medications significantly decrease the risk of subsequent OCF by 20%. Only 7.3% of patients received a prescription for an anti-osteoporotic medication following initial OCF. Physicians should be aware of this large gap in osteoporosis management and pathways to increase initiation of anti-osteoporotic medication should be created and implemented.

A168: Impact of patient-specific factors and spinopelvic alignment on the development of adjacent segment degeneration after short-segment lumbar fusion Laszlo Kiss 1 , Zsolt Szoverfi 1 , Ferenc Bereczki 1 , Peter E. Eltes 1 , Balazs Szollosi 1 , Julia Szita 1 , and Aron Lazary 1 1 National Center for Spinal Disorders, Budapest, Hungary Introduction: Degeneration in adjacent segments (ASD) is a major complication after instrumented lumbar surgeries. Various papers report factors that influence the development of ASD. Most of these are related to the patients' demographics, spinopelvic anatomy or lumbar intervertebral disc conditions. These studies mainly focused on long lumbar-, thoracolumbar surgeries, and only few papers published the consequence of the most frequent, short-segment lumbar fusions. Despite the multifactorial nature of the condition, most studies have investigated only one or few risk factors, thus the literature lacks of multiparametric studies. The aim of this study was to analyse the role of various factors such as demographical, surgical or morphological parameters on the development of adjacent segment degeneration after short-segment, one-or two level lumbar fusions. Material and Methods: A prospective study of 100 patients who underwent one-or twolevel open lumbar transforaminal interbody fusions due to a lumbar degenerative pathology was conducted. Demographic, radiographic (spinopelvic X-ray parameters and preoperative MRI features) and long-term (5-year) outcome data (ODI, VAS) were analysed. Results: ASD patients showed higher level of pain (4.6 ± 2.9 vs. 6.5 ± 2.5, p = 0.004) and disability (27.0 ± 20.3 vs. 38.4 ± 21.8, p = 0.020) at follow-up. In univariate analysis, older age (47.1 ± 11.6 vs. 54.2 ± 10.4 years, p = 0.007), upper-level lumbar fusion (3/51 vs. 8/ 23, p = 0.007), lower L4-S1 lordosis (32.9°± 8.8°vs. 29.0°± 7.3°, p = 0.039), PI-LL mismatch (-2.3 ± 9.7 vs. 3.2 ± 11.5, p = 0.021), Pfirrmann grade III or higher disc degeneration (13/54 vs. 16/31, p = 0.002) and the presence of disc bulge/protrusion (6/54 vs. 11/31, p = 0.007) were associated with ASD. In multivariate analysis, the presence of major degenerative sign (disc degeneration and/or disc bulge) was significant predictor for developing ASD (OR: 3.85, p = 0.006). Conclusion: Despite the multitude of studies published, the causes of ASD are not understood completely as well as the role of spinopelvic parameters or other factors, that influence the changes in the adjacent mobile segments. By examining the effect of these factors, we found that preoperative major degenerative signs increase the risk of ASD. Adjacent disc conditions should be considered carefully in surgical planning. Introduction: The modified frailty index (mFI) is a tool to determine physiological reserve by incorporating preexisting comorbidities with functional status. Previous studies have evaluated the usage of the mFI in predicting postoperative outcomes in patients; however, there is limited data to support its use as a predictive tool for complications and clinical outcomes in patients undergoing transforaminal lumbar interbody fusion (TLIF). The purpose of this study, therefore, was to determine the predictive value of mFI scores in predicting sarcopenia status and postoperative outcome measures in patients undergoing one-or two-level TLIF procedures. Material and Methods: A retrospective cohort study was conducted using a database query of patients in a singlecenter, high volume academic center. Patients over 18 years of age who underwent a one-or two-level transforaminal lumbar interbody fusion (TLIF) between 2008 and 2020 were retrospectively identified and included in the analysis using CPT codes and a structured query language (SQL) search. Patients were excluded from the study if they lacked a preoperative lumbar spine MRI, had incomplete preoperative patient-reported outcome scores, or received surgical intervention for any malignant tumors, infections, trauma, or revision at the index level. Patient outcomes were obtained from our prospectively maintained database, OBERD (Columbia, MO). A mFI score was calculated for each patient using 11 clinical factors: 1) non-independent functional status, 2) history of diabetes mellitus, 3) history of chronic obstructive pulmonary disease, 4) history of congestive cardiac failure, 5) history of myocardial infarction, 6) history of percutaneous coronary intervention, cardiac surgery, or angina, 7) history of hypertension requiring medication, 8) history of peripheral vascular disease, 9) history of impaired sensorium, 10) history of transient ischemic attack or cerebrovascular accident without deficit, and 11) cerebrovascular accident with deficit. Measurements of psoas muscle cross sectional areas (CSAs) were made at the level of the L3-4 intervertebral disc on the preoperative lumbar spine MRI. Established thresholds of height-adjusted CSAs of 545 mm 2 /m 2 and 385 mm 2 /m 2 from current literature were utilized to determine sarcopenia status for male and female patients, respectively. Univariate analysis was used to compare cohorts with regards to demographics, comorbidities, sarcopenia status, and clinical outcomes. Results: The study included a total of 505 patients (208 one-level TLIFs, and 297 two -level TLIFs) with 72 patients assigned to the sarcopenic cohort. No significant correlation was found between mFI scores and sarcopenia status in patients undergoing TLIF (p = 0.081). At 1-year follow-up, increased mFI scores were associated with worse ODI (p = 0.002), PCS (p = < 0.001), VAS Back (p = 0.020), and VAS Leg (p = 0.034) outcome measures. Conclusion: Our data suggests there is no significant correlation between mFI scores and sarcopenia in patients undergoing one or two-level TLIF. Higher mFI scores were associated with worse patient reported outcome measures at 1-year follow-up. Utilization of mFI may help surgeons stratify patients into high and low preoperative risk categories for suboptimal 1-year postoperative outcomes in patients undergoing one-or two-level TLIFs. Introduction: Lumbar disc herniation (LDH) a frequent indication for spine surgery. The few available long-term follow-up studies focus mainly on repeated surgery for recurrent herniations. The aim of this study was to analyze all causes of repeat surgery, not only recurrent LDH, for patients operated for primary LDH. Material and Methods: We obtained data from the Swedish spine register on 3291 patients that underwent surgery for LDH from January 2007 to December 2008. These patients were followed through December 2020 to record all reasons for additional lumbar spine operations. Results: 681 (21%) of the 3291 patients had one or more additional operations. More than three additional operations were uncommon (2%). In total 906 additional operation were identified during the time-period with mean time to first additional operation 3.7 years. The most common cause for additional operation was recurrent LDH (47%) followed by spinal stenosis / degenerative spondylolisthesis (31%) and segmental pain (16%). The most common surgical procedure was discectomy (43%), followed by instrumented fusion (22%). Degenerative spinal conditions became a more frequent cause of additional surgery during the follow-period. Majority of patients achieved MIC for the patient reported outcomes after the index surgery. After the third additional surgery only 20% reached MIC in terms of leg pain and 24% in terms of the Oswestry disability index (ODI). Conclusion: One in five patients operated for LDH needed further surgery during the thirteen-year follow-up period. Recurrent LDH was the most common reason for additional surgery. Spinal stenosis and segmental pain were also common reasons for additional surgery. This study shows additional operations after primary LDH surgery to be more frequent than previously reported and the outcome profoundly deteriorates after the second additional surgery. The findings from this study can be used in the shared decision-making process.

Introduction: Degenerative lumbar spondylolisthesis (DLS) is a debilitating condition associated with poor preoperative functional status. Surgical intervention has been shown to improve outcomes in this population though the nature of the most appropriate surgical intervention is controversial. The importance of maintaining and/or improving sagittal and pelvic spinal balance parameters has faced increasing emphasis in the DLS surgical population. However, little is known about the radiographic parameters most associated with improved functional outcomes among patients undergoing surgery for DLS. Thus, the objective of this study was to identify the radiographic parameters that correlate with functional outcomes after DLS surgery. Material and Methods: Retrospective analysis of the prospectively collected cohort of consecutively enrolled patients in the Canadian Spine Outcomes and Research Network (CSORN) database was performed. All enrolled study patients had a DLS diagnosis and underwent decompression in isolation or with posterolateral or interbody fusion. Patients reported their baseline and one-year post-operative leg and back pain on a 10-point logarithmic scale of severity in addition to completing the Oswestry Disability Index (ODI). Furthermore, multiple global and regional alignment parameters were documented at baseline and one-year postoperative including sagittal vertical axis (SVA), pelvic incidence (PI) and lumbar lordosis (LL). Results: Two-hundred forty-one patients were available for analysis. Among participants, the mean age was 66 with 63% (152/241) female and a primary surgical indication of neurogenic claudication in 188/241 (78%) of patients. By Pearson correlation coefficient, worsened PI-LL mismatch > 9 cm was correlated with increased one-year postoperative ODI (.134, p = 0.05), leg pain (.143, p = 0.05) and back pain (0.189, p = 0.01). A multiple linear regression was performed adjusting for baseline patient age, BMI, gender and preoperative presence of depression. From this regression analysis, worsening of a PI-LL mismatch was associated with a higher one-year postoperative ODI score R 2 0.179 (95% CI 0.080, 0.415, p = 0.004), back pain R 2 0.152 (95% CI 0.021, 0.070, p < 0.001) and leg pain R 2 0.059 (95% CI 0.008, 0.066, p = 0.014) score. Likewise, reduction of LL was associated with a higher ODI score R 2 0.168 (-0.387, -0.024, p = 0.027) and back pain R 2 0.135 (95% CI -0.064, -0.010, p = 0.007). Interestingly, worsened SVA > 5 cm was not statistically significant for worse one-year post-operative ODI, leg pain nor back pain scores. Conclusion: In our longitudinal multi-centre cohort study worsening of sagittal balance and loss of lumbar lordosis with lumbar degenerative spondylolisthesis correlates with worse postoperative outcomes. Accordingly, preoperative emphasis on regional and global spinal alignment parameters must be considered in order to optimize surgical procedure indication and functional outcome in lumbar degenerative spondylolisthesis treatment. Introduction: Next to a patient reported outcome measure, there is also need for a simple, reliable and quick to administer tool that is completed by the treating surgeons and reflects their perspectives adequately. Consisting of the most relevant clinical and radiological assessment parameters, the AO Spine CROST (Clinician Reported Outcome Spine Trauma) was developed by the AO Spine Knowledge Forum Trauma. The development of the tool and initial reliability results are presented in the current study. Material and Methods: The development of the AO Spine CROST initiated by the identification of the most relevant parameters from the clinicians' perspective for outcomes measurement of spine trauma patients. An iterative approach of multiple cycles of development, review and revision including an expert clinician panel was conducted. This was followed by a reliability study among an expert panel who were provided with 20 spine trauma cases, administered twice with a four-week interval. Descriptive statistics were used to analyze the developmental process. In the reliability analysis Kappa statistics was used to analyze the reliability per parameter. The inter-rater agreement was analyzed using Intraclass Correlation Coefficient (ICC). Finally, Cronbach's alpha was used for the assessment of the internal consistency. Results: After completing the iterative approach in the initial phase the AO Spine CROST was developed, consisting of 10 parameters. Two of those 10 parameters are only applicable to surgically treated patients ('Wound healing' and 'Implants'), the remaining 8 parameters are applicable to both surgically and conservatively treated patients. The scoring system includes a dichotomous 'yes or no'-response which expresses expected problems for both the short-term and long-term. In the reliability study, 16 (84.2%) participated in the first round and 14 (73.7%) in the second. Fair to good intra-rater reliability was found for both time-points (κ = 0.40-0.80 and κ = 0.31-0.67). Results of inter-rater reliability per item were lower (κ = 0.18-0.60 and κ = 0.16-0.46). The inter-rater agreement for the total scores showed better results (ICC = 0.52-0.60). The internal consistency seemed acceptable (α = 0.76-0.82). Conclusion: Following a comprehensive approach led to the development of the AO Spine CROST. This tool is completed by the treating surgeons and enables them to evaluate and predict outcomes of spine trauma patients. Fair to moderate results and acceptable internal consistency were found in an initial reliability study. Currently, further studies are being performed to analyze the reliability and clinical evaluation of the tool in a prospective setting. Satisfactory results are expected from these studies which would contribute to increased value of the tool for the daily clinical practice and research, leading to improved care and outcomes for spine trauma patients. Introduction: Patients with traumatic cervical spinal cord injury (SCI) typically experience severe respiratory complications necessitating prolonged ventilatory support. Tracheostomy is frequently employed in these circumstances, although there is currently no consensus on the optimal time to perform this technique. Previous studies have commonly used a threshold of 7 days to dichotomize patients into receiving either early or late tracheostomy. It is thought that early tracheostomy in patients with cervical SCI may lessen the risk of developing complications and reduce the duration of mechanical ventilation and critical care stay. This study aims to assess clinical practices and the safety of performing tracheostomy early across a large sample of North American trauma centers. Materials and Methods: We conducted an observational cohort study using data from the American College of Surgeons (ACS) Trauma Quality Improvement Program (TQIP) database from 2010 to 2016. Adult patients with a complete cervical SCI (ASIA A) who underwent surgery and tracheostomy were included. Patients were stratified into those receiving tracheostomy at or before 7 days and those receiving delayed tracheostomy. Propensity score matching was then used to assess the association between delayed tracheostomy and the risk of in-hospital adverse events including mortality, major complications, and immobility-related complications. Risk-adjusted variability in tracheostomy timing across trauma centers was also investigated using mixed-effects regression. Results: 1,100 patients from 234 North American trauma centers were included. Median time-to-tracheostomy was 9.1 days (interquartile range [IQR]: 6.3-13.0 days), with 349 patients (31.7%) undergoing tracheostomy within 7 days. After propensity score matching, the odds of having a major complication were significantly lower for patients that had a tracheostomy within 7 days (odds ratio [OR]: 0.70; 95% confidence interval [CI]: 0.51 to 0.95). Patients were also significantly less likely to experience an immobility-related complication (OR: 0.69; 95% CI: 0.50 to 0.93). Patients in the early group spent 6.3 fewer days in the critical care unit on average (95% CI: -8.49 to -4.03) and 5.4 fewer days on ventilation (95% CI: -7.95 to -2.89). Furthermore, case-mix and hospital-level characteristics explained only 1.1% and 6.5% of the variability in tracheostomy timing both between-centers and within-centers. Conclusion: Physicians should strive to implement tracheostomy in this patient population within the 7day threshold to improve outcomes and reduce length of stay. Further research is important to fully characterize the impact of early tracheostomy on mortality risk, in addition to its effects on patient comfort and long-term outcomes. Introduction: The AO Spine injury classifications divide the spinal column into four segments based on the varying biomechanical responsibilities and inherent stability of the spinal segment: upper cervical, subaxial cervical, thoracolumbar, and sacral. The upper cervical spine is heavily reliant on ligamentous attachments for its stability due to the unique anatomy required to provide flexion at the craniocervical junction (CCJ) and rotation at the atlantoaxial joint. Although there is an abundance of previous upper cervical spine classifications focusing on individual levels of the cervical spine, no previous universal classification system incorporates the occipital condyle, craniocervical junction, atlas, atlantoaxial junction, dens, C2 ring, and C2-3 joint into an easy to use classification system. The strength of the AO Spine injury classification systems are the hierarchical classification system with proven reliability in organizing injuries into stable (bony injury -nonoperative), potentially stable versus unstable (tension band injuries without displacement of the vertebral bodywhich may be treated operatively versus nonoperatively based on further testing), or unstable (ligamentous injuries with translation of the vertebral bodyoperative). Categorization of injuries in this manner allows for a simple, comprehensive, and management-driven classification system. Methods: Thirteen AO Spine Knowledge Forum Trauma members participated in a live webinar based classification of 29 upper cervical spine injuries. Comparison to a "gold-standard" committee was calculated as percent correct and kappa coefficient (ƙ) was calculated to determine the interobserver reliability and intraobserver reproducibility. Results: Our validation members had an 80.8% accuracy with correct identification of the injury classification on assessment 1 and an 82.7% accuracy on assessment 2. Almost perfect interobserver reliability was found for injury location (ƙ = 0.922 and ƙ = 0.912) on both assessments, while injury type was substantial (ƙ = 0.689 and 0.699) on both assessments. This correlated to a substantial overall interobserver reliability (ƙ = 0.729 and 0.732). Further, the injury classification intraobserver reproducibility was almost perfect (mean, [range] ƙ = 0.82 [0.58-1.00]). Conclusion: Our pilot study demonstrated the AO Spine Upper Cervical Injury Classification yields a greater than 80% accuracy with injury classification. There is a higher accuracy identifying injury location compared to injury type. The intraobserver reliability was almost perfect, while the interobserver reliability was substantial. Introduction: Patients with motor complete traumatic spinal cord injury (tSCI) have a low potential to recover ambulation. Motor level recovery, adjacent to the level of injury, could influence functional independency. This study examines the effect of early (<24 hours) surgery on neurological recovery, including motor level lowering, in patients with sensorimotor complete (AIS A) and motor complete sensory incomplete (AIS B) tSCI. Material and Methods: A retrospective cohort study was performed in the Netherlands in patients with motor complete tSCI (C2-L2), who consecutively underwent surgery between January 2010 and April 2020. Neurological examination was performed directly at presentation to the ER and at discharge from the rehabilitation facility. Motor level lowering, AIS grade and Upper and Lower Extremity Motor Score (UEMS and LEMS) recovery were calculated for patients who underwent early (<24 h) and late (24 h+) surgery. Results: A total of 96 patients met the inclusion criteria. In the multivariate analysis late surgical decompression (24 h+) was negatively associated with ≥ 1 motor level lowering and ≥ 2 AIS grade improvement (Odds Ratio (OR) 0.11 (95% CI: 0.01, 0.67) p = 0.046, OR 0.06 (95% CI: 0.00, 047) p = 0.030). The presence of sacral sparing (AIS B) at initial examination, and cervical level of the tSCI were associated with ≥ 1 motor level lowering. In addition, AOSpine C-type injuries were negatively associated with any type of neurological recovery, except motor level lowering. Conclusion: Although sensorimotor complete injuries as well as thoracolumbar injuries negatively influence neurological recovery, early surgical decompression (<24 h) appears independently associated with enhanced neurological recovery in patients with traumatic spinal cord injury despite level and severity of injury.

A176: Is only anterior stabilization enough in three column injury of sub-axial cervical spine? -A long-term retrospective analysis of 78 patients Manojkumar Gaddikeri 1 and Sudhir Srivastava 1 1 Orthopaedics, Seth GSMC and KEM Hospital, Mumbai, India Introduction: Cervical spine is functionally the most important region of the spine. Sub-axial region of the cervical spine accounts for 65% of all cervical spine injuries. Threecolumn injuries are highly unstable and can lead to severe neurological deficit if not adequately treated. They are caused by high velocity trauma and the patient often suffers multiorgan injuries. Dislocations are common example of three column injuries (AO type-C) and are classified as uni-facetal or bi-facetal. Sub-axial spine injuries can be treated by either an anterior, posterior, or combined approach. The simplest and most direct strategy is to base the approach on the area of greatest structural injury. Three column injuries often require combined approach which increases the surgical time and morbidity. The above study is done to find out whether we get away with only anterior stabilization in three column injuries avoiding the need for global fusion. Material and Methods: Total of 105 patients of three-column injury operated by anterior approach were chosen for the study, but only 78 patients (with follow-up of at least 2 years) were included and retrospectively analyzed as only those met our inclusion criteria. Clinical data regarding age, sex, time to surgery, affected level, methods of reduction, post-op mobilization and neurological evaluation using American Spinal Injury Association scale (ASIA)were collected. Radiological data included pre&post reduction X-ray, CT, MRI and post-operative X-rays at 1, 3, 6 months, 1 year & 2 years. Variables like classification of fracture (AO type), alignment, kyphosis angle, time & grade of fusion mass were also assessed. Results: Of 78 patients, 61 had bi-facetal dislocation &17 uni-facetal. Most common site was C5-6 followed by C3-4 & C6-7. Mean patient age was 35.98 years with 60 male & 18 female. Mean time to surgery was 4.4 days. 40 dislocations were reduced by closed method & 38 by open method using anterior approach. 56% patients had traumatic disc injury on MRI. All patients were managed by single level ACDF with iliac crest autograft for fusion. Mean pre-op lordosis was 4.44°(range -13.4°to 25°) & mean post-op lordosis was 28.57°(p < 0.0001), mean loss of alignment was 2.59°by the end of 2 years, 100% fusion was seen with mean time of 22.82 weeks. Neurological recovery seen in 34.6% with at least one grade improvement in ASIA scale. No neurological worsening or need for revision surgery was observed. Conclusion: Goals of management in any cervical injury are timely reduction of dislocation, maintenance of alignment, thorough cord & root decompression, bony stabilization & fusion using an approach that is least morbid & has good long-term outcome. Above study confirms that only anterior stabilization after reduction of three column injury would suffice with very good long-term satisfactory outcome without the need for global fusion. This drastically decreases the surgical risk in patients who are already compromised. Introduction: Acute traumatic Central Cord Syndrome (ATCCS) of the cervical levels, presents with predominantly upper extremity motor weakness. Studies have evaluated long-term outcomes of neurologic status in patients with ATCCS treated operatively and non-operatively, with less attention focused on acute outcomes. A primary concern patients have during their inpatient treatment is how, if at all, will their acute neurologic deficit change before being discharged. The purpose of this study was to evaluate changes in motor function in the acute management of patients with ATCCS. Material and Methods: We retrospectively identified patients treated operatively and non-operatively for ATCCS of the cervical spine (C1-C7) at a single-centered level 1 trauma center within the last 10 years. Specifically, we considered ASIA motor scores on admission and at discharge as a function of patient demographics, injury patterns (e.g., low-versus high-impact), comorbidities (Charlson Comorbidity Index (CCI)), and treatment modalities (operative versus non-operative). To better understand factors that contributed to more favorable acute outcomes patients were further stratified into groups based on age (<50, 50-75, >75) and presenting ASIA motor scores (low, intermediate, and high). Statistical analysis was done using a chi-square and ttest within each treatment group. Results: Of the 142 patients admitted for treatment of ATCSS, 104 (73%) were treated operatively and 38 (27%) were treated non-operatively. Mean ages for operative and non-operative patients were 58 (18-88) and 63 (16-90), respectively (p = 0.05). Mean time (days) from admission to discharge for operative (7.4 [ ± 3.8]) and nonoperative (3.5 [ ± 1.5]) was not statistically significant (p > 0.05). Mean initial ASIA motor score was higher in nonoperative patients compared to operative patients (80.2 vs. 64.1, p < 0.01). Overall, ASIA motor scores improved more following operative treatment (40.1% [operative] vs. 9.6% [non-operative], p < 0.05). For those receiving operative treatment, these improvements were most pronounced in patients between the ages of 50 to 75 (49.7%) in comparison to the younger (<50; 25.5%) and older (>75; 22.1%) age cohorts. Baseline motor scores also influenced acute operative outcomes. Specifically, patients with low initial ASIA motor scores benefited most from surgical intervention (140.8% improvement) relative to patients with intermediate baseline motor scores (10.3%) (p < 0.05). Mechanism of injury, previous neurologic injury, and CCI were not associated with motor score changes in operative and nonoperative patients (all p's > 0.05). Conclusion: Across a large cohort of patients with ATCCS, operative treatment was associated with more favorable acute outcomes. These favorable outcomes were most pronounced in middle-aged patients with low initial motor scores. Additional research is needed to better understand how the factors considered here relate to more objective measures of spine trauma (e.g., radiologic findings). Collectively, however, these findings may aid in the decision-making process to identify patients most likely to benefit from surgical intervention and to provide more accurate expectations for acute changes to patients.

A178: The role of mechanism of injury in neurological outcomes after cervical sensorimotor complete acute traumatic spinal cord injury: a pooled analysis of four clinical trials and registries Introduction: Mechanism is an understudied descriptor of acute traumatic spinal cord injury (at-SCI). Previous studies have been limited in sample size and long-term follow-up to control for potential confounders and clearly establish a relationship between mechanism of injury and neurological outcomes. The aim of the study was to compare the impact of high-energy (HEMI) and low-energy (LEMI) mechanisms of injury on neurological outcomes of cervical sensorimotor complete at-SCI. Material and Methods: Adult at-SCI patients were identified in four prospective, multicenter clinical trials and registries. ASIA Impairment Scale (AIS) grade was assessed ≤72 hours post-injury and followed up between 12 to 52 weeks. Patients were included if they had a cervical and sensorimotor complete (AIS grade A) injury at baseline. Primary outcome was change in AIS grade. Secondary outcomes were changes in light-touch, pinprick, lower extremity motor (LEMS), upper extremity motor (UEMS), and total motor (TMS) scores. Missing information was imputed with multiple imputation. Propensity-score matching between HEMI (e.g., sports, motor vehicle collisions) and LEMI (e.g., falls) groups was performed using a caliper width of 0.2 for baseline variables that were significantly different (p < 0.05). Results: Of 706 patients eligible for inclusion, 546 experienced HEMIs (77.3%). HEMI patients were younger, had lower BMI, more associated fractures or dislocations, and lower baseline LEMS. After propensity-score matching of these baseline variables, 142 pairs were matched. Upon matching, there were no significant between-group differences on early surgery or steroid administration. HEMI patients experienced significantly worse AIS grade conversion (HEMI: 38.7%, LEMI: 54.9%, p = 0.009) compared to LEMI patients. HEMI patients had worse improvements in UEMS (HEMI: 7.9 ± 8.0, LEMI: 10.7 ± 9.6, p = 0.008) and TMS (HEMI: 13.3 ± 16.2, LEMI: 18.8 ± 21.1, p = 0.015). Difference in LEMS recovery was not statistically significant (HEMI: 5.6 ± 10.5, LEMI: 8.5 ± 14.0, p = 0.052). HEMI patients also struggled more to recover light-touch (HEMI: 20.7 ± 27.1, LEMI: 29.0 ± 31.1, p = 0.018) and pinprick (HEMI: 16.4 ± 24.5, LEMI: 23.6 ± 27.9, p = 0.021) sensory function. Conclusion: Cervical sensorimotor complete HEMIs were associated with significantly poorer motor and sensory recovery compared to LEMI patients, which reflects the severity of outcome. Our findings suggest that energy of trauma should be considered in modelling prognosis and in understanding the heterogeneity of outcomes after at-SCI. Introduction: Sensorimotor complete cervical acute traumatic spinal cord injury (at-SCI) requiring a tracheal tube (TT) for ventilation or assistance represent among the most severe patients. Predictive factors associated with respiratory recovery in these patients are unknown. Material and Methods: At-SCI patients were identified in a multicentre, prospective registry between 2001 to 2017. ASIA Impairment Scale (AIS) grade was assessed at baseline (≤72 hours postinjury) and followed up between 12 to 52 weeks post-discharge. Spinal Cord Independence Measure III (SCIM-III) respiration scores were assessed at discharge and followed up at 12 to 52 weeks. Surviving patients who had a cervical, AIS-A SCI with SCIM-III respiration score between 0-4 at discharge were eligible for inclusion. Primary outcome was change in SCIM-III respiration score at follow-up. Missing data was imputed with multiple imputation. Multi-level mixed-effects ordered logistic regression with a random intercept at the hospital site level was used to calculate odds ratios with 95% confidence intervals and with a significance level set as p < 0.05. Results: Of a total of 119 patients (38.5 ± 16.0 yr, 53.8% female) that were included, 17 did not recover (14.3%). Most injuries were at the C4 spinal level (51. were associated with greater recovery. Conclusion: Our findings suggest that cervical sensorimotor complete at-SCI patients with TT-assisted ventilation at discharge that have a history of hypertension and pulmonary disease and those with crush injuries are less likely to recover their respiratory function. These patients may benefit from specialized respiratory rehabilitation and management. The impact of posterior surgical approaches as well as ceiling effects on respiratory recovery needs to be further investigated. Introduction: Atlanto-axial instability is a rare entity in individuals without predisposing factors. It can occur due to traumatic or non-traumatic (congenital, inflammatory, degenerative etc.) causes. Atlanto-axial arthrodesis is usually indicated for C1-C2 instability. Good biomechanical and clinical results have been reported with Harms technique for C1-C2 arthrodesis. However, neck pain may persist after C1-C2 arthrodesis in some patients. We assume that the differences between the pathologies of C1-C2 instability may affect the sagittal parameters after Harms arthrodesis. Chronic pathologies for C1-C2 instability may cause compensatory and rigid changes in the sub-axial cervical spine which affect the sagittal parameters post C1-C2 arthrodesis. In conditions such as rheumatoid arthritis, post-operative subaxial lesions may develop because of disease progression thereby affecting the sagittal parameters. We attempted to explore the differences in sagittal parameters post atlantoaxial arthrodesis changes between traumatic and non-traumatic pathologies. Material and Methods: The medical records of 81 consecutive patients who underwent Harms arthrodesis at our institute between 1 st January 2010 and 31 st December 2018 were retrospectively reviewed. After excluding patients who underwent additional procedures and those who had missing radiological data and lost to follow up, 53 patients were included in the study. The patients were divided into two groups based on the pathology of C1-C2 instability, Group A (traumatic) and Group B (nontraumatic). The parameters before and after C1-C2 arthrodesis were compared between the two groups. Surgical protocol: Dynamic X rays were used to assess the C1-C2 instability. Lateral mass screws were utilized for C1 fixation. The choice of C2 screw (pedicle/pars screw) depended on the vascular anatomy, diameter of the pedicle and choice of the surgeon. Bone graft from the posterior superior iliac spine was utilized for arthrodesis. Clinical parameters: VAS (Visual analogue scale) and NDI (Neck disability index) were utilized to assess the clinical status preoperatively and at the last follow-up. Radiological parameters: C0-C1 angle, C1-C2 angle, C2-C7 angle and T1 slope were measured on the neutral lateral radiographs of the cervical spine at three time points: preoperatively, post operatively and at the last follow-up. The correlation of C1-C2 fixation angle with other radiological parameters has been analysed in the study. Results: The 53 patients [Group A (n = 24,) and Group B (n = 29)] had a mean age of 49.98 ± 21.82 years (42 males, 11 females). Mean follow up duration was 48.9 months. Δ C1-C2 angle is significantly correlated with Δ C2-C7 angle (Group A, p = 0.004; Group B, p = 0.015) but not with Δ C0-C1 angle (Group A, p = 0.315; Group B, p = 0.938). Though significant improvement in the clinical parameters (VAS/NDI) has been noted in both groups, Group A showed a greater improvement in VAS scores [Group A, (p < 0.001); Group B, (p < 0.023)]. Conclusion: The sub-axial sagittal profile was strongly correlated with the Δ C1-C2 angle in both groups. Group B showed greater changes in sagittal parameters after Harms fixation and Group A showed greater improvement in long-term functional outcomes. The final functional outcomes were not related to the initial or final radiological sagittal profile in both groups. Introduction: Spinal cord injury (SCI) is a devastating condition that carries substantial burden on the inflicted individual. The most common etiology of SCI is Motor Vehicle Accidents (MVAs). The incidence of SCI after MVAs appears to be higher in the USA than other countries; possible explanations for these findings have been attributed to less use of seat belts, different road conditions and driving habits compared with other countries. This study aims to examine the relationship between injuries to the cervical and thoracolumbar spines and the type of occupant restraint systems for front-seat occupants involved in frontal impact MVAs. Material and Methods: The National Trauma Data Bank (NTDB) was queried from the years 2016-2018 for patients with MVAs. The primary outcome of interest was the anatomical location of SCI. The primary predictor was the use of protective restraints (shoulder belt use and airbag deployment). This was classified as no restraint, shoulder belt use alone, lap belt use, airbag deployment alone and combined use of airbag and shoulder belt together. Patient level covariates of interest included demographics such as age, sex, race, body mass index (BMI), and injury severity score (ISS). Results: A total of 521,860 patients were identified. The median age at the time of MVA was 37 (34-56), with majority males (62.9%), white (62.5%) and a median BMI of 27 (IQR 23-33). The incidence of vertebral injuries were significantly higher amongst unrestrained vs restrained occupants. Cervical injury was seen more frequently in individuals without airbag deployment or restrainment (p < 0.001) compared to other vertebral regions. Moreover, the odds of SCI in the cervical spine were significantly lower in occupants using shoulder belts compared to no restraints (p < 0.001). The odds of spinal cord injury in the thoracic region were the same in shoulder and lap belts, while lower in the occupants that had used both types of restraints (p < 0.001). As for airbag deployment, the odds of SCI in the cervical region were lowest in accidents with frontal airbag deployment (OR = 0.51 95% CI 0.47, 0.66, p < 0.001) and with combined use of seatbelts (OR = 0.39 95% CI 0.35,0.44, p < 0.001). However, the odds of SCI in the thoracic region were the lowest in both airbag deployment compared to frontal and side deployment (OR = 0.59 95% CI 0.48, 0.73, p < 0.001). Similarly, the odds of SCI in the thoracic region were lowest in accidents with combined use of seatbelts and airbag deployment (OR = 0.39 95% CI 0.32,0.49, p < 0.001). Conclusion: The advantageous impact of seatbelts and airbags is uniformly recognized. Increasing compliance for both lap and shoulder belt is of high priority to reduce the incidence of SCI after MVAs. Efforts to translate these variables to legislative and educational initiatives as well as car manufacturing standards across the USA are of paramount importance. Introduction: Pain experienced by patients undergoing major spine surgery is often severe and difficult to control. This pain negatively affects postoperative recovery. Although opioids are effective in reducing postoperative pain, opioid-related adverse drug events (ORADEs) are common and have been associated with worse patient outcomes. In addition, the expanded prescription of opioids has led to a concurrent increase in the number of opioid overdose hospital admissions, addictions, and overdose deaths. Therefore, postoperative hospital-based opioid use remains a growing medical and societal concern. This ambispective study aimed to evaluate postoperative pain severity, utilized opioids, and the incidence of potential ORADEs in patients who underwent surgical stabilization of the spine. Materials and Methods: A single tertiary center observational cohort study was performed. Adult patients who suffered from spinal trauma, metastatic spinal disease or degenerative spinal disease requiring surgical stabilization of the spine were included. Patients were part of the Pain Out study; a European study aiming to improve postoperative pain management (clinicaltrials.gov; NCT02083835). Demographic data, surgical details, and preoperative analgesics use were prospectively collected as Pain Out study data. Pain scores, postoperative analgesics utilization, the incidence of potential ORADEs and patient outcomes were retrospectively collected from electronic medical records. Opioid dosages were converted into oral morphine milligram equivalents (MME). ORADEs were classified as mild, moderate, or severe based on potential harm for patients. Results: A total of 64 patients were included for analysis. All patients required opioids during hospitalization, and the median postoperative opioid use was 63.8 oral MME per 24 hours (IQR, 37.5-94.9). On the first postoperative day patients reported pain scores of NRS 5 in rest (IQR, 3-6) and NRS 6.5 with movement (IQR, 5-8). The median pain scores during admission were NRS 4 in rest (IQR, 3-6) and NRS 6 with movement (IQR, 5-7). For 13 patients (20.3%), pain control was insufficient resulting in readmission to the recovery room to receive a new loading dose of IV opioids. During hospitalization, 60 patients (93.8%) developed adverse events most likely caused by opioid utilization. Thirty-six patients (56.3%) developed mild ORADEs (e.g. constipation), 50 patients (78.1%) developed moderate ORADEs (e.g. confusion), and 17 patients (28.3%) developed severe ORADEs (e.g. acute respiratory depression). The median time needed before independent mobilization was 48 hours (IQR, 24-72), and the median length of hospital stay was 7 days (IQR, 4-9). Conclusion: Patients who undergo major spine surgery experience moderate to severe postoperative pain despite the use of high doses of opioids and various other analgesics. Almost all patients suffered from ORADEs illustrating the delicate balance between adequate pain relief and risk of developing these events. The results of this study stress the necessity for more research on implementation of opioid-sparing strategies and opioid replacement techniques as integral parts of multimodal pain treatment regimens following major spine surgery.

Kevin Mertz 1 , Zoe Fresquez 1 , Jeffrey C. Wang 1 , and Zorica Buser 1 Introduction: Surgery of the lumbar spine has been shown to alter the mechanics of the hip and knee joints, leading to osteoarthritis and eventually, joint arthroplasty. Minimally invasive spinal (MIS) surgery has been shown to lead to decreased complication rates and improved range of motion when compared to open spinal surgery. In this retrospective analysis, we examine the incidence of hip and knee pathologies and procedures following MIS and open lumbar fusion. Material and Methods: Using the PearlDiver Mariner database of insurance claims from 2010 to 2018, patient receiving MIS or open lumbar fusion (single-and multi-level) were selected using ICD-10 procedural codes. MIS and open cohorts were matched based on age, sex, and Charlson Comorbidity Index. Matched cohorts were followed longitudinally for the length of the database to determine rates of the following outcomes: hip/knee pain, hip/knee osteoarthritis, total hip arthroplasty (THA) and total knee arthroplasty (TKA). The mean days to each outcome were also determined. Purpose: Given the increasing prevalence of lumbar spine surgery, a novel method of reducing acute postoperative opioid dosages by matching the discharge daily opioid dose with 24-hour predischarge opioid dosage is proposed. Methods: A retrospective, observational study of 612 opioidnaïve adult patients undergoing a lumbar spinal surgery from June 2012 to December 2019 was performed at a large, quaternary care institute. In 2018, the use of a novel opioid equivalent calculation tool was implemented to reduce opioid prescriptions. All opioids consumed in the 24 hours prior to hospital discharge were converted to standardized oral morphine equivalents (OMEs) and physicians were made aware of each patient's unique personalized opioid needs. Opioid discharge prescriptions were then matched to inpatient use. The impact of this personalized protocol was assessed with regard to opioid refills. Results: Of the 612 included in the study cohort, 538 (88%) received opioid medications during their inpatient stay and 472 (77%) were discharged with an opioid prescription. After the implementation of the hospital's opioid calculation tool in 2018, there was a significant decrease in outpatient daily opioid prescription doses from 2012 to 2019 (p = 0.0098). Despite an observed reduction in opioid discharge prescriptions, opioid refill rates did not increase. Conclusion: This study proposes a simple, effective opioid calculation tool that matches daily discharge opioid prescription dose with a patient's personalized inpatient opioid requirement. Increased physician awareness regarding individual opioid requirements in the postoperative period following lumbar spinal surgery may help curb the opioid epidemic by decreasing discharge prescription doses.

A185: Telemedicine improves access to care for spine patients with low socioeconomic status Ivan Ye 1 , Alexandra Thomson 1 , Vincent Miseo 1 , Julio Jauregui 1 , Daniel Cavanaugh 1 , Eugene Koh 1 , Daniel Gelb 1 , and Steven Ludwig 1 objective of this study is to compare the likelihood of missing an appointment between scheduled telemedicine visits and in-person appointments for spine patients of varying socioeconomic status. Materials and Methods: Patients with scheduled outpatient appointments with the orthopaedic spine division between 2019 and 2021 were retrospectively evaluated. Patients were divided into the two cohorts by appointment type: telemedicine visit (N = 4,387) and in-person appointment (N = 3,810) . Home addresses were used to calculate the Area Deprivation Index (ADI), a validated measure of socioeconomic status reported as a percentile with 100 representing the most disadvantaged neighborhood. ADI was also stratified into low (<25), medium (25-75), and high (>75) levels of deprivation. The primary outcome measure was missed clinic appointments, which was defined as having at least one appointment that was cancelled or labeled as 'no show'. Statistical analysis included Student's T-test or Wilcoxon's rank-sum test for continuous variables and Chi-square analysis for categorical variables. Results: Patients with in-person appointments were significantly more likely to miss an appointment compared with patients with telemedicine visits (51% versus 25%, p < 0.001). Patients with high ADI were also more likely to miss in-person appointments than patients with medium and low ADI (60% versus 52% and 48%, p < 0.001). However, there was no significant difference in the likelihood of missing a telemedicine visit between patients with high, medium, and low ADI (28% versus 25% versus 24%, p = 0.294). Patients who missed an appointment were 42% more likely to be high ADI (OR 1.42, 95% CI 1.20-1.68, p < 0.001) and 13% more likely to be medium ADI (OR 1.13, 95% CI 1.03-1.26, p = 0.015) and compared with patients with low ADI. Conclusion: Patients with low socioeconomic status were more likely to miss in-person appointments than patients of higher socioeconomic status. However, there was no difference in the likelihood of missing a telemedicine appointment among patients of different socioeconomic status, suggesting that telemedicine may aid in reducing the barriers to healthcare access. Spine surgeons should consider offering telemedicine as an option to patients, particularly those with low socioeconomic status. Introduction: The ability to calculate quality-adjusted lifeyears (QALYs) for degenerative cervical myelopathy (DCM) would enhance treatment decision making and facilitate economic analysis. QALYs are calculated using utilities. We sought to develop a technique for calculating utilities from the modified Japanese Orthopedic Association (mJOA) Score. Material and Methods: We recruited a sample of 760 adults from a market research panel. Using an online discrete choice experiment (DCE), participants rated 8 choice sets based on mJOA health states. A multi-attribute utility function was estimated using a mixed multinomial-logit regression model (MIXL). The sample was partitioned into a training set used for model fitting and validation set used for model evaluation. Results: The regression model demonstrated good predictive performance on the validation set with an AUC of 0.81 (95% CI: 0.80-0.82)). The regression model was used to develop a utility scoring rubric for the mJOA. Regression results revealed that participants did not regard all mJOA domains as equally important. The rank order of importance was (in decreasing order): lower extremity motor function, upper extremity motor function, sphincter dysfunction, upper extremity sensation. Conclusion: This study provides a simple technique for converting the mJOA score to utilities and quantify the importance of mJOA domains. The ability to evaluate QALYs for DCM will facilitate economic analysis and patient counselling. Clinicians should heed these findings and offer treatments that maximize function in the attributes viewed most important by patients.

A187: Impact of COVID-19 on patients who underwent the lumber spine surgery Yoko Ishikawa 1 , Terufumi Kokabu 1 , Ryo Sasaki 1 , Hiroyuki Tachi 1 , Yuichiro Abe 1 , Yasushi Yanagibashi 1 , and Takahiko Hyakumachi 1 1 Orthopedics, Eniwa Hospital, Eniwa, Japan Introduction: COVID-19 occurred in late 2019 and subsequently spread globally, resulting in the declaration of the pandemic by the World Health Organization in March 2020. As a results, the increase in patients with COVID-19 affected general practice and reduced the number of outpatients due to patients' avoidance of consultation. The purpose of this study was investigating the influence of COVID-19 on patients underwent lumbar spine surgery at our hospital. Material and Methods: We retrospectively reviewed the medical records of patients who underwent thoracolumbar and lumbar spine surgery in our hospital from April 2019 to March 2021. The cohort was divided into two group according to before or after the pandemic of COVID-19. The number of outpatients and surgeries were counted in each group. From the medical records, information about age, gender, waiting period to the surgery and diseases for which surgery is required. The low back pain and leg pain were assessed using visual analogue scale (VAS) at the admission and discharge, respectively. Oswestry Disability Index (ODI) was measured to evaluate the functional disability at the admission and discharge. Results: The total number of outpatients and surgeries decreased after the pandemic of COVID-19, respectively (Pre-pandemic group: 17635 and 588, post-pandemic group: 15407 and 530). The mean ages in the pre-pandemic group and post-pandemic group were 64.5 years and 63.9 years, respectively, and there was no significant difference between two groups (P = 0.51). The waiting period to the surgery was significantly shorter in the post-pandemic group (35.8 days) than the pre-pandemic (45.6 days) (p < 0.01). The rate of patients with the lumbar herniation increased from 32% to 37% after the pandemic. In the total cohort, the averages of the VAS for the lower back pain, the VAS for the leg pain and ODI were higher in the postpandemic group, however, there was no significant difference between two groups ( Table 1 ). The VAS and ODI categorized by the disease are summarized in the (Tables 2 and 3) In patients with the lumbar herniation, the post-pandemic group had the significantly higher score in the preoperative VAS for leg pain (P = 0.02). On the other hand, the degenerative diseases included lumbar spinal canal stenosis and degenerative spondylolisthesis had no significant difference in VAS and ODI between the pre-pandemic and post-pandemic group. Conclusion: The number of outpatients in our hospital decreased due to the impact of COVID-19, resulting in the decrease of the lumber surgeries. Although the total cohort had no significant difference in VAS and ODI between the pre-pandemic and postpandemic group, the patient with lumbar herniation had higher score of the preoperative VAS for the leg pain in post-pandemic group, indicating that COVID-19 could influenced the patients with lumbar herniation than the degenerative diseases. However, according to the postoperative VAS and ODI, it was considered that the COVID-19 didn't affect the prognosis after the surgery in the field of lumbar spine diseases. cohort study was performed to include all patients who underwent a single-level or two-level ALIF between 2012 and 2020. Exclusion criteria included a revision procedure or incomplete/inadequate radiographic imaging preoperatively, intraoperatively following instrumentation, and postoperatively within the first month of the procedure and a second date at 6 months post-operatively. Lumbar lordosis and segmental lordosis were compared between the radiographic timepoints using a patient archiving and communication system. Radiographic parameters were compared using paired t-tests. Alpha was set at 0.05. Results: A total of 121 patients were included in the study. Seventy-eight patients had a single level fusion and 43 had a 2-level fusion. Lumbar lordosis was found to significantly increase from preoperative to intraoperative radiographs following instrumentation (delta 4.8, p < 0.001). Lumbar lordosis was found to significantly decrease from intraoperative to postoperative radiographs at 2-4 weeks (delta -2.8, p = 0.002) but have no change at >6 months (delta -0.5, p = 0.584). Segmental lordosis was found to significantly increase from preoperative to intraoperative radiographs following instrumentation (delta 10.7, p < 0.001) and significantly decrease from intraoperative to postoperative radiographs at 2-4 weeks (delta -2.6, p < 0.001) and >6 months (delta -4.1, p < 0.001). Conclusion: Sagittal alignment in the immediate postoperative period may not accurately reflect the improvement in lumbar lordosis seen on intraoperative radiographic imaging due to continued pain and muscle spasm, but they are predictive of long-term sagittal alignment. This is important information for surgeons as it provides additional context for interpreting radiographs in the immediate postoperative period. Surgeons should understand lumbar lordosis will increase to a similar level seen intraoperatively by the sixmonth postoperative visit. Introduction: Posttraumatic syringomyelia can occur in up to 28% of patients with spinal cord injury. Surgery is the main approach in symptomatic disease but the literature is controversial about the best technique. Several studies analyze the number of vertebral levels affected but syrinx diameter is also relevant although data regarding this are scarce. The objective of this study is to compare adhesiolysis and syringo-pleural shunt under radiological aspects pre-and post-surgery including spinal cord levels affected by syringomyelia and cyst area. Material and Methods: A retrospective study was carried out, clinical and radiological data were extracted from January 2000 to December 2018. PTS cysts were measured using magnetic resonance imaging (MRI) and computed tomography (CT). CT and MRI scan reports were retrospectively reviewed by consensus opinion of two reviewers, one radiologist and one neurosurgeon, using AquariusNET Viewer 4.4. The radiological variables evaluated are cyst area: determined from T2 axial MRI scans (1.5 T) in two dimensions measured in mm 2 . Cyst area at the level of maximum distension of the syrinx was also measured postoperatively at the same level as preoperative MRI measurements; number of spinal segments involved: determined from T2 sagittal MRI (1.5 T) scans of the cervical spine; residual deformity in the sagittal plane: assessed from MRI scans and measured as the angle between the cranial and caudal margin of the vertebrae involved in the trauma. Results: A total of 920 patients diagnosed with SCI were recorded and 85 patients met the inclusion criteria for diagnosis of PTS. The results of surgical treatment of PTS (adhesiolysis and shunting) were assessed by the reduction in the size (largest area) and extension (number of vertebral levels) of the syrinx. After surgery, a significant reduction in size was observed after adhesiolysis (p = 0.01), whereas a significant reduction in extension was observed after syringopleural shunting (p = 0.04). When considering the entire sample, a significant reduction both in the number of vertebral levels involved (p = 0.05) and in the largest area of the syrinx (p = 0.001) were observed after surgical treatment. Conclusion: Most studies have assessed the impact of surgical treatment by the extent (number of vertebral levels) rather than the diameter of the syrinx. A more comprehensive radiological analysis is needed because, in some cases, there is a postoperative reduction in the extent of the syrinx with a paradoxical increase in its size. In the current study, magnetic resonance imaging with T2 axial scans of the spinal cord was performed pre-and postoperatively to determine the maximum area of the syrinx, which effectively revealed a reduction in the diameter of the syrinx and spine cord decompression around the syrinx cavity. Study Design: A radiographic study. Objective: To figure out which risk factor drive the occurrence of proximal takeoff phenomenon (PTO) in congenital cervicothoracic scoliosis (CTS). Summary of Background Data: Congenital vertebral malformation in cervicothoracic region can bring about PTO which usually causes remarkable cosmetic issues including head shift, torticollis and trunk imbalance. The underlying mechanisms are currently not fully illustrated, making precise design of treatment strategy unattainable. This study aimed to identify the key deformity parameter in head-neck-shoulder complex being responsible for occurrence of PTO. Method: CTS patients were stratified into case and control groups according to the presence of PTO. The radiographic deformity parameters of head-neck-shoulder complex were measured and compared between the two groups involving head shift, head tilt, neck tilt, clavicle angle (CA), radiographic shoulder height (RSH) and C5-T1 tilt angle etc. The main risk factor for PTO was identified through logistic regression analysis. Result: 16 CTS patients with PTO were recruited, and the control group consisted of 16 matched CTS patients without PTO. The average Cobb's angle was 77.6 ± 25.6°in PTO group and 57.5 ± 21.4°in control group (p < 0.05). Significant difference could be observed for head shift, neck tilt, CA, RSH and C5-T1 tilt (p < 0.05) between PTO and control groups. Multiple logistic regression analysis revealed that head shift, but not head and neck tilt was significantly correlated with the occurrence of PTO (p < 0.05). Conclusion: Development and progression of head shift rather than head tilt is a significant causative factor initiating the occurrence of PTO in CTS. A fully understanding of this mechanism is beneficial for correcting this complicated and annoying congenital spinal deformity. Introduction: Machine-learning algorithms (Artificial Intelligence) have demonstrated remarkable progress in image recognition tasks, especially in the medical field. In our setting, radiologist reporting on x-rays is often not available in peripheral hospitals. X-rays often need to be interpreted by junior doctors working after hours in busy emergency departments, leaving room for radiological errors. AI could prove to be the ideal diagnostic tool where swift and accurate diagnosis of cervical spine injuries are required. Machine-learning networks originally developed for other tasks can be applied to skeletal x-rays with minimal intervention. Machine-learning is increasingly being used in diagnosis and can be expected to gradually change clinical practice, assisting clinicians, and improving inter-rater reliability. We aimed to evaluate the diagnostic accuracy of AI in interpreting lateral cervical spine x-rays. Material and Methods: From the Groote Schuur Hospital PACS database, images from 2015-2020 were searched for patients between ages of 18-45 who had cervical spine X-rays and CT scans. 924 lateral c-spine images were exported in a standardized format and annotated on a spreadsheet with descriptors for the various conditions we wanted to include in machine learning. To interpret the X-rays, deep neural networks (DNN) were used. For each labelled condition a separate DNN was trained to predict whether that pathology was present, but not exactly where on the X-ray the pathology occurred. This allows for a human-in-the-loop style of AI, bringing doctors into the prediction process, by using the DNN prediction as a guide doctors can then diagnose the exact location of the pathology. Results: This dataset was unbalanced, most labels having less than 10% positive examples. The preliminary results from looking only at fracture pathology on lateral views, found 14.18% positive examples. The DNN achieved a sensitivity of 68%, specificity 84% and accuracy of 79%. In comparison, radiologists with 5 years' experience achieve sensitivity 89.6%, specificity 87.8% and accuracy of 88.5% using 3 trauma xray views. Conclusion: The preliminary results observed for the fracture pathology were promising in terms of accuracy and precision, however the recall was low. Preponderance of negative x-rays made it harder to learn the positive cases, so while positive predictions were mostly correct, it was less likely to identify true positives due to the data imbalance. Our results were based on single lateral views only, often poor quality and incomplete LODOX images and this speaks to the potential power of machine learning in assessing x-rays. We plan to improve the recall by weighting the true positives significance in the deep neural networks as well as incorporating a significantly larger unlabeled dataset for semi-supervised learning.

Stephan Aynaszyan 1 , Luis Devia 1 , Siddharth Badve 2 , and Edward DelSole 2 1 Geisinger Commonwealth School of Medicine, Scranton, USA 2 Division of Spine Surgery, Geisinger Musculoskeletal Institute, Scranton, USA Introduction: Osteoporosis (OP), a condition characterized as low bone mineral density (BMD), is a rising issue in the postmenopausal and aging population. By 2025, the prevalence and cost of fractures in the USA is expected to exceed $25 billion. Greater emphasis towards the diagnosis and management of OP is critical to improve quality of life, reduce hospitalizations, and decrease the economic burden of our health care system. The dual energy x-ray absorptiometry (DEXA) scan is the current gold standard for measuring BMD. Recent studies suggest it is insensitive for diagnosis, and perhaps inferior to computed tomography (CT). Our study aims to identify the prevalence of OP determined by CT in patients who have normal or osteopenic bone determined by DEXA. Materials and Methods: We retrospectively reviewed all patients with DEXA scans and non-contrast CTs of the lumbar spine over a 10-year period. Patients with OP diagnosed by DEXA were excluded from our sample. CT measurements were made by two trained researchers and interrater reliability was assessed. Patients were diagnosed as non-OP if they had a normal DEXA T-score (≥ -1) or osteopenic DEXA T-score (-1 to -2.4). Patients were considered osteoporotic by CT if L1-HU ≤ 110. T-tests, Mann Whitney U tests, and Chi-square tests were used to compare diagnostic and demographic variables between non-OP and OP groups. Results: A total of 74 patients were included for analysis. The inter-rater reliability between the two reviewers was excellent (axial ICC: 0.97, sagittal ICC: 0.95). All patients were demographically, similar, and the average patient age was 70 years. The prevalence of OP determined by CT L1-HU was 46% (normal DEXA: 9%, osteopenic DEXA: 63%). A significant number of males in our study were considered osteoporotic by L1-HU ≤ 110 (74%, p = 0.03). Among those patients with normal DEXA scans, T-scores were significantly lower for those with CT L1 HU ≤ 110 (-0.1 ± 0.48 vs. -0.95 ± 0.07, p = 0.04). For patients with osteopenia by DEXA, the Tscores were indistinct between CT L1-HU groups (-1.76 ± 0.33 vs. -1.83 ± 0.36, p = 0.54). All individual axial and sagittal lumbar HU measurements including L1-L5 average lumbar HUs were statistically significant among non-OP and OP groups except for the L4 spinal level (p > 0.05 for L4 axial, sagittal HUs). Conclusion: The prevalence of osteoporosis among patients with normal or osteopenic DEXA scans is high. Among those with osteopenia by DEXA, more than 50% may lack appropriate medical treatment in anticipation of reconstructive spine surgery. The DEXA scan may be particularly insensitive to male bone quality making the CT HU the diagnostic method of choice for detecting OP. DEXA imaging also appears inadequate for diagnosing osteoporosis among the geriatric spine surgery population. CT may be the best way to diagnose these patients and bring them to treatment. Introduction: Ligamentum flavum (LF) induced lumbar spinal stenosis (LSS) is conditioned not only by its "gathering" but especially by hypertrophy. Previous studies have examined the pathophysiology and biochemical changes that cause the hypertrophy. Some studies have described a link between chronic LF inflammation and neovascularization but others have reported highly hypovascular LF tissue in LSS patients. Currently, there is no practical application for our knowledge of the pathophysiology of the LF hypertrophy. Considerations for future treatment include influencing this hypertrophy at the level of tissue mediators, which may slow the development of LSS. To our knowledge, there is no study of micromechanical properties of native LF to date. Purpose of our study was: 1) To clarify the changes in vascularization, chondroid metaplasia, and the presence of inflammatory cell infiltration in ligamentum flavum associated with lumbar spinal stenosis. 2) To quantify changes in the micromechanical properties associated with LF degenerative processes. Design of study: Vascular density analysis of degenerated and healthy human ligamentum flavum combined with measurement of micromechanical properties. Materials and Methods: The study involved 35 patients who underwent surgery between November 1, 2015 and October 1, 2016. The LSS group consisted of 20 patients and the control group consisted of 15 patients. LF samples were obtained during the operation and were used for histopathological and nanoindentation examinations. Sample vascularization was examined as microvascular density (L v ), which was morphometrically evaluated using semi-automatic detection in conjunction with NIS-Elements AR image analysis software. Samples were also histologically examined for the presence of chondroid metaplasia and inflammation. Mechanical properties of native LF samples were analyzed using the Hysitron TI 950 TriboIndenterÔ nanomechanical testing system. Results: Vascular density was significantly lower in the LSS group. However, after excluding the effect of age, the difference was not significant. There was high association between L v and age. With each increasing year of age, L v decreased by 11.5 mm 2 . Vascular density decreased up to the age of 50. Over the age of 50, changes were no longer significant and L v appeared to stabilize. No correlation was observed between L v and the presence of inflammation or metaplasia; however, LSS patients had a significantly increased incidence of chondroid metaplasia and inflammatory signs. The mechanical properties of control group samples showed significantly higher stiffness than those samples obtained from the LSS group. Conclusion: 1. This study showed that L v changes were not dependent on LSS but were age-dependent. Vascular density was found to decrease up to the age of 50. A significantly higher incidence of chondroid metaplasia and inflammation was observed in LSS patients. 2. The mechanical property values measured by nanoindentation showed high microstructural heterogeneity of the tested ligaments. Our results showed that healthy ligaments were significantly stiffer than LSS ligaments. Prevention of the loss of LF vascularization during aging may influence stiffness of LF which in turn may slow down the LF degenerative processes and delay onset of LSS. 666 A200: Increased expression of bone morphogenetic protein 2 in intervertebral discs with vertebral endplate defects Sumera Imran 1 , Ijaz Ahmad 2 , Amer Aziz 2 , and Uruj Zehra 1 1 Anatomy, University of Health Sciences, Lahore, Pakistan 2 Orthopedics & Spine Surgery, Ghurki Trust Teaching Hospital, Lahore, Pakistan Introduction: Intervertebral disc calcification is considered an important feature of degeneration. However, whether it is a cause or consequence of disc degeneration remains unknown. Its presence in scoliotic spines has been associated with altered mechanical loading which may adversely affect disc cell function. Defects in the vertebral endplate have similarly been linked with altered loading of the disc, and with disc degeneration, but their effects upon disc calcification have been little investigated. The current study aims to explore the calcification potential (BMP2 expression) of intervertebral discs and its association with histological degeneration score and more specifically with the presence of vertebral endplate defects visible on MRI. Methods: Forty seven lumbar disc samples were obtained from patients aged 20-76 (31M/16F) undergoing surgery for lumbar disc prolapse. 5 µm thin sections were stained with H&E in order to assign a histological degeneration score (HDS) from 0-15. Scores were assigned on the basis of cell density (0-5), structural alterations (0-4), granular changes (0-3) and mucus degeneration (0-3). Sections were immuno-stained with anti BMP-2 antibodies to observe the calcification potential in these discs. In addition, pre-operativeT2-T1 W MRI images of the lumbar spine were analyzed for the presence and type (typical or atypical) of vertebral endplate defects, grade of disc degeneration (Pfirrmann grade I-V), presence of high intensity zones (HIZ), and Modic changes at the operated level. Data were analyzed using t test, one way ANOVA and Pearson correlation coefficient. Results: Disc levels ranged from L3-4 to L5-S1, and Pfirrmann grades ranged from II to V. Vertebral endplate defects were observed in 38/47 (9 typical /29 atypical defects), Modic changes in 14/47 and HIZ in 10/47 patients. Histological degeneration scores ranged from 5-12 (mean 9 ± 2) and BMP-2 expression ranged from 22-220 (mean 71 ± 36) spots/mm 2 . Discs with adjacent vertebral endplate defects showed increased cell density (p = 0.004), mucus degeneration (p = 0.002), HDS (p = 0.01) and BMP-2 expression (p = 0.01). However, none of these parameters varied significantly between specimens with typical and atypical defects. Discs with high Pfirrmann scores and Modic changes showed a trend towards increased HDS and BMP-2 expression but this was not significant (p > 0.05). Discs with HIZ also had increased HDS, but significance was seen with increased BMP2 expression (p = 0.006). HDS showed a positive correlation with BMP 2 expression (r = 0.30, p = 0.04). Conclusion: Vertebral endplate defects have been linked previously to nucleus decompression and increased disc degeneration. This study has shown that such defects are also linked to increased BMP-2 expression. These findings suggest that the altered mechanical environment of disc cells when endplate defects are present may influence mechanotransduction and more specifically BMP signaling. Nucleus decompression due to vertebral endplate defects may therefore be important in the pathogenesis of intervertebral disc calcification. Introduction: Spinal alignment (SA) is described using functional spino-pelvic parameters. However, these are dependent on the patient's current posture at the moment of documentation and thus susceptible to variation. This is in contrast to the constant pelvic parameters, which do not suffer from posture-dependent variation. These include the pelvic radius (PR), pelvic incidence (PI), and sacral table angle (STA) parameters. Lumbosacral transitional vertebrae (LSTV) can have an influence of spinopelvic alignment. The aim of this study was to investigate the influence of LSTV, four (4 LV) and six (6 LV) free lumbar vertebrae on the constant anatomical spinopelvic parameters. Material and Methods: A retrospective analysis of 819 CT scans of the abdomen and pelvis was performed. CT scans were taken due to exclude hemorrhage, infectious focus search, trauma exclusion and tumor staging from 2016 to 2019. 53 patients with LSTV were identified by two radiologists via consensus reading. We compared these patients with a cohort without LSTV, matched for age and sex. In a matched-pair analysis, we examined the influence of LSTV and the 4 LV (n = 9) and 6 LV (n = 11) subgroups on PR, PI, and STA. LSTVs were classified according to the Castellvi classification. The vertebra below the last ribbearing vertebra was defined as L1. Free vertebrae were defined as any vertebra with a cranial and caudal adjacent complete disc space. In patients with 6 LV, measurement points at the superior endplates of L6 and S1 were additionally compared. A significance level of p < 0.05 was defined. Matching pairs were analyzed using the Wilcoxon rank sum test. Results: PI was significantly increased (p < 0.001), STA significantly decreased (p < 0.001), PR (p = 0.051) was not significantly different in patients with LSTV compared to the control population. Same results were observed for the subgroup with 4LV, it showed significantly increased PI (p < 0.021), reduction of STA (p < 0.011) and no significant differences in PR (p < 0.678). The same observations were obtained in the subgroup with 6LV at S1 PI (p = 0.010), STA (p = 0.004) and PR (p = 0.859) measurement point, but not at the L6 measurement point. Conclusion: Patients with LSTV, 4LV, and 6LV showed significant differences in PI and STA compared to a matched control group. PR did not show significant differences. When correcting spinal deformities, PI should be approximately equal to lumbar lordosis. Accordingly, LSTV should be confidently diagnosed during deformity surgery and the influence of LSTV on PI should be considered for sagittal profile restoration.

Carlos Mariano Nirino 1 1 

Introduction: We present a study carried out in lumbosacral spine surgeries regarding to blood debit during the surgical procedure, which is a very important factor to consider. There are many risk factors such as coagulopathies, anemia, morbid obesity and others. These help us to predict an excessive blood loss during it, but the position of the patient during the surgical procedure is vital; we consider this the main factor to keep in mind in the final result. Heavy bleeding obstructs the surgical field which has negative consequences on the final result, while coagulopathies predispose to postoperative hematomas that can cause infections or neurological compression injuries. In this paper we describe the results obtained in more than 400 randomized patients who were operated of their lumbosacral spine due to disc pathology, lysis, listhesis and hernia recurrences without the use of waxes, vasoconstrictors or fibrin and collagen sealants as hemostats to control bleeding with excellent results thanks to the excessive care of the surgical field and the correct patient position. All the procedures were performed between January 2017 and July 2021 in our department of Orthopedics and Traumatology in Santamarina Hospital of Monte Grande in Buenos Aires, Argentina. All the patients were treated by the same spinal team. Material and Methods: More than 400 randomized patients who were operated of their lumbosacral spine because of herniated discs, hernia recurrences, lysis and listhesis with fixations of up to 4 lumbosacral levels, were evaluated. Implants removal were also included. Morbidly obese patients and those who were operated by tumor pathology, medullar canal narrowness, infectious processes, fixations of more than 4 lumbosacral levels were excluded from this paper; also patients who underwent vertebral punctures for vertebroplasties, kyphoplasty or biopsies. The main care of the surgical field was carried out with a very meticulous hemostasis using the electro coagulation and using gauze pressure on the bleeding. In no case we used hemostatic agents to control the bleeding. Results: In more than 400 patients operated in our service the average bleeding was between 75 ml to 110 ml per treated level without weighing the discarded gauze during the entire procedure; the blood debit was very low for these types of surgeries considering that in no case we used wax or hemostatic to be able to control the bleeding during them but we rigorously took care of the patient position. No patient had postoperative complications due to intra surgical bleeding. Conclusion: After analyzing this large number of cases, we believe that the main objective during a lumbosacral spine surgery is to control the source of bleeding through the care and meticulous hemostasis with electro coagulation and gauze pressure but the correct position of the patient is essential. It is really not necessary and it makes no sense to use waxes or other hemostatics to control the intra surgical bleeding unless the patient requires it due to some risk factor. Introduction: Alterations in the collagen (COL) composition have been correlated to degenerative disc disease (DDD). Though 28 different types of COLs are present in humans, most of the literature is focused only on COL-1 and COL-2. The current study aimed to analyze the entire COL composition of human intervertebral disc (IVD) across fetal (developmental-FD), normal (healthy-ND), scoliotic (early degeneration-SD), herniated (degenerate-DH), and degenerated (DD) disc phenotypes using high-end proteomic technology. Methods: Forty Nucleus pulposus (NP) tissues segregated from five different disc phenotypes (eight each) under sterile conditions were snapfrozen in liquid nitrogen ((LN 2 ) -196⁰C) immediately before subjecting to proteomic and bioinformatic analysis. Results: Tandem mass spectrometric analysis revealed a total of 1050 proteins in fetal discs (FD); 1809 in ND; 1487 in SD; 1859 in DH and 1538 in the DD group. Out of 28 major collagens reported in the human body, this study identified 24 different Collagens with 34 subtypes in NP. Fibril forming collagens (COL-1,2 and 11A1) and Fibril associated collagens with interrupted triple helices (COL-9A1,12A1 and 14A1) were abundantly expressed in fetal discs representing their role in the development of NP. More importantly, Multiplexin (COL-15), a hybrid proteoglycan/ collagen molecule was found only in fetal discs. Downregulation of COL2A1 and upregulation of COL-10A1 was associated with degeneration. Conclusion: COL10 was identified as a novel biomarker for disc degeneration. Apart from COL-1 and 2, other important COLs (6, 9, 11, 12, 14 and 15) with anabolic potential abundantly expressed in fetal phenotype could be explored for tissue engineering and regenerative therapies for DDD. Introduction: Microbial etiology has been recently postulated as a cause of degenerative disc disease (DDD) leading to randomized trials of probiotics and antibiotics to treat chronic LBP. Recently the presence of disc microbiome in both healthy and diseased discs has been established by next-generation sequencing. However, the origin of disc microbiome has not been investigated. This study aims to trace the origin of human IVD microbiome by a comparative metagenomic approach. Methods: Lumbar discs from brain dead organ donor volunteers and patients undergoing microdiscectomy/spinal fusion were procured for this study. Normal discs (ND) group had 26 NP (Nucleus Pulposus) tissues and 17 EP (Cartilaginous Endplates) tissues excised from 10 MRI normal asymptomatic organ donor volunteers. Amplicon-sequencing was done to explore the microbial population in endplate (EP) tissues of human intervertebral disc (IVD) using NGS sequencing platform. A comparative analysis of the NP microbiome with that of EP microbiome was performed. Results: In total, four dominant phyla were detected in our samples: Proteobacteria, Firmicutes, Actinobacteriota and Bacteroidetes. Proteobacteria was identified as the dominant phyla in both NP and EP disc with 72% and 68% mean relative abundance respectively. Overall NP and EP had similar microbiome. A marginally higher relative abundance of Actinobacteria in NP and minor difference in relative abundance of Firmicutes were the only differences found between EP and NP. The predominant bacterial genus was again Pseudomonas in both EP and NP. However, the second predominant genus was Anoxybacillus in EP in contrast to Brevundimonas in NP. Higher abundance of bacteria in EP compared to NP measured by beta diversity was noted. Conclusion: Our study explores the route of microbial entry into intervertebral disc. We found that the microbiome of nucleus pulposus and end plates are similar suggesting that the endplate could be gateway for establishment of disc microbiome. Introduction: L5 nerve palsy is a well-known complication following reduction of high-grade spondylolisthesis. While several mechanisms for its occurrence have been proposed, the hypothesis of L5 nerve root strain or displacement secondary to mechanical reduction remains poorly studied. The aim of this cadaveric study is to determine changes in morphologic parameters of the L5 nerve root during simulated intraoperative reduction of high-grade spondylolisthesis. Material and Methods: In this cadaveric study we performed a standard posterior approach to the lumbosacral junction with lumbosacral or lumbopelvic screw fixation in eight fresh-frozen cadavers. Wide decompressions of the spinal canal and L5 nerve roots with complete facetectomies were accomplished with full exposure of the L5 nerve roots. A 100% translational slip was provoked by release of the iliolumbar ligaments and cutting the disc with the attached anterior longitudinal ligament. To evaluate the path of the L5 nerves during reduction maneuvers, metal bars were inserted bilaterally at the inferomedial aspects of the L5 pedicle at a distance of 10 mm from the midpoint of the L5 pedicle screws. Results: There was no measurable change in length of the L5 nerve roots after 50% and 100% reduction of spondylolisthesis. Conclusion: Mechanical strain or displacement during reduction is an unlikely cause of L5 nerve root injury. Further anatomical or physiological studies are necessary to explore alternative mechanisms of L5 nerve palsy in the setting of high-grade spondylolisthesis correction, and surgeons should favor extensive surgical decompression of the L5 nerve roots when feasible.

A206: An in vitro large animal model to investigate the effect of celecoxib on discogenic pain-associated sensory neuronal sensitization Introduction: Chronic low back pain (LBP) is the world leading cause of disability. The intervertebral disc (IVD) is known to be a prominent source of LBP. This study aims to investigate the communication between IVD cells and dorsal root ganglion (DRG) neurons using a large animal DRG cell culture model. The effect of celecoxib (cxb) on inflammatory IVD cell induced DRG sensitization was evaluated. Material and Methods: Human annulus fibrosus (hAF) cells were harvested from surgical IVD samples of 2 patients with traumatic disc injury. The hAF cell culture was stimulated with IL-1β (10 ng/mL). Celecoxib (1 or 10 µM) was added on day 2. Levels of prostaglandin E2 (PGE2), IL-8, IL-6 and NGF in the conditioned medium (CM) were measured using ELISA. CM was then added to primary neuron cell cultures harvested from bovine DRG. After 2 days of CM stimulation, the sensitization of the bovine DRG neurons was evaluated using calcium imaging. To characterize calcium signals in different subtypes of DRG neurons, immunofluorescent labelling of neurofilament 200 (NF200) and calcitonin gene-related peptide (CGRP) was performed. The immunofluorescent images were captured at the same field of calcium imaging. Both spontaneous and bradykinin (0.5 µM) induced calcium responses in CGRP+ and CGRP-DRG neurons were evaluated. For spontaneous calcium response, proportion of neurons with spontaneous response, calcium peak number and peak height were quantified; for bradykinin-induced calcium response, proportion of neurons responding to bradykinin, calcium peak duration and peak height were analyzed. DMSO application was used as carrier control when testing the effect of celecoxib. Results: IL-1ß stimulation significantly enhanced the release of PGE2, while this increase was suppressed completely in hAF cells treated with 10 µM celecoxib. Cytokine treatment of hAF cells also enhanced the release of IL-8 and IL-6, which was reduced by the addition of 10 µM cxb. Interestingly, IL-1ß stimulation of hAF cells did not show consistent influence on DRG neuronal calcium signals. However, spontaneous and bradykinin stimulated calcium response in CGRP+ neurons was decreased by celecoxib. Particularly, 1 µM celecoxib reduced the spontaneous peak height, proportion of CGRP+ neurons responding to bradykinin, bradykinin induced calcium peak duration and peak height. Likewise, 10 µM celecoxib reduced the spontaneous peak number which showed the same trend in the 2 hAF cell donors. Calcium signal in NF+ and CGRP-DRG neurons was not found to be on the patient perception and preferences within orthopaedics.

The purpose of our current study is to evaluate satisfaction and preferences of telemedicine from the perspective of patients within an orthopedic spine clinic. Material and Methods: A cross-sectional, anonymous survey was implemented as a prospective quality improvement initiative. The survey was sent to patients who had an in-office visit or a telemedicine visit with a provider in our orthopaedic spine clinic. The survey consisted of ten questions with a combination of multiple choice and yes/no questions. Four questions pertained to patient demographics including age range, race, gender, and proximity to the orthopaedic clinic. The remaining questions pertained to previous exposure to telemedicine, reasons patients would prefer telemedicine or in-office visits, for what types of visits patients would accept a telemedicine visit, and overall satisfaction with the visit. Univariate analysis was utilized to compare survey responses among groups.

Results: The survey was sent to 1129 patients and a total of 316 patients responded. Twenty-one percent of respondents had a telemedicine appointment. There was no difference in satisfaction among patients who had a telemedicine or inoffice visit (p = 0.288). Those that had telemedicine appointments were more likely to have had a previous experience with this type of visit (p = 0.004) and were more inclined to use it in the future (p < 0.001). Patients preferred telemedicine because of the ability to get earlier appointments (p < 0.001) and the convenience of the visits (p < 0.001). Patients preferred in-office visits because they received hands-on physical exams (p = 0.003) or imaging (p = 0.041). Conclusion: Telemedicine is a viable alternative to in-office appointments as spine patients had similar levels of patient satisfaction when compared to traditional, in-office appointments. Sooner appointments and convenience are attractive elements of telemedicine visits, while the desire for a physical examination and imagingoften needed during new patient appointmentsremain potential barriers to further adoption in this population. Introduction: Racial and financial disparities in healthcare remain an obstacle to providing quality patient care. Although previous studies have identified these disparities as being risk factors for postoperative complications, none have examined the preoperative variables that may contribute to these disparities. The purpose of this study is to explore preoperative factors that may contribute to racial disparities after spine surgery in Washington State and investigate whether race is an independent predictor of surgical outcomes. Material and Methods: The Washington State Surgical Clinical Outcomes Assessment Program (Spine COAP) database was queried for elective spine surgery performed between 2015 and 2020. Adult patients (>18 yo) undergoing four or fewer spinal levels procedures were included. Patient's race and ethnicity were selfreported by patients in the survey of Spine COAP into White-Non-Hispanic (WNH, 87.7%), White-Hispanic (WH, 3.4%), African-American (AA, 3%), Asian (AS, 2.7%), and other (2.1%) groups. Demographical, economic, preoperative, and postoperative variables were collected and analyzed. All variables were adjusted for a gender, patient age, and BMI prior to analysis. Results: A total of 43,288 spine surgical procedures were performed at seventeen hospitals in the Washington State. Minority groups were younger, compared to the WNH group. The AS group had higher proportion of females, and lower mean BMI compared to all the racial/ethnic groups. Minority groups, in particular the AA group, reported higher prevalence of diabetes, hypertension and current smoking status compared to the WNH group. Minority groups showed higher proportions of uninsured status and unemployment compared to the WNH group. Compared to the WNH group, minority groups were less likely to undergo conservative management and more likely to pursue pain management strategies prior to surgery (p < 0.05). The proportion of patients receiving opioid type of pain management were lower in the AS group compared to the other racial/Ethnic groups. Among the patients with diabetes, the minority groups were more likely to have pre-operative glucose management compared to the WNH patients (p < 0.05). Minority groups were significantly more likely to have hospital stay greater than 4 days and significantly less likely to be discharged home compared to the WNH group (p < 0.01). Postoperative complications were significantly higher in the WH and AA groups compared to the WNH group (p < 0.01). Conclusion: Our results indicate differences on the pre-operative management and postoperative outcomes among the racial/ethnic groups. This suggests that disparities among minority groups still exist in spinal surgery in Washington State. Introduction: Augmented reality head mounted display (AR-HMD) systems offer the potential for efficient, safe, and accurate instrumentation of the spine. Previous data from clinical studies have reported the accuracy of AR-HMD guided pedicle screw insertion to range from 98%-100% which is not inferior to the accuracy of robotic technology and superior to free-hand instrumentation techniques. Little is known about the cost of adding this technology to the operating room, particularly in comparison with parallelly evolving novel enabling technologies such as robotic assisted computer navigation. This study was performed to compare the cost of AR-HMD assisted spine surgery procedures related to robotic assisted spine procedures. Material and Methods: Retrospective analyses were performed for thirty-six consecutive patients who underwent pedicle screw placement guided by AR-HMD (n = 8) or a robotic technology (n = 28) from January 1, 2021, to July 1, 2021, in a single institution. Procedural costs for each procedure were calculated using regional data for diagnosis related group reimbursement codes (MS-DRG) for specific spinal procedures. Data was compared using independent t tests. Results: The weighted average diagnosis-related group reimbursement for spine procedures for a hospital system was calculated to be $105062+/-32940 for robotic-assisted procedures and $120533+/-54659 for AR-HMD assisted procedures. No statistical differences were noted between the two groups after an independent samples t test. Given the initial acquisition cost of $165K for sole commercially available AR-HMD system versus robotic platforms acquisition costs ranging $1.0 -$1.5 MIL; this may translate into immediate conservative savings for equitable safety and accuracy. Conclusion: AR-HMD has the potential to reduce the costs associated with the instrumentation of the spine via reduced enabling technology acquisition costs. Additional studies are needed to better delineate the economic differences among different enabling technologies and the costeffectiveness of AR-HMD assisted procedures relative to robotic assisted surgery. Introduction: TDABC has been suggested as the cost accounting arm of value-based care organizations by measuring costs across entire episodes of care. Lean methodology is a system used to understand pathways of care at a granular level, allowing for standardization. We hypothesize that combining these two methodologies can detect meaningful variation in a patient's episode of care for a single-level spinal fusion for degenerative pathology. Material and Methods: This is a retrospective cross-sectional study. We identified 157 consecutive patients who underwent singlelevel spinal fusion from October 10, 2013, to December 31, 2020, had inpatient stays from 1 to 3 days, were discharged to home, and had no readmission within 30 days. Time spent on activities by personnel was recorded in 15-minute increments and aggregated by role and stage of care (e.g. Pre-op, Intra-op and PACU). Patients were analyzed in three groups based on the duration of their in-hospital stay (1 day, 2 day and 3 day inpatient stays). Results: We used a cutoff of p < .001 to establish significance. The amount of time spent with patients did not differ during the preoperative (all ps < .30) or PACU (p = .03) phases for any of the personnel. As expected, time spent in the postoperative inpatient stay differed significant by discharge day for all roles (all ps < .0001). Time in surgery also differed significantly by discharge day for personnel roles that were always present for surgery (spine surgeon (p = .0003), anesthesiologist (p < .0001), circulator (p < .0001), and scrub tech (p < .0001)), but notfor any roles that were inconsistently present (e.g., surgery resident (p = .58). Conclusion: Our novel combination of lean methodology and TDABC can detect meaningful variability in an episode of care for single-level spinal fusion for degenerative pathology. Clinicians and administrators can use this combination to allocate costs appropriately. Outcomes included monthly rates of HCRU (15 categories) and monthly gross covered payments (2015 US dollars) overall, by HCRU category, and by whether they were spine versus non-spine-related. All available patients were utilized for analysis of HCRU. For analysis of payments, patients on non-capitated health plans providing accurate financial information were analyzed. Trends in payments and HCRU were plotted on a monthly basis pre-and post-surgery and assessed with regression models. Relationships with demographics, surgical factors, and comorbidities were assessed with repeated measures generalized estimating equations. Results: The final cohort included 22,182 patients (age 58 ± 13 years, 48.9% female). 27.1% of cases involved a fusion. Payments rose steeply 6 months prior to surgery, reaching a peak of $1,402 ($634, $2,827) 1 month prior to surgery. This was driven by an increase in radiology, office visits, PT, injections, prescription medications, ER encounters, and inpatient admissions. In the first month postoperatively, payments achieved levels lower than 5 months preoperatively. The median monthly payments continued to decline gradually over the 2 years postoperatively primarily due to a decrease in non-spine-related payments. Most HCRU categories remained elevated 2 years postoperatively relative to 2 years preoperatively; however, patients aged 4 years over the course of follow up. Patients with a fusion component to their surgeries had higher payments and HCRU preoperatively, and this did not resolve postoperatively. Variations in payments and HCRU were evident among plan types, with patients on employersponsored supplemental Medicare coverage utilizing more inpatient, ER, and inpatient rehabilitation & skilled nursing facilities. Patients on high-deductible plans had fewer payments and HCRU across all categories; however, we are unable to distinguish whether this was due to using fewer services or due to payment out of pocket. By 2 years postoperatively, 54% of patients had lower median monthly healthcare payments relative to 2 years preoperatively, and when looking at spine-related care, specifically, 68% had lower payments Conclusion: This is the first study to characterize time trends in direct healthcare payments and HCRU over an extended period preceding and following spine surgery. Despite patients aging 4 years over the course of longitudinal follow up, half lower overall median monthly healthcare payments and nearly 7 in 10 had lower spine-related healthcare payments 2 years postoperatively relative to 2 years preoperatively. Differences among plan types potentially highlight disparities in access to care and plan-related financial mediators of patients' healthcare resource utilization. Severe sagittal deformity was defined by a SVA > 9.5 cm and "match" was defined by meeting ideal age-adjusted alignment. Conclusion: Over a ten-year period, the rates of 3CO usage have declined, including in cases of severe deformity, with an increase in the usage of PJK prophylaxis. A better understanding of the utility of 3CO, along with a greater implementation of preventative measures, has led to a decrease in complications, PJF, PJK, and a significant improvement in patient reported outcome measures.

A218: Response to pre-operative steroid injections predicts surgical outcomes in patients undergoing fusion for isthmic spondylolisthesis

Joel Turtle 1 , Zane Randell 1 , Ryan Spiker 1 , Darrel Brodke 1 , and Nicholas Spina 1 1 Orthopaedic Surgery, University of Utah, Salt Lake City, USA Introduction: The decision to pursue operative intervention for patients with isthmic spondylolisthesis is complex. While steroid injections are a well-accepted therapeutic modality that may delay or obviate surgery, little is known regarding their ability to predict surgical outcomes. Here we examine whether response to pre-operative steroid injections can accurately predict an individual patient's response to surgical intervention. Materials and Methods: A retrospective cohort analysis was performed on adult patients undergoing primary posterolateral lumbar spine fusions for isthmic spondylolisthesis. Data were stratified into a control (no pre-operative injection) group and an injection group (received a pre-operative diagnostic and therapeutic injection). We collected demographic data, peri-injection VAS pain scores, PROMIS pain interference (PI) and physical function (PF) scores, ODI, and VAS pain (back and leg). Student t test was utilized to compare baseline group characteristics. Linear regression was performed comparing changes in peri-injection VAS pain scores and post-operative measures. Results: 73 patients were identified that did not receive a pre-operative injection and were included in the control group. 59 patients were included in the injection group. Of patients who received an injection, 73% had greater than 50% relief of their pre-injection VAS pain score. Linear regression revealed an interaction between the injection efficacy and post-operative pain relief as measured by VAS leg scores (p < 0.05). There was also an association between injection efficacy and back pain relief, though this did not achieve statistical significance (p = 0.068). Conclusions: Steroid injections are often utilized in the conservative therapeutic management of patients with lumbar spine disease. Here, we demonstrate the diagnostic value of steroid injections in predicting the response of patients with isthmic spondylolisthesis to lumbar fusion.

Introduction: One of the most frequent complications following adult spinal deformity (ASD) surgery is rod fracture (RF). Occurrence of RF often reflects pseudarthrosis and may result in pain, disability, loss of deformity correction and need for revision surgery. Previous reports of RF in ASD have been limited by heterogeneous patient populations, limited follow-up rates, and relatively shortterm follow-up. However, since the majority of RFs present > 2 yrs after surgery, true incidence and revision rates remain unclear. Material and Methods: Patient records were obtained from the ASLS-1 database, an NIHsponsored multicenter prospective study. Inclusion criteria were: primary (no prior spine fusion) instrumented fusions of ≥ 7 levels that included the sacrum/pelvis in patients aged 40-80 years with ASLS (Cobb ≥ 30 o and Oswestry Disability Index ≥ 20 or Scoliosis Research Society-22 ≤ 4.0 in pain, function and/or self-image). The primary outcomes of interest were to better assess the rate of, and risk factors for RF and revision surgery. Results: Inclusion criteria were met by 160 patients (141 women) with a mean age of 61.4 ± 8.8 yrs. At a mean follow-up of 5.0 ± 2 yrs (range 0.1-9.2 yrs) we encountered 93 RFs in 62 (37.8%) patients, including 41 that were unilateral and 21 that were bilateral at presentation. Baseline radiographic, clinical and demographic characteristics were similar among patients with and without RF. Mean time to RF was 3.4 ± 2.2 yrs (range 0.8-8.7 yrs), 73% occurred >2 yr following surgery and RF incidence at 2 and 4 yrs after surgery was 11% and 24%, respectively. The most common levels for RF were L3-L4 (31.2%), L4-L5 (28%), and L5-S1 (21.5%). Greater postoperative PI-LL missmatch and PT were observed in the RF group (p < 0.05). In Cox regression models only diabetes (p = 0.029, OR = 3.27, 95% CI = 1.12-9.5) and titanium cages (p = 0.036, OR 2.56, 95% CI 1.06-6.16) were associated with RF. At last follow-up, patients with RF had worse PROs in terms of SRS subscore, SRS pain and VAS back pain (p < 0.05). Within 2 yrs after RF, 66% of patients underwent revision surgery and overall a total of 38 patients (61% of all RF) underwent revision surgery. 13 (34%) of the 38 revised patients later developed another RF, with 4 of the fractures at the same level of the previous RF and 11 at a different level. Bilateral RF was predictive of revision surgery (HR = 3.52, 95% CI = 1.8-6.9, p = 0.0002), while patients with unilateral non-displaced RF were less likely to require revision (HR = 0.39, 95% CI = 0.18-0.84, p = 0.016). Conclusion: This study provides benchmarks for RF rates following ASLS surgery, and although instrumented fusions for ASLS offer substantial improvement in patient-reported outcomes, RF remains a significant challenge that can affect patients long after surgery. These findings demonstrate that longer-term follow-up is warranted for these patients and that careful preoperative planning and better preventive strategies are needed to improve fusion and reduce RF incidence. Patients undergoing ASD surgery were stratified into 3 cohorts: non-anemia (hematocrit > 36% for women, >39% for men), mild anemia (hematocrit 33%-36% for women, 33%-39% for men), and moderate to severe anemia (hematocrit < 33% for both women and men), based on World Health Organization definitions. In this analysis, 30-day wound, cardiac, pulmonary, renal, and thromboembolic complications, as well as sepsis, mortality, postoperative transfusions, extended length of stay, and reoperation were assessed. Bivariate analyses and multivariable logistic regression were performed. Results: Of 2,173 total patients undergoing ASD surgery, 1,694 (70%) did not have anemia, 307 (13%) had mild anemia, and 172 (7%) had moderate or severe anemia. Following adjustment, patients with mild anemia were more likely to have postoperative blood transfusion (odds ratio [OR] 1.80, p < .001) and extended length of stay (OR 1.43, p < .001). Patients with moderate to severe anemia were at increased risk of organ space infection (OR 3.27, p = .028), death (OR 13.15, p = .001), postoperative blood transfusion (OR 2.81, p < .001), and extended length of stay (OR 3.02, p < .001).

Conclusion: From mild anemia to moderate to severe anemia, there was a stepwise and approximately 2-fold increase in the odds ratio of postoperative transfusion and length of stay. Moderate to severe anemia is associated with increased odds of death and organ space infection. Patients with moderate to severe anemia should be medically optimized before they undergo ASD surgery. . The median EQ-5D score was 0.74 (range 0.19 to 1.0), which compared favorably to patients with hip/knee osteoarthritis (EQ-5D 0.63) and approaches scores for patients with DM (0.78) and HTN (0.81). In terms of ADLs, 10 (56%) patients exercised regularly a mean 4.5 days/week. 11 (61%) could do light aerobic activity (e.g. stationary bike). 10 (55%) were able to play with children as desired. 8 (44%) hiked, and 2 (11%) drove independently. 11 (61%) could tolerate short air-travel comfortably. Of the patients who could toilet and perform basic hygiene preoperatively, 94% (16 of 17) were able to do so postoperatively. Conclusion: Patients requiring C2-sacrum instrumented fusion have a significant improvement in SRS (p = 0.001) and ODI scores (p = 0.013). 2.4 years after their C2sacrum fusion, 61% could do light aerobic activity. A median EQ-5D of 0.74 suggests that this population fares better than those with degenerative hip/knee arthritis and similarly to those with common chronic conditions like DM and HTN.

A222: Catastrophic acute failure of pelvic fixation in adult spinal deformity requiring revision surgery: a multi-center review of incidence, failure mechanisms, and risk factors

Introduction: There are few prior reports of acute failure of pelvic instrumentation in spinal deformity surgery. Material and Methods: 13 academic medical centers performed a retrospective review of 18 month's of consecutive adult spinal fusions extending 3 or more levels, and which included new pelvic screws at the time of surgery. Acute pelvic fixation failure was defined as occurring within 6 months of the index surgery and requiring surgical revision. Results: Failure occurred in 37 of 779 cases (5%), and consisted of either slippage of the rods or displacement of the set screws from the screw tulip head (17 cases), screw shaft fracture (9 cases), screw loosening (9 cases), and/or resultant kyphotic fracture of the sacrum (6 cases). Revision strategies involved new pelvic fixation, and/or multiple rod constructs. 6 patients (16%) revised with less than 4 rods to the pelvis sustained a second acute failure, but no secondary failures occurred when at least 4 rods were used. In the univariate analysis, the magnitude of surgical correction was higher in the failure cohort (higher pre-op T1PA, presence of a 3 column osteotomy, p < 0.05). Uncorrected post-operative deformity increased failure risk (PI-LL mismatch greater than 10, higher post-op T1PA, p < 0.05). Use of pelvic screws less than 8.5 mm in diameter also increased the likelihood of failure (p < 0.05). In the multivariate analysis, a larger pre-operative global deformity as measured by T1-Pelvic Angle was associated with failure, males were more likely to fail than females, and there was a strong association with implant manufacturer (p < 0.05). Anterior column support with an L5-S1 interbody was protective against failure (p < 0.05). Conclusion: Acute catastrophic failures involved large magnitude surgical corrections and likely resulted from high mechanical strain on the pelvic instrumentation. Patients with large corrections may benefit from anterior structural support placed at the most caudal motion segment and multiple rods connecting to more than 2 pelvic fixation points. If failure occurs, salvage with a minimum of 4 rods and 4 pelvic fixation points can be successful. Introduction: Little published data currently exist regarding the potential relationships between spondylolisthesis and clinical outcomes following total knee arthroplasty (TKA). Recently a correlation between Mismatch Deformity (MD) and poor TKA outcomes was noted in the literature. We hypothesize that pre-existing spondylolisthesis will similarly result in decreased functional outcomes after TKA. Material and Methods: This retrospective cohort comparison of 933 TKAs was performed between January 2017-2020. TKAs were excluded if they were not performed for primary osteoarthritis (OA) or if preoperative lumbar radiographs were unavailable/inadequate to measure the degree of spondylolisthesis. 95 TKAs were subsequently available for inclusion and divided into two groups: those with spondylolisthesis and those without. Within the spondylolisthesis cohort, pelvic incidence (PI) and lumbar lordosis (LL) were calculated on lateral radiographs to determine the difference (PI-LL). Radiographs with PI-LL > 10°were then categorized as having mismatch deformity (MD). The following clinical outcomes were compared between the groups: need for manipulation under anesthesia (MUA), total postoperative arc of motion (AOM) both pre-MUA or post-MUA/revision, incidence of flexion contracture, and a need for later revision. Results: 49 TKAs met the spondylolisthesis criteria, while 44 did not have spondylolisthesis. There were no significant differences in gender, body-mass-index (BMI), preoperative knee range of motion (ROM), preoperative AOM, or opiate use between the groups. TKAs with spondylolisthesis and concomitant MD were more likely to have MUA (p = 0.016), ROM < 0-120 (p < 0.014), and a decreased AOM (p < 0.02) without interventions. The odds of concomitant spondylolisthesis for those with MD was 2.8 when compared to the control (CI 1.2-6.5, p = 0.02). The incidence of Mismatch deformity was higher in those with any grade of spondylolisthesis. Lastly, 9.7 degrees more sagittal imbalance noted on average compared to those without spondylolisthesis (CI 4.6-14.8, p = 0.0003). Conclusion: Introduction: Vacuum discs, the collection of gas within the intervertebral disc space, are believed to represent end-stage disc degeneration. However, relationships between vacuum discs and pain severity are unknown. The goals of this study are to identify the prevalence of vacuum discs in patients with lumbar spinal deformities and determine whether there is an association between the presence of these discs and low back or leg pain severity. Material and Methods: Patients evaluated at a single institution from 2013-2019 were included if they were aged > 18 years, had a CT including the T12-S1 discs, and had a diagnosis of scoliosis, kyphosis, or flat back. Patients with prior thoracolumbar fusion or a history of spinal malignancy or inflammatory arthritis were excluded. Patient reported outcomes included numeric pain rating scales (NPRS) for back and leg pain, and the Oswestry Disability Index (ODI). CTs were evaluated for the presence and size of vacuum discs from T12-S1. Univariate relationships between pain and the presence of vacuum discs (chi-squared/Fisher's exact, Mann-Whitney U), number of levels with vacuum discs (Mann-Whitney U, linear regression), and maximum vacuum size (Fisher's exact & Kruskal Wallis) were first assessed. Subsequently, multivariable GEEs were constructed to relate the presence of vacuum discs to back pain, leg pain and ODI. Analyses were performed with SAS v9.4 with a two-sided α = 0.05. Results: The final cohort included 130 patients [62.3% female, median age = 71.8 years (interquartile range (IQR)) = 65.5, 76.6]. 95.4% of patients had a vacuum in ≥ 1 disc, and 61.6% had a vacuum in ≥ 4 levels. The most common level was L3-L4 (72.9% of patients). Vacuum discs were associated with older age, both when considered overall (p < 0.006), or by individual level (p < 0.037 for each). Older age was associated with a greater number of vacuum discs, with age increasing 3.5 (2.5, 4.5) years per additional vacuum (p < 0.001). Older age was also associated with increased vacuum size (p < 0.001). Patients with vacuum size > 50% had a higher median age [72.9 (IQR: 66.8, 77.5) years] than those with a vacuum size < 50% [65.9 (IQR: 62.4, 67.4), p < 0.001], and those with no vacuum [43.9 (IQR: 21.0, 70.8), p < 0.011]. Males were more likely to have more levels with vacuum discs [median (IQR) males = 5 (3, 5) , females = 4 (3, 5); p = 0.031]. Males also trended towards larger vacuum discs (p = 0.089). Considering all levels together, vacuum discs at L4-L5 were associated with higher NPRS back pain [+1.5 (0.2, 2.7), p = 0.023]. Vacuum discs at L5-S1 were associated with greater leg pain [+2.1 (0.4, 3.9), p = 0.016]. There was also a trend towards higher ODI (greater disability) with a vacuum at L5-S1 [+5.9, (-0.6, 12.4) p = 0.071]. The number of vacuum levels and vacuum size were not associated with pain or ODI. Conclusion: The presence, number, and severity of vacuum discs increased with age, and males had more vacuum discs than females. Vacuum discs were associated with increased pain and potentially increased disability at L4-L5 and L5-S1. These findings are pertinent to surgical planning in spinal deformity, as vacuum discs at these levels may be associated with more severe symptoms.

A225: Outcomes of operative treatment for adult spinal deformity: a prospective, multicenter assessment with minimum 3-year follow-up Introduction: Although operative treatment for adult spinal deformity (ASD) has the potential to significantly improve health-related quality of life (HRQL), current literature has primarily focused on two-year outcomes. Given the invasiveness, associated complications, and cost of these procedures, assessment of longer-term durability of outcomes is important. The aim of this study was to assess minimum 3year patient-reported outcomes (PROs) and complications associated with ASD surgery. Material and Methods: This is a multicenter, prospective cohort study of consecutive ASD patients (age > 18 years) electing for operative treatment. Patients were assessed at baseline and at standardized followup intervals and through direct mailing to collect clinical data and outcomes measures. HRQL was assessed using the Oswestry Disability Index (ODI), Scoliosis Research Society-22r (SRS), the mental and physical components scores (MCS/ PCS) of the Short Form-36 (SF-36), and the numeric rating scale (NRS) for back and leg pain. Complications were classified as perioperative (≤ 90 days from surgery), delayed (90 days to 2 years after surgery), and long-term (≥2 years after surgery). Analyses focused on patients with minimum 3year follow-up. Results: Of 569 ASD patients who met the inclusion criteria, the 427 (75.0%) who achieved minimum 3year follow-up (mean = 4.1 years, SD = 1.1 years, range = 3 to 9.6 years) had a mean age of 60.8 years (SD = 14.3) and 74.6% were women. Operative treatment included a posterior approach in 426 (99%), with a mean of 11.6 (SD = 3.9) fusion levels. Anterior and lateral lumbar interbody fusion was performed in 35 (8.2%) and 19 (4.4%) patients, respectively, and 89 (20.8%) had a three-column osteotomy. All PROs assessed demonstrated significant improvement from baseline to last follow-up, including ODI (45.4 to 30.5), PCS (31.0 to 38.5), MCS 45.3 to 50.6), SRS Total Score (2.7 to 3.6), SRS Activity (2.8 to 3.5), SRS pain (2.3 to 3.4), SRS Appearance (2.4 to 3.5), SRS Mental (3.4 to 3.7), SRS Satisfaction (2.7 to 4.1), back pain NRS (7.1 to 3.8), and leg pain NRS (4.8 to 3.0) (all p < 0.001). The percentages of patients reaching at least 1 minimum clinically important difference improvement from baseline to last follow-up was 48.6% for ODI, 59.4% for PCS, 67.4% for SRS Pain, 69.0% for SRS Appearance, 64.3% for SRS Activity, 41.7% for SRS Mental, 79.6% for back pain NRS, and 49.1% for leg pain NRS. Overall, 277 (64.9%) patients had one or more complication, including 185 (43.3%) perioperative, 118 (27.6%) delayed, and 56 (13.1%) longterm. Notably, compared with the patients who achieved minimum 3-year follow-up, the 142 patients who did not achieve this follow-up were similar based on demographics, baseline deformity, and baseline PROs and had similar rates and types of complications as of last follow-up. Conclusion: This multicenter, prospective analysis demonstrates that operative treatment for ASD provides significant improvement in HRQL at minimum 3-year (mean 4.1-year) follow-up. These findings suggest that the benefits of surgical treatment for ASD remain durable at longer-term follow-up than provided by previous reports. Collectively, these findings should prove useful for patient counseling, future cost-effectiveness assessments, and ongoing efforts to improve the safety of patient care. Introduction: Spinal navigation allows for accurate pedicle screw placement, even in anatomically challenging cases. However, the required three-dimensional (3D) imaging and navigational equipment is often heavy, cumbersome, and expensive. To facilitate low-cost and easy to use 3D navigation without disrupting the routine two-dimensional (2D) fluoroscopy-guided workflow, we developed a new 2D3D registration algorithm for potential use in spine surgery. In this study, we assessed the accuracy of the new registration algorithm, and explored anatomical and radiologic parameters affecting the registration accuracy. Material and Methods: The 2D3D registration algorithm was based on a non-invasive skin marker model and required imaging data (a pre-existing CT scan (3D) and two angulated fluoroscopic images (2D)) to register the position of a vertebra in 3D. The registration process did not require the fluoroscopic imaging device to be calibrated or tracked. The algorithm registered five adjacent vertebrae and was tested in the thoracic and lumbar spine from three human cadaveric specimens. The registration accuracy was calculated for each registered vertebra and was measured through the target registration error (TRE) in millimeters: a low TRE indicated a high accuracy. We used multivariable analysis to identify parameters that independently affected the algorithm's accuracy such as the angulation between the two fluoroscopic images (between 40 and 90 degrees), the detectorskin distance, the number of skin markers applied, and waist circumference. Results: The algorithm registered 780 vertebrae with a median TRE of 0.51 mm [interquartile range 0.32-0.73 mm] and a maximum TRE of 2.06 mm. The TRE was most affected by the angulation between the two fluoroscopic images (p < 0.001): larger angulations resulted in higher accuracy. The algorithm was more accurate in thoracic vertebrae (p = 0.004) and in the specimen with the smallest waist circumference (p = 0.003). The algorithm registered all five adjacent vertebrae with similar accuracy. Conclusion: We studied the accuracy of a new 2D3D registration algorithm based on a non-invasive skin marker model. The algorithm registered five adjacent vertebrae with similar accuracy in the thoracic and lumbar spine and showed a maximum target registration error of approximately two millimeters. To further evaluate its potential for navigated spine surgery, the algorithm may now be integrated into a complete navigation system.

A227: Bony bridging at the interface using Titanium-nanocoated PEEK cages: a radiological observation Karel Willems 1 1 Orthopedics, AZ Delta, Roeselare, Belgium Introduction: Posterior interbody fusion is frequently used to treat degenerative low back pain. There is a strong correlation between the grade of bony fusion and the clinical results. The observation of faster and more intense bone at the boneimplant interface is a crucial area to achieve definite fusion.

PEEK is an inert material that does not promote bony ingrowth. Several types of coating have been used to combine the mechanical characteristics of PEEK with a bioactive layer. Titanium coating at low temperature and high energy results in a coating with a thickness in the nano range. This coating is a dense, non-porous metallic layer on the surface of the implant, not harming the micro surface topography, the radiolucency and the elasticity of the implant. An animal study was previously performed to validate this concept. Long bones of sheep (femur and tibia) were implanted with coated and uncoated dowels, comparing the osseointegration of uncoated PEEK dowels to PEEK dowels coated with CaP or with Titanium. Histology showed direct bone implant contact with the Ti-nanocoated and the CaP-nanocoated dowels. The surface was covered with bone trabeculae, whereas on the sections of the uncoated control PEEK dowel a fibrotic layer was seen between the dowel and the surrounding bone tissue. In this clinical randomized controlled, multicentric study we examined the radiological outcome of posterior lumbar interbody fusion (PLIF) for implantations of PEEK cages, with Ti coating (TSC) or CaP coating (osteoCon) or uncoated (reCreo) cages. Material and Methods: Patients between 18 and 75 years with chronic mechanical low back pain were included in a blinded randomized radiological study. The primary radiological outcome was the implant stability and fusion status assessed with X-ray, standing A/P and lateral radiographs and CT-scan at 6 and 12 months. The CT-scans were evaluated by an independent experienced spine radiologist, blinded to the used spacer. The area of interest was the interface between the implanted cage and the endplates of the fusion level. An independent radiologist scored from probable pseudarthrosis to definite fusion. Results: At 6 months, we observed significantly more halo around the cage implant in the group treated with uncoated cages. In the Ti-nanocoated cohort, there was no radiological evidence for halo formation (e. g. due to Ti nanocoating debris). One year after the surgery, 65.6% of patients with uncoated PEEK cages achieved definite fusion. Significantly more patients with nanocoated PEEK cages achieved definite fusion: 93.9% for Ti nanocoating (p = 0.0034) and 88.0% for CaP nanocoating (p = 0.032). Conclusion: Titanium-nanocoated PEEK cages with an optimized topography accelerate the osseointegration process, effectively increasing the bony bridging. The radiological results in this clinical trial corroborate the results of the animal study: there is faster and more bone formation at the interface between the cage implant and endplates. This is a significant predictor of a positive longterm clinical outcome when using the Ti-nanocoated PEEK cages.

A228: Outcomes of 2-levels versus 3-or4-levels anterior cervical discectomy and fusion using titanium cage with Introduction: The titanium cage with nano-surface technology was recently FDA approved. It utilizes nanotechnology due to its ability to elicit an endogenous biochemical and cellular response which can lead to a better fusion. We aimed to analyze the differences in clinical and radiographic outcomes between multilevel anterior cervical discectomy and fusion (ACDF) operations using the new titanium cages with nano-surface technology. Material and Methods: A retrospective chart review of data for patients who underwent multi-level (two, three and four level) ACDFs using titanium cages with nano-surface technology for degenerative cervical spine disease was conducted in 4 centers. Ninety-two patients (two-level (n = 49) and three/four-levels (n = 43)) who met our inclusion and exclusion criteria were compared in terms of clinical and radiographic outcomes. Results: The mean follow-up duration was 20.3 ± 16.6 months. At 3 months, the fusion rate was 85.7% in the 2-levels ACDF versus 71.8% in the 3-or-4 levels ACDF (p = 0.1). At 6 months, the fusion rate increased to 97.9% in the 2-levels ACDF versus 95.3% in the 3-or-4 levels ACDF (p = 0.5). Furthermore, there was no significant difference in terms of PROMS (neck and arm Visual analogue scale [VAS] and neck disability index [NDI]). All patients were discharged home with no significant difference in the postoperative complications, reoperation rate, and 90-days readmission. None of the patients of both groups required posterior supplemental fusion. Conclusion: Three and four level ACDFs using titanium cages with nano-surface technology are shown to be radiographically and clinically equivalent to the two-level ACDF. Furthermore, the use of this technology lead to better fusion rates with no requirement of posterior supplemental fusions.

A229: Chest tube optimization following anterior vertebral body tethering for idiopathic scoliosis chest tube optimization following anterior vertebral body tethering for idiopathic scoliosis Leslie James 1 , Zoe Norris 2 , Alexandra Agris 1 , Ashley McCormack 1 , Brooke O'Connell 2 , Constance Maglaras 2 , Michael Zervos 1 , Juan Carlos Rodriguez-Olaverri 2 , and Costas Bizekis 1 Introduction: Anterior Vertebral Body Tethering (AVBT) warrants an anterior approach to the spine to achieve surgical correction using a number of approaches. To facilitate this exposure, the lungs are selectively ventilated and the convex lung is allowed to collapse. Thereby increasing the risk of pulmonary complications. Given that chest tubes are routinely used to reduce the incidence of postop pulmonary complications, best practices are needed to define their management in AVBT of Idiopathic Scoliosis (IS) patients. Material and Methods: Institutional Review Board approval was attained; charts for 56 consecutive IS patients who underwent AVBT with 30-day follow-up were reviewed from 2020-2021.We collected pertinent preoperative, intraoperative, and short-interval post-operative data. Statistical analysis was performed via t-tests, significant set at p < 0.05. Results: Included 56 patients treated with AVBT for IS: 46 females (82.14%), age 14.2 ± 2.4 years, and BMI 20.7 ± 2.7, and an average of 8.6 ± 2.1 levels were treated. 17 (30.4%) were for bilateral curves and 39 (69.6%) for single curves. 3 patients (5.4%) who underwent revision procedures for existing AVBT constructs. After tethering, a 24-Fr chest tube was positioned posteriorly and superiorly in each corrected side and secured with heavy braided silk suture. 73 chest tubes were analyzed, with average chest tube duration 2.2 ± 1.9 days, and average length of stay (LOS) 5.1 ± 1.2 days. There was a difference in mean duration of right-sided versus left-sided chest tubes (2.5 vs. 1.9 days, p = 0.009) and patients who underwent thoracic approach to tethering had a longer chest tube duration compared to patients who had a thoracolumbar approach (2.5 vs. 1.9 days, p = 0.027). Average chest tube output 8 hours prior to removal was 68.7 ± 47.8 mL (IQR 20.9-116.5). There was no difference in average LOS for patients who underwent correction of a single curve versus a double curve nor was there a difference in average LOS or chest tube duration for revisions compared to the entire cohort. For the entire cohort, the rate of 30-day readmission was 3.6% (n = 2). One patient was admitted for dehydration and the other was admitted for postoperative chest and difficulty breathing; both patients had negative workup for any intrathoracic complications. Conclusion: This early review of our AVBT experience demonstrates the importance of finding a balance between preventing pulmonary complications with chest tube placement while also minimizing the duration of chest tubes. Risk factors for longer chest tube duration include right-sided surgeries and a thoracic approach, which may be a consequence of greater lung manipulation intraoperatively. We believe that chest tube duration can be minimized with early and aggressive physical therapy and frequent use of incentive spirometry. We found that removal of a chest tube with less than 100 mL of output over the preceding 8 hours was safe, as none of our patients required chest tube reinsertion.

Introduction: Radiolucent carbon-fiber reinforced PEEK (CFRP) implant materials have helped improve oncological follow-up and radiation therapy planning in spinal oncology. However, little is known about the performance of CFRP pedicle screws in the context of real-time spinal navigation with different intraoperative imaging technologies. Here, we investigated different intraoperative imaging modalities for navigated instrumentation and blinded assessment of radiolucent, CFRP pedicle screws across the thoraco-lumbar spine. Material and Methods: In this retrospective, single-center cohort study, 33 patients with spinal tumors underwent posterior CFRP instrumentation with intraoperative CT (iCT), robotic cone-beam CT (rCBCT) or cone-beam CT (CBCT) spinal navigation. Demographic, clinical and outcome data was assessed and 4 blinded observers with different levels of experience (PGY1 resident, PGY6 resident and 2 spine surgeons) rated the perceived image quality, screw assess ability and placement accuracy of CFRP pedicle screws. Interobserver reliability was determined with Fleiss`Kappa analysis. Results: Between 2018 and 2021, 243 CFRP pedicle screws were implanted (iCT:93, rCBCT: 99, CBCT: 51), of which 13 screws were non-assessable (iCT: 1, rCBCT: 9, CBCT: 3; *p = 0.0475; iCT vs. rCBCT). Accuracy was highest using iCT (74%), followed by rCBCT (69%) and CBCT (49%) imaging (*p = 0.0064; iCT vs. CBCT and rCBCT vs. CBCT). Experts as well as residents perceived iCT image quality of the control scan following screw implantation highest. Although inter-observer agreement for CFRP screw accuracy was lowest for CBCT imaging and between resident observers, relevant pedicle breaches (>2 mm) of radiolucent CFRP screws were identified with substantial agreement by each imaging modality and all users, regardless of their experience. Conclusion: Navigation accuracy for CFRP pedicle screws was considerably lower than expected from accuracy rates reported for titanium implants and assess ability of radiolucent CFRP implants as well as inter-observer reliability depended more on the perceived imaging quality than on the users' experience in rating pedicle screw breaches. Overall, our findings challenge the reliability of real-time spinal navigation and for the first time suggest that true (fan-beam) CT imaging may be best suited for robust assessment of radiolucent CFRP screws. Introduction: Magnetically controlled growing rods (MCGRs) are increasingly used in the treatment of early onset scoliosis (EOS). Few studies have reported whether desired lengthening can reliably be achieved, or if large tissue depths or pre-operative flexibility of curve affect lengthening. In this clinical study of EOS patients, it was hypothesized that increases in rod length would equal programmed increases, patients with greater flexibility pre-operatively would have improved successful lengthening, and larger tissue depths would decrease lengthening success. Material and Methods: A retrospective chart review was conducted on EOS patients with single and dual MCGRs placed 4/2014-12/2020 and distracted at a single institution. Rod distraction was measured at each visit using ultrasound. Pre-operative major curve at time of implantation and pre-operative traction curve measurements were used to determine flexibility. Differences between programmed and actual distraction for each patient were determined by 2-tailed t-tests. Regression and correlation were used to determine the relationship between tissue depth, length increases, and changes in pre-operative flexibility.

Results: Fifty-two patients were included, 24 males, 28 females, age 7.7 (± 2.5) years, with major curves measuring 60 (± 11.5) degrees and traction curves measuring 39 (± 11.4) degrees (40.3% ± 13.4% change) pre-operatively. Total lengthening was inversely proportional to tissue depth at 1 year (r 2 = 0.36, p = 0.011) and overall (r 2 =. 419, p = 0.002); percent intended lengthening was also inversely proportional to tissue depth at 1 year and overall (r 2 = 0.49, p < 0.001 and r 2 = 0.491, p < 0.001 respectively). Percent of first and year 1 intended lengthening were positively correlated to percent change in major curve with traction (r 2 = 0.393, p = 0.004 and r 2 = 0.374, p = 0.007 respectively) as well as with total overall lengthening and percent change in curve with traction (r 2 = 0.305, p = 0.03). Conclusion: Magnetically controlled growing rods are effective and increasingly utilized in management of early onset scoliosis. This research has found there is significant correlation between successful programmed distraction and tissue depth. Additionally pre-operative flexibility of curve measured by percent change in major curve with traction is significantly correlated to intended lengthening. Clinicians can utilize this information when planning management of early onset scoliosis and ensure proper patient and caregiver education on goals of rod placement.

Introduction: Single level discectomy (SLD) is one of the most commonly performed spinal surgery procedures. Two key drivers of their cost-of-care are duration of surgery (DOS) and postoperative length of stay (LOS). The ability to preoperatively predict SLD DOS and LOS therefore has substantial implications for both hospital and healthcare system finances, scheduling and resource allocation. As such, the goal of this study was to predict DOS and LOS for SLD using machine learning models (MLMs) constructed on preoperative factors using a large North American database. Material and Methods: The American College of Surgeons (ACS) National Surgical and Quality Improvement (NSQIP) database was queried for SLD procedures from 2014-2019.The dataset was split in a 60/20/20 ratio of training/validation/ testing based on year. Various MLMs (traditional regression models, tree-based models, and multilayer perceptron neural networks) were used and evaluated according to 1) mean squared error (MSE), 2) buffer accuracy (the number of times the predicted target was within a predesignated buffer), and 3) classification accuracy (the number of times the correct class was predicted by the models). The results of the models were compared to a mean regressor model. Results: A total of 11,525 patients were included in this study. During validation, the neural network model (NNM) had the best MSEs for DOS (0.99) and LOS (0.67). During testing, the NNM had the best MSEs for DOS (0.89) and LOS (0.65). The NNM yielded the best 30-minute buffer accuracy for DOS (70.9%) and ≤ 120 min, >120 min classification accuracy (86.8%). The NNM had the best 1-day buffer accuracy for LOS (84.5%) and ≤ 2 days, > 2 days classification accuracy (94.6%). All models were more accurate than the mean regressors for both DOS and LOS predictions. Conclusion: We successfully demonstrated that MLMs can be used to accurately predict the DOS and LOS of SLD based on preoperative factors. This big-data application has significant practical implications with respect to surgical scheduling and inpatient bedflow, as well as major implications for both private and publicly funded healthcare systems. Incorporating this artificial intelligence technique in real-time hospital operations would be enhanced by including institution-specific operational factors such as surgical team and OR workflow.

A233: The safety and efficacy of computer-assisted virtual surgical planning based on computed tomography data in severe spinal deformity patients Yiqi Zhang 1 , Yong Hai 1 , Jingwei Liu 1 , and Junrui Jonathan Hai 2 radiological spine parameters, accuracy of pedicle screw insertion and surgical complications were documented and analyzed, and screw placement was evaluated according to Gertzbein-Robbins classification in grades A to D, while A and B were defined as satisfactory, and C to D were unsatisfactory. Results: The average preoperative main curve in CAVSP Group and Non-CAVSP Group were 118.50°± 19.96°and 116.76°± 19.25°, and these were corrected to an average of 55.00°± 10.03°and 55.71°± 7.04°postoperative, respectively, with no significant difference. The accuracy of satisfactory pedicle screws inserting in CAVSP Group and Non-CAVSP Group were 96.43% and 84.55% (p < 0.05), and the incidence of neurologic deficits severally were 0% and 14.2%. Conclusion: Computer-assisted virtual surgical planning in severe spinal deformity patients can gain a safer and more accurate instruments fixation, with this technique, spine surgeons can make a detailed and personalized surgical plan preoperatively to reduce neurologic complications during the operation. Previously published studies on SPS have shown that it is a safe alternative approach to traditional anterior or lateral interbody approach with prone fixation. The role of direct decompression in SPS surgery has been less widely examined, and there is a paucity of data on outcomes and complications related to performing a direct decompression without repositioning. Material and Methods: This was a retrospective analysis of 92 patients ≥18 years with radiculopathy or neurogenic claudication undergoing lateral or prone ALIF, and LLIF with bilateral PSF in the same position, with minimum 1 year follow up. Of the 92 patients, 17 (18%) underwent direct decompression without repositioning. Outcomes assessed included neurological deficits, perioperative complications, unplanned reoperation, and resolution of neurologic symptoms. Results: 92 SPS patients were included: direct decompression (n = 17, Age: 62.1 ± 11.7, BMI: 29.8 ± 5.1) and indirect decompression (n = 75, Age: 59.9 ± 9.5, BMI: 30.6 ± 5.8). There was no difference in patient characteristics between the groups. There was a higher rate of neurologic complications in the direct decompression group (n = 8, 47.1%) compared to those that did not receive a direct decompress (n = 10, 13.3%). Specifically, neurologic complications included new onset motor weakness postoperatively, thigh dysesthesias, and hip flexor weakness. Within the direct decompression cohort, patients that underwent Prone LLIF in the had a lower rate of sustaining a neurological complication (0% vs. 61.5%, p = 0.031). At final follow-up, there was no difference in rate of resolution of preoperative symptoms of radiculopathy or neurogenic claudication between the two groups. Conclusion: The rate of neurologic complications is higher in patients for whom a direct decompression was performed during single position surgery, with no differences seen in rate and extent of resolution of preoperative symptoms compared with indirect decompression alone. Introduction: Malignant recurrent/ residual tumors involving the vertebral body and ribs heads spanning across multiple sclerotomes, often necessitate excision of multiple ribs/ vertebral bodies in order to radically excise the tumor en bloc, leaving behind a large chest wall defect, which are difficult to manage. If chest wall defects are not adequately reconstructed they are likely to adversely affect the pulmonary function. These large chest wall defects are also vulnerable sites for potential injuries to the lung following blunt trauma. Hence reconstruction is desirable. Study type & Objective-We present a short case series of three cases where in large chest wall defects spanning across 5 to 6 rib segments were reconstructed using titanium mesh. The objective is to highlight the importance of chest wall reconstruction of the large residual defects in ribcage following en bloc excision of large malignant or locally aggressive recurrent or residual tumors. Materials & Methods: Our first case was a patient with large neurosarcoma, arising from the left 8 th and 9 th ribs (8 cm x 5 cm x 6.5 cm), who had an unsuccessful attempt at tumor excision elsewhere. He had a large intercostal scar which made radical excision challenging. En bloc excision of tumor necessitated removal of 5 contiguous ribs, leaving behind a large thoracic wall defect which was reconstructed with titanium mesh. The second patient had a large Ewing's sarcoma arising from the 9 th rib (12.5 cm x 10 cm x 5.4 cm) with the tumor engulfing the 8 th and the 10 th ribs. En bloc excision of the tumor warranted removal of 5 contiguous ribs leaving behind a large chest wall defect which was adequately reconstructed with titanium mesh. The third patient was a case of a residual GCT arising from D9 vertebrae and involving proximal 8 cm of left D9 rib. He also had a large intercostal scar from the previous unsuccessful attempt at tumor excision, He underwent en bloc excision of the D9 vertebrae and bilateral 3 ribs excision and titanium mesh reconstruction of the chest wall defect. Results: All three patients had an uneventful postoperative period with respect to any pulmonary complications. All 3 patients underwent intercostal drain removal on 2 nd post-operative day and they could tolerate coughing and respiratory physiotherapy adequately. Unrestricted mobilization was possible on 3 rd postoperative and they were discharged on 5 th Post-Op day. Pulmonary function test at one month post-op was at 90% of preoperative level. Conclusion: The novel technique of chest wall reconstruction with titanium mesh makes our case series unique. Ours is probably the first case series of large residual malignant / locally aggressive vertebral tumors where chest wall reconstruction was done using titanium mesh. This case series also highlights the importance of multi-disciplinary approach for management for large and complex spinal tumours. Considering also the increasing life expectancy of our patients thanks to the improvements in chemotherapy and radiotherapy protocols, reducing the rate of revision surgery for mechanical failure is a main issue. The aim of our study is to investigate if postoperative sagittal alignment in long spinal fusions after thoracolumbar or lumbar en bloc resections can affect patients outcomes in a long-term follow-up study. Material and Methods: Study data were obtained from a retrospective review of a multi-centric prospective database of patients that underwent an en bloc resection of the lumbar spine for oncological purpose. All the patients that underwent surgery from June 1992 to July 2020 were analyzed. Patients older than 14, with complete demographic and oncological data, with a neurological postoperative function that allowed walking and standing and with a full set of radiological examination were included. Demographic and oncological data of the patients were collected, as well as sagittal spinopelvic parameters and the difference between ideal and postoperative lumbar lordosis (LLM). Data on causes of revision surgery were analyzed. Quality of life of patients at the final follow-up was evaluated based on Karnofsky performance status. Results: 36 patients fulfilled the inclusion and exclusion criteria and were definitively enrolled (M = 15, F = 21, mean age = 48.4). The average number of resected vertebrae was 1.5 and the average length of fusion of 5.9 vertebrae. 26 patients that underwent an en bloc resection received a carbon stackable cage, 1 received a metallic dual mesh, 4 received a carbon custom made cage, 1 a piramid carbon, 3 received bone graft and 1 a bone and mesh support. In the follow-up period, 6 patients (17%) received revision surgery, for implant related problems or junctional disease. Patients who developed a mechanical complication showed higher values of PI-LL and LLM. Conclusion: En bloc surgery is a proficient technique in selected patients, allowing an increased life expectancy also when combined with adjuvant therapies. This should be joined to a longterm effectiveness and stability of spinal implants, in order to avoid reductions of quality of life and autonomy due to implant failure and re-hospitalizations for revision surgery. From our long-term follow-up study it seems that the sagittal alignment of the spine after the reconstruction of thoracolumbar en bloc resections plays a major role in predicting outcomes and less implant-related complications in the majority of patients.

Giulia Cavazzoni 1,2 , Luca Cristofolini 2 , Giovanni Barbanti Bròdano 3 , Enrico Dall'Ara 1 , and Marco Palanca 1,2 3 

Introduction: Bone metastases affect the spine by reducing the load-bearing capacity of the vertebrae and increasing their risk of fracture. The metastases appear radiographically as regions with high (i.e. blastic metastases) or low (i.e. lytic metastases) bone mineral density. The diagnosis of the spine instability and the measurement of the size of the metastases are based on computed tomography (CT). However, it is still unclear if the actual size of the metastases can be accurately assessed from the CT images and if the bone microstructure in the regions surrounding the metastases is altered [1] . The aim of this study is to evaluate the capability of CT in evaluating accurately the volume of the lesion and if metastases affect the bone microstructure around them. Materials and Methods: Nine spine segments were obtained through an ethically approved donation program. Each segment consisted of a vertebra with lytic or mixed metastases and an adjacent control (radiologically healthy). The specimens were scanned with clinical CT (AquilonOne, Toshiba: slice thickness: 1 mm, inplane resolution: 0.45 mm), in order to evaluate the clinical metastatic features, and with micro-CT (VivaCT80, Scanco, isotropic voxel size of 0.039 mm), in order to evaluate the detailed microstructure of the tissue. The volume and location of each metastasis were evaluated from the CT and micro-CT images [2] , and compared (linear regression analysis). A volume of interest (VOI) was defined in the micro-CT images as the volume of the control or metastatic vertebral body excluding the metastatic lesions. Three threedimensional microstructural parameters were calculated in the VOI (CTAn, Bruker SkyScan): Bone Volume Fraction (BV/TV), Trabecular Thickness (Tb.Th.), Trabecular Spacing (Tb.Sp.). Medians of each parameter calculated for the metastatic and control vertebrae were compared (Kruskal-Wallis, level of significance 0.05). Results: The volume of the metastases was not measured in two specimens as it was not possible to define the boundary region of the lesions in the CT scans. A strong correlation between the volume evaluated from the CT and micro-CT images was found (R 2 = 0.91, Slope = 0.97, Interecpt = 2.55, RMSE = 5.7%, MaxError = 13.12%). The differences in BV/TV, Tb.Th. and Tb.Sp. among vertebrae with lytic metastases, mixed metastases and control vertebrae were not statistically significant (p-value > 0.6). Similar median BV/TV was found in vertebrae with lytic (13.2 ± 2.4%) and mixed (12.8 ± 9.8%) metastases, and in control (13.0 ± 10.1%). The median Tb.Th. was 176 ± 18 μm in vertebrae with lytic metastases, 179 ± 43 μm in vertebrae with mixed metastases and 167 ± 91μm in control vertebrae. The median Tb. Sp. was 846 ± 26 μm in lytic metastases, 849 ± 286 μm in vertebrae with mixed metastases and 880 ± 116 μm in control vertebrae. Conclusions: The microstructural parameters measured were comparable with those reported in the literature for healthy vertebrae [2, 3] . These results showed that the metastases do not alter the microstructure of the bone surrounding the lesion. In order to generalize the findings, further analyses are still ongoing. alignment disorder or hints for an instability like looseninghem. The overall survival was, at the follow-up, 57% in the conservative group and 75% in the interventional group. Analyzing the quality of life, we choose the walking ability as a main feature. 92% in the interventional group are still able to walk, in contrast 80% in the conservative group (p = 0.24). Conclusion: SINS is a very useful tool for assess stability of a pathologic fracture due to spinal metastases after radiotherapy for spinal metastases. Moderate or high SINS are associated with a very high risk of fracture progression as well as risk for neurological deterioration. A treatment according to the SINS-Score show a satisfying result with conservation of the walking ability. Furthermore, there are hints, that a corpectomy is not always necessary due to the secondary strengthening of the vertebral body by radio oncology. April 2020, the assistance activity changed progressively with the suspension of elective surgeries and giving priority to urgent cases and emergencies. The objective of the present study is to retrospectively analyze two groups of patients with metastatic spinal pathology surgery, before and after the diagnosis of the first SARS-CoV-19 case in Argentina. The hypothesis is that patients with metastatic spinal pathology present a more advanced neurological state (Frankel scale) at the time of surgery than before the pandemic, due to SARS-CoV-19. Material and Methods: The present is a retrospective observational study of surgically treated patients from January 1 st , 2016 to May 15 th , 2021 with a diagnosis of metastatic spinal pathology. Data collected: age, sex, comorbidities, neurological status (Frankel scale), Tomita and Tokuhashi scores, SINS score, ESCC scale, days of hospitalization, complications, type of discharge, mortality and unscheduled hospital readmission, number of spinal metastases and type of surgery. A comparative analysis between two groups which were treated surgically before and after the appearance of the first SARS-CoV 19 case in Argentina was performed in order to evaluate the impact of SARS-CoV-19 spreading in patients with surgery for metastatic spinal pathology Results: A total of 20 surgical procedures were analyzed, 9 patients in the Covid group and 11 patients in the no-Covid group. The analysis showed no statistically significant difference in: days of hospitalization, reoperation within 30 days, mortality within 30 days after surgery, mortality within 90 days after surgery, unscheduled hospital readmission at 90 days, SINS score, epidural spinal cord compression (ESCC) scale, Frankel scale preoperative and Frankel scale postoperative, and number of spinal metastases at diagnosis (p = 0399, p = 0.178, p = 0.353; p = 0.769, p = 0.881, p = 0.199). Significant differences were observed in unscheduled hospital readmissions at 30 days (p = 0.024). 55% of the patients in the Covid group were readmitted to the hospital within 30 days. One of the patients died related to covid within 90 postoperative days. Proportionally in time, more patients were surgically treated since the pandemic was confirmed in Argentina than before it. Conclusion: During the SARS-CoV-19 pandemic lockdown, more surgeries were performed for metastatic spinal pathology in our hospital in comparison to previous months. Our hypothesis was not proven, since no statistically significant differences were found in the groups regarding the preoperative Frankel scale. As a main limitation, the sample was small, with only 20 patients. Despite this, we believe that this one could be a preliminary investigation to carry out multicenter research and obtain results about spinal oncologic surgery in Argentina and Latin America during the pandemic lockdown.

A240: Return to work, activities of daily living and sports after spinal ependymoma resection: a monocenter experience with long-term follow-up Vicki Butenschön 1 , Till Gloßner 1 , Bernhard Meyer 1 , Isabel Hostettler 1 , and Maria Wostrack 1 performing physical activities in which they previously engaged due to pain, coordination problems and fear of injuries. We detected a shift from full-to part-time employment and patients unable to work, independently from tumor dignity and neurological function. Conclusion: Despite its benign nature and mild formal neurological deficits occurring in patients suffering from spinal ependymoma, the studied population described severe difficulties returning to their preoperative physical activity and profession. Clinical scores such as the McCormick grade and muscle strength may not reflect the entire self-perceived impairment appropriately. Introduction: The aim of this study is to evaluate the incidence and types of implant failure observed in a series of spinal metastases (SM) in patients treated with minimally invasive stabilization surgery without fusion. Material and Methods: This is a multicentric, retrospective and observational study. We reviewed the files of patients over 18 years old, operated on for SM using percutaneous spinal stabilization without fusion, minimum 3-month follow-up. The following variables were included: demographics, clinical findings, prior radiation history, SM location, epidural spinal cord compression score (ESCC), spinal instability neoplastic scale (SINS), neurologic exam and surgery related data. Primary outcome measure was implant failure rate, observed in the patients' last CT scan. Multivariable analysis was performed to identify baseline and factors associated with implant failure. Results: Seventy-two patients were analyzed. Mean age was 62 years old, 39 were men and 75% had an intermediate SINS score. In 48.6% tumor separation surgery was performed. Short instrumentation was indicated in 54.2% of patients. Three patients (4.2%) experienced implant failure (2 screw loosening, 1 screw cut-out) and none of them required revision surgery. In 73.6% of cases, survival was longer than 6 months. No significant predictors of failure were identified in the multivariate analysis. Conclusion: A low implant failure rate was observed over the short and medium term, even when short instrumentations without fusion were performed. These findings suggest that this technique may be both an effective and safe way to treat complicated spinal metastases. Introduction: The improvements in cancer treatment have increased the survival of patients with metastatic disease and the rate of metastatic epidural spinal cord compression (MESCC). Surgical intervention is often undergone to reduce pain, stabilize the spine or address the neurologic deficit and give a better result than conservative treatment, especially in patients with MESCC. Determination of appropriate surgical strategies based on the estimation of postoperative survival, which the previous studies had been reported with many prognostic scoring systems, such as Revised Tokuhashi Score, Tomita score, and SORG. However, those tools had been reported the decreasing accuracy overtime because each prognostic scoring system has its own suitable and specific population study, also the changes of the disease and patient's characteristics, the improving result of concurrent therapy, and many mortality and/or survival-related factors which are not included in those predictive tools. Previously, there are many machine learning approaches on survival prediction in these population. However, some studies showed the decreasing accuracy on the different population when the machine learning tools were used in different country. We aim to develop the predictive tools by using machine learning approach and identify the survival related factors in these population. 24-160 mouths), there were totally 6 patients had local recurrence (6/50, 12.0%) in study. The recurrence rate of in intralesional marginal resection cases was 9.3% (4/43), curettage cases was 50.0% (2/4), and no recurrence in en bloc resection cases (0/4, 0%). In St.3 lesions, the recurrence rate of intralesional marginal resection was 7.7% (2/26), which was slightly lower than St.2 lesions (2/17,11.8%) without statistical difference. There were 5 patients with surgical complications in intralesional marginal resection cases (5/ 43, 11.6%), and 1 in curettage cases (1/4, 25 Introduction: Cement augmentation of pedicle screws is one of the most effective strategies to improve pedicle screw stability in osteoporotic vertebral bodies. However, the technique is associated with some serious complications. This applies particularly to long segmental posterior stabilization, which provides a better load distribution compared to short segmental constructs. Thereby, it can be assumed that the stress level at the screw-bone interface is greatest at the most cranial and most caudal screws. This represents the transition between the rigid instrumented and the freely flexible spine. For this reason, it can be presumed that restricted cementation of long segmental posterior stabilization limited to the most cranial and most caudal vertebrae may achieve comparable stability compared to complete pedicle screw cement augmentation. Restricting cement application can effectively reduce the complication rate. Additionally, it can help to decrease implant cost and surgery time. The goal of this study is to compare the construct stability of long segmental dorsal stabilization in unstable midthoracic osteoporotic fractures with complete pedicle screw cement augmentation (ComPSCA) versus restricted pedicle screw cement augmentation (ResPSCA) of the most cranial and caudal pedicle screws under cyclic loading. Material and Methods: Twelve fresh frozen human cadaveric specimens (Th4-Th10) from individuals aged 70 years and older were tested in a biomechanical cadaver study. All specimens received a DEXA scan and computer tomography (CT) scan prior to testing. All specimens were matched into pairs. These pairs were randomized into the ComPSCA group and ResPSCA group. An unstable Th7 fracture was simulated.

Periodic bending in flexion direction with a torque of 2.5 Nm and 25,000 cycles was applied. Markers were applied to the vertebral bodies to measure segmental movement. After testing, a CT scan of all specimens was performed. Results: The mean age of the specimens was 87.8 years (range: 74 to 101). The mean T-score was -3.6 (range: -1.5 to -5.3). Implant failure was visible in three specimens, two of the ComPSCA group and one of the ResPSCA group, affecting only one pedicle screw in each case. Slightly higher segmental movement could be evaluated in these three specimens. No further statistically significant differences were observed between the study groups. Conclusion: The construct stability under cyclic loading in flexion direction of long segmental posterior stabilization of an unstable osteoporotic midthoracic fracture using ResPSCA is comparable to ComPSCA. Thus, a limited augmentation strategy might be sufficient helping to reduce surgery time, radiation exposure and limiting the complication rate. Introduction: During the last decades the incidence and the number of surgical treatments of pelvic ring fractures including Os sacrum fractures increased. The AO Spine Sacral classification system is a validated system and it is associated with a treatment algorithm. The Sacroiliac screw (SI screw) is well established and a minimally invasive fixation technique. However, SI screw loosening is observed in up to 20% and alternative fixation techniques are required. The aim of the present biomechanical study was to compare the single SI screw, the use of two SI screws placed in the S1 and S2 bodies and the cement augmentation of the SI screw. It was hypothesized that augmentation of the SI screw would be biomechanically superior. Material and Methods: Unstable fractures of the pelvic ring (AO 61-C1.3) were simulated in 21 artificial pelvises by means of vertical osteotomies in the ipsilateral anterior and posterior pelvic ring. A supraacetabular external fixator was applied to address the anterior fracture. The pelvises were assigned to three groups of 7 specimens each for application of the following fixation methods: one (group 1) or two (group 2) standard SI screws and one SI screw with additional cement augmentation (group 3). Biomechanical testing was performed on an electrodynamic material testing machine equipped with a 3.0 kN load cell in a setup simulating a one-legged stance position with applied load on the right hemipelvis. All specimens were tested under progressively increasing cyclic loading until failure, with monitoring by means of motion tracking. Fracture site displacement and cycles to failure were evaluated. Results: Fracture displacement after 500 cycles was lowest in group 3 The three tested fixation techniques show equal biomechanical competence at the beginning and during the early phase of testing and loading. Significant differences were measured over the time points as described previously. After 1000 cycles fracture displacement was significantly less observed in the augmented SI screw group. This reduced displacement may clinically result in less implant loosening. No significant differences of cycles to failure between the different techniques were observed in the present study. This result is in accordance with previous biomechanical data. From a biomechanical point of view cement augmentation of one SI screw is superior compared to the use of one or two SI screws. Cement augmentation seems to increase boneimplant anchorage and therefore presents a successful alternative for B2 fractures of the Sacrum, especially in osteoporotic bone. being proposed as the treatment of choice of these fractures. Complications of these invasive procedures affecting the elderly with significant comorbidities are well described. A novel minimal invasive procedure of percutaneous PPMA-augmented pedicle screw ring osteosynthesis of the fractured vertebra is being proposed. The biomechanical primary and secondary stability of this procedure was investigated in a human osteoporotic Cadaver model. Material and Methods: An OF-4`P incer``fracture was experimentally induced in 8 bisegmental cadaveric lumbar specimen (Ø Age 73,6; BMD 68,4 mg/ccm) and then instrumented with a PMMA-augmented pedicle screw ring osteosynthesis of the fractured vertebra. An axial loading was then applied with a stepwise increasing force for 15500 cycles (initial 100-500N with 50N increase every 500 cycles). The vertebral height was measured on lateral fluoroscopy ventrally, dorsally and in the center of the vertebral body. Measurements were taken on the intact, fractured and instrumented vertebra as well after every 500 cycles. The range of motion (RoM) was measured in the flexibility tests with pure moments of 3,75N before and after instrumentation as well every 5000 cycles of axial loading. Results: There was a significant height loss after fracture induction (p < 0.005). The median height loss in the vertebral body center was 52% and was reduced to 17% after instrumentation (p < 0.005). An increase of height loss to 26% was shown during the axial loading but was significantly lower to the initial 52% of the fractured vertebra (p < 0.005). At the ventral and dorsal aspects of the vertebral body there was a similar trend of height loss but in a lower extend in comparison to the vertebral body center. The flexibility testing showed an increase in the RoM after fracture induction (p < 0.005) which was significantly decreased with the instrumentation (p < 0.005) but at a greater level in comparison to the intact specimen (p < 0.005) and increased slightly throughout the axial loading. This was probably attributable to RoM measurements which included the adjacent noninstrumented intervertebral disc spaces. Conclusion: The results of these study show a sufficient biomechanical stability of the PMMA-augmented pedicle screw ring osteosynthesis in vitro and suggest that it could be a minimally invasive alternative for the treatment of osteoporotic lumbar OF-4 ''Pincer'' fractures in geriatric patients with significant comorbidities. Introduction: The role of the cranio-cervical complex in spinal sagittal alignment has rarely been analysed and described but it may play a fundamental role in postoperative mechanical complications. The aim of the study is to analyse the normative value of the CIA angle for each thoracic vertebra in an adult asymptomatic multi-ethnic population. Material and Methods: Standing full-spine EOS of adult asymptomatic volunteer subjects from 5 different countries (France, Japan, Singapore, Tunisia and USA) were analysed. The CIA was first analysed globally and then in each decade of life (< 20 years; 21-30 years; 31-40 years; 41-50 years; 51-60 years; 61-70 years; 71-80 years). Different ethnicities were compared. Comparisons between different age and ethnicities groups was performed using a t-test and statistical significance was considered with a p value < 0.05 Results: EOS of 468 volunteers were analysed. The global mean CIA angle was 80.2°with a maximum difference of 9°between T1 and T12 (p < 0.001; range 77.05°to 86.05°). The CIA angle remains constant until 60 years old then it decreases significantly passing from a mean value before 20 years old of 82.25°to 73.65°after 70 years old. A statistically significant difference was found between the Arabics and all other ethnicities with the formers having an inferior CIA angle: this was related to a mean older age (45.48 vs 39.35 years; p < 0.05) and higher BMI (27.13 vs 23.86 kg/m 2 ; p < 0.05) in the Arabics population. Conclusion: The CIA remains constant through ages until 60 years old and the reduces slightly but never lower under 70°. This angle might be a helpful tool to evaluate the lever arm on the thoracic spine after an ASD surgery and could predict the occurrence of a proximal junctional kyphosis when its value is lower than normal. Further clinical studies must confirm this theory.

A248: Patient perspectives on the use of robotic navigation in spinal surgery instrumentation. However, patient perspectives on the influence of robotic navigation in spinal surgery remains unknown. This is the first study completed in a large cohort of patients following spinal surgery. The aim of this investigation is to evaluate and improve robotic-assisted spinal surgery through evaluating patient perceptions. Material and Methods: This study is an evaluation of patient perspectives following Mazor XTN system (MA-ZOR Robotics Inc, Orlando, Florida) robotic-assisted surgical cases from a single surgeon experience at a tertiary medical center. The survey was completed for patients (N = 148) 1 year post-operative following spinal surgery. Image-guided spinal navigation has emerged as a useful tool to improve accuracy of pedicle screw placement compared to freehand fluoroscopic techniques. The precision of navigated techniques may allow safe and accurate placement of longer and wider screws, possibly yielding superior cortical bone purchase and biomechanically stronger pedicle fixation. However, the effect of navigation on intraoperative selection of pedicle screw size remains unknown. Methods: A prospectively maintained single surgeon deformity registry of 16 patients (198 pedicle screws) who underwent instrumented posterior thoracolumbar fusions under computer navigation was retrospectively queried. These patients were control matchedaccording to age, medical comorbidities, and operative levelsto a cohort of 16 patients (212 pedicle screws) who underwent freehand fixation. Demographic characteristics, operative parameters, and follow-up outcomes were collected. Each instrumented pedicle's cross-sectional diameter, screw diameter, and screw length were radiographically measured by a blinded reader. Pedicle screw size and percentage pedicle fill were compared between groups via independent t-test. The threshold for statistical significance was established at p < .05. Results: A total of 32 patients underwent instrumented spinal fusion at 205 levels (410 screws). There were no significant baseline differences between freehand and navigation patients in mean age (p = .612), body mass index (p = .158), gender distribution (p = .288), medical comorbidities (p > .05), and smoking history (p > .05). There were no significant differences in operative time (p = .350) or estimated blood loss (p = .661). When evaluating concomitant procedures performed at each level, there was a similar rate of laminectomies (p = .904), transforaminal lumbar interbody fusions (p = .264), and pedicle subtraction osteotomy (p = .333); however, there were significantly more posterior single column osteotomies among navigated levels (p = .003). Pedicle screw insertions under navigation achieved significantly greater pedicle fill compared to freehand insertions (p < .001). Overall, navigation enabled the use of significantly wider (p < .001) and longer thoracolumbar screws (p < .05). However, navigation guided the placement of significantly shorter screws at S1 and pelvis (p < .001). No complications of pedicle breach or neurovascular injury were reported in the freehand or navigated cohorts, despite the use of overall larger pedicle screws via navigation. Two cases in the freehand cohort required revisions for screw loosening and hardware failure, respectively. No navigated cases required revision. Conclusion: We found that spinal navigation facilitates safe and accurate insertion of significantly longer and wider thoracolumbar screws, compared to freehand techniques. Clinically this may relate to improvements in construct stability and rigidity. Conversely, significantly shorter S1 and pelvic screws were utilized under navigation, possibly to mitigate the risk of anterior breach that could result in injury to the L5 nerve root or internal iliac vasculature that run in close proximity to the sacrum. Future comparative studies are warranted to correlate these radiographic findings with long-term clinical outcomes. Introduction: When placing pedicle screws in the spine, screw misplacement can lead to severe complications. Therefore, the accuracy of screw placement plays a crucial role. Studies have shown that the use of 3D navigation can reduce the rate of pedicle perforation not only in comparison to freehand technique and fluoroscopy-guided screw placement but also in comparison with 2D navigation and conventional CT navigation. Nevertheless, according to recent studies, the improved accuracy comes at the cost of higher radiation exposure. So far, only few imaging systems have been analysed regarding accuracy and radiation exposure and even fewer have been compared under similar conditions. Therefore, the aim of this study was to compare navigation with Cone Beam CT (Medtronic O-arm/Medtronic Stealth) and C-arm Cone Beam CT (Siemens Cios Spin/NuVasive Pulse) regarding accuracy of screw placement and radiation exposure in an experimental setup with artificial bone models. Material and Methods: With both imaging and navigation systems, spine levels L1 to S1 were instrumented with 12 screws each in ten artificial spine models. The procedure was performed by two experienced surgeons. After screw implantation two 3D scans were performed to evaluate screw position. All screws were classified according to Gertzbein and Robbins. As suggested in the literature, perforations > 2 mm (Gertzbein and Robbins grade C-E) were considered as potential cause for complications and therefore not acceptable. Additionally, two radiation detectors were installed at standardized positions in the spine bed in which the bone models were placed in to measure radiation exposure. Results: In total, 236 screws were placed. Four screws could not be placed due to material defects on the artificial bone models, three with the Cone Beam CT, one with the C-arm CBCT. For C-arm CBCT-guided screw placement, 0.8% of screws perforated the pedicle wall by more than 2 mm, compared to 8.6% of the CBCT-guided screws. Pearson's Chi 2 test showed a significant difference between the systems (p = .005). The average radiation dose measured during the procedure using the C-arm CBCT was 3.64 ± 0.31 mGy. The mean radiation exposure for the CBCT-guided procedure was 10.34 ± 5.67 mGy. Comparison of the results with Student's t-test showed a significant difference (p < .005). Conclusion: Both C-arm CBCT and CBCT guided navigation allow accurate placement of pedicle screws in the lumbar spine. Yet, the accuracy of screw placement regarding perforations of the pedicle wall was significantly higher with C-arm CBCT. At the same time, the radiation exposure for the C-arm CBCT-guided procedures was significantly lower than in the CBCT-guided procedures. Thus, in direct comparison, C-arm CBCT guided navigation for lumbar pedicle screws might be favored to achieve highest accuracy and minimization of radiation exposure. To assess the clinical relevance of the results presented further cadaver experiments and clinical studies are needed. Introduction: Pedicle screws are the primary form of spinal instrumentation. Accuracy of screw placement by freehand, fluoroscopy guided, and image guided placement has been well studied. Efficiency of screw placement has been less well studied. The purpose of this study is to prospectively evaluate screw placement time while observing workflow. Material and Methods: This study evaluated patients ≥ 8 years old having surgery involving pedicle screw placement utilizing intraoperative cone beam CT and image guidance. The in-light camera was used to record the operative site during pedicle screw placement. Demographics, screws per case, pedicle breeches, and intraoperative repositions were recorded. Screw time began at first placement of the navigated probe/awl and ended once the navigated screwdriver is removed from the screw head. Confirmatory check spins were performed to assess screw placement. Primary outcomes include per screw placement time and incidence of intra-operative screw repositioning. Results: 44 patients had 780 screws placed (745 pedicle, 2 iliac, 33 S2AI), sizes ranged 4.5-7.5 x 30-65 mm for pedicle, 5.5-8.5

x 50-70 mm for iliac, and 8.5-9.5 x 90-100 mm for pelvic screws. Average number of levels instrumented per case: 9 (2-18). Average screws per case were: 17.7 (4-35). Number of breaches and repositions were 3 (0.4%) and 5 (0.6%), respectively. Average time to place each pedicle screw and pelvic screws: 135 sec (2min 15sec) and 195 sec (3 min 15 sec), respectively. Conclusion: Average placement time was 2 min 15 sec for pedicle screws and 3 min 15 sec for pelvic screws. This study provides a more precise reporting of screw placement as compared to current literature which reports 4.3 to 12 min. Disruption to workflow, such as aberrant anatomy, body habitus, neuromonitoring complications, and navigation difficulties hinder screw placement efficiency. Clinical factors affecting screw placement include surgeons experience, single or co-surgeon placement, and scrub tech efficiency. following spine surgery in adults can lead to significant morbidity and even mortality. Our study aims to assess the validity of the Caprini Risk Assessment Tool in such patients in order to emphasize specific risk factors and to identify threshold scores for high-risk patients. Material and Methods: Two cohorts of patients who had undergone spine surgery at a single center from 2016-2021were identified. One cohort of 31 patients had confirmed evidence of VTE (VTE Group) and the other cohort of 32 randomly selected patients had no evidence of VTE (control group). Modified Caprini scores were calculated for both cohorts and a two-sample t-test was used to identify significance between the two groups (α = 0.05.) All scores were evaluated with a receiver operating characteristic curve, and sensitivity and specificity values were calculated for each numerical score for both cohorts combined. The following risk factors were collected using manual chart review as outlined in the modified Caprini Score. Results: After calculation of the modified Caprini Score, the control group ranged from 3 points to 9 points, with a mean of 4.88 ± 0.56, while the VTE group ranged from 2 points to 18 points, with a mean of 7.58 ± 1.17 (p < 0.0001). Key factors include surgery > 6 hours, restricted mobility > 72 hours, previous history of DVT/PE, and presence of genetic mutations increasing risk for thrombophilia. Based on the ROC curve, at the current recommended prophylaxis cutoff of four points, the sensitivity would be 90.3%, while the specificity would be 15.6% (LR+ = 1.07). Adjusting the cutoff to be six points (sensitivity = 71.0%, specificity = 78.1%, LR+ = 3.24) makes the modified Caprini Score more effective tool in deciding which patients should receive VTE chemoprophylaxis. Conclusion: The modified Caprini Score has been previously validated in using certain pre-operative risk factors to calculate a patient's risk of VTE following spine surgery. However, selecting an original cutoff of four points to indicate VTE risk and need for subsequent chemoprophylaxis may not be sufficiently specific in the context of spine surgery. Instead, since sensitivity and specificity, and LR+ were significantly higher when a cutoff at six points was selected, we recommend using the six point cutoff when utilizing this screening tool for patients undergoing spine surgery. Future directions may include incorporating a larger patient cohort in assessing and validating the recommended cutoffs from this study. Introduction: Historically, spine surgery patients undergo routine type and screen (T&S) (ABO group, Rh type, and antibody screen) lab testing prior to surgery in case a blood transfusion is required. With advances in minimally invasive techniques, the advancement of hemostatic agents, and increased use of tranexamic acid, rates of transfusion after spine surgery have declined nationally in recent years. At our institution, routine T&S continues to be performed on all patients undergoing emergent or elective spine surgery. The purpose of this work was to evaluate risk factors for transfusions in this population and to develop and evaluate a guideline for selective performance of preoperative T&S testing. Material and Methods: A retrospective, observational study of all patients undergoing emergent or elective spine surgery at a single institution from January 1, 2016 to November 1, 2021 was performed. Univariate comparisons of demographics, comorbidities, type of surgery performed, operating room (OR) time, and number of levels treated were performed between patients who did and did not require postoperative transfusion. A multivariate logistic regression model was developed to evaluate predictors of postoperative transfusion, and the accuracy of the model was evaluated using the area under the curve (AUC) of the receiver operating characteristics (ROC) curve. A guideline for targeting patients that should undergo T&S testing was developed and applied to cohort to evaluate its accuracy. Results: A total of 6,022 spine surgeries were reviewed; postoperative transfusion was required in 120 (2.0%) of cases. Transfusions were ordered intraoperatively in 58 (0.9%) and postoperatively in 64 (1.1%) of cases. Transfusion rates ranged from 0.0% in cervical disc arthroplasty and sacroiliac fusion to 10.5% in corpectomy cases. In multivariate analysis, female sex, end-stage renal disease or chronic kidney disease, anemia, a coagulation defect or hemorrhagic condition, ASA ≥ 3, thoracolumbar fusion, OR time ≥ 4 hours, 3-5 level surgery, and 6+ level surgery were independent predictors of transfusion. The AUC of the model was 0.900, indicating excellent predictive accuracy. The following guideline for ordering preoperative T&S was developed: a) in low transfusion risk procedures (<5%) including ACDF, PCF, cervical disc arthroplasty, kyphoplasty, SI-fusion, and thoracolumbar decompression: do not order T&S; b) in high transfusion risk procedures (>5%) including anterior-posterior cervical fusion and corpectomy: order T&S; c) in medium transfusion risk thoracolumbar fusion procedures (5%): order T&S if one of the following risk factors is present -ESRD or CKD, anemia, coagulation defect or hemorrhagic condition, expected OR time ≥ 4 hours, or 6+ level fusion. When applied to the historical cohort the guideline yielded a sensitivity of 88.3%, specificity of 72.9%, positive predictive value of 6.2%, and negative predictive value of 99.7%. Sensitivity and specificity for transfusions ordered intraoperatively and postoperatively were 94.6%/72.3% and 82.8%/72.3%, respectively. Using the guideline 4,316 (71.6%) of preoperative T&S tests would be eliminated, yielding a cost savings of $164,008. Conclusion: A risk-based approach can accurately identify patients at the greatest risk for transfusion after spine surgery. Utilization of this protocol can eliminate unnecessary type and screen testing and generate institutional cost savings without compromising patient care.

A255: Complications of C2-T1 pedicle screws versus lateral mass screws: meta-analysis of 4165 patients and 16669 Screws strength of the pedicle screws. To our knowledge, we conducted the first meta-analysis comparing the complication rates during and/or after CPS and LMS placement for different pathologies causing C2-T1 cervical spine instability. Material and Methods: A systematic literature search of PubMed and EMBASE was performed to identify studies reporting CPS and/or LMS-related complications. All studies that met the prespecified inclusion criteria were pooled and cumulatively analyzed. Subgroup meta-analysis of complications was done to assess the effect of navigation. Results: We identified 60 studies conducted between 1994 and 2020 and comprising 4,165 participants and 16,669 subaxially placed screws that met our inclusion criteria. Otherwise, there was no significant difference between the LMS and CPS groups. On meta-analysis of the CPS group, regardless of whether navigation was used, the individual complication rates were non-significant; however, the fixed-effects model showed significantly fewer complications generally with navigation (OR = 5.29, 95%CI = 2.03-13.78). Navigation was not used in any LMS studies. Conclusion: The CPS group had significantly fewer lateral mass fractures, cervical revision surgeries, and SSI. Furthermore, navigation-assisted CPS placement was associated with a significant reduction in complications overall.

Introduction: The quality of paraspinal musculature at the UIV is an understudied risk factor for PJK after spine deformity surgery. We propose an easily distinguishable classification to categorize the different grades of preoperative paraspinal fat atrophy and correlate that with postoperative radiographic outcomes. Material and Methods: A radiographic review was performed on 116 deformity patients from 2015-2018. The paraspinal muscle at the UIV were assessed using the preoperative axial MRI imaging. Grade 1 was defined as fatty infiltrate between 0-10%, grade 2 between 10-50%, and grade 3 over 50%. Pre, immediate postop and 2yr postop standing full length spine films were assessed to evaluate for sagittal alignment and PJK. PJK was defined as proximal junctional angle > 15°. Logistic regression and Chisquare analyses were performed to study the relationship be- Introduction: Incidental durotomy is a common complication of spine surgery with an average incidence of approximately 5% in primary short segment fusions, but this rate has a large fluctuation based on the healthcare group reporting the results. While direct repair with nonabsorbable suture has been considered the gold-standard intraoperative treatment, many different options are now available, such as the application of fat patches, fibrin glue, or other synthetic sealants. Given the large disparity in rates of incidental durotomy and method of dural repair, this study sought to objectively determine our hospitals incidental durotomy incidence and then analyze how repair technique affects pain and functional status. Material and Methods: All patients over 18 years of age who underwent primary or revision lumbar fusion and/or decompression at a single tertiary academic center consisting of eleven fellowship-trained spine surgeons between April 2017 to June 2021 were retrospectively identified. The use of dural tear repair equipment was collected from hospital inventory logs to determine the incidence of intraoperative dural tear. Patient demographics, surgical characteristics, readmissions rates, and patient reported outcomes measures (PROMs) were collected and compared between patients who had a surgery complicated by incidental durotomy and those who did not. Subgroup analysis was performed based on the type of dural repair. Both univariate and multivariate comparisons were utilized. Alpha was set at 0.05. Results: A total of 3,823 patients were included in the final analysis with 546 (14.3%) patients having a dural tear and subsequent repair. Patients with a dural tear were older (59.4 years vs 63.5, p < 0.001), had higher ASA (2.34 vs 2.45, p = 0.002), more levels fused (2.1 vs 2.5, p = 0.001), longer operations (191 minutes vs 254, p < 0.001), longer length of stay (3.2 days vs 3.9, p < 0.001), more estimated blood loss (259 mL vs 358, p < 0.001), higher rates of revision procedures (18.1% vs 29.7%, p < 0.001), higher rates of postoperative drain use (1.1% vs 1.4%, p = 0.007), longer drain duration (2.4 days vs 2.8, p < 0.001), and more drain output (572 mL vs 661, p = 0.001). Regression analysis determined that a dural tear was not a significant independent predictor of change in PROMs following surgery, nor was it a significant predictor of readmission rates following surgery. Repair types included 125 patients with both Duragen and suture, 114 with suture alone, 160 with Duragen alone, and 147 with neither. Regression analysis did not identify a particular repair type to predict differences in readmissions or length of stay. However, on regression analysis, repair with both Duragen and suture was a significant independent predictor of increased improvement in VAS Back compared to Duragen alone (β = -2.51, p = 0.004), suture alone (β = -1.99, p = 0.006), or repair with neither (β = -2.84, p = 0.012). Conclusion: The incidence of dural tear in our cohort was 14.3%. Having an operation complicated by incidental durotomy was not an independent predictor of hospital readmissions rates or changes in patient reported outcome measures. However, repair with both Duragen and suture (compared to Duragen alone, suture alone, or neither) was an independent predictor of greater improvement in VAS Back following surgery.

Introduction: The coronavirus (COVID-19) pandemic has presented healthcare workers with one of the most significant global health crises to date. Prior studies have not identified an increase in complications or readmissions in COVID-19 negative patients undergoing emergency or essential surgery during the pandemic. Similar findings have been found in the urgent and elective surgery population. However, no study has shown the risks of all spine surgeries during this time period. Therefore, the purpose of this study is to measure the rates of complications and readmissions for all patients who underwent spine procedures (elective, urgent, and emergent) since the beginning of the COVID-19 pandemic compared to historical averages. Material and Methods: A retrospective review was performed on patients who underwent any spine procedure performed by one of our fellowship-trained spine surgeons at a single tertiary academic center from January 1 st , 2019 to June 22 nd , 2021. Patients were split into Pre-COVID or Post-COVID cohorts based on the timing of their surgery. March 23, 2020 was designated as the bifurcation based on the first issuance of a Stay at Home Order for COVID-19 in our city. Inpatient complications, 90-day readmission, and inpatient mortality were compared between the two cohorts. Secondary analysis included multiple logistic regression to determine independent predictors of inpatient complications, 90-day readmission, and inpatient mortality. Study Design: Retrospective study Objective: To investigate the coronal decompensation (CD) in patients with congenital cervicothoracic hemivertebra (CTH) scoliosis undergoing posterior-only hemivertebra resection and to propose possible mechanisms of this specific phenomenon. Methods: A consecutive series of 51 patients with CTH undergoing posterior-only hemivertebra resection with a minimum of 2-year follow-up were reviewed. At preoperation, post-operation, and each follow-up, the local scoliosis, clavicle angle, head shift, neck tilt, Cobb angle of compensatory curve were measured. The CD was defined as compensatory curve beyond 20°and progression more than 10°compared with immediate post-operation during follow-up. The incidence and possible mechanisms of CD were recoded and analyzed. Results: A total of 12 patients (23.5%) presented postoperative CD. The values of compensatory curve were 11.3 ± 7.1°before surgery and 4.6 ± 4.1°after surgery (p = 0.001), which was 28.0 ± 2.6°when diagnosed as CD and developed to 21.3 ± 2.5°at the last follow-up. The CD was classified into compensatory and idiopathic types according to the curve characteristics. The compensatory type of CD usually presented within 6 months after operation and was responsible for further reconstruction of shoulder balance. The idiopathic type of CD occurred at adolescent which may be attributed to the rapid body growth. Conclusions: The CD would be often presented in patients with CTH undergoing posterior hemivertebra resection, of whom the prevalence was 23.5%. The CD could be divided into compensatory and idiopathic types, of which the reconstruction of shoulder balance and rapid body growth were 2 key mechanisms, respectively. Keywords: Cervicothoracic hemivertebra; hemivertebra resection; coronal decompensation; compensatory curve progression; emerging scoliosis OP30: Degenerative Cervical 4 694 A262: Allograft cellular bone matrix versus ultra low dose BMP-2 as an augment in 3-level ACDF Introduction: Degenerative cervical myelopathy (DCM) is a heterogeneous disease that is currently difficult to stratify. The objective of this study was to explore whether machine learning can identify clinically meaningful groups of patients based on symptoms alone. Material and Methods: Design: A mixedmethods cross-sectional conducted by a team from the University of Cambridge through Myelopathy.org. A focus group session of people with DCM and their supporters was used to inform the development of an online survey to explore the consequences of living with DCM (https://doi.org/10.1177% 2F2192568220953811). Survey participants were asked to specify the symptoms that they had experienced, their principal presenting complaint, and time to diagnosis, as well as demographic information including disease severity, age, and sex. Subjects: 189 individuals (female: 134, male: 49) who reported living with DCM (mild: 29, moderate: 68, severe: 92). Respondents were on average 54.1 years old (SD: 9.5). The majority reported having had surgery for DCM (69%, 131/189). Methods: K-means clustering was used to divide respondents into clusters according to their symptomatology using the Euclidean distance measure. The optimal number of clusters was computed using principal component analysis and the within sum of squares. The clinical significance of groups was explored by comparing their time to presentation, time with disease severity, and other demographics. DCM severity was assessed using total Modified Japanese Orthopaedic Association scores. All analyses were conducted in R 4.1.0. Results: Cluster analysis suggested three optimal subgroups of symptoms, which matched to differing disease severities and principal presenting complaint but not to time with disease or gender. The distinguishing symptoms between clusters appeared to be presence of neck pain and Lhermitte's sign or pins and needles in their hands. Conclusion: Machine learning can identify different groups of patients based on symptoms. The generalisation of these patterns and their significance requires further enquiry.

A264: Long-term survivorship of cervical spine procedures; a survivorship meta-analysis and meta-regression accelerating in the USA and increased 206% between 1992 and 2005. Generally, surgical approaches to manage DCM and/or radiculopathy can be divided into anterior and posterior. Anterior approaches include anterior cervical discectomy and fusion (ACDF), and cervical disc replacement (CDR). Surgeries utilizing posterior approach include laminoplasty and posterior spinal instrumented fusion (PSIF). Though there are some indications and preferences for certain approaches over others depending on the pathology; the choice of implant is commonly dependent on surgeon preference with no suggestion in the literature regarding a superior approach or technique. The purpose of this study was to synthesize available data on long-term survivorship for commonly performed cervical spine procedures using cutting-edge metaanalytic techniques. Material and Methods: A systematic review of OVID MEDLINE, EMBASE, and CENTRAL databases was conducted following the PRISMA guidelines. Title, abstract, and full text screening was done in duplicate with Kappa scores used to measure agreement. Only articles with cohorts of greater than 20 patients followed for a minimum of 36 months and with available survival data were included. Procedures included were anterior cervical discectomy and fusion (ACDF), cervical disc arthroplasty (CDA), laminoplasty and posterior laminectomy and fusion. Reconstructed individual patient data were pooled across studies using a Bayesian random-effects meta-regression. Results: Our search identified a total of 1456 citations after exclusion of duplicates. After a full text review of 156 titles, we included 20 studies including eight randomized controlled trials. The total sample included 43,487 patients undergoing ACDF, 6,800 patients undergoing laminoplasty, 2075 patients undergoing CDA, and 32,871 patients undergoing posterior laminectomy and fusion. Our meta-regression of synthesized follow-up data with summary curves to 150 months for each of the aforementioned procedures. Posterior laminectomy and fusion was found to have significantly higher rates of secondary reoperation. At 60 months, implant survival was 94% (95%CI = 80-95%) for laminoplasty, 87% (65-96%) for laminectomy and fusion, 93% (83%-97%) for CDA, and 92% (80-96%) for ACDF. At 150 months, implant survival was 90% (68%-93%) for laminoplasty, 82% (55%-92%) for laminectomy and fusion, 90% (70%-95%) for CDA, and 89% (68%-93%) for ACDF. Conclusion: This is the first study to use rigorous statistical techniques to generate statistical models for time to failure of cervical spine procedures analyzing a total of over 85,000 patients. Based on longterm survival data from high-quality publications, posterior laminectomy and fusion appears to have a significantly higher risk of secondary surgery when compared to ventral approaches or posterior laminoplasty. The granular survival curves produced by this study can be used to inform key decision makers, counsel patients, and aid in future trial design. Introduction: Degenerative cervical myelopathy is a common cause for neurologic dysfunction and rates of surgical treatment are increasing. Treatment guidelines report clinical equipoise between conservative and surgical treatment for patients with mild disease states. Currently there is a paucity of literature supporting surgical treatment for mild and moderate myelopathy. The purpose of this study is to synthesize accurate time-based estimates of meaningful neurologic decline in patients with degenerative cervical myelopathy managed conservatively. Material and Methods: Following the Cochrane Prognosis Methods as well as the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we conducted a broad systematic search of OVID MEDLINE, EMBASE, and CENTRAL databases. Title, abstract, and full text screening was done in duplicate. Based on best available evidence, we utilized a change in mJOA of 2 to signify meaningful neurologic decline. Survival curves were pooled across studies using a fixed effects approach of individual patient data meta-analysis and a parametric survival curve was fit to the pooled data. Results: 9570 studies were identified for title and abstract screening, ultimately yielding six studies for inclusion. Our final analysis included two level 1 prospective randomized control studies, one level 2 prospective cohort study, two level 3 retrospective cohort studies and one level 4 retrospective case series. Overall, 674 patients underwent conservative treatment for cervical myelopathy (range 35-247 per study) with an average mild-moderate initial modified Japanese Orthopedic Association (mJOA) score of 14.23 (range 8.5-18) amongst the five studies where this was reported. Of these, 65 patients would convert to surgical intervention for either neurologic decline or patient preference. The average reported age amongst the six included studies is 56.88 (range 28-80), with 50% males. Mean final follow-up was 24.5 months (range 5-208). Our pooled analysis showed that in a population of patients with mildmoderate mJOA scores, 61% had no meaningful neurologic decline at five years, and 48% had no such decline at 20 years. Introduction: Degenerative Cervical Myelopathy (DCM) is the most common cause of spinal cord impairment. Unfortunately, the condition remains poorly recognized and underdiagnosed. To better identify these patients, screening tests that target individuals at high risk such as those with known comorbidities would be helpful. One group in particular known to have a high prevalence of DCM are patients with lumbar degenerative disease (LDD), with the combined presentation referred to as tandem stenosis. It is estimated that tandem stenosis presents in 10-20% of patients with LDD. Given that LDD is one of the most common presentations in neurosurgical practice and primary care, it is the objective of the proposed study to administer a screening test to these patients as well as those with risk factors or symptoms which raise the suspicion of underlying DCM. Materials and Methods: A screening test based on the number of clinical sign/symptoms and known patient risk factors of DCM was designed and performed in our neurosurgical consultations primarily for patients with LDD or those with any suspicion of myelopathy. A survey of 13 neurosurgeons was used to develop and modify screening criteria and to define the minimum threshold of factors present before undertaken a cervical MRI. Points are attributed based upon the presence of signs or symptom of DCM (e.g. Hoffman sign, Hyperreflexia) as well as for comorbidities that predispose or are frequently associated with cervical myelopathy (e.g. Rheumatoid arthritis, carpal tunnel syndrome). Patients with ≥ 3 points undergo cervical MRI examination. Patients with positive MRIs will be consulted and receive assessment via mJOA and NDI scores, and subsequent clinical management will be based on practice guidelines. An exploratory multivariate analysis of the effectiveness and efficiency of this proposed screening test will be evaluated after positively screening 50 patients for DCM. Results: Out of 97 patients screened, 26 screened positive (≥ 3 points) and 18 had a subsequent cervical MRI. Of the 18 patients, 7 (38.9%) were diagnosed with cervical myelopathy. The average number of points for patients screening positive with a diagnosis of myelopathy was 4.71 vs 3.75. All patients with myelopathy were considered as mildly myelopathic. Five out of the 7 positive patients had T2WI hyperintensity signal changes on MRI. Conclusions: Screening for DCM in patients with lumbar pathology appears to be effective with a rate of cervical myelopathy uncovered in nearly 40% of patients screening positive. These are preliminary results and a complete and more extensive analysis from this multicenter study are expected later this year. . Through a consensus process, research questions are generated and ranked. The inclusion of people with cervical myelopathy [PwCM] is central to the process. We hypothesized that presenting PwCM experience through word cloud generation would stimulate other key stakeholders to generate research questions better aligned with PwCM needs. This protocol outlines our plans to evaluate this as a nested methodological study within our PSP. Material and Methods: An online poll asked PwCM to submit and vote on words associated with aspects of DCM. After review, a refined word list was repolled for voting and word submission. Word clouds were generated and an implementation plan for AO Spine RECODE-DCM PSP surveys was subsequently developed. Results: Seventy-nine terms were submitted after the first poll. Eighty-seven refined words were then re-polled (which added a further 39 words). Four word clouds were generated under the categories of diagnosis, management, long-term effects, and other. A 1:1 block randomization protocol to assess word cloud impact on the number and relevance of PSP research questions was generated. Conclusion: We have shown it is feasible to work with PwCM to generate a tool for the AO Spine RECODE-DCM nested methodological study. Once the survey stage is completed, we will be able to evaluate the impact of the word clouds. Further research will be needed to assess the value of any impact in terms of stimulating a more creative research agenda. Introduction: Degenerative Cervical Myelopathy (DCM) is a growing disorder. Standardization of its assessment tools is an integral part of its management. The modified Japanese orthopedic association (mJOA) score is one of the most commonly used tools. Currently, there is no available Arabic translated version of any cervical myelopathy functional score. This study aimed to translate, culturally adapt, and measure the psychometric properties of an Arabic translated version of the mJOA. Material and Methods: After translation of the score using the standard forward-backward translation procedure, a validation study including 100 patients was carried out from June 2019 to June 2020. The following psychometric properties were measured: feasibility, reliability, internal consistency, validity, minimal clinically important difference (MCID), ceiling, and floor effect. Results: No problems were encountered during the process of translation and cross-cultural adaptation of the score. The mJOA-AR was found to be a feasible score. It showed high inter-observer reliability (r = 0.833, p < 0.001), test-retest reliability (r = 0.987, p < 0.001) and good internal consistency using Cronbach's alpha (0.777) and Pearson interclass correlation coefficient (r = 0.717). The score showed good convergent and divergent construct validity correlating it to the Arabic validated version of the neck disability index (NDI). The mJOA-AR had an MCID of 1.506. Both the ceiling and floor effects of the total score and the first and second domains were within the acceptable range, while the third and fourth domains had a high ceiling effect (30% and 39%, respectively). Conclusion: Our translated version of the mJOA score was found to be a feasible score with acceptable psychometric properties. This score can be utilized as a good outcome measure tool in Arabic-speaking countries.

Introduction: Patients with spinal metastases often receive palliative surgery or radiation therapy in order to maintain or improve health related quality of life (HRQOL). Patients with unrealistic expectations regarding treatment outcomes have been shown to be less satisfied with their post-treatment health status. This study evaluated expectations of patients with spinal metastases scheduled for surgery and/or radiation therapy. Material and Methods: Individual semi-structured interviews were conducted with patients with symptomatic spinal metastases before, and six weeks after surgery and/or radiation therapy. Expectations regarding treatment outcomes were discussed pre-treatment, and level of fulfillment of these pre-treatment expectations were discussed post-treatment. Interviews were recorded and transcribed, and analyzed according the thematic analysis method to identify themes. Results: Pre-treatment, patients felt they were not, or minimally, informed about (expected) treatment outcomes, but they felt well informed about treatment procedures and possible complications. Although patients expected pain relief and improvement in daily functioning, they found it difficult to describe any recovery timeline or the impact of these expected improvements on their daily life. Patients generally understood that treatment was not curative, but lacked insight into the impact of treatment on life expectancy as this was hardly discussed by their surgeon and/or radiation oncologist. Pretreatment expectations regarding pain and daily functioning were only partially met in most patients posttreatment. Conclusion: Patients felt they were not, or only minimally, informed about expected outcomes after surgery and/or radiation therapy for symptomatic spinal metastases. Improvements in patient-physician communication and counseling could help guide patients towards realistic pretreatment expectations. Introduction: Despite our inability to accurately predict survival in many cancer patients, a life expectancy of at least 3 mo is historically necessary to be considered for surgical treatment of spinal metastases. The objective was to compare health-related quality of life (HRQOL) in patients surviving <3 mo after surgical treatment to patients surviving > 3 mo to assess the validity of this inclusion criteria. Material and Methods: Patients who underwent surgery for spinal metastases between August 2013 and May 2017 were retrospectively identified from an international cohort study. HRQOL was evaluated using generic and disease-specific outcome tools at baseline and at 6 and 12 wk postsurgery. The primary outcome was the HRQOL at 6 wk post-treatment measured by the Spine Oncology Study Group Outcomes Questionnaire (SOSGOQ). Results: A total of 253 patients were included: 40 patients died within the first 3 mo after surgery and 213 patients survived more than 3 mo. Patients surviving <3 mo after surgery presented with lower baseline performance status. Adjusted analyses for baseline performance status did not reveal a significant difference in HRQOL between both groups at 6 wk post-treatment. No significant difference in patient satisfaction at 6 wk with regard to their treatment could be detected between both groups. Conclusion: When controlled for baseline performance status, quality of life 6 wk after surgery for spinal metastasis is independent of survival. To optimize improvement in HRQOL for this patient population, baseline performance status should take priority over expected survival in the surgical decision-making process.

A273: Sarcopenia as a predictor of survival in oncological spine surgery: validation of CT morphometric measurements of posts size Rafael De la Garza 1 , Joshua Benton 1 , Yaroslav Gelfand 1 , Saikiran Murthy 1 , and Reza Yassari 1 1 Neurosurgery, Montefiore Medical Center, New York, USA Introduction: Sarcopenia is a syndrome characterized by loss of muscle mass and strength. In patients with metastatic spine disease, it was recently proposed as a biomarker associated with postoperative survival. The objective of this study is to validate the use of sarcopenia as a prognostic factor for survival in our population and to validate specific proposed cut-off measurements used to define this condition. Material and Methods: A total of 104 patients with complete preoperative computed tomography imaging who underwent oncological spine surgery at our institution between 2013 and 2021 were identified. Sarcopenia was defined as a cross-sectional area of the psoas muscle at the L4 pedicle level less than 10.5 cm 2 for men and less than 7.2 cm 2 for women based on the work by Zakaria et al. The main dependent variable was overall survival (OS). 30-day survival (30S) and 90-day survival (90S) were also examined. All survival analyzes were done following Kaplan-Meier methods. Results: The average age of all patients was 62 years and 61/104 were male (58.7%). Sarcopenia was diagnosed in 40/104 patients (38.5%); its prevalence was 46.5% in women and 32.8% in men (p = 0.157). Median OS was 19.5 months for all patients. However, median OS was 4 months for sarcopenic patients and 26 months for nonsarcopenic patients (log-rank, p = 0.005). 30S and 90S were significantly lower for patients with sarcopenia (p = 0.009 and p = 0.003, respectively). After controlling for age, sex, BMI, functional status, rapid-growing tumor type, and presence of pathologic vertebral compression fracture, sarcopenia remained as an independent significant risk factor for mortality (Hazard Ratio 2.2; 95% CI, 1.06-4.56; p = 0.035). Conclusion: Sarcopenia is an important and significant risk factor for survival after oncological spine surgery. The proposed cut-off values were significant in our population and can be used for preoperative risk stratification and improved decision-making. Future research into preoperative optimization and treatment of sarcopenia is needed. Introduction: Neuropathic pain presents a burdening and impairing condition which may occasionally occur after surgery. While its occurrence has been described in peripheral nerve sheath tumors, data on other intradural tumor patients is sparse. We hereby present a large cohort population undergoing intradural spinal tumor surgery with assessment of early postoperative and follow-up outcomes, focusing on the occurrence of neuropathic pain. Material and Methods: We performed a retrospective monocentric study including all patients treated for intradural spinal tumors between 2009 and 2020. We extracted surgical aspects as well as pre-and postoperative clinical courses from the records. Statistical analysis of potential contributing prognostic factors was performed. Results: In total, 360 patients were included for analysis. At a median follow-up of two years, 26/360 patients complained of a neuropathic pain syndrome (7.2%) requiring continuous medication. Of these patients only 50% complained preoperatively of pain. Tumor entity did not significantly influence the incidence of postoperative neuropathic pain (p = 0.91). Sacrifice of the tumor carrying nerve root and tumor recurrence also did not increase the risk for this condition. Conclusion: Persistent neuropathic pain requiring continuous treatment occurred in 7.2% of patients undergoing intradural spinal surgery in our cohort. This frequently underestimated postoperative adverse event represents a disabling condition leading to a substantial impairment in the quality of life among the affected patients. Objective: Spinal metastases may present with different degrees of mechanical instability. The Spinal Instability Neoplastic Score (SINS) was developed to assess spinal neoplastic-related instability. Few have validated it clinically. This study aimed to compare the progression of a pathologic fracture due to spinal metastases between a conservative treated group and a group treated according to the SIN-Score. Methods: A retrospective analysis of patients with a pathologic fracture due to a spinal metastasis between January 2018 and December 2018 was performed. We selected patients with a minimum follow-up of 12 months and analyzed them according to the SINS criteria. All patient in this group did not underwent any spinal surgery. For the interventional group, we selected all patient with initial diagnosis of spinal metastasis in 2020. For the further analyzation we collected all patient, which underwent a spinal surgery by our department of neurosurgery in 2020 and a minimum follow-up of 12 months. For both groups were the primary endpoint the progression of vertebral body fracture following radiotherapy. Results: In the conservative group 332 Patients were identified. Median age was 68 SD ± 10,3. 38% were Female. Median follow-up was 26 months (range 12-29). 30, 283 and 19 Patients presented with low (0-6), moderate (7-12) and high (13-18) SINS, respectively. Fracture progression following radiotherapy was seen in 30%, 30% and 42% in cases with low, moderate, or high SINS (p = 0.522), respectively. (44% of progression cases in the low group progressed to the moderate group without neurological deficits. 17% of the progression cases in the moderate group developed neurological deficits). In the interventional group 35 patient were identified. Median age was 66 SD ± 14.17. 60% were female. Median follow up was 12.2 months (12-21). 3, 24 and 8 Patient presented with low (0-6), moderate (7-12) and high (13-18) SINS, respectively. Fracture progression following radiotherapy was not seen in any case. In 21 case we performed 360°stabilization. In 7 cases only a laminectomy was necessary by intraspinal tumor cuff and low / moderate SIN-Score. In other 7 cases we only performed a dorsal stabilization without a corpectomy. In all cases we did not see any secondary alignment disorder or hints for an instability like loosening-hem. The overall survival was, at the follow-up, 59% in the conservative group and 75% in the interventional group. Analyzing the quality of life, we choose the walking ability as a main feature. 92% in the interventional group are still able to walk, in contrast 86% in the conservative group. Conclusion: SINS is a very useful tool for assess stability of a pathologic fracture due to spinal metastases after radiotherapy for spinal metastases. Moderate or high SINS are associated with a very high risk of fracture progression as well as risk for neurological deterioration. A treatment according to the SINS-Score show a satisfying result with conservation of the walking ability. Furthermore, there are hints, that a corpectomy is not always necessary due to the secondary strengthening of the vertebral body by radio oncology.

tumors make for only about 10% of spinal tumors, with 90% being metastasis originating from another primary tumor. These patients are at high risk from suffering a pathological fracture (9-29%), and possible subsequent neurological deficits and uncontrollable pain. Treatment of spinal metastases in terminal patients is a great challenge for orthopedic surgeons as there are no guidelines to treatment, and clear consensus does not exist. The aim of this review article is to analyze available literature, and make suggestions that would benefit terminal cancer patients, and improve their quality of life. Material and Methods: We conducted an electronic search of PubMed, MEDLINE, EMBASE and Cochrane collaboration. We used keywords 'spinal metastasis'', ''terminal patients'' and ''surgical treatment''. Inclusion criteria were review articles, original articles and articles including adult cancer patients with spinal metastases that were published in the last 10 years in relevant scientific orthopeadic and neurosurgical journals. Case reports, articles about pediatric population and conservative treatment were excluded. Results: In our review of literature we found that there have been multiple attempts by a number of authors to generate an algorithm for treatment of these patients. Tukahashi et al proposed their original scoring system, as Harrington and Kostuiri et al did. We also found that most authors agree that primary aim of treatment is pain relief, followed by motor function and ambulation. If pain control can be achieved, spinal stability and myelodecompression are further steps to prevent patients further reduction of QOL and development of neurological deficits. Multidisciplinary approach is required to make the best patient oriented treatment decision. MRI is the golden diagnostic standard. If all non-surgical pain relief methods have failed and original tumors do not respond to it, pain is a justified indication for surgery, although the patient must be able to withstand the stress of surgery. Minimally invasive surgery techniques are preferable. When opting for surgical treatment it must be decided if the surgery is curative or palliative as postsurgical morbidity incidence and severity is related to extent of resection. Ewer and Ali developed risk categorization geared to oncologic patients that might be useful in decision making. All authors agree that spinal surgeons main goal should be improving patients QOL. Conclusion: We conclude that expected treatment outcome and its impact on terminal cancer patients with spinal metastases QOL is a main factor in decision making. Pain relief in these patients is a priority, and adequate indication for surgery. Achieving spine stability is an added benefit, but not a priority since many patients in this stage of disease are nonambulatory. We acknowledge that there is a lack of available literature considering a growing number of patients. Multicentric studies are required to establish the guidelines for care and pain control in terminal patients with spinal metastases.

A279: Preoperative embolization in surgical treatment of spinal metastases originating from non-hyper vascular primary tumors: a propensity score matched study using 495 patients Olivier Groot 1 , Paul Ogink 2 , Jorrit-Jan Verlaan 2 , Joseph Schwab 1 , and Bas Bindels 1 1 Massachusetts General Hospital, Boston, USA 2 University Medical Center, Utrecht, The Netherlands

Introduction: Preoperative embolization (PE) reduces intraoperative blood loss during surgery for spinal metastases of primary thyroid and renal cell tumors. However, most spinal metastases originate from primary breast, prostate, and lung tumors and it remains unclear whether these and other spinal metastases benefit from PE. Therefore, the primary aim of this study is to assess the efficacy of PE on the amount of intraoperative blood loss in patients with spine metastases originating from primary non-thyroid and non-renal cell tumors. The secondary aim is to assess differences in perioperative allogeneic blood transfusion, anesthesia time, hospitalization, 90-day and 1-year survival, postoperative complication within 30 days, and reoperation. Material and Methods: We retrospectively performed a matched cohort study utilizing a database of 495 operative patients including 54 PE patients and 441 non-PE. After matching on 20 variables, including primary tumor, visceral metastases, number of levels operated, and surgical treatment, 53 PE patients were matched to 53 non-PE patients. The primary outcome was assessed by the Wilcoxon signed-rank test. The extent of tumor blush to the spinal metastases was assessed in the week prior to surgery by a trained radiologist. Tumor blush reduction of >80% was achieved in 87% (47/54) PE patients. Results: The intraoperative blood loos did not differ between non-PE and PE patients (median blood loss with IQR: 0.6 (0.4-1.2) vs. 0.9 (0.6-1.2); p = 0.32). Regarding secondary outcomes, there were no differences between both groups in perioperative allogeneic blood transfusion (p = 0.65), anesthesia time (p = 0.13), hospitalization (p = 0.86), 90-day (p = 0.63) and 1-year (p = 0.69) survival, postoperative complication within 30 days (p = 0.35), and reoperation (p = 0.37). Conclusion: Preoperative embolization before surgery on non-thyroid and non-renal cell spine metastases does not significantly influence the estimated amount of intraoperative blood loss, while accounting for 20 covariates through propensity matching. Our data suggest that patients with these types of spine metastases might not benefit from PE. Larger studies could aid in finding a subset of spine metastases that may benefit from PE.

Introduction: Minimally invasive and Endoscopic spine decompressions are unique based on their bone-, joint-, and tissue-sparing characteristics. Age-induced spinal degeneration results in significant spinal elements and canal changes, often resulting in lumbar spinal stenosis (LSS). When symptomatic LSS occurs, it results in significant pain, disability, and poor-quality outcomes in patients. The treatment thereof, should not compound the morbid status of the already affected patients. Minimally invasive approaches such as microscopic or endoscopic unilateral decompression guarantee less radical approach to patients with overall better clinical outcome compared to conventional open decompressive procedures. Since they are very similar in nature, differences in complication outcomes between these two approaches in the context of bilateral decompression in LSS patients would be an interesting facet of discussion for spine surgeons. However, clinical evidence comparing complication outcomes in microscopic or endoscopic is weak. Hence, strong clinical evidence on this proposition would be appreciated. Materials and Methods: A comprehensive literature review was performed from January 2000 to September 2021. We aimed to investigate if Endo-ULBD and MIS-ULBD show similar surgical and medical complication rates. The selection criteria for included studies comprised: i) comparative studies of Endo-ULBD versus MIS-ULBD for managing LSS, ii) case series of ≥ 10 patients, iii) reported complication incidence, iv) English-only articles, and v) a ≥ 1-year follow-up period. The main outcomes compared between Endo-ULBD and MIS-ULBD surgical approaches included: overall surgical complication incidence, intraoperative, immediate postoperative (defined as: <2 weeks post-surgery), and later postoperative (defined as: ≥2weeks post-surgery) surgical complication, and overall medical complication incidence. The assessed surgical complications included: incidences of dural tear, cerebrospinal fluid (CSF) leak, epidural hematoma, wound dehiscence/exploration, superficial or deep wound infections, chronic low back pain/ failed back syndrome, and re-operation after 2-week postoperative. Odds Ratios (ORs) and Confidence intervals (CIs) were computed for each studied variable. Significance was set at (p < 0.05). Results: Of the 633 LSS patients, 52.76% (n = 334) and 47.24% (n = 299) were Endo-ULBD and MIS-ULBD, respectively. Significantly lower incidences of overall associated medical complications; [OR = 0.14; 95% confidence interval (CI) = (0.03 to 0.59); I 2 = 0%, (p = 0.008)] and overall surgical and medical complication rates; [OR = 0.44; 95% CI = (0.28 to 0.68); I 2 = 0%, (p = 0.0003)] were observed in the Endo-ULBD approach compared to the MIS-ULBD. No significant incidence outcomes were observed for dural tear, cerebrospinal fluid (CSF) leak, epidural hematoma, wound dehiscence/exploration, superficial or deep wound infections, chronic low back pain/failed back syndrome, and re-operation after 2-week postoperative, overall intraoperative, and later postoperative complications (p > 0.05). Conclusion: Generally, individually assessed surgical complication incidence outcome was not significant between the Endo-ULBD and MIS-ULBD approaches. Even though patients treated with Endo-ULBD showed significantly lesser incidence of overall medical and surgical complication rates, both Endo-ULBD and MIS-ULBD are undoubtedly safe and effective for managing LSS patients. Computer tomographic evaluation for fusion were scored by Bridwell and Kim's Fusion Classification. Subsidence grading performing and presence of Halo sign were evaluated at 6 months CT. Results: 57 levels of Endo-TLIF in 47 patients and 50 levels of TLIF in 35 patients were included, with a mean follow up of 14 (9-25) and 23 (13-30) months respectively. There was significant improvement in decreasing pain score in Endo-TLIF and TLIF at 1 week post operation, 3 months post operation and at final follow up were 4.26 ± 1.1, 5.21 ± 1.13 and 5.75 ± 1.18 respectively in Endo-TLIF and 4.36 ± 1.06, 4.84 ± 1.08 and 5.18 ± 1.14 in TLIF respectively, p < 0.05. There was significant improvement in Oswestry Disability index in Endo-TLIF and TLIF at 1 week post operation, 3 months post operation and at final follow up were 41.54 ± 8.19, 48.70 ± 7.72 and 51.74 ± 7.85 respectively in Endo-TLIF and 42.5 ± 8.12, 46.6 ± 8.37 and 49.4 ± 7.79 respectively, p < 0.05. At 6 months radiological evaluation between Endo-TLIF and TLIF, the CT Bridwell Fusion grades were 1.86 (1-2) and 2.5 (2-3) respectively, Kim's CT fusion grade were 3.018 (2-4) and 2.2 (2-3) respectively, Subsidence grades were 0.12(0-2) and 0.7(0-3) respectively. There were more Halo sign in Endo-TLIF (6) than TLIF (2) . Comparison of the Endo-TLIF and TLIF showed significant with more favorable fusion rate in Endo-TLIF of -0.62 ± 0.85 in Bridwell's grading and 0.82 ± 0.91 in Kim's stage and also superior subsidence rate with less subsidence of 0.577 ± 0.121, Kim's subsidence grade. Clinical parameters at final follow up showed Endo-TLIF had significant improved VAS 0.574 ± 0.225 respectively but no statistical difference between Endo-TLIF and TLIF in VAS and ODI in other period between the 2 cohorts Conclusion: Application of Uniportal Endoscopic Posterolateral Lumbar Interbody Fusion achieved comparable clinical outcomes and better fusion with less subsidence than Open Transforaminal Lumbar Interbody Fusion in mid-term evaluation. Introduction: There is limited literature comparing the uniportal full endoscopic posterolateral transforaminal lumbar interbody fusion outside-in approach (ETLIF(O)) with the inside-out approach (ETLIF(I)). Material and Methods: Radiological evaluation was performed on disc height restoration and coronal wedging angle, and operation time (inferior articular process resection time/total operation time) and clinical evaluation were made. Results: 48 cases of insideout and 38 cases of outside-in cases were included. Compared to inside-out, the outside-in approach had significantly less operative time required to resect inferior articular process: 36.55 ± 10.37, and total operative time: 87.45 ± 20.14 min compared to 49.83 ± 23.97 and 102.56 ± 36.53 min, respectively, for the inside-out approach, p < 0.05. Compared to the preoperative state, both cohorts achieved significant improvement of VAS and ODI at postoperative 1 week, 3 months and at final follow up. Both cohorts achieved statistically significant increased disc height with 5.00 ± 2.87 mm, 5.49 ± 2.33 mm and statistically significant improvement in coronal wedge angle with 1.76 ± 1.63°, 3.24 ± 2.92°in the inside-out and outside-in approaches respectively. Conclusion: Complete removal of inferior articular process is the key part of endoscopic fusion with two methods that can be applied: an inside-out approach or an outside-in approach. Comparing both techniques, the outside-in approach has a shorter operative time required for inferior articular process resection and total length of operation with similar good clinical and radiological outcomes. ± 30.28) min; intraoperative blood loss was (20-80) ml, with an average of (55.35 ± 28.32) ml. Among them, 2 cases had marrow after operation. The nucleus protruded again and squeezed the dural sac, and improved after endoscopic repair. One case developed numbness of the lower limbs, which was cured by conservative treatment. The VAS level and ODI scores at 1 day, 3 months, and 6 months after operation were significantly different from those before operation (p < 0.05). The postoperative follow-up period was (12-29) months, with an average of (24.52 ± 8.35) months. At the last follow-up, the modified MacNab standard was used to evaluate the efficacy results, and the excellent and good rate was 94.8%. Conclusion: The percutaneous bilateral foraminal approach endoscopy for the treatment of central bilateral posterior edge rupture has the advantages of less trauma, less bleeding, simple operation, quick recovery, etc., and the early clinical effect is satisfactory. Key words: Percutaneous endoscopy; minimally invasive; foraminal approach; posterior edge rupture of vertebral body; lumbar intervertebral disc herniation. Objective: To compare the short-term clinical effects of unilateral biportal endoscopic (UBE) technique and full-view endoscopic technique for single-segment lumbar fusion. Methods: A retrospective collection of 64 patients who underwent lumbar fusion surgery for lumbar disc herniation from January 2020 to March 2021 in our hospital, including 25 patients with unilateral biportal endoscopic (UBE-PLIF group), 39 cases using full-view endoscopy (Endo-PLIF group). To analyze and compare the general information, operation time (OT), estimated blood loss (EBL), hospital stay (HS), preoperative and postoperative visual analogue scales (VAS) of low back and leg pain, and Oswestry dysfunction index (ODI) and statistical differences in the incidence of postoperative complications and reoperation. At the last followup, the excellent and good rate of postoperative curative effect was evaluated according to the modified MacNab standard. Results: There was no statistical difference in general information (age, gender, diseased segment, etc.) between the two groups (p > 0.05), and there was no statistical difference in the amount of intraoperative blood loss between the two groups (p > 0.05). The operation time of the UBE-PLIF group was significantly shorter than that of the Endo-PLIF group (t = -3.09, p < 0.05). The VAS scores, ODI, and average hospital stay of the two groups of patients before and 6 months after surgery were not statistically significant (p > 0.05). There were no complications or reoperations in the two groups. The two groups of patients were followed up for more than half a year, and there was no statistical difference in the excellent and good rate according to the modified MacNab standard (p > 0.05). Conclusion: Both unilateral biportal endoscopic and full-view endoscopy for single-segment lumbar fusion have achieved short-term clinically satisfactory results, but the unilateral biportal endoscopic technique is more operational than the full-view endoscopy technique. It has the advantages of wider field of view, more flexible operation, simple requirements for surgical instruments, and short operation time. It is worthy of promotion. Background: Lumbar canal stenosis is most common disease of spine affecting the elderly population. In majority of the cases ligamentum hypertrophy is the offending element leading to radiculopathy and canal stenosis. Conventional laminectomy for spine has its inherent complication and minimal invasive techniques was developed to prevent these complication. Enbloc removal of flavum totally from its attachments leaves no residual flavum reducing the incidence of recurrence and creates an expansile space for thecal sac and nerves. With expanding horizons in management of lumbar canal stenosis, endoscopic decompression is getting popularized with satisfying results and outcome. Objective: This study aims to describe the technique of enbloc removal of ligamentum flavum by lumbar endoscopic lumbar decompression which is unilateral approach for bilateral decompression with minimal facet resection in lumbar spine. We also report early clinical outcomes data, highlight the advantages and a proctorship technical guidance. Methods: Total of 18 patients underwent endoscopic en bloc flavectomy for lumbar spinal stenosis with Schizas grade C or D as evident on lumbar MRI (magnetic resonance imaging). Oswestry Disability Index (ODI) and visual analogue scale (VAS) score of the leg and back, duration of walking at once, satisfaction rates was were assessed pre and postoperatively at 1and 3 months. Recommendation to others regarding undergoing the procedure was also recorded. Results: The VAS score preoperatively for back and leg were 4.9 and 6.8 which showed reduction with scores of 1.2 and 2.7 at first month and 2 at third month,1.8 at 6th month for back and leg pain respectively. ODI scores showed a reducing trend with preoperative score of 49.72 and 28.5, 22.5, 24.5 at first, third and sixth month respectively. The duration of walking at once showed upward trend, with duration of 17.1 minutes preoperatively, 27.6, 35 and 32 minutes at first, third and sixth month respectively. Satisfactory rate of 80% was observed in 6 patients and all 18 patients recommended the procedure to others with no intraoperative complications and only 2 patients were not able to return normal life at 3 months and one patient underwent minimal invasive transforaminal lumbar interbody fusion due foraminal disc prolapse and stenosis. Conclusion: Full endoscopic techniques not only provide adequate decompression as conventional surgery but also minimises collateral damage permitting circumferential vision with better delineation of anatomical structures. Removing the flavum en bloc leaves no residual flavum behind achieving adequate decompression and preventing recurrence with favourable postoperative clinical results. Introduction: We designed Percutaneous Transforaminal Endoscopic Surgery (PTES) under local anesthesia and OLIF with self-lock cage through abdominal lateral retroperitoneal approach in a right oblique position for the treatment of L5 spondylolisthesis in order to obtain the direct neurologic decompression, rigid fixation and high fusion rate, and protect the rectus abdominis and its sheath, paraspinal muscles, and bone structures as much as possible. The purpose of study is to evaluate the feasibility, efficacy and safety of this surgical method. Material and Methods: Twelve cases of L5 spondylolisthesis with neurologic symptoms were included in this study. PTES was performed under local anesthesia in a prone position, and then the patients underwent OLIF with selflock cage through abdominal lateral retroperitoneal approach with the external oblique, internal oblique and transverse abdominal muscles bluntly separated in turn for L5/S1 in a right oblique position under general anesthesia. Back and leg pain were preoperatively and postoperatively evaluated using VAS. And the clinical outcomes were evaluated with Oswestry Disability Index (ODI) at the 2-year follow-up. The fusion status was assessed according to the Bridwell's anterior fusion grades. Results: The mean duration of operation was 47.6 ± 6.8 minutes per level for PTES and 79.4 ± 11.7 minutes for OLIF. The mean frequency of intraoperative fluoroscopy was 5 (4-10) times per level for PTES and 6 (5-9) times for OLIF. There was a mean blood loss of 20 (15-50) ml. The mean stay at the hospital was 4 (3-5) days. The average follow-up duration was 26 (24-36) months. For the clinical evaluation, the VAS pain index and the ODI showed excellent outcomes. Fusion grades based on the Bridwell grading system at 2-year follow-up were grade I in 8 segments (66.7%), grade II in 4 segments (33.3%). No patients had any form of permanent iatrogenic nerve damage and a major complication. No failure of instruments was observed. Conclusion: PTES and OLIF with self-lock cage is a good choice of minimally invasive surgery for L5 spondylolisthesis, which can get direct neurologic decompression, easy reduction, rigid fixation and solid fusion, and hardly destroy the rectus abdominis and its sheath, paraspinal muscles and bone structures. OLIF for L5/S1 in a right oblique position could let abdominal contents move to contralateral side with gravity, which makes exposure of surgical vision easier. Introduction: Lumbar spinal stenosis (LSS) is an increasingly frequent pathology, wich accompanies the increase in average life expectancy and entails high costs for our society. Patients with LSS complain of low back and lower extremity pain and have a functional disability. Surgical treatment for (LSS) has been a controversial topic over the last 3 decades. The concept of Full endoscopic surgery, development of specific instruments and equipment, has become a trend to become a gold standard for the treatment of LSS due the advantages in concerning traditional techniques. This cohort study aimed demonstrate the clinical outcomes and any details. Material and Methods: A total of 126 patients with diagnosis of lumbar spinal stenosis were included in this cohort study (66 males, 60 female -the mean age = 58 yo) who underwent a full endoscopic procedure by unilateral interlaminar approach, by the author, between January 2018/ January 2021 using standardized stenosis endoscope following the technical guide purposed by the author. The mean follow up was 25 months. The following measuring instruments were used for the investigation: Oswestry disability index (ODI), the visual analog scale (VAS) of the leg and lower back pain at 1 week, 1 month, 3 and 6 months and 1 year post surgery. At the final follow up, we used modified MacNab criteria to assess the clinical efficiency of surgery. Results: The results show that 76% No longer have leg pain or it was nearly completely reduced and 22% experienced occasional pain. levels operated L4L5 mostly, mean time 85 min, time of hospitalization, a day, return to the work in a average of 10 weeks. Conclusion: The results show that the full endoscopic surgery decompression by unilateral interlaminar approach is a efficient and safe option to the treatment of lumbar spine stenosis. offers advantages in relation to conventional surgery, when the indication criteria and standardized instruments are fulfilled.

A288: Ultrasonic bone scalpel in unilateral biportal endoscopic spine surgery: technique note and preliminary findings Sung Huang Laurent Tsai 1 , Chia-wei Chang 1 , Tung-Yi Lin 1 , Tsai-Sheng Fu 1 , and Mohamad Bydon 2 Introduction: Ultrasonic bone scalpel (UBS) has been extensively used in open surgery. However, the use of UBS in unilateral biportal endoscopic spine surgery (UBESS) has not been reported in the literature. The new technique is sought to protect soft tissue and recover faster with minimal blood loss, faster operation, and shorter hospital stay. The aim of this study is to introduce a new spinal surgical technique of the use of UBS during UBESS and to report the preliminary results of this technique. Material and Methods: Patients with lumbar spinal stenosis who were to undergo single-level L4-5 UBESS were enrolled. All patients underwent follow-up for more than 12 months. Two portals were used for the surgery. Unilateral laminotomy was followed by bilateral decompression under endoscope. We used the UBS system after direct visualization of the target for bone cut. Demographic characteristics, diagnosis, operative time, estimated blood loss were evaluated. Clinical outcomes were analyzed in view of Visual analog scale (VAS), Oswestry Disability Index (ODI), Kirkaldy-Willis scores, and postoperative complications. Results: A total of 10 patients (1 men and 9 women) were enrolled in this study. The mean follow-up period was 13.6 months. VAS, ODI, and Kirkaldy-Willis scores improved after the surgery (p < 0.05). Only one patient experienced neuropraxia and resolved within 2 weeks. There was no durotomy, iatrogenic pars fracture, and infection. Conclusion: UBS under the use of UBESS is safe and efficient from our preliminary results. Long-term follow-up and larger clinical studies are needed to validate the clinical results of this use. Introduction: The impact of low socioeconomic status on delayed presentation to specialists for adolescent idiopathic scoliosis (AIS) remains unclear. The objective of this study is to compare the degree of curvature at initial presentation to a spine surgeon and patients' socioeconomic status. Materials and Methods: Consecutive patients who presented to the orthopaedic spine division for scoliosis evaluation were included in this retrospective study. Cobb angles were then measured from the scoliosis radiographs. Patients with Cobb angle < 10°were excluded. Home addresses were used to calculate the Area Deprivation Index (ADI), a validated measure of socioeconomic status reported as a percentile with 100 representing the most disadvantaged neighborhood. ADI was also stratified high (≥75) and low (<75) levels of deprivation. BMI percentile was calculated using age, sex, height, and weight from Center for Disease Control and Prevention guidelines. A 1:3 propensity score matching (one high ADI patient matched to three low ADI patients) was then performed using age, sex, race, and BMI percentile. Standardized differences less than 0.1 indicated a good match between cohorts. Using the matched cohorts, statistical analysis included Student's T-test or Wilcoxon's rank-sum test for continuous variables and Chi-square analysis for categorical variables. Results: From a total of 425 patients, 131 patients were included in the matched cohorts: 39 high ADI patients (mean 84.6) and 92 low ADI patients (mean 35.8). There was no difference in mean Cobb angle at initial presentation between the high and low ADI cohorts (30.7°vs. 32.5°, p = 0.503). There was also no difference in the Cobb angle severity (p = 0.888) or Lenke Classification (p = 0.862) between the matched cohorts. In the high ADI cohort, 30.8% required surgical treatment within 4 years of initial presentation compared to 23.9% in the low ADI cohort (p = 0.413). Conclusion: Patients with lower socioeconomic status did not present with a higher Cobb angle on initial presentation in AIS in matched cohorts. Further studies are needed to identify other factors associated with disparities in access to care that may influence the degree of curvature at initial presentation in AIS.

A290: The use of artificial intelligence in AIS surgery -Did the predictive model accurately depict the postoperative compensatory sagittal spinopelvic parameters?

Afshin Aminian 1 , John Ngo 2 , Ezra Levy 2 , Noah Boyer 1 , and Evelyn Thomas 1 1 Orthopedics, Children's Hospital Orange County, Orange, USA 2 Orthopedic Surgery, Community Memorial Health System, USA Introduction: Utilization of AI in preoperative sagittal plane planning of adult spinal deformity (ASD) has shown benefits in predicting the compensatory changes in the unfused segments and assists in rod shape design. This is the first reported series of the use of AI in sagittal plane planning in adolescent idiopathic scoliosis (AIS) surgery Methods: From 7/2018 to 12/2020, 54 consecutive cases of patients with AIS underwent posterior spinal fusion (PSF), by a single surgeon, with 6.0 mm Ti precontoured patient specific rods (PSR). Surgeon-planned thoracic kyphosis (TK) and pre-contoured rod shape were used to achieve desired TK and the location of the inflection point. A model was used to predict postoperative pelvic tilt (PT) and lumbar lordosis (LL). Sagittal and coronal radiographic measurements were obtained at preoperative visit and 1-year postoperative visits. 45 patients with minimum 1-year follow-up were included. Statistical analysis was performed, including the Wilcoxon rank-sum test for the TK, PT, and LL between the planned and 1 year follow-up data. Results: Median TK gain from preoperative to 1-year follow-up period was 8°for the whole cohort (p = 0.002). The predicted PT and LL compared to the respective 1-year follow-up data showed no statistical significance. The hypokyphotic subgroup (TK < 20°) (n = 15) demonstrated no statistical significance among planned and 1-year data. Conclusion: The predictive model accurately depicts postoperative compensatory changes in sagittal spinopelvic parameters in patients with AIS undergoing spinal fusion with implantation of pre-contoured patient-specific rods (PSR). Introduction: The optimal technique to surgically correct Adolescent Idiopathic Scoliosis is still today matter for wide debate. Ideally, the optimal surgical technique should allow for substantial correction of the curve on the coronal plane and restoration of the correct thoracic kyphosis, while being safe. High density or 'all-screws' constructs have shown greater correction of the curve on the coronal plane, and are thus considered the 'gold standard'. Here we present a new correction technique based on the combination of screws and sublaminar bands in the apex of the curve (AVDT-apical vertebral derotation and translation technique). Aim of this study is to evaluate the corrective power and safety profile of the presented technique. Material and Methods: The present study is a Retrospective Cohort Analysis. Through a database search, patients surgically treated for AIS in a single Institution were retrieved. We divided the patient cohort into two groups based on the type of instrumentation and the corrective surgical technique adopted. Patients in group A (N = 66) underwent a corrective surgery with all screws or hybrid screws-hooks construct and single rod derotation maneuver. Patients in group B (N = 127) underwent a corrective surgery with hybrid screws-sublaminar bands construct and apical vertebral derotation and translation technique (AVDT). In brief, the technique involves the use of low-density implant, with monoaxial screws in the convex side and sublaminar bands in the concave side of the deformity, with a correction based on a simultaneous direct derotation and translation of the curve apex using screws in the convexity and sublaminar bands in the concavity. Radiographic coronal and sagittal parameters, surgical time, blood loss and complication rates were compared between two groups. Results: The overall cohort consisted in 193 patients, (39 males and 154 females (M:F ratio = 1:3.9) with a mean age of 15.7 years). The mean improvement of the Main Thoracic curve was 70% in the group A and 60.6% in the group B, while the mean improvement of the TL/L curve was 65.5 and 72.4%, respectively (p = ns). No significant differences were found concerning the sagittal parameters; however, Group B. Group A had a total rate of complications of 9.1% (6/66) while group B had a rate of 6.29% (8/127, p = ns). Group A and group B does not show significant differences in risk of wound infection (p = 0.21), neurologic complication (p = 0.97) and risk of implant related complications (p = 0.62). Group B showed a reduction of the surgical time (average reduction of 38 min) and of the blood loss (mean reduction of 188 ml), compared to Group A. Conclusion: The AVDT technique appears to be effective in coronal and sagittal plane correction, with a similar rate of implant related complications when comparing the all screws or hybrid screws-hooks construct and single rod derotation technique. AVDT Technique is easy, with less operative time, less blood loss and a comparable corrective power and safety profile to high density construct. Introduction: Closed-incisional negative pressure therapy (ci-NPT) was designed for the management of closed surgical incisions and for removing fluid away from it using a continuous application of negative pressure. This device is a new measure that has been taken to reduce the incidence of wound complications, including wound infections, wound dehiscence, and seromas, which are some of the most common complications following spinal operations. Still, it is important to select patients appropriately with emphasis on risk factors that increase wound complications as neuromuscular or syndromic diseases. This case series aims to report the results of the PREVENA ® ci-NPT used as a prophylactic measure in closed surgical wounds in patients with risk factors for wound complications after scoliosis correction surgery. Materials and methods: A descriptive retrospective case series is presented. Patients taken to a scoliosis correction surgery with a ci-NPT PREVENA ® system applied, between January 2019 to December 2020, were included. Patients with postoperative follow-up in other institutions, surgical site infection or tumoral spine precedent, and durotomy or spinal fluid fistula were excluded. A frequency analysis was performed and particularities of some cases were presented. Results: Seven patients met the inclusion criteria and had a PREVENA ® ci-NPT applied. Six patients had NM scoliosis and one had syndromic scoliosis. Three were females and four were males. The mean age was 14.4 years (min 12 year -max 18 years). The mean BMI was 15.97 kg/m 2 (min 14.56 kg/ m 2 -max 21.50 kg/m 2 ). The comorbidities associated with scoliosis were cerebral palsy (3 cases), Dandy Walker Syndrome (1 case), Friedreich Ataxia (1 case), myelomeningocele (1 case), and partial trisomy 6 (1 case). Two patients had staged scoliosis correction surgery. The mean time of use of PREVENA ® was 6.2 days (min 5 days-max 7 days). None presented surgical site infection nor inadequate soft tissue coverage. A patient with NM scoliosis who had a two-staged correction surgery, with a ci-NPT system applied on the first surgery, but not after the second-stage, presented wound dehiscence that required outpatient wound clinic. Conclusions: ci-NPT is a recent instrument for preventing wound complications, as well as promoting early wound closure. Thus, an individual approach is required to achieve a lower rate of complications. More evidence is necessary regarding its use in spine surgery and mostly, the prophylactic use in selected cases of severe scoliosis correction surgery.

which extends the Lenke classification to the AdIS population. The purpose of this study is to analyze the ability of this classification system to classify a consecutive series of operatively treated AdIS patients and predict operative management. Material and Methods: 71 consecutive AdIS patients treated at a single-institution with posterior spinal instrumentation and fusion were evaluated. Cases were classified by the new triad AdIS classification, which consists of curve type(1-6), lumbosacral modifier (LS): nonstructural (NS) or structural (S), and global alignment modifier: Aligned (A), Sagittal Malalignment (SM), Coronal Malalignment (CM), Combined Sagittal and Coronal Malalignment (CSCM). All curves were classified and fusion levels were correlated with classification recommendations. (6), CM: 9.9% (7); CSCM: 8.5% (6) . The 4 most frequent curve patterns were 1/NS/A, 3/NS/A, 6/S/A, and 5/ S/A, accounting for 49.3% of cases. Mean fusion levels were 14.4levels. Mean OR time was 424min. Mean EBL was 1164mL, and mean length of stay (LOS) was 5.4 days. Fusion levels followed classification guidelines in 72% of cases overall, and in 79% of type 1 curves, 67% of type 2 curves, 62% of types 3 curves, 80% of type 4 curves, 64% of type 5 curves, and 79% type 6 curves. 32/34 (94%) structural versus 18/37(49%) NS LS curves were fused (p < 0.001). 18/ 19(95%) pts with global malalignment had fusion constructs extending to S1/ilium. Significant improvement in SRS and ODI scores was seen after 2 years (Preop:SRS = 70.3, ODI = 29.1; 2-year:SRS = 89, ODI = 13.6; p < 0.001). Conclusion:

The new AdIS classification successfully classified 71 consecutive operative AdIS patients. The most prevalent curve patterns were 1/NS/Aligned, 3/NS/Aligned, 6/S/Aligned, and 5/S/Aligned. Treatment adhered to classification guidelines in 72% of cases. Introduction: Successful full-time bracing in adolescent idiopathic scoliosis is dependent upon good brace weartime adherence. Self-reported orthosis wear time is unreliable and overestimated. Previous bracing studies have utilised an array of thermal sensors with great variability in the methodology to validate such sensors, many of which use self-reported wear-time diaries as the "gold standard" to which the sensor is tested against. No previous studies have used a fixed don-doff protocol to characterise the thermal profile of the sensor. Little is known about the optimum anatomic position to fit the sensor in the brace, or the thermal micro-climate in each position. We aimed to identify the best position within the brace to fit the temperature sensor, to quantify warm up and cool down effect, and calculate the optimum threshold temperature for agreement between measured and true wear time. The outcomes of this paper will inform the upcoming BASIS multicentre national RCT brace trial evaluating full-time versus night-time bracing. Material and Methods: Seven Orthotimer and five iButton (DS1925L) sensors were synchronised to record temperature at five-minute intervals. Three healthy participants donned a rigid spinal brace, embedded with both sensors across four anatomical locations (abdomen/axilla/lateral-gluteal/sacral). Universalcoordinated-time wear protocols were performed in/outdoors. Intraclass correlation coefficient (ICC) assessed sensor-measured and true wear time agreement at thresholds 15-36 o C. Results: Optimal thresholds, determined by largest ICC estimate: An inverse relationship exists between warm-up and cool-down time, thus ideal threshold for each sensor and location was identified when mean warm-up and cool-down times were equal. Orthotimer thresholds as follows, abdomen 26degrees (ICC 0.901, p < 0.001), axilla 27degrees (ICC 0.966, p < 0.001), lateral-gluteal 24degrees (ICC 0.898, p < 0.001), and sacrum 22.5degrees (ICC 0.184, p = 0.284). iButton thresholds as follows, abdomen 26.5 degrees (ICC 0.888, p < 0.001), axilla 28degrees (ICC 0.947, p < 0.001), lateral-gluteal 23.5degrees (ICC 0.673, p = 0.006), and sacrum 24degrees (ICC 0.404, p = 0.079). Mean warm up and cool-down time to optimal temperature in each location for Orthotimer: abdomen 10 minutes, axilla 12 minutes, lateral-gluteal 17 minutes, and sacrum 13 minutes. Mean warm up and cool-down time to optimal temperature in each location for iButton: abdomen 6 minutes, axilla 6 minutes, lateral-gluteal 8 minutes, and sacrum 11 minutes. Warm-up time and error at optimal thresholds increased for moulded sensors covered with lining. Conclusion: Location: anterior abdominal wall. Excellent reliability and higher optimal thresholds, less likely to be exceeded by ambient temperature; not a pressure area. Sensor: iButton. Longer battery life and larger memory than Orthotimer; allows recording at 10 min intervals for life of brace; Orthotimer only able to record every 30 mins increasing error between true and measured wear time; Orthotimer needs 6-monthly data download. Threshold: 26 o C is optimal threshold to balance warm-up and cool-down times for accurately measuring wear time. Sensor should not be covered by lining foam as this significantly prolongs warmup time. Introduction: Scoliosis is a medical condition diagnosed in numerous adolescents affecting the spine by causing a threedimensional deformity along three planes. The three planes involved are frontal, horizontal, and sagittal planes. Untreated, especially at an age where children have yet to skeletally mature, may lead to the rapid deterioration of the deformity. There are currently multiple approaches to treat severe scoliosis in adolescents, one of them being Vertebral Body Tethering (VBT) surgery. VBT is a novel surgical technique used on adolescents; it is often referred to as a "growth modulating technique." It allows for children who undergo this surgery to maintain the natural growth potential of the spine, guided by the tethers, to grow in a healthier direction with the intention to correct the extreme scoliotic curvatures. Material and Methods: This study is designed as a retrospective analysis of the XRAY scans taken pre-and postsurgery of adolescent patients diagnosed with scoliosis. As of August 2021, the number of VBT surgical procedures performed in Hong Kong is 22. 20 of the 22 patients were recruited for this study given their surgical dates and time frame. All patients and their caregivers were consented to allow for our use of their data. Results: In the sagittal view, thoracic kyphosis, lumbar lordosis and PT were measured. Patients were grouped according to their angle values. For Thoracic kyphosis, 12 patients were within the normal range (10-40°), 5 were hypokyphotic (50°). For Lumbar Lordosis, 4 patients were within the normal range (25-45°) while the remaining 15 patients were hyperlordotic (>45°), the ranges were as described by Lin et al5. With PT, patients were grouped using their PI value where they were either within normal ranges (35-55°), greater than (>55°) or below normal range (<35°) with 10, 4 and 5 patients in each group respectively. Pre-op and latest post-op follow up data was taken for analysis. Coronal Cobb angles were analysed at 6 months post-op follow-up. The mean Cobb angle of the tethered section at pre-op, immediate post-op, and 6 months post-op, is 49.81 ± 8.38, 26.32 ± 7.11, and 23.13 ± 8.67 respectively. The mean change in Cobb angle of the tethered section is 26.68 ± 9.23. Concerning the untethered sections, the average Cobb angle measurement at pre-op, immediate post-op, and 6 months post-op follow up are 28.72 ± 12.26, 21.25 ± 9.6, 20.13 ± 10.30 respectively. The mean change in Cobb angle from pre-op to 6 months post-op follow up is 8.59 ± 6.64. Conclusion: To conclude, through observation, the results have shown that the VBT procedure has positive impacts for curve correction, despite the lack of statistical testing to support, due to limited sample size. For future directions, a similar study can be conducted for patients undergoing the spinal fusion surgical procedure. Results from the two studies can then be compared to understand which procedure may be more beneficial for the patient's condition and overall wellbeing. In addition, the psychological impact of the VBT procedure can be analysed to potentially understand how the patient and their family members are affected psychologically from diagnosis to surgery to recovery. The objective of this study is to examine which intervention (anterior or posterior spinal correction and fusion) has the best functional clinical outcome (in terms of pain, participant satisfaction and function), the best radiographic results and the lowest complication rates in people with AIS. Material and Methods: English-language literature on selective fusion treatment of AIS published before January 2019 was retrieved from the PubMed, Embase, Cochrane and Medline databases. Searches were undertaken to identify relevant papers on the surgical treatment of Adolescent Idiopathic Scoliosis. The search strategies (keywords) were developed specifically for each database. Searches were not limited by language, publication status (unpublished or published) or date of publication. Only studies conducted in humans were sought. Studies were manually selected for inclusion based on preset criteria. Two review authors (MH and PW) will independently perform the first screening based on title and abstract and subsequently apply the selection criteria to the articles. Results: 11,017 articles were found in the search and 33 eligible studies were found that compare anterior versus posterior instrumentation and spinal correction and instrumented fusion in people between 10 and 21 years old. 5 of these articles met the Cochrane criteria of being a prospective study or randomized controlled trial. Of the 5 articles that met the Cochrane criteria, 3 articles concerned thoracic scoliosis and 1 concerned (thoraco) lumbar scoliosis. Curve correction is comparable in both groups, post-operative pulmonary function is significantly lower in the anterior group. Operative time and blood loss is significant higher in anterior spinal fusion (p < 0.05). Instrumented levels are lower in anterior spinal fusion, however, is this approach limited suitable. The severity and amount of complications are higher anterior spinal fusion group p < 0.046). Conclusion: Both anterior and posterior approaches are effective for treatment of AIS. Not every Lenke curve type and pattern is suitable for only the anterior approach. From the results we found in our meta-analysis we conclude that in AIS, a posterior approach is most suitable in most of Lenke curve types. In our analysis we saw a lower complication rate, less severe types of complications, less blood loss and overall the same or better satisfaction in outcome. Weill Cornell Brain and Spine Center, Neurosurgery, New York, USA Introduction: Blended learning, which combines in-person learning and e-learning, has grown rapidly in education. Advantages of this modality include control over content, learning sequence, and pace of learning, allowing participants to tailor their experiences to meet their personal learning objectives. Blended learning enables adaptive and collaborative learning and transforms the teacher's role from transmitting knowledge (instructing) to facilitating learning. Objectives: Our study aimed to assess the efficacy of blended learning in a pediatric scoliosis training program through the largest Surgical Training Institution in Sub-Saharan Africa, The College of Surgeons of East, Central and Southern Africa (COSECSA). Material and Methods: The course comprised of three parts; 1-the online portion, which allowed participants to review lectures, papers, and audiovisual materials over a 3-week period; 2-the in-person session, where participants spent a full day with an international expert, reviewing cases in a team-based approach and coming to a consensus on treatment strategy; and 3-a one week, in-person experience where participants were exposed to pre-surgical planning conferences, clinic, casting, and scrubbing into surgeries with international experts. All participants completed a Needs Assessment (NA) and quiz prior to the course. The NA contained 6 various topics, with 3 questions for each topic scored by a 10-point scale in pediatric spine deformity. The quiz included 15 surgical and clinical questions related to the pediatric spine deformity topics. The NA and quiz were taken before the course, after the online session, and after the in-person session. A final survey was conducted at the end of the in-person surgical week. Results: Thirty-six orthopedic surgeons and neurosurgeons enrolled in the course primarily from Tanzania, Kenya, and Malawi. The NA assessment scores improved significantly over the course of the three surveys from 67.3 prior to the course, to 90.9 mid-course, and 94.0 after the course (p = 0.0007). The clinical quiz scores improved over the 3 time points from 9.91 to 11.9, and 12.3, respectively. At the end of the in-person surgical week, 100% of respondents stated that they had improvement in knowledge and 92% considered the knowledge sufficient to change their clinical practice. In surveying the persistent obstacles to translating knowledge gained through blended learning to clinical practice, the top responses were constraints in personnel and cost of implants at their home institution. Conclusion: The blended learning approach in a pediatric spine deformity program is effective, feasible, and shows a statistically significant change in participants' confidence and knowledgebase in these complex pathologies. Our results are limited due to the small sample size. Future studies will evaluate larger number of participants in the post-COVID era and translation to other areas of spine surgery, such as minimally-invasive surgery.

OP34: Tumors: Outcomes 1246 A298: Local control and retreatment rates favor spine stereotactic body radiotherapy as compared to conventional external beam radiotherapy: a retrospective analyses from an institutional cohort of patients enrolled in a phase II/III randomized controlled trial with mature follow-up Introduction: Metastases can modify the load bearing capacity of the vertebra and trigger catastrophic events, such as paralysis. In case of vertebrae with lytic lesions, which appear as voids in the radiographical images, lesions size and position are fundamental predictors of the bone strength [1] . By contrast, it is not clear how blastic tissues, which appear as radiographically dense regions, affect the vertebral strength. In fact, while blastic lesions increase the bone mineral density and would be expected to improve bone strength, fractures frequently occur in patients with these metastases. The aim of this study was to evaluate if the radiographical images reflect the mechanical behaviour of vertebrae with different types of metastases. Methods: 20 thoraco-lumbar cadaveric spine segments were obtained through an ethically-approved donation program. Each consisted of one vertebra with radiologically observable lytic (n = 13) or blastic tissue (n = 7), and one adjacent vertebra without visible lesions, serving as a control. Each segment was loaded in compression, while the specimen geometry and microstructure were acquired with time-lapsed microCT imaging (Scanco VivaCT80, isotropic voxel size = 39 um) from the unloaded condition and up to failure. From these images, a global Digital Volume Correlation approach (BoneDVC [2] ) was used to quantify the strains distribution at fracture within the vertebral bodies, with a measurement spatial resolution of 1.95 mm. The failure load was recorded for each spine segment. The three-dimensional strain distributions were compared between the metastatic and the control vertebrae (Kolmogorov-Smirnov test). Compressive strains were averaged on each metastatic and control vertebra to identify the vertebra undergoing the largest deformations, which are indicators of tissue failure. Results: The volume of the lytic or blastic lesions ranged 1%-36% or 4%-24% of the vertebral body volume, respectively. The failure load of the specimens with lytic or blastic metastases was 1859 ± 929N or 2903 ± 2180N (mean ± SD), respectively. These failure loads correspond to the lower range of the typical healthy thoracic and lumbar vertebrae [3, 4] . Significant differences were found between the strain distribution of the metastatic and control vertebrae (p < 0.05). The failed bone tissue was localized in the metastatic vertebra for all specimens with lytic lesions (13/13). In the specimens with blastic lesions failure was either localized in the metastatic (3/7) or control vertebra (4/7) for. Surprisingly, some regions of blastic tissue (high bone density) experienced larger (>1%) local deformation and more heterogeneous strains than regions with low bone density. Conclusions: Size and position of lytic lesions are confirmed as fundamental predictors of the bone strength. Conversely, vertebrae with blastic tissue showed a complex mechanical behavior which cannot be predicted with only lesions size and position. In some specimens, the radiographically dense regions seem to be weaker than the healthy trabecular tissue. This could be due to the different local mechanical behavior of the blastic tissue [5] , as highlighted for the first time by the unexpected deformation pattern within the vertebrae. Acknowledgements: The study was partially funded by AOSpine ( Introduction: Best available evidence supports highly invasive en bloc resection for primary tumors of the spine to decrease local recurrence. These operations are however challenging and associated with a high rate of adverse events (AE). The impact of adverse events on patient reported outcomes is unknown and is critical to the shared decision making process and to quality improvement initiatives. Our objectives were to assess the rate of surgical adverse events from a large multicenter registry and their impact on patientreported outcomes and prognosis. Material and Methods: The Primary Tumors Research and Outcomes Network (PTRON) is a multicenter international prospective registry. We selected adult patients with documented surgical treatment and available follow-up data at 3 months. Our primary outcome was the risk of adverse events (total, intraoperative and post-operative). The secondary outcomes were patient-reported quality of life (measured with SOS-GOQ, SF-36 and EQ-5D), readmission, reoperation and mortality at 3 and 12 months post-op. We performed a descriptive synthesis of our results as well as a multivariate logistic regression model to assess the impact of adverse events on outcomes. Results: From the 944 patients enrolled in PTRON, 362 met inclusion criteria (211 males/ 151 females). The mean age of the cohort (±SD) was 48.2 years (±17.0). The most frequent histology was chordoma (33.7%) followed by MPNST (15.2%) and chondrosarcoma (10.5%). The thoracolumbar spine (T3-L5) was the most frequent location (54.7%). Sixty-two percent of the patients did not have prior surgical treatment. Sixty-nine patients (19.1%) experienced at least one intra-operative adverse event and 116 patients (32.0%) had at least one post-operative adverse event within 3 months. Overall, 157 patients (43.4%) experienced AE. After univariate analysis, results showed that the risk of readmission was significantly higher in patients who experienced adverse events (23.1 vs 6.1% at 12 months; p ≤ 0.001). Health related quality of life measured with EQ-5D showed a significantly smaller change from baseline to 12 months in patients with AE (0.0 vs 0.1; p = 0.015). Risk of reoperation and mortality were similar regardless of AE status. Conclusion: The rate of surgical adverse events is considerable in this patient population, but lower than what was previously reported in previous single center studies. Surgical adverse events seem to be associated with a higher risk of readmission and a smaller improvement of patient-reported health status, but don't seem to result in higher risk of reoperation or mortality. 1265 A301: Development and external validation of predictive algorithms for 6-weeks mortality in spinal metastasis using 3675 patients from 4 institutions Aditya Karhade 1 , Olivier Groot 1 , Joseph Schwab 1 , and Bas Bindels 1 1 Massachusetts General Hospital, Boston, USA Introduction: Historically, spine surgeons used expected postoperative survival of 3-months to help select candidates for operative intervention in spinal metastasis. However, this cutoff has been challenged by the development of minimally invasive techniques, novel biologics, and advanced radiotherapy. A recent study from AOSpine showed that life expectancy of 6 weeks may be enough to achieve significant improvements in postoperative health-related quality of life. The purpose of this study was to develop a model capable of predicting 6-week mortality in patients with spinal metastases treated with radiation or surgery. Material and Methods: Retrospective review was conducted at 4 large tertiary centers throughout the USA. The development cohort consisted of 3,001 patients undergoing radiotherapy and/or surgery for spinal metastases from one institution. The validation institutional cohort consisted of 674 patients from three independent, external institutions. Five models were considered to predict sixweek mortality, and the model with the best performance across discrimination, calibration, decision-curve analysis, and overall performance was integrated into an open access web-based application. Results: The most important variables for prediction of 6-week mortality were albumin, primary tumor histology, absolute lymphocyte, three or more spine metastasis, and ECOG score. The elastic-net penalized logistic model was chosen as the best performing model with AUC 0.84 on evaluation in the independent testing set. On external validation in the 674 patients from the three independent institutions, the model retained good discriminative ability with an area under the curve of 0.81. The model is available here: https://sorg-apps.shinyapps.io/ spinemetssurvival/. Conclusion: As more patients with spinal metastasis are considered for operative intervention, the algorithm developed and externally validated in this study may be helpful for preoperative planning, multidisciplinary management, and shared decision making. Introduction: Surgery and radiotherapy have shown to be effective treatments to improve pain and health related quality of life (HRQOL) in patients with spinal metastases. However, up to 23% of patients report being dissatisfied with the outcomes of their treatment. A discrepancy between patient expectations regarding their treatment outcome and the actual perceived treatment outcome is thought to be a common course of dissatisfaction. Currently, no clinical tools exist to verify patient expectations in patients undergoing treatment for spinal metastases. The purpose of this study was therefore to develop a questionnaire to evaluate patient expectations in patients with spinal metastases. Material and Methods: An international qualitative study was conducted in 3 phases to develop the PEPSO questionnaire. Phase 1 included individual semi-structured interviews with patients with spinal metastases, family members of patients, and health care professionals involved in the care of patients with spinal metastases. Phase 2 included the development of an item pool and development of a preliminary version of the questionnaire based on the findings in the interviews. Phase 3 involves administering the preliminary version of the questionnaire to patients and the final selection of items. Results: In phase 1, a total of 24 patients, 13 family members and 22 physicians were interviewed. In phase 2, a preliminary version of the questionnaire was developed. Items in the preliminary version addressed expectations regarding goals of surgery; treatment outcomes including physical functioning, pain and social activities; recovery timelines, and life expectancy. Phase 3 is nearly completed and based on the results of administering the preliminary version of the questionnaire, a final selection of items will be made. Conclusion: The Patient Expectations in Spine Oncology (PEPSO) questionnaire to evaluate patient expectations regarding outcomes of treatment for spinal metastases was developed based using a qualitative study involving patients and health care professionals. The questionnaire will allow verification of patient expectations in the clinical setting and will help clinicians to guide patients towards realistic expectations. The next step will be to evaluate the validity and reliability of the PEPSO questionnaire. We analysed patients who underwent surgery for thoracolumbar metastatic spine disease (MSD) from Jan2011-Oct2017. Patients were divided into minimally invasive spine surgery (MISS) and open spine surgery (OSS) groups. Spinal instability patients were treated with PPSF/OPS with pedicle screws. MSCC patients were treated with MASS/OPSD. Outcomes measured included intraoperative blood loss, operative time, duration of hospital stay and ASIA-score improvement. Time to initiate radiotherapy and perioperative surgical/non-surgical complications were recorded. Propensity-scoring adjustment-analysis was utilized to address heterogenicity of histological tumor subtypes. Results: Of 200 eligible patients, 61 underwent MISS and 139 OSS for MSD. There was no significant difference in baseline characteristics between MISS and OSS groups. In the MISS group, 28 (45.9%) patients were treated for spinal instability and 33 (54.1%) patients were treated for MSCC. In the OSS group, 15 (10.8%) patients were treated for spinal instability alone and 124 (89.2%) were treated for MSCC. Patients who underwent PPSF had significantly lower blood loss (95 mL vs 564 mL; p < 0.001) and surgical down regulation of the major lactate transporters, the monocarboxylate transporters (MCT 1 and 4) . Methods: Gene expression profiles of various OS cell lines (SaOs, MNNG and HOS) in varying metabolic conditions (i.e varying lactate and glucose concentrations) were analyzed. Immunblotting and qPCR were used to analyze expression patterns of overall MCT1 and MCT4, and surface expression of MCTs were determined using immunofluorescence microscopy. For each trial, cell proliferation was analyzed via CyQuant direct cell proliferation kit (Fischer Sci). Experiments were performed in triplicate. Conditions included combinations of low, normal, and high glucose (1, 6, and 20mM respectively) with low, normal, and high lactate (0.1, 1, and 5mM respectively). All data are presented as the means ± SD where appropriate. We performed statistical analysis using Student's t-test; p less than 0.05 was considered statistically significant. Results: MCT1 and MCT4 were expressed in OS cell lines. MCT4 expression was upregulated in high glucose conditions. Conversely, MCT1 and MCT4 expression did not change in varying lactate concentrations or lactate only conditions. Further, cells were not viable when cultured with lactate alone. Finally, use of commercial MCT inhibitors resulted in decreased cell survival, demonstrating inhibition of both MCT1 and MCT4. However, inhibition of MCT4 led to the most profound effects. Conclusion: The main lactate exporter, MCT4, was upregulated in high glucose conditions, indicating an increased glycolysis to lactate with increased lactate export. Further, cells were not viable when cultured with lactate alone, unlike numerous other non-tumorous tissues that uptake and use lactate as a fuel. OS cells appear to preferentially produce and export lactate, particularly if glucose is abundant, even in non-hypoxic conditions (the "Warburg effect"). Together these data suggest that lactate exportation via MCT4s is critical to osteosarcomagenesis, and may serve as a unique target for spinal osteosarcomas. Development of therapies targeting lactate transportation could lead to novel adjuvant therapies for patients with OS. cervical discectomy and fusion (ACDF). However, allograft height selection mostly relies on intraoperative assessment and surgeon's subjective judgment. If preoperative radiographic parameter is correlated to optimal allograft height that can result in high fusion rate and less subsidence, it would be an objective guide for allograft height selection. Furthermore, surgeons would also understand how much distraction should be made during the operation. Therefore, the present study was conducted to determine the radiographic parameter than can help surgeons select optimal allograft height for ACDF which could result in improved outcome. Materials and Methods: A total of 148 patients who underwent ACDF using allografts and were followed-up for more than 1 year were retrospectively reviewed. Segments were divided into two groups according to whether the inserted allograft height was within 1 mm from the following three reference radiographic parameters: 1) uncinate process height, 2) adjacent disc height, and 3) preoperative disc height +2 mm. Fusion rates, subsidence, segmental lordosis, and foraminal height were compared between the two groups for all parameters. Results: This study included 101 patients with 163 segments. Segments with an allograft-uncinate height difference of ≤ 1 mm had a significantly higher fusion rate at 1-year follow-up compared to segments with allograft-uncinate height difference of >1 mm (85/107 [79.4%] vs. 35/56 [62.5%]; p = 0.025). Subsidence, segmental lordosis, and foraminal height did not significantly differ between the groups when segments were divided according to uncinate height. In addition, using preoperative disc height +2 mm or adjacent segment height as a reference was not significant in terms of fusion and subsidence. Multivariate logistic regression analysis demonstrated that allograft-uncinate height difference of ≤ 1 mm and allograft failure were factors associated with fusion. Conclusions: The uncinate process height reflects normal patient anatomy and can guide optimal allograft height selection for ACDF. Using an allograft with an allograft-uncinate height difference of ≤1 mm resulted in a higher fusion rate. Therefore, the uncinate process height should be checked preoperatively and used intraoperatively when selecting an allograft height. 757 A308: Predicting head position change in long-term radiographic assessment of occipitocervical fusion: age is key Anthony Oyekan 1 , Stephen Chen 1 , Gannon Rooney 1 , Sumail Bhogal 1 , Aaron Zheng 1 , Asher Mirvish 1 , Raghav Ramraj 1 , Joshua Adjei 1 , Jeremy D. Shaw 1 , and Joon Y. Lee 1 1 Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, USA Introduction: Occipitocervical fusion (OCF) is indicated to treat a wide variety of craniocervical junctional pathology.

Intraoperative imaging is frequently used by surgeons to guide alignment due to the importance of head position when fusing across the occipitocerval junction. Careful attention is paid to head position to avoid excessive flexion or extension. Post-operative imaging studies are routinely performed to assess head position and / or hardware complication. While several studies have assessed radiographic outcomes in patients with OCF, none to date have assessed predictors of head position change in long-term radiographic imaging. This study's aim was to determine the risk factors for head position change following OCF over time. Material and Methods: Retrospective analysis of a prospectively collected database identified forty-one patients who underwent OCF between January 2005 and January 2021, of that cohort, patients were selected for those having both immediate post-operative and long term outpatient radiographic assessments of the upper cervical spine. Their medical records were reviewed for comorbid conditions including diabetes mellitus, tobacco use, and rheumatoid arthritis/autoimmune conditions. Body mass index (BMI) was also recorded. Head position was determined by the occipitoaxial angle (OC2A) and posterior occipitocervical angle (POCA). Head position was recorded in immediate post-operative imaging, at 6-week post-operative assessment, and at most recent radiographic assessment as available. Difference in head position between assessments was calculated. Two-tailed paired ttests were used to determine differences in head position at given intervals. Multivariable linear regression was used to predict change in head position incorporating age, sex, BMI, presence of diabetes mellitus, presence of tobacco use, and history of rheumatoid arthritis/autoimmune condition. p < 0.05 was considered statistically significant. Results: Forty-one subjects (21 M, 20 F; age 65.0 ± 15.6 years) had both immediate post-operative and longterm cervical radiographs. Mean follow-up was 859 days ± 1205 days. At mean 2.4 years ± 3.3 years post-operatively, ΔOC2A decreased (3.2°± 7.2°; p = 0.012) from postinstrumentation OC2A of 26.7°± 6.6°to most recent assessment OC2A of 23.4°± 8.9°. There was no change in ΔPOCA at most recent assessment (0.9°± 11.0°; p = 0.622). At 6 weeks post-instrumentation, there was no change in, ΔOC2A (0.1 ± 3.5; p = 0.826) or ΔPOCA (0.9 ± 3.8; p = 0.175). Results of multivariate logistic regression showed that the independent risk factors for ΔOC2A is age (OR 0.552; 95% CI 0.148-0.645). There was no association with other comorbidities (p > 0.1). Conclusion: The data suggest that OC2A can detect change in head position over time following OCF. Change in head position using OC2A between early post-operative and long-term radiographs at more than 2 years of follow up is strongly associated with increased patient age. Surgeons should beware that head position may change significantly over time following OCF.

Arun Kanhere 1 , Mark Lambrechts 1 , Khoa Tran 1 , Brian Karamian 1 , Taylor Paziuk 1 , Alan Hilibrand 1 , Christopher Kepler 1 , Alexander Vaccaro 1 , and Gregory Schroeder 1 1 Rothman Orthopaedic Institute at Thomas Jefferson University, Philadelphia, USA Introduction: Cervical spondylosis resulting in radiculopathy and myelopathy are common diagnoses for which anterior cervical discectomy and fusion (ACDF) is performed. Although the procedure is generally well tolerated, postoperative dysphagia is a common complication with prevalence ranging from 2% to 71%. Risk factors may be attributed to longer operative times with prolonged retraction, extensive exposure for multi-level procedures, iatrogenic nerve sacrifice, and post-operative edema/hematoma formation. Intervertebral disc space distraction is a necessary step in ACDFs to visualize the operative field, prepare the endplates for fusion, and facilitate graft insertion. However, the degree of distraction tolerated, prior to onset of complications related to dysphagia, is not well characterized. Further, the relationship between facet and disc space distractions with clinical outcomes and complication rates is unknown. Under-distraction predisposes the surgeon to limited visualization to appropriately and adequately manipulate the disc space, while overdistraction has the risk of post-operative pain and subsidence. The current literature is unclear on the optimal relationship between facet distraction/intervertebral disc height and the incidence of dysphagia post-operatively. Material and Methods: After IRB approval, a retrospective cohort study of 70 patients who underwent ACDF between June 2018 and January 2019 commenced. All patients had pre-operative and post-operative radiographs measured for interfaced distraction distance (IFDD) and anterior, middle, and posterior intervertebral distraction distance (IVDD) by two independent reviewers, with intra-reviewer reproducibility measurements after 1 month. In the case of multi-level surgery, the level with the greatest distraction was measured. Primary outcomes were numerical dysphagia (0-10), Eating Assessment Tool (EAT-10), and Dysphagia Symptom Questionnaire (DSQ) score collected at initial visit and 2-, 6-, 12-, and 24-weeks postoperatively. Results: A total of 70 patients met inclusion criteria including 41 females and 29 males, with an average age of 54.6 ± 11.6 years. The number of levels fused were primarily single-level (40%) and two-level procedures (42.9%) with the remaining surgeries comprised of three-level procedures (17.1%). Intra-reviewer reproducibility and interreviewer reliability analysis demonstrated strong agreement between reviewers (Intraclass Correlation Coefficients (ICC) > 0.8 for all measurements). Preoperatively, 13% of patients reported symptoms of dysphagia, which subsequently increased postoperatively at 2, 6, 12, and 24 weeks. The prevalence of dysphagia postoperatively was 34.3%, 22.9%, 15.7%, and 13.4%. There were no differences in prevalence or outcome scores when separated by median IFDD or IVDD. Spearman Rho correlations found no relationship between IFDD/IVDD and dysphagia prevalence, numerical rating, EAT-10, or DSQ. Conclusion: Patients who had an ACDF have an increased risk of dysphagia in the short-term, however, this resolved without intervention by 6 months. Our data suggests increased facet and intervertebral disc distraction does not influence postoperative dysphagia rates. 600 A310: Structural allograft versus synthetic interbody cage for anterior cervical discectomy and fusion: a comparison of one-year outcomes from a national database Justin Turcotte 1 , Elliott Holbert 1 , Nandakumar Menon 1 , and Chad Patton 1 1 Luminis Health Anne Arundel Medical Center, Annapolis, USA Introduction: Anterior cervical discectomy and fusion (ACDF) has emerged as the most commonly performed surgical treatment for degenerative cervical spine disease. Since early descriptions of anterior surgical approaches in the 1950's, advancements in techniques, instrumentation, and implant materials have focused primarily on achieving more reliable fusion of unstable or symptomatic segments. Options for interbody grafts have evolved from tricortical iliac crest autograft to structural allograft (SA) or synthetic cages (SC) of various materials. The potential for graft site complications and additional operative time has led surgeons to increasingly substitute autograft with structural allograft or synthetic cages of various materials such as polyetheretherketone (PEEK) and titanium alloys. Our objective was to further understand potential differences in one-year clinical outcomes between structural allograft and synthetic cages. Material and Methods: The TriNetX Research Network was retrospectively queried. Patients undergoing initial single or multi-level ACDF surgery between October 1, 2015 and April 30, 2019 were propensity score matched based on age and comorbidities. The rates of one-year revision ACDF surgery and reported diagnoses of pseudoarthrosis, surgical site infection (SSI) and dysphagia were compared between structural allograft and synthetic cage techniques. Results: A comparison of oneyear outcomes between propensity score matched cohorts was conducted on 3,056 patients undergoing single level ACDF and 3,510 patients undergoing multi-level ACDF. After propensity score matching, no differences in race, or rates of cervical disc disorders, chronic pain, disorders of bone density and structure, cervical radiculopathy, nicotine dependence, or malnutrition were present. In single-level ACDF patients, there was no difference in one-year revision ACDF surgery (p = 0.573), reported diagnoses of pseudoarthrosis (p = 0.413), SSI (p = 0.620), or dysphagia (p = 0.529) between structural allograft and synthetic cage groups. In multi-level ACDF patients, there was a higher rate of revision surgery (SA: 3.8% vs. SC: 7.3%, OR = 1.982, p < 0.001) in the synthetic cage group, and a higher rate of dysphagia in the structural allograft group (SA:15.9% vs. SC: 12.9%, OR = 0.782, p = 0.011). Conclusion: While the overall revision and complication rate for single-level ACDF remains low despite interbody graft selection, synthetic cage implant selection may result in higher rates of revision surgery in multi-level procedures despite yielding lower rates of dysphagia. Further prospective study is warranted. Introduction: With the advancement of 3D-print technology, porous titanium cages mimicking trabecular bone structure have been suggested to decrease the incidence of postoperative subsidence and enhance bony fusion. The purpose of this study is to demonstrate the clinical and radiologic results of single-level anterior cervical discectomy and fusion (ACDF) using stand-alone 3D-printed porous titanium cage (3D-PTC) in minimum 24-month follow-up in a single institute. Material and Methods: Forty-five patients with single or two level cervical disc disease (CDD) underwent ACDF surgery using stand-alone 3D-PTC implant between December 2016 and December 2018. Operations were conducted by a single surgeon in a single institute under same surgical protocol without any bone graft substitute. All patients completed at least 24 month postoperative follow-up survey. The clinical outcomes were evaluated using the Visual analogue scales (VAS) scores for neck and arm pain, neck disability index (NDI) scores and recovery of postoperative dysphagia. The radiologic results were evaluated with serial plain film and 3D-CT to assess fusion status and device-related complications. Results: The VAS and NDI scores significantly improved compared with preoperative values and maintained until the last follow-up survey. Only 6 (13.6%) patients complained immediate postoperative dysphagia with complete recovery after 1 month. All patients achieved solid bony fusion at the final follow-up with clear visible bone bridge formation across the index level in 3D-CT. No device-related complications were observed except 8 (18.1%) cases of cage subsidence without neurologic deterioration. In the subsidence-group, all of the cages were positioned posteriorly (more than 3 mm distance from the anterior margin of the vertebral body) and none of the anteriorly placed cages (24 patients, 54.5%) showed radiologic signs of subsidence. However, subsidence did not correlate with fusion rate or clinical outcomes. Conclusion: ACDF surgery using stand-alone 3D-PTC demonstrated favorable clinical and radiographic outcomes in minimum of 24-month follow-up. Relatively high rate of postoperative subsidence was occurred in more posteriorly placed cages. 3D-PTC should be placed within 3 mm distance from the anterior margin of the vertebral body to prevent unwanted subsidence. Introduction: There is a paucity of comparative evidence supporting surgical treatment of degenerative cervical myelopathy (DCM). Only one randomized controlled trial has been conducted which found no benefit to surgery. Systematic reviews of observational comparative studies have also not found surgery to be superior to non-operative care. Given the known risks of surgery, with as yet unclear benefits amongst various populations, treatment decisions should be made by synthesizing risk-benefit trade-offs. We have recently completed meta-analyses on (i) the risk of neurologic progression for DCM patients treated conservatively, and (ii) the survivorship of cervical spine surgery. In this paper we present a decision analysis comparing the effectiveness and qualityof-life benefit of conservative care vs surgery for DCM. In this paper we present a decision analysis on the role of surgery in DCM. Material and Methods: A probabilistic patient-level simulation with 100 000 replications was developed using parametric survival models for neurologic progression in CSM and the survivorship of cervical procedures fitted using rigorous meta-regression studies on cohorts of 674 and 98 075 patients respectively. Utilities (QALY weights) for the mJOA were obtained from a general population utility valuation study. Overall survival was obtained from life tables published by Statistics Canada. In Analysis #1, we calculated the time to neurologic progression (TTNP) for DCM patients treated conservatively, and time to second surgery (TTSS) for patients undergoing cervical surgery. In Analysis #2, we compared the QALYs lived by CSM patients treated conservatively and surgically. Results: For Analysis #1, under all simulation conditions, patients were less likely to neurologically decline under conservative care than to either (i) die or (ii) undergo a second surgery if undergoing surgery (TTNP was shorter than death or TTSS in <50% of patients). The results of Analysis #2 varied with baseline myelopathy severity. For moderate myelopathy, 95% CIs for Δ QALYs included 0 for all simulation conditions. For severe myelopathy, 95% CIs for Δ QALYs were greater than 0 patients ≤60 years of age for both non-PDIF and PDIF. Conclusion: If we consider neurologic progression and second surgery as equally undesirable events, Analysis #1 suggests that conservative care is the superior treatment approach. Analysis #2 indicates that we cannot be confident that patients with moderate myelopathy can expect a net QALY benefit with surgery. However, we are 95% confident that patients with severe myelopathy ≤ 60 years of age have net QALY benefit with non-PDIF and PDIF surgeries. Our findings suggest equipoise on the role of surgery for moderate and severe myelopathy. The decision to undergo cervical surgery to prevent neurologic decline must involve shared decision making with the patient. Background: Unexpected intraoperative positive (UIPC) culture has recently become an increasingly important area in revision spine surgery, and it has been reported as an underestimated underlying cause of revision spine surgery, such as pseudoarthrosis. This study aimed to investigate the prevalence of UIPC in patients following presumed aseptic revision spine surgery. Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, several databases were searched until October 2021, and reference articles were searched also. Studies that reported the prevalence of unexpected intraoperative culture in assumed aseptic spine revision surgery. The primary outcome was the pooled rate of UIPC, whereas secondary outcomes included the microbiological profile of UIPC, the relationship of UIPC to the different patient and surgical variables. Results: Of the 1036 articles identified, 11 studies were eligible for the meta-analysis, with a total of 1055 patients. The pooled rate of UIPC was 28.2% [CI: 19.1,39.1, I 2 = 91%, p < 0.01]. Subgroup analysis showed that the UIPC rate was higher when both conventional wound culture and sonication were used together compared to sonication alone or conventional wound culture alone. The rates were 31.5%, 28.6%, and 18.6%, respectively. The most commonly reported organism was Propionibacterium acnes (50%), followed by coagulase-negative staph (36%). Male patients had a higher UIPC (OR: 2.7, 95% CI: 1.88, 3.92, p < 0.001), as did patients with a longer involved spine segment (MD 0.76, 95% CI: 0.27, 1.25, p < 0.001). Conclusions: The pooled rate of UIPC in aseptic spine revision surgery was 28.2%. The most common organisms were P. acne and CNS. There is not enough evidence to recommend treatment. Further studies are needed to establish comprehensive treatment guidelines and diagnostic criteria.

A317: Efficacy of anti tubercular medical treatment in cervical spine tuberculosis patients and its predictors affecting outcome Shah Waliullah 1 Introduction: Spinal tuberculosis is a medical disease. Majority of patients with spinal tuberculosis can be treated by adequate and timely started anti-tuberculous therapy (ATT). Patient presenting with neurological deficit and deformity requires early surgical intervention to prevent catastrophic sequelae. In this prospective cohort study, we evaluated the efficacy of ATT and tried to predict the clinic-radiological factors affecting recovery in conservatively managed cervical spinal tuberculosis patients. Methods and Material: A total of 42 patients (29 males and 13 females) with an average age of 42.5 ± 7.4 years, presented with cervical spinal tuberculosis, were enrolled. All patients underwent either CT guided or fluoroscopic guided biopsy and pus aspiration. ATT was started as per drug sensitivity and institutional protocol. All cases were followed up clinically, radiologically, haematologically and neurologically. Patients were followed up initially at one monthly interval for four months than at three monthly intervals to access long term complications. Functional outcome was accessed in terms of Visual Analog Score (VAS), and disability was assessed in Modified Barthel index (MBI). Results: Out of 42 patients, nine patients required surgical intervention, while the rest were managed conservatively. Patients managed with ATT showed significant progressive improvement in VAS and MBI scores (p < .05) and were associated with good outcomes. On multivariate analysis, we found late presentation, older age, radiological significant cord compression, and a large abscess had a significant correlation and poor prognosis Conclusion: We observed timely started ATT as per drug sensitivity proved to be an effective treatment in most cervical spine tuberculosis patients, so conservative management should be tried firstly in all patients with cervical spine tuberculosis.

A318: Is six months of anti-tubercular chemotherapy as effective as more than 6 months regimen in tuberculosis of the spine? A systematic review and metaanalysis Aayush Aryal 1 , Bhavuk Garg 1 , Nishank Mehta 1 , Vivek Gupta 1 , and Shubhankar Shekhar 1 1 Orthopaedics, All India Institute of Medical Sciences, New Delhi, India Introduction: Historically, osteoarticular tuberculosis (TB), including spinal TB, has been treated with prolonged course of antitubercular therapy (ATT). Due to various challenges, there has been a reluctance to explore the use of short-course ATT regimen in spinal TB. However, with the success of shortcourse ATT being demonstrated in other forms of extrapulmonary tuberculosis, the subject is open for debate again. We therefore systematically reviewed various published literature to determine whether short-course treatment regimen (6 months) of ATT gives equivalent results in terms of healing of the disease as longer treatment regimen (9 months or more) in the management of spinal tuberculosis. Material and Methods: Five electronic databases (PubMed, MEDLINE, EMBASE, CENTRAL, and Web of Science) and their reference lists were searched to identify relevant randomized controlled trials (RCTs) with at least one year of follow-up that compared short-course with standard course of ATT for treatment of spinal tuberculosis. The methodological quality of included studies was assessed and their data was extracted. Meta-analysis was used to calculate pooled effect sizes and 95% confidence interval. The outcome measure was healed status of disease at final follow-up. Results: Out of the 331 publications identified through literature search, 8 publications describing six randomized studies were included. 375/414 patients (90.58%) who received 6 months of ATT had healed status at their final follow-up, compared to 404/463 patients (87.26%) who received 9 months or more of ATT. Overall, the healed status of spinal tuberculosis was equivalent among patients in both groups (pooled RR 0.98; 95% CI 0.92-1.04; p = 0.439). However, there was a considerable heterogeneity among the trials (I 2 = 40.8%; p = 0.149). Conclusion:

The results suggest that the use of short-course (6 months) chemotherapy may be considered for the treatment of spinal TB in view of the similarity in the healing response achieved when compared to treatment regimens of longer duration.

A319: Relative lymphocyte count is lower when the etiological agent in Pott's disease is successfully isolated Igor de Barcellos Zanon 1 , Giselle Burlamaqui Klautau 1 , and Robert Meves 1 culture, or positive molecular rapid test) and unsuccessful isolation (UI) of the etiological agent. Results: From a total of 26 patients diagnosed with tuberculosis in the spine, 21 were male (80.7%) with a mean age of 40 ± 22.5 years. The average lymphocyte counts were higher in the UI group (25.35 ± 13.08, p = 0.025) compared to the SI group (14.18 ± 7.48). Moreover, the monocyte/ lymphocyte ratio was lower in the UI group (0.39 ± 0.22, p = 0.009) in relation to the SI group (0.89 ± 0.65). Relative lymphocyte counts higher than or equal to 16.7, had a sensitivity of 76.9% and specificity of 62.5% for the UI group. Values higher than or equal to 0.58 for the monocyte/lymphocyte ratio showed a sensitivity of 84.6% and specificity of 75.0% for the SI group. Conclusion: No differences were observed in relation to the clinicalepidemiological and radiological characteristics between the two experimental groups. However, the UI group had higher lymphocyte counts and a lower monocyte/ lymphocyte ratio, implying that this group of patients may have a better immunological response. Introduction: One of the most emerging challenges in treatment of tuberculosis is drug resistance. Furthermore, treatment of drug resistant TB is difficult due to duration of treatment, drug toxicities encountered and cost of the treatment. In recent years, only few studies have analyzed outcome of DR-TB. So aim of this study is to compare the outcomes of drug resistant (DR) and non-drug resistant (non-DR) spinal tuberculosis (TB) in children treated conservatively. Methods: This is retrospective analysis of clinical and radiographic data of children treated for spinal TB at a single centre with minimum two-year follow-up. Details of ATT were noted. Outcomes in terms of neurological status and kyphosis angle at final follow-up and complication rates along with conversion to surgery were compared between DR and non-DR cohorts. Drug resistance was diagnosed primarily on sensitivity testing and/or GeneXpert; alternatively, when these were negative, it was diagnosed presumptively on the basis of inadequate clinical and/or radiological response to first-line anti-tubercular therapy. MRI was studied at presentation and at time of discontinuing ATT for resolution of the disease. Results: 118 consecutive children (mean age 8.6 ± 2.5 years, 59 boys, 59 girls) were treated for spinal TB with a mean follow-up of 30 ± 6 months. Of 90 conservatively treated patients, 37 patients had DR TB (41.1%). The mean kyphosis angle at presentation was 13.17°± 4.24°. Neurological deficit or new onset deficit was present in 24 patients. Steroids were administered in 30 patients. Kyphosis angle at final follow-up was significantly higher in DR (mean 39.84°± 19.73°) compared to non-DR group (20.23°± 10.14°) respectively, p = 0.04). Conversion to surgery while on conservative treatment was necessary in 15 patients of which 11 were in the DR group. Complications in terms of rapid progression of kyphosis angle, poor response to treatment, conversion to surgery was more common in DR group than non-DR group. Conclusion: Conservative treatment is an effective method for treatment of Potts spine in children, however close monitoring is required especially in DR group as rate of complications are more. Background: Treatment of infectious spondylodiscitis is based on an antimicrobial therapy for several weeks with an external orthosis. Surgery is not usually required for non-complicated cases. Internal orthosis which is a minimally invasive percutaneous pedicle screw-rod can be an alternative for the external orthosis. Objectives: Our objectives were to asses the clinical and radiological results of a posterior percutaneous fixation in patients with infectious spondylodiscitis. Study Design and Methods: We here report our experience in treating patients suffering from infectious spondylodiscitis with a minimally invasive percutaneous pedicle screw-rod between 2015 and 2019. Postoperative evaluation was clinical with the visual analog scale (VAS) of pain and radiological with the measurement of the regional kyphosis. Results: In this series, 21 patients were treated with mean age of 49 years. Sex-ratio was 0,4. Bacteriological identification was possible in every case. Mycobacterium tuberculosis was present in 12 cases, 7 patients had staphylococcus aureus and 1 had brucellosis. one patient had simultaneous infection with Mycobacterium tuberculosis and Staphylococcus aureus. 10 patients suffered from thoracolumbar, 7 from thoracic and 4 from lumbar spondylodiscitis. None of our patients had neurological deficits (ASIA E). All patients were mobilized on the day after surgery. A significant reduction in the VAS from 7,2 in preoperative to 3,1 in postoperative was noted. The mean angle of regional kyphosis correction was 5.6°with a minor loss of correction of 1.5°. No major complications were noted. Conclusions: The principle of Introduction: To investigate the influence of vertebral subluxation (VS) on vertebral remodeling in ankylosing spondylitis (AS) patients with thoracolumbar kyphosis after closing-opening wedge osteotomy (COWO). Methods: Standing lateral radiographs were taken to evaluate sagittal parameters including thoracic kyphosis (TK), lumbar lordosis (LL), C7 sagittal vertical axis (SVA), global kyphosis (GK), sacral slope (SS), and pelvic tilt (PT). Vertebral parameters including osteotomized vertebra angle (OVA), sagittal translation (ST), anterior height (AH), posterior height (PH), and middle height (MH) of osteotomized vertebrae. Furthermore, lateral area of the vertebral body to evaluate the remodeling of the osteotomy vertebrae after surgery. Results: Sixty AS patients which underwent single-level lumbar COWO and finished a 2-year follow-up were included, consisted of 54 males and 6 females with an average age of 36.6 years (range, 21-63 years). All patients were divided into two groups according to the value of ST, 45 in non-VS group (ST ≤ 5 mm), 15 in VS group (PI ≥ 5 mm). There was no significant difference in sagittal parameters between AS patients with or without vertebral subluxation after COWO. However, significant difference in vertebra-related parameters regarding AH and OVA was found among two groups (p < 0.05). Besides, the mean recovery rate of the lateral area of the vertebral body at the final follow-up in non-VS group is larger than that in VS group. Conclusion: Although the bone fusion and adaptive remodeling during follow-up was surprisingly favorable, the effect of vertebral remodeling is relatively worse in patients with vertebral subluxation after COWO.

A326: Custom made PMMA spacer works as well as preformed PEEK spacer in TLIF with some advantages -mid-term results of a prospective randomized study with a minimum of 12 month follow-up Márton Rónai 1 , Kristóf József 1 , and Julia Szita 1 1 National Center for Spinal Disorders, Budapest, Hungary Introduction: Bone cement is widely used in musculoskeletal surgery to fill in cavities or narrow spaces without the aim of fusion. Another area of use is osteoporotic spine. For biologic reasons there exist a fear of using this material in non-porotic patients when the aim of surgery is fusion. In a retrospective study evaluating sporadic cases with PMMA intervertebral spacers we found very good results. In this prospective randomized study, our aim was to compare outcomes of TLIF surgery using custom made PMMA spacer versus preformed PEEK interbody spacer Material and Methods: 182 consecutive patients to whom we 1 Division of Spine Surgery, Department of Orthopedic Surgery, Nanjing Drum Tower Hospital, The Affiliated Hospital of Nanjing University Medical School, Nanjing, China

Introduction: Few studies have reported the results of twolevel pedicle subtraction osteotomy (PSO) for correction of severe thoracolumbar kyphosis caused by ankylosing spondylitis (AS). However, the remodeling of harmonious physiological curvature has not been well described. Materials and Methods: 26 AS patients treated with two-level PSO were reviewed, and 20 healthy volunteers were enrolled as a control group. Conventional parameters included global kyphosis (GK), thoracic kyphosis (TK), lumbar lordosis (LL), pelvic tilt (PT), sacral slope (SS), sagittal vertical axis (SVA) and osteotomized vertebra angle (OVA). The lordotic angle of the upper and lower arc of lumbar spine, and single segment of the lower arc were recorded. Osteotomized vertebra-end vertebra vertical tilt (OET), end vertebrae vertical tilt (EVT), thoracic SVA (TSVA), lumbar SVA (LSVA), the superior/ inferior endplate angle of OV (SOV/IOV) and OV tilt were newly designed. Results: Significant improvement of all the spinopelvic parameters except TK were observed postoperatively. After surgery, TSVA, LSVA and the lower arc of lumbar spine in patients with relocated LL apex at L3 or L4 were similar to the control group. Additionally, higher levels of OV and ventrally leaning inferior OV were observed in these patients. Nevertheless, TSVA, LSVA and parameters reflecting the magnitude of lumbar spine in patients with relocated LL apex at L5 or others were significantly different from the control group. Conclusions: Higher level of osteotomy sites (T12+L3 or L1+L4) where ventrally leaning wedge-shaped inferior OV is combined with dorsally leaning superior OV contributes to a harmonious physiological curvature. For AS patients with more severe thoracolumbar kyphosis, two-level PSO performed at L2+L5 is recommended to achieve satisfying sagittal balance. Severe scoliosis or hyper-kyphosis patients underwent posterior fixation and fusion surgery using the 3DP spine models were reviewed (3DP group). Spinal deformity surgeries operated by free-hand screw implantation during the same period were selected as the control group after propensity score matching (PSM). The correction rate, pedicle screw accuracy, and complications were analyzed. Class A and B screws were defined as accurate according to Gertzbein and Robbins criteria. Results: 35 patients were enrolled in the 3DP group and 35 matched cases were included in the control group. The perioperative baseline data and deformity correction rate were similar between both groups (p > .05). However, the operation time and blood loss were significantly less in the 3DP group (296.14 ± 66.18 min vs. 329.43 ± 67.16 min, 711.43 ± 552.28 mL vs. 1322.29 ± 828.23 mL, p < .05). More threecolumn osteotomies (Grade 3-6) were performed in the 3DP group (30/35, 85.7% vs. 21/35, 60.0%. p = .016). The screw placement accuracy was significantly higher in the 3DP group (422/582, 72.51% vs. 397/575, 69.04%. p = .024). The screw misplacement related complication rate was significantly higher in the free-hand group (6/35 vs. 1/35, p = .046). Conclusion: The study provided solid evidence that 3DP spine models can enhance surgeons' confidence in performing higher grade osteotomies and improve the safety and efficiency in severe spine deformity correction surgery. 3D printing technology has a good prospect in spinal deformity surgery.

A330: Tandem spondylolisthesis and the rising psoas: the danger of the direct lateral trans-psoas approach Anthony Oyekan 1 , Dominic Ridolfi 1 , Brandon Couch 1 , Aaron Zheng 1 , Asher Mirvish 1 , Jonathan Dalton 1 , Audrey Chang 1 , Christopher Gibbs 1 , Jeremy D. Shaw 1 , William F. Donaldson 1 , and Joon Y. Lee 1 1 Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, USA Introduction: The direct-lateral (trans-psoas) approach to the spine is a popular choice for interbody fusion procedures in the management of spondylolisthesis and degenerative disc disease. There is known risk of lumbar plexus and femoral nerve injury making preoperative planning essential. Previous investigators have described "the rising psoas sign" where the psoas muscle drifts anteriorly away from the vertebral column on advanced imaging axial views creating increased risk with the direct lateral approach. The purpose of the present study was to examine the association of sequential multilevel (tandem) spondylolisthesis and psoas position at the L4-L5 lumbar level. Material and Methods: Subjects with lumbar spine MRIs and/or full-length spine films were identified and stratified into 3 age and gender matched cohorts: 1) No spondylolisthesis, 2) Single level lumbar spondylolisthesis, & 3) sequential multilevel lumbar spondylolisthesis. Medical records were retrospectively reviewed. The position of the psoas muscle (centrally and apically) relative to a tangent line at the posterior aspect of the L4-5 disc was measured. Spinopelvic parameters were recorded in all patients with full length spinal films. Chi-square analysis was used to determine differences in gender. Two-tailed unpaired t-tests were used to identify differences in continuous variable demographics and radiographic measurements. p < 0.05 was considered statistically significant. Results: Two hundred and one subjects (75M, 126F; age 63 ± 13 years) were identified. No spondylolisthesis patients (n = 52, 20M, 32F, age 61 ± 19, BMI 30.80 ± 7.03, aCCI 3 ± 2), single level spondylolisthesis patients (n = 110, 41M, 69F, age 63 ± 12, BMI 31.44 ± 6.95, aCCI 3 ± 2), and tandem spondylolisthesis patients (n = 39, 14M, 25F, age 65 ± 8, BMI 30.66 ± 7.29, aCCI 3 ± 2) had no differences in demographics (p > 0.1) (The center (C) psoas and apical (A) psoas position was more ventral in patients with tandem spondylolisthesis (n = 39) (C: 28.9 mm ± 10.1 mm & A: 50.9 mm ± 11.3 mm) as compared to patients with single level spondylolisthesis (n = 110) (C: 24.3 mm ± 7.3 mm; p = 0.012 & A: 46.7 mm ± 8.4 mm; p = 0.041) and no spondylolisthesis (n = 52) (C: 23.4 mm ± 8.0 mm; p = 0.007 & A: 45.3 mm ± 9.9 mm; p = 0.019). Tandem spondylolisthesis was associated with increased pelvic tilt (27°± 11°) vs. single level spondylolisthesis (21°± 11°; p = 0.002) and no spondylolisthesis (17°± 12°; p < 0.001). Pelvic incidence was increased in subjects with tandem spondylolisthesis (65°± 19°; p = 0.001) and single level spondylolisthesis (61°± 23°; p = 0.026) compared to patients with no spondylolisthesis (54°± 25°). Tandem spondylolisthesis was also associated with increased pelvic incidence-lumbar lordosis mismatch (18°± 16°) vs. single level spondylolisthesis (7°± 13°; p < 0.001) vs. no spondylolisthesis (11°± 19°; p = 0.059). There were no significant differences for the tandem spondylosis group in lumbar lordosis angle, sacral slope, or sagittal vertical axis angle (p > 0.1). Single level spondylolisthesis was associated with increased lumbar lordosis (52°± 17°vs. 43°± 20°; p = 0.003) compared to patients with no spondylolisthesis. Conclusion: Tandem spondylolisthesis is associated with a more ventrally positioned psoas muscle which poses a danger in trans-psoas approaches to the lumbar spine. Careful preoperative planning with attention to the psoas position for lateral interbody fusion candidates is recommended. and FR (15% versus 38%, p = 0.045). Differences in revision rates for PJK were found in studies concerning tethers (4% versus 18%, p = 0.002), 2-PVP (0% vs 13%, p = 0.031) and TPH (0% vs 7%, p = n.a.). Conclusion: Although the studies are of low quality, the most frequently studied techniques, namely 2-PVP as anterior reinforcement and (tensioned) tethers or TPH as posterior semi-rigid fixation, show promising results. To provide a reliable comparison, more controlled studies need to be performed, including the use of clinical outcome measures and a uniform definition of PJF.

A332: Central sacral pelvic line (CSPL) is a useful radiographic parameter that correlates with clinical outcomes of coronal balance after spine deformity surgery mean age of 56.5 ± 11.3 years were part of the study. The mean VAS score for back and leg pain were 6.3 ± 1.1 and 7.6 ± 1.3 respectively. The mean mODI score was 47 ± 13.8. Central, lateral and foraminal stenosis were noted in 71, 41 and 38 patients respectively. Mild, moderate, severe and extreme stenosis were reported in 63, 42, 28 and 17 patients respectively. MRI grade of LCS does not correlated with mODI score (p = 0.082) or VAS score for back pain (p = 0.092) but strong correlation with VAS score for leg pain (p = 0.023). Of all the MRI parameters studied, Anteroposterior (AP) diameter of the bony canal, diameter of the foramen, height of lateral recess and cross-sectional area of the dural sac showed strong correlation with both the mODI and VAS scores. Conclusion: Quantitatively on MRI, central spinal canal cross-section (less than 75 mm 2 for central stenosis) and lateral recesses cross-section (less than 20 mm 2 for lateral stenosis) had the highest sensitivity and specificity for LSS diagnosis in symptomatic patients. Strongest observed correlation was between neurogenic claudication and LSS diagnostic radiological markers. MRI grade of LCS was not correlated with mODI scores or VAS scores for back pain but strong correlation was observed with VAS score for leg pain.

A339: Preoperative disc angle is an important predictor of segmental lordosis after degenerative spondylolisthesis fusion Introduction: Lumbar spine stenosis (LSS) can result in debilitating and disabling pain in affected patients especially, when complicated with neurogenic claudication. These symptoms result in prolonged hospital-stay and sometimes, require needless imaging exposure and costs. Current advancement in technology has paved a path for LSS patients to be accommodated for minimally invasive surgical procedures that can be performed within the outpatient settings while fostering value-based care delivery to spine patients. Hospital stay is associated with significant increase in hospital charges. Outpatient surgeries performed in ambulatory centers in less-morbid patient populations are intended for same-day hospital discharge. However, due to a high prevalence of certain underlining medical conditions in the elderly, concomitant with symptomatic spine degenerative presentations, it is often skeptically difficult to admit these patients to the ambulatory surgical settings. Based on this observation, identifying ambulatory surgical procedures that hold significance for a shortened hospital length of stay may offer great clinical benefit in addressing spine patients' clinical symptoms and cutting down hospital costs. Material and Methods: A comprehensive literature review with meta-analysis was performed from January 2000 to September 2021. We aimed to investigate if Endo-ULBD approach resulted in shorter hospital stay in lumbar spinal stenosis (LSS) patients than those surgically decompressed and treated with MIS-ULBD approach. The selection criteria for included studies comprised: i) comparative studies of Endo-ULBD versus MIS-ULBD approaches in LSS patient management, ii) case series of ≥ 10 patients, iii) pain and functional outcomes with reported standard deviations, iv) English-only articles, v) report of hospital stay days, and vi) a ≥ 1-year follow-up period. Primary outcomes included: baseline, back and leg pain Visual Analogue Scale (VAS), and Oswestry Disability Index (ODI) scores. Secondary outcomes included: peri-operative variables, [mean operation time, estimated blood loss (EBL), post-decompression dural expansion, and hospital stay (HLoS)], final follow-up back and leg pain VAS, and ODI scores. Weighted mean differences (WMDs) or standardized mean differences (SMDs) were statistically generated along with their confidence intervals (CIs) while significance was set at (p < 0.05). Results: A total of LSS 633 patients from 9 comparative analyses from 8 multi-institutional studies were observed. Of the 633 LSS patients, 52.76% (n = 334) and 47.24% (n = 299) were Endo-ULBD and MIS-ULBD, respectively. Baseline and ≥ 1-year postoperative back and leg pain VAS, and ODI score outcomes were equivalent between the two surgical groups. While significantly shorter HLoS; [WMD = -2.11; 95% CI = (-3.48, -0.75]); I 2 = 96%, (p = 0.002)] was observed in the Endo-ULBD surgical group, the mean operative time, EBL, and postdecompression dural expansion outcomes were comparable between the Endo-ULBD and MIS-ULBD surgical techniques. No other significant differences were observed between the Endo-ULBD and MIS-ULBD surgical techniques. Conclusion: Albeit, postoperative pain and functional outcomes demonstrated comparable effectiveness, endoscopic technique with unilateral approach for bilateral decompression (Endo-ULBD) was associated with significantly shorter hospital stay compared to microscopic technique for bilateral decompression via unilateral approach (MIS-ULBD).

A345: Evaluating patient outcome post tubular lumbar micro-discectomy Aftab Younus 1 , Mohammad Hamza Aftab 1 , Robert Fernandes 1 , and Adrian Kelly 1 elderly. These usually respond to conservative treatment but sometimes chronic pain result from incomplete vertebral healing and progressive collapse. There is a risk of altered spine kinematics as a consequence of junctional kyphosis and development of a pseudoarthrosis. The evidence is very sparce regarding the radiological outcomes and its correlation with clinical outcomes after kyphoplasty. The aim of the present study is to treat patients with chronic pain or non union with kyhoplasty and study the efficacy of pain relief and deformity correction. Material and Methods: Prospective analytical study was conducted on 32 patients of OWCF (failed conservative treatment) for a period of 2 years from June 2019 to May 2021. All the patients are operated by same surgeon in single center. Biplanar fluoroscopy was used and bipedicular approach was followed and PMMA injected (approx 4cc) until good filling was seen on Fluoro. Thoracolumbar AO type A1 or A2 fractures included. Pre op, 6 months 1 year and 2 years assessment of Clinical parameters -Visual analogue scale score (VAS) Oswestry disability index (ODI) and radiological parameters -Anterior vertebral body height and Cobb's angle of kyphosis (on standing lateral) radiographs was done. Statistical analysis was done using the SPSS software version 17.0. Results: 32 Patients with average age of 65 years with average BMD T score-3.4 were analysed. Average surgical time is 40 minutes with negligible blood loss. Average Pre operative ODI and VAS scores are 66and 7.2 respectively, and 2 year post op ODI and VAS scores are 22 and 2 respectively (p < 0.05). Average pre op vertebral height and kyphotic COBB angle are 22 mm and 7.9 deg res respectively and 2 year post op vertebral height and kyphotic COBB angle are 28 mm and 5 degrees respectively (p < 0.05). Conclusion: Kyphoplasty in patients with failed conservative treatment results in long term pain reduction with statistical significance. There is also significant vertebral body height and kyphotic angle improvement which is sustained at 2 years follow up.

A354: Rates of early complications and mortality in patients over the age of 80 after surgical treatment of acute traumatic spinal fractures: ankylosing spondylitis versus osteoporotic fractures Basem Ishak 1,2 , Dr. Sven Frieler 3 , Tarush Rustagi 4 , Alexander von Glinski 3 , Andreas W. Unterberg 1 , Rod Oskouian 2 , and Jens Chapman 2 SD = 207 cc). Average fluoroscopy time was 39 seconds per case (Range = 0-88 sec, SD = 28 sec). There were three post-operative infections reported, each requiring a second operation for irrigation and debridement without subsequent hardware removal. There were no post-operative neurological complications. Conclusions: Robotic-assisted spine placement of pedicle screws with the Mazor X robot, is a safe and effective modality for the treatment of unstable spine fractures. However, we reported two instances in which the pre-planned pedicle screw trajectory was not able to be executed by the robotic arm. Both instances involved cases of significant kyphotic deformity at the T4 level. Our review included two cases of robotic assisted lumbopelvic fixation which may be an area of future study. While our experience demonstrates that the Mazor X robotic arm is a useful adjunct in the treatment of spine trauma, the robotic assisted procedure may not be best for all levels nor for all cases. Additional research is needed to look at greater patient numbers, overall radiation exposure times, and pedicle screw revision rates. Introduction: Despite the importance of posterior ligamentous complex (PLC) in thoracolumbar classification, there no consensus on CT criterion for PLC injury. The purpose of this study is to analyze the diagnostic accuracy of combined CT findings for detecting posterior ligamentous complex (PLC) injury in thoracolumbar fractures (TLFs) using MRI as a reference study. Materials and Methods: A retrospective review of 275 consecutive patients with TLFs (T1-L5) presented to a tertiary referral level 1 trauma center between 2014-2021. All patients underwent CT and MRI within ten days of injury. Patients with translation injury, osteoporotic fracture, or pathological fractures were excluded. Two reviewers (a spine surgeon and a neuroradiologist) independently evaluated CT for the following findings suggestive of PLC injury: Facet joint malalignment (FJM), facet joint widening (FJW), horizontal laminar fracture (HLF), spinous process fracture (SPF), and interspinous widening (ISW). We used multivariate logistic regression analysis to elucidate the independent association of each CT findings with PLC injury before calculation the accuracy measures of combined CT findings [sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), positive likelihood ratio (+LR), and negative likelihood ratio (-LR)]. PLC injury was defined as a black stripe discontinuity due to rupture of the supraspinous ligament or ligamentum flavum. We used Cohen's kappa (k) statistic to assess the inter-and intraobserver agreement on each CT finding's binary results and PLC injury by MRI. Results: FJM, SPF, HLF, and ISW were independently associated with PLC injury (Adjusted odds ratio range 4.1-25.4). A negative CT for all four findings had an NPVof 94% (95% CI 89-97) for PLC injury. A single positive CT finding yielded a +LR of 1.0 (95% CI 0.65-1.6) and -LR of 0.99 (95% CI 0.87-1.1) for PLC injury. ≥ 2 CT findings yielded a PPV of 91% for PLC injury (95% CI 89-97) and an NPV of 85% (95% CI 81-89), and accuracy 87% (95% CI 82-91). The inter-intraobserver agreement on each CT finding was substantial to excellent (k range 0.57-0.91 and 0.65-0.93, respectively), while agreement on PLC status by MRI was excellent (k = 0.78, 0.86, respectively). Conclusions: The analysis of combined CT findings could improve the ability to confirm or rule-out PLC injury. A negative CT for the four CT findings, independently associated with PLC injury, provided a high NPV for PLC injuries and can be used as a screening tool for PLC injury. A single CT finding lacks sufficient predictive value to confirm or rule-out PLC injury. A combination of ≥ 2 CT findings provided the highest correct classification accuracy (87%) for PLC injury; thus, it can be proposed as a CT criterion for injured PLC. Introduction: The aim of the multicenter study (EOFTT) was to evaluate the recently developed OF-score and treatment recommendations for osteoporotic thoracolumbar fractures. Material and Methods: Monocentric evaluation of a multicenter prospective cohort study. All inpatients with osteoporotic thoracolumbar fractures with a follow-up between 6 weeks and 12 months were included and evaluated clinically and radiologically. Treatment was based on the recommendations of the OF-score 1.2 which considers radiological and clinical patient data and suggests treatment (<6 points conservative, >6 points surgery). Results: Over a period of 28 months 60 (69%) of 87 treated inpatients fulfilled the inclusion criteria. 82% were female. T-score was 4.04 g/m 2 ± 0.73, average age 76 ± 8.1 years and 25% had more than one fracture. Classification according to OF was: OF 1: none, OF 2: 25% OF 3: 23% OF 4: 45% OF 5: 7%. Three patients (5%) suffered from a fracture related neurological deficit. The median OF-score (25% / 75% quartile) was 7 (5/9). 37 patients (62%) were treated according to the score recommendations including 2 (3%) conservative treatments, 30 (50%) surgical treatments, and 5 (8%) relative indications for surgery. 17 patients (28%) were treated surgically despite a conservative recommendation and 6 patients (10%) vice versa. Subsequently, after discharge 3 conservative treated patients (5%) needed surgery. Overall, 90% of all patients were treated operatively of whom 28 (55%) received kyphoplasty, 11 (22%) stabilization with pedicle screws, and 12 (24%) a combination of both. The overall complication rate was 24% including one surgical revision due to a hematoma. 9 (15%) patients developed adjacent fractures. The average follow-up time was 32 ± 19 weeks (range 6-72). The clinical parameter improved significantly (p < 0.05) from preop to last follow-up (preoperative, day of discharge, final follow-up, mean ± standard deviation): VAS back 8.2 ± 2.1; 4.4 ± 2.3; 3.1 ± 2.7. ODI: 71% ± 16%; 61% ± 12%; 36% ± 19%. Barthel-scale: 72 ± 23; 80 ± 14; 91 ± 13. 98% were ambulatory. The local bisegmental kyphotic angle (GDW) showed no significant improvement over time (preoperative, day of discharge, final follow-up, mean ± standard deviation): -3°± 21°; -0°± 19°; -3°± 20°(all kyphosis). Significant better outcome was found with regard to pain, ODI, and Barthel-scale in the group of score-concordant treated patients. Conclusion: The recommendations according to the OF-Score, whether surgical or non-surgical, lead to clinical favorable results after 8 months on average, However, with 24% the overall complication rate is rather high. The typical minimal-invasive surgical techniques (kyphoplasty, pedicle screws) do not improve the local kyphosis, but improve Barthel-scale.

Global Spine Journal 12(3S)

PREVENA incision management system. 2020. Available at

Negative pressure wound therapy in spinal fusion patients

Clinical Experiences with Closed Incisional Negative Pressure Wound Treatment on Various Anatomic Locations

the North American Spine Society (NASS) issued a newsletter for a 30-day public comment-period for feedback on NASS' recently developed draft on Lumbar Decompression recommendations. Clearly, the spine practice is globally taking a major turn towards more minimally invasive approaches in the management of lumbar spine degenerative disorders. In the setting of performing transforaminal lumbar interbody fusion (TLIF), beside mastering of surgical techniques, whether minimally invasive or endoscopic TLIF offers better pain outcomes in patients remains uncertain. Robust comparative pain and disability outcomes of managed lumbar spine stenosis patients with MIS-or Endo-transforaminal lumbar interbody fusion are inconclusive. Material and Methods: A comprehensive literature review was performed from

Weighted Mean Differences (WMDs) or Standardized Mean Differences (SMDs) were statistically generated along with their Confidence Intervals (CIs) while significance was set at (p < 0.05). Results: A total of 509 LSS patients from 7 multi-institutional studies met the inclusion criteria. Of the 509 LSS patients analyzed, 45.58% (n = 232) and 54.42% (n = 277) were Endo-TLIF and MIS-TLIF, respectively. The mean operation time was significantly higher for Endo-TLIF

Significantly lower EBL

were observed for Endo-TLIF-treated patients. Significantly, higher JOA score

at 3-month postoperative, and a significant drop in back pain VAS score

at ≥ 1-year postoperative were observed for Endo-TLIF approach compared to MIS-TLIF approach. There were no other significant outcomes between the two surgical approaches. Conclusion: Except for surgical duration time, 5/6 (83.33%) of the meta-analyzed outcomes, thus, EBL, ambulation time, HLoS, JOA score at 3-month and back pain VAS score at ≥ 1-year postoperative were significantly in favor of Endo-TLIF for the effective management of LSS patients

Objective: We aimed to examine the long-term radiological and clinical outcomes after stand-alone anterior cervical discectomy and fusion (ACDF). Materials and Methods: In total, we enrolled 53 patients and 79 segments with degenerative cervical disease treated with stand-alone ACDF with ≥ 60 months of follow-up. The segmental angle (SA), cervical sagittal alignment (CSA), subsidence, and fusion were evaluated. The visual analogue scale (VAS) scores and Neck Disability Index (NDI) were also recorded. Results: Subsidence occurred in 24 (45.2%) patients and 38 segments (48.1%) at the last follow-up. The mean VAS and NDI scores had improved in both groups with and without subsidence. The mean SA at the last follow-up had increased to 1.3°± 8.5°in the subsidence group and to 1.5°± 5.2°in the non-subsidence group compared to the post-operative SA (p < 0.001). The overall mean CSA at the last follow-up increased over time in both groups compared to the post-operative CSA (p = 0.003). The fusion rate at 1 year after surgery was 86.8% in the subsidence group and 82.9% in the non-subsidence group. However, the differences in the SA, CSA, and fusion rates between the two groups were not statistically significant (p = 0.119, 0.98, and 0.682, respectively). Conclusion: After stand-alone ACDF, subsidence occurs to some extent, but it does not appear to have a significant impact on radiologic and clinical outcomes, if foramen decompression is adequately and sufficiently performed during surgery. It seems to have a positive influence on the fusion rate. Key words: stand-alone, anterior cervical discectomy and fusion, long-term, subsidence, cervical alignment

Introduction: The use of telemedicine has expanded amid the COVID-19 pandemic. Previous studies have described the feasibility of telemedicine, however, little has been reported Introduction: The aim of the present research was to explore the efficiency and reliability of the computer-assisted virtual surgical planning (CAVSP) based on computed tomography data spinal reconstruction in severe spinal deformity patients. Material and Methods: Thirty-nine patients diagnosed as severe spinal deformity accepted correction surgery were divided into two groups depending on whether computerassisted virtual surgical planning was produced, and the plan was made in Group CAVSP (18 patients) and not in Non-CAVSP Group (21 patients). The demographic data, 820 A238: Treatment of spinal metastasis in the 21st century. A comparative single center study

Objective: Spinal metastases may present with different degrees of mechanical instability. The Spinal Instability Neoplastic Score (SINS) was developed to assess spinal neoplastic-related instability. Few have validated it clinically. This study aimed to compare the quality of life and the overall survival in a matched pair analysis at a group of patients with spinal metastasis. Methods: A retrospective analysis of patients with a pathologic fracture due to a spinal metastasis between January 2018 and December 2018 was performed. We selected patients with a minimum follow-up of 12 months and analyzed them according to the SINS criteria. All patient in this group did not underwent any spinal surgery. For the interventional group, we selected all patient with initial diagnosis of spinal metastasis in 2020. For the further analyzation we collected all patient, which underwent a spinal surgery by our department of neurosurgery in 2020 and a minimum follow-up of 12 months. In the end, we made a matched pair analysis (sex; age; tumor; SINS; co-morbidity). Results: In the interventional group 35 patient were identified. Median age was 66 SD ± 14.17 and 60% were female. In the matched-pair conservative group was the median age 65 SD ± 11.4. Here got 29% of the patient a fracture progression following radiotherapy. In sum 20% of all matched pair patient got a neurological deterioration. In contrast, a fracture progression following radiotherapy was not seen in any case at the surgical treated group. In 21 case we performed 360°stabilization. In 7 cases only a laminectomy was necessary by intraspinal tumor cuff and low / moderate SIN-Score. In other 7 cases we only performed a dorsal stabilization without a corpectomy. In all cases we did not see any secondaryIntroduction: Adult spinal ependymoma presents a rare benign tumor entity. Due to its incidence peak in the fourth decade of life, it mostly affects patients during a professionally and physically active time of life. Material and Methods: Monocentric analysis, including patients operated upon for spinal ependymoma between January 2009 and September 2020. We prospectively collected data on professional reintegration, physical activities and qualityof-life parameters using EQ-5D, SF-36 and free text questionnaires. Issues encountered in returning to work and physical activities were assessed using existing spinal-cord-specific questionnaires. Results: Overall, 65 of 114 patients operated agreed to participate. Most patients suffered from only mild pre-and postoperative impairment on the modified McCormick scale, but 67% confirmed difficulties Introduction: Cauda equina syndrome (CES) is a surgical emergency that occurs due to compression of the nerve roots in the lumbosacral spine. Wide or full laminectomy is often necessary to alleviate the compressive pathology; however, with more bone resection, patients may be at risk for increased long-term instability. The aim of this study was to identify long-term rates of conversion to lumbar fusion in CES patients initially treated with decompression alone. Material and Methods: Patients who underwent decompression alone for CES were identified in a national insurance database and matched to control patients who underwent decompression for lumbar spinal stenosis (LSS) not associated with CES. The 1year, 3-year, and 5-year rates of conversion to a fusion procedure were compared between the two groups. Multivariate logistic regression analysis was employed to investigate the impact of patient demographic and comorbidity risk factors. A sub-analysis was performed to determine if the timing between CES diagnosis and decompression surgery affected long-term rates of conversion to fusion. Results: A total of 1,288 CES patients who underwent decompression alone were identified and matched to 1,288 LSS control patients. The rate of conversion to fusion in the CES cohort was 3.6% after 1 year, 6.7% after 3 years, and 7.8% after 5 years, which was significantly higher than the LSS control at all timepoints (1year: 1.6%, p = 0.001; 3-year 3.0%, p < 0.001; 5-year: 3.8%, p < 0.001). In the multivariate analysis, CES was shown to be independently associated with increased risk for conversion to fusion (OR: 2.13; 95% confidence interval [CI]: 1.56-2.97; p < 0.001). The timing of CES diagnosis to decompression was not significantly associated with long-term conversion to fusion. Conclusion: Patients with CES treated with decompression were found to be at higher risk for conversion to lumbar fusion compared to LSS matched control patients. Since the need for additional surgery is associated with increased morbidity and financial implications, setting realistic postoperative expectations is important for patient satisfaction and wellbeing. Additionally, these findings may be valuable for stratifying decompression patients regarding their risk for future lumbar fusion. Notably, this investigation also found that the timing of decompression surgery in CES did not impact the risk for conversion to lumbar fusion. Introduction: Outpatient spine surgery has markedly grown in popularity over the past decade; nonetheless, the incidence of ED visits after outpatient spine surgery is not well established. This study sought to characterize the incidence and timing of postoperative Emergency Department (ED) visits after common outpatient spinal surgeries performed at Ambulatory Surgery Centers (ASCs) and at Hospital Outpatient Departments (HOPDs). Material and Methods: This study was a retrospective analysis of the MarketScan (IBM Watson Health, Ann Arbor, Michigan) commercial claims database. Patients < 65 years old who underwent single-level anterior cervical discectomy and fusion (ACDF) (CPT: 22551, 22554), laminectomy (CPT: 63047), and microdiscectomy (CPT: 63030) at ASCs or HOPDs from 2010 to 2019 were identified. Patients with diagnosis codes for trauma, infections, or oncology-related causes were excluded. Incidence, timing, and diagnoses associated with ED visits within the postoperative global period (90 days) after surgery were assessed. Results: In total, 202,202 patients received outpatient spine surgery (19.1% in ASC vs. 80.9% in HOPD). Collectively, there were 22,198 ED visits during the 90-day postoperative period. Approximately 9.0% patients had at least 1 ED visit, and the incidence varied by procedure: ACDF 9.9%, laminectomy 9.5%, and microdiscectomy 8.5% (p < 0.0001). After adjusting for age, sex, and comorbidity index, the odds of at least 1 ED visit were higher among patients who received surgery at HOPD vs. ASC for all 3 procedures. The majority (56.1%) ED visits occurred during the first month postoperatively; 30.8% (n = 6,841) occurred within the first week postoperatively, and 10.7% (n = 2,370) occurred on the same day as the surgery. Postoperative pain was the most common reason for ED visits. Conclusion: Among commercially insured patients who received outpatient spine surgery, the incidence of ED visits during the 90-day postoperative period was non-trivial at approximately 9%. A substantial portion of ED visits (10.7%) occurred on the day of surgery, which suggests that a subset of patients could have benefited from overnight stays. Pain was the most common reason for ED visits, indicating that some ED visits could have been prevented with better pain control regimens and patient education and counseling. The higher utilization of HOPDs vs ASCs has important implications on costs as HOPDs have been found to be more expensive than ASCs despite no detectable difference in outcomes with regards to spine surgery. Our results highlight opportunities for improved postoperative care planning and may aid decision makers better understand patterns of resource utilization after outpatient spinal surgery.Introduction: Consistently high fusion rates can be difficult to achieve in complex multilevel cervical fusions. Additionally, Bone Morphogenetic Protein use in cervical spine surgery is off label. Thus, finding an FDA-approved bone graft substitute as a valuable augment to aid in achieving fusion in these cases is imperative. Material and Methods: Clinical and radiographic outcomes of all 3-level ACDF patients since 2014 with a minimum follow-up of 2 years were reviewed. 105 consecutive patients were treated with ACBM and 69 patients were treated with ultra-lowdose rhBMP-2 (0.26 to 0.35 mg/level) to augment 3-level ACDF. Patients were monitored for dysphagia and duration of complaints were noted. Sequential post-operative radiographs were analyzed for fusion and revision surgeries were reviewed. During each visit, VAS pain and NDI scores were recorded. Results: In the ACBM cohort, 28 patients (28.9%) reported dysphagia at 2-week followup; 25 mild, 2 moderate and 1severe. The moderate cases were treated with oral steroids and severe cases were treated with hospitalization and IV steroids. All cases resolved by 6-week post-operative follow-up. In the rhBMP-2 cohort, 12 (17.4%; 11 mild, 1 moderate) patients reported dysphagia at 2-week follow-up, 19 (27.5%; 19 mild) had dysphagia at 6 weeks, and 6 (8.7%; 6 mild) reported dysphagia at 6 months. All dysphagia had resolved by final follow-up. There was no significant difference between groups in regard to patients who developed pseudarthrosis with 2 of 97 (2.1%) in the ACBM cohort versus 1 of 69 (1.5%) in the rhBMP-2 cohort (p= 0.770). The proportion of patients revised secondary to ASD was insignificant between cohorts (6 of 97, 6.2% ACB vs 1 of 69, 1.5% rhBMP-2; p= 0.128). Patients in both cohorts experienced significant improvements in VAS-arm, VAS-neck and NDI scores at 2-year follow-up compared to their pre-operative scores (p ≤ 0.001) with no significant differences in score improvement between groups. Conclusion: ACBM did not differ from rhBMP-2 in any outcome measure for patients who underwent 3level ACDF, including revision surgery rate. Introduction: Degenerative Cervical Myelopathy (DCM) is the most common form of adult spinal cord dysfunction worldwide; however, symptom heterogeneity complicates diagnosis and prediction of patient outcomes. MicroRNAs (miRNAs) are short, regulatory RNA sequences that can serve as useful biomarkers of human disease. We hypothesized that DCM would alter the expression of miRNAs and that DCMrelated miRNAs would predict patient outcomes. Material and Methods: In this prospective cohort study, DCM subjects (with imaging confirmation of cervical cord compression and at least one neurological sign) and healthy volunteers were assigned to a discovery cohort (20 mild DCM, 10 moderatesevere DCM, and 10 healthy subjects) or a validation cohort (21 mild DCM, 18 moderate-severe DCM, and 10 healthy subjects). DCM severity was defined using the modified Japanese Orthopedic Association scale (mJOA), with mild DCM being classified as mJOA ≥ 15. Blood was collected at initial visit and 1 year follow-up to determine whether plasma miRNAs were predictive of patient outcome. Results: Plasma was profiled for 179 miRNAs in the discovery cohort, and 8 miRNA candidates were chosen. LET7f-5p (Cohen's d = 0.9604, p = 0.006), MIR132-3p (Cohen's d = 1.316, p = 0.004), MIR136-5p (Cohen's d = 1.1392, p = 0.013), MIR154-5p (Cohen's d = 1.0850, p = 0.010), MIR484-5p (Cohen's d = 1.4920, p = 0.002) were differentially expressed between mild DCM and healthy controls in the validation cohort. Expression of MIR132-3p (Cohen's d = 0.9548, p = 0.008) was significantly different among DCM patients that demonstrated worse surgical outcomes after one year. Conclusion: Altered microRNA expression was observed between both mild as well as moderate-severe DCM severity groups and/or healthy control subjects at baseline. MIR132-3p was associated with surgical outcome of DCM after one year. These results raise the possibility of non-invasively detecting insidious neurodegenerative mechanisms involved in DCM and using these data to inform clinical decisions. OP31: Tumors 3 1056 A271: Patient expectations about palliative treatment for symptomatic spinal metastases: a qualitative study Introduction: Giant Cell Tumours (GCT) of the spine may be large at presentation and cause severe pain. The current recommended treatment is en bloc excision but is associated with significant morbidity and mortality. Denosumab is a monoclonal RANKL inhibitor that may be used neoadjuvantly. The goal of this study was to assess the effect of Denosumab on tumour characteristics and symptom relief. Material and Methods: We performed a retrospective review of 10 patients treated with denosumab as neo adjuvant and stand -alone treatment. Tumour measurements were taken before and after treatment, PET SUV capitation was measured, and patients were interviewed for subjective pain responses. Clinical response was determined by volumetric reduction in tumour size, PET SUV capitation, the Boriani Classification and improvement in pain symptoms. Results: Following treatment 70% of patients were pain free, 50% noting improvement within 48 hours. Mean relative volumetric reduction in tumour volume was 40%. All pathology specimens confirmed elimination of giant cells. Improvement in Bilsky grading occurred in 4/10 cases and progression was halted in the remainder. Median baseline SUVmax was 14.7, median SUVmax post treatment was 6.2. Seventy-eight percent of patients demonstrated intra-lesional bone formation following treatment. Conclusion: This study demonstrates that neo-adjuvant denosumab facilitates en bloc resection of GCT of the spine, reduces the likelihood of intra -operative morbidity and improves preoperative pain. We recommend routine use when W-B-Bbased criteria are fulfilled for en-bloc excision. Assuming that margins are diseasefree following surgery, we advocate cessation of treatment post-operatively.

A277: Timed 10 meter walk test for objective measurement of gait improvement following separation surgery for metastatic epidural compression Kimberly Ashayeri 1 , Cordelia Orillac 1 , John Theodore 2 , Sean Neifert 1 , Darryl Lau 1 , and Ilya Laufer 1 1 Neurosurgery, NYU Langone Health, New York City, NY, USA 2 Columbia University, New York, NY, USA Introduction: Metastatic epidural spinal cord compression (MESCC) occurs in 2-5% of all cancer patients and can present with severe neurologic deterioration. Timely surgical decompression leads to neurological recovery among a subpopulation of patients who lost ambulation due to MESCC. However, very little objective ambulation measurement has been reported in the setting of MESCC with many existing measures of functional improvement requiring equipment and technologies that are not readily available. The timed 10meter walk test (10MWT) requires no special equipment, can be easily performed, and is easy to interpret. This study seeks to determine whether the 10MWT can assess functional improvement in ambulation following surgical decompression for MESCC. Material and Methods: This is a retrospective review of patients who underwent surgery for MESCC between January 2017 and December 2019. Patients were included if they were 18+ years old, presented with preoperative gait disturbance, and were admitted to inpatient rehabilitation program following discharge from hospital. Self-paced 10MWT was compared between first postoperative assessment and last test administered prior to discharge. Paired t-tests were utilized order to determine if 10MWT significantly improved from one time point to another. p-value < 0.05 was deemed significant. Results: 6 patients (3 male, 3 female) met inclusion criteria. The mean initial to discharge 10MWT velocity improved from 0.39 meters/second to 0.51 meters / second (p = 0.047). Average time between tests was 5 days apart (2-8 days) . Conclusion: This proof-of-concept study indicates that the 10MWT can successfully detect improvements in ambulation in patients recovering from surgery for MESCC. Furthermore, the 10MWT is easily administered and interpreted. Larger cohort studies are warranted to further elucidate the utility of 10MWT in the measurement of ambulation in the setting of MESCC and in objective reporting of functional recovery. Purpose: Spine stereotactic body radiotherapy (SBRT) improves complete pain response rates compared to conventional external beam radiotherapy (cEBRT). Durability of tumor control is increasingly recognized as an important endpoint given that patients with metastatic disease are surviving longer. Methods: The Canadian Clinical Trials Group (CCTG) Symptom Control (SC)-24 phase II/III trial included 229 patients randomized to either 24 Gy in 2 SBRT fractions or 20 Gy in 5 cEBRT fractions. 137/229 (60%) patients were enrolled from our institution. We retrospectively identified 66 patients with 119 spine segments treated with SBRT, and 71 patients with 169 segments treated with cEBRT. Our primary outcomes consisted of MR-based local control, overall survival (OS) and retreatment rates. Results: The median follow-up was 11.3 months (interquartile range: 5.3-28.5 months) and median OS was 21.6 and 18.9 months in SBRT and cEBRT cohorts, respectively. The SBRT and cEBRT cohorts were balanced with respect to radioresistant vs radiosensitive histology and presence of "Mass" (paraspinal and/or epidural disease extension). Risk of local failure at 6, 12 and 24 months were 2.8% vs.11.2%, 6.1% vs. 28.4% and 14.8% vs. 35.6%, favouring SBRT vs. cEBRT, respectively. cEBRT (HR: 3.48, 95%CI: 1.94-6.25, p < .001) and presence of "Mass" (HR: 2.07, 95%CI: 1.29-3.31, p = 0.002) were independent significant predictors of local failure on multivariate analysis. The 1-year retreatment rates were 3.4% and 20.3% after SBRT vs. cEBRT, respectively (p = 0.004). The median time to retreatment was 22.9 months vs. 9.5 months in the SBRT vs. cEBRT cohorts, respectively. Radioresistant histology (HR: 2.94, 95%CI: 1.62-5.35, p < 0.001), cEBRT (HR: 2.36, 95%CI: 1.13-4.95, p = 0.023) and "Mass" (HR: 1.83, 95%CI: 1.01-3.34, p = 0.048) independently predicted retreatment. Conclusions: The risk of local failure is 3.5-fold greater after cEBRT compared to SBRT for spinal metastases. cEBRT is also associated with greater retreatment rates. SBRT may be particularly indicated for "Mass" type and radioresistant spinal metastases. Introduction: The quality of life of patients with symptomatic spinal metastases can be severely affected by local tumor pain, pain during movement, deformity and neurological deficits. The optimal treatment for patients with multiple unstable metastases in the cervical spine is unknown as many relevant factors (e.g. range of motion remaining, stability and alignment, neurological function, local tumor control, and risk for complications) need to be balanced carefully. Radiotherapy has been shown to be effective for palliation and local control, but cannot provide immediate mechanical stability, while surgery will provide stability but may severely impair range of motion and carries a high complication rate when long bridging constructs are used. In the current study we present clinical results of patients with multiple high-SINS cervical metastases treated with temporary halo-fixation and radiotherapy aiming for immediate cervical stabilization, palliation and local control, reossification of the metastases, and long-term preservation of mobility in the neck. Patients and Methods: Twenty patients with multiple painful unstable (SINS 12 or higher) cervical metastases from a variety of histological origins were included in this retrospective study. All received halo-fixation for an intended duration of approximately three months to allow for reossification of the lesions after radiotherapy. External beam radiotherapy was administered with a fractionation scheme best suited to the histological origin of the tumor and highest chance for reossification (preferably 10x3Gy if physical condition allowed, and combined with bisphosphonates). Halo-fixation was removed after a CT scan of the cervical spine confirmed acceptable alignment and ongoing reossification. Endpoints were neurological status, Karnofsky Performance Score (KPS), neck pain (NRS) and semiquantitative assessment of reossification on CT images at time of halo-fixation removal and last follow-up. Results: The patients were 11 females and 9 males with an average age at treatment of 62 years old (range 45-82 years) and metastatic lesions originating from radiosensitive tumors including breast (n = 6), multiple myeloma (n = 7), prostate (n = 3), and more radioresistant tumors (n = 5). All patients were ASIA E or non-progressive ASIA D in neurological function at baseline. The period of immobilization with halo-fixation ranged from 69 to 132 days, in three patients the halo-fixation was removed earlier due to rapidly progressive disease. The KPS at time of removal of the halo-fixation had improved or was stable in 14/18 patients, at last follow-up (range 3-52 months) this was 12/17. The median NRS for neckpain at baseline was 8 and at halo removal it was 0, at last follow-up it was 0. Most patients (n = 14) received hyper-fractionation schemes to promote reossification. No patient deteriorated in neurological function during treatment. The majority of patients (17/18) showed some or substantial reossification of the metastases at the time of halo-removal and latest follow-up. Overall, younger patients and patients with radiosensitive metastases had the best clinical outcomes. Discussion: Temporary halo-fixation and radiotherapy aiming for palliation, local control and reossification may be an attractive alternative for long-construct spinal fixations in patients with multiple high-SINS cervical metastases originating from radiosensitive tumors. Neurological deterioration did not occur and mechanical pain was controlled well after treatment. Introduction: Giant cell tumors of bone (GCTs) are locally aggressive and destructive tumors. Denosumab, a monoclonal antibody, has been used either as a neo-adjuvant in resectable tumors or as a stand-alone treatment in unresectable tumors. While denosumab has been increasing used, different patterns of response have been observed clinically. The objectives were to establish a cohort of denosumab-treated spinal GCTs, and to perform an exploratory study to identify putative molecular biomarkers of treatment response in patients treated with denosumab. Material and Methods: Pre-treatment specimens of patients with spinal GCT treated with denosumab were collected at 2 centres. Clinical data was extracted retrospectively. Total mRNA was extracted by using a formalin-fixed paraffin-embedded extraction kit and we determined the transcript profile of 730 immune-oncology related genes by using the Pan Cancer Immune Profiling panel (Nanostring). The gene expression was compared between patients with good and poor response to Denosumab treatment by using the nSolver Analysis Software (Nanostring). Results: Nine pre-treatment specimens were acquired. Of these, 4 had denosumab used as a neo-adjuvant treatment, 3 received the treatment as a stand-alone and 2 received denosumab as an adjuvant treatment. Two patients showed poor clinical response with tumor progression and metastasis. The statistical analysis showed clear differences between good and poor responders to Denosumab treatment through hierarchical clustering analysis. The specific gene analysis, based on expression of specific cell markers and cytokine pattern reveals that good responders had a higher innate immune response with a marked macrophage and dendritic cell populations, while poor responding patients presented with a higher lymphocytic response in the lesions, with marked B-cells, and T-cell populations with enhanced Th1, Th2 and Th17 response. Conclusion: Despite small numbers, this novel experimental approach revealed differences in the immune response in GCTs that predispose to the clinical response to Denosumab. Further validation using a larger independent cohort will be required but these results could potentially identify the patients who would most benefit from Denosumab therapy. Aim: Degenerative cervical myelopathy (DCM) is a progressive cervical spinal cord injury brought about by mechanical stress from degenerative changes in the cervical spine. It is typically diagnosed on clinical symptoms and examination findings together with MRI findings. The objective was to determine the significance of category of degenerative pathology (identified in Nouri et al, 2017) to onset of DCM, by comparing symptomatic and asymptomatic populations. Methods: A systematic review and meta-analysis were conducted in accordance with the PRISMA guidelines, cognizant of their adaptation for epidemiological studies. A search strategy was used to identify original research carrying out MRI screening of cervical spines of asymptomatic patients in MEDLINE and Embase from 1985 to the present day. Results: The search yielded a total of 1,098 studies of which 17 were included in this metaanalysis covering a total of 5,059 patients. Ossification of posterior longitudinal ligament (pooled asymptomatic prevalence of 0.4%), enlargement of ligamentum flavum (pooled asymptomatic prevalence of 11.8%) and degenerative multilevel disc pathology (pooled asymptomatic prevalence of 64.5%, I 2 100%) were found to be significantly lower in asymptomatic populations (factor of 25 times, 4 times and 1.5 times respectively), and thus associated with DCM. Conclusions: Ossification of posterior longitudinal ligament and enlargement of ligamentum flavum were found to be markedly lower in asymptomatic populations. Understanding the natural history of DCM is a recognised research priority, and whilst these perspectives require further evaluation, they may be of significant relevance to the evolving biomechanical understanding of the disease.

Group cervical deformity classification should not be utilized in isolation as an indication for realignment surgery Richard Cowley 1 , Fred Nicholls 1 , and Taryn Ludwig 1 1 

Introduction: The Ames-International Spine Study Group (AMES) classification is used as a tool for stratifying severity in degenerative cervical deformity. The AMES sagittal modifiers include C2-7 sagittal vertical axis (cSVA), chinbrow vertical angle (CBVA) and T1 slope-cervical lordosis mismatch (TS-CL). Each modifier stratifies patients as grade 0,1 or 2. We aimed to compare the sagittal modifier grades in a normal population for Health Related Quality of Life (HRQOL) scores and global sagittal alignment. Material and Methods: Five hundred healthy asymptomatic volunteers from 20-40 years without prior spinal pathology or surgery were enrolled. The Oswestry Disability Index (ODI) and Neck Disability Index (NDI) were ascertained prior to EOS imaging scans. Results: Four hundred and ninety seven patients were scanned, with 19 exclusions for incidental finding of scoliosis or spondylolisthesis. The cSVA was not analyzed because 495/ 497 individuals were grade 0 (<4 cm). The CBVA was grade 0 in 65% of individuals and grade 1 in 35%. There was no difference between grades in HRQOL and alignment. The TS-CL modifier was grade 1 (15-20) in 92% of individuals and grade 0 (<15 degree) in 8%. There was no difference in HRQOL scores. Grade 1 individuals had a negligible difference of C2 SVA (1.25 cm vs 0.7 cm), a more kyphotic thoracic spine (37.8°vs 24.3°), greater PI (55.4 vs 40.5) and greater PT (16.5°vs 2.4°). Conclusion: When applied to a normal population the AMES classification sagittal modifier TS-CL is frequently grade 1. These grade 1 individuals are asymptomatic, have a balanced sagittal alignment and exhibit no abnormal compensation. In grade 1 or greater TS-CL patients careful attention must be paid to thoracic and lumbopelvic alignment to ensure no abnormal compensation is present. In the absence of abnormal compensation grade 1 TS-CL represents normal alignment and correction should not be pursued. Introduction: The aim of this study is to identify predictive factors associated with 1-year mortality in patients treated for Spinal Epidural Abscess (SEA). Failed or delayed treatment of SEA can have severe sequelae. Knowledge of patient factors associated with poor outcomes should guide treatment selection. There is little evidence regarding mortality over a longer timeframe that considers both operatively and nonoperatively managed patients. Materials and Methods: Retrospective review of electronic record between January 2007 and January 2017 identified 120 patients 18 years or older treated for spinal epidural abscess (SEA) at a tertiary referral centre. Patients with chronic SEA, children, and those with less than 2 years follow-up were excluded. Details on presenting complaint, laboratory parameters, radiographic evaluation, demographics, comorbidities, and neurologic status (Frankel Grade A-E) were collected. Primary outcome assessed was mortality at 1-year following diagnosis. Secondary outcome was neurologic status at final follow-up. Results: 94 patients were suitable for analysis. Median age was 62.5 years (± 16.5, range 16-93). The majority of patients were male (67%). Assessing predictors of mortality at one year, four variables remained significant in logistic regression: age > 65 years (OR 12.7, p = 0.02), initial decision to treat non-operatively (OR 19.7, p = 0.009), concurrent pneumonia (OR 6.4, p = 0.02), and Frankel < E (OR 11.7, p = 0.01). Baseline mortality risk for a patient with any one of these four variables sits at 22.5%. With all four variables, mortality risk increases to 100%. Patients treated operatively were more likely to experience improvement in neurology by 1 Frankel grade compared with those in the non-operative category (59% vs. 27%, p = 0.03). Conclusions: 1-year mortality risk is elevated in certain elderly patients with SEA treated nonoperatively. Aggressive early surgical management appears appropriate in those with multifocal infection. Surgeons should be wary of potentially poorer outcomes associated with non-operative management.

A323: Is anti-infective treatment necessary for subclinical bacterial contamination of the surgical site in same-level reoperation due to recurrent degenerative spine disease?Sebastian Siller 1 , Benjamin Skrap 1 , and Joerg-Christian Tonn 1 1 Department of Neurosurgery, LMU Hospital, Munich, Germany Introduction: Surgical site infections (SSIs) are a dreaded cause for recurrent symptomatology requiring reoperation after degenerative spine surgery. In contrast to clinically obvious SSIs (with e.g. purulent discharge, fever, elevated serum markers and radiological signs of inflammation), subclinical SSIs (with bacterial contamination of the surgical site but without clinical/laboratory/imaging inflammatory response) are still under debate with regard to their best postoperative management. Material and Methods: In a large single-center cohort of 2552 patients with elective degenerative noninstrumented spine surgery between 2014 and 2019, we selected all patients undergoing reoperation in the previously affected segment due to recurrent symptomatology during followup. We analyzed clinical, laboratory and imaging data and routinely performed microbiological cultures via multiple intraoperative smear tests of the surgical site to rule out clinical and subclinical SSIs at the timepoint of reoperation. Outcomes and management of those patients were analyzed and compared to patients with aseptic recurrence of the degenerative spine disease. Results: A total of 62 patients (m:f = 1.6:1, median 69 years) underwent same-level reoperation due to recurrent symptomatology (mean Δ-time:17 ± 36 months), accounting for a samesegment reoperation-rate during follow-up of 2.4%. 9 of the 62 patients suffered from a clinically obvious SSI demanding an ivand subsequent po-anti-infective postoperative treatment for a total of 8-12 weeks. In contrast, 53 patients showed no clinical/ imaging/laboratory/intraoperative signs for SSI. However, microbiological culturing of smear testing during reoperation showed pathogen growth in 8 of the 53 patients raising suspicion for subclinical SSI respective bacterial contamination of the surgical site; these patients underwent close postoperative surveillance without initiation of an anti-infective treatment. Outcomes of those patients were similar to the 45 patients with aseptic recurrence of the degenerative spine disease in terms of pain reduction (VAS, p = 0.990), general performance in dailylife (Barthel-Index, p = 0.957), and re-reoperation rate (p = 1.000). Conclusion: Withholding anti-infective treatment in subclinical SSIs with bacterial contamination of the surgical site but without clinical/laboratory/imaging inflammatory response at same-level reoperation after non-instrumented degenerative spine disease is a viable option with unimpaired outcome. A324: Presence of bacteria in healthy spinal bone meal collected during instrumentation: colonization or evidence for future low-grade infection?Vicki Butenschön 1 , Ann Kathrin Joerger 1 , Raimunde Liang 1 , Maximilian Schwendner 1 , Melanie Barz 1 , Bernhard Meyer 1 , and Sandro M. Krieg 1 1 Department of Neurosurgery, Technical University Munich, Munich, Germany Introduction: Cutibacterium acnes is suspected to cause low grade infections and screw loosening after dorsal instrumentation and gains more and more interest for its role in spine pathology. While C. acnes belongs to the standard skin flora, its pathogenic role remains a question of debate. Methods: We prospectively enrolled patients undergoing spinal instrumentation for trauma or degenerative indications. Patients suffering from previous instrumentations or infections were excluded. Bone meal was collected from each screw placement and analyzed separately; preoperative antibiotics were analyzed in parallel. We stratified patients in native and preoperated patients who underwent a previous spinal decompression. Results: We included 180 patients and analyzed a total of 995 screws. The presence of bacteria was detected in 61.2% of the cases, in only 5.7% we detected abundant bacteria, in 20.8% we detected single bacteria and in 52.2% the bacteria were identified only in enrichment medium. C. acnes was the most often encountered bacteria (28.4%) in healthy bone meal specimens, followed by Staphylococcus epidermidis (25.3%) and Staphylococcus hominis (11.7%). We saw no difference between patients with a native or preoperated spine, nor between percutaneous and open instrumentation. Discussion: Overall, bacterial presence was detected in more than half of the healthy bone specimens. Our preliminary data suggest a ubiquitous colonization, and screw loosening remains a complex and probably multicausal pathology. Clinical symptoms and imaging should be correlated with positive microbiological results to correctly detect and not overestimate its pathogenicity.OP37: Deformity-Thoracolumbar (Adult) -Techniques 1243 A325: Vertebral remodeling after vertebral subluxation in closing-opening wedge osteotomy for correction of thoracolumbar kyphosis secondary to ankylosing spondylitis Xiao-lin Zhong 1 , Bangping Qian 1 , Yong Qiu 1 , Ji-chen Huang 1 , and Yao Li 1 suggested to perform single level TLIF were randomised into three groups by the GraphPad QuickCalcs software. Group A is standard TLIF with PEEK spacer. Group B is standard TLIF with PMMA spacer positioned in the anterior part of the intervertebral space. Group C is standard TLIF with PMMA spacer formed in the posterior part of the intervertebral space. We included patients between 18-65 y/o. Exclusion criteria were high-grade spondylolisthesis, metabolic bone disease, spinal infection, cancer, severe scoliosis (Cobb over 30°). We excluded twenty patients (surgery not performed following randomization, no consent because of pregnancy, not fitting inclusion criteria). 162 patients were included. Three of them after surgery denied participating. Radiological evaluation focused on the process of bony fusion, loosening of any instrument implanted (PMMA spacer or screws), osteolysis around the cement, subsidence. Adverse Event (AE: consistent complaint related to the lumbar spine), and Serious Adverse Event (SAE: revision surgery at the lumbar spine) were also analysed. We divided SAEs into index level revisions (SAE IL) and adjacent level revisions (SAE AL). Statistical analyses were made with chi-square test in SPSS v. 23 software. Results: 149 from the 159 enrolled patients (94%) have at least 12 month follow up. The median follow-up of these 149 patients is 3 years. Sixty subjects are in Group A, forty-three in Group B, and forty-six in Group C. Overall fusion rate at 24 months is 93%, without difference between the groups (p = 0.96). Overall subsidence rate was 13% and was significantly higher in group A (p = 0.046). We found a sign of loosening in 6.6% of all the cases, most in group A, but this difference was not significant (p = 0.165). AEs were distributed similarly in the groups (p = 0.490). There were 21 SAEs (14%), seven in each group (p = 0.487), nine are related to the index level (SAE IL: 6%) most in group C without significant difference between groups (p = 0.360). Conclusions: These results show a better performance of custom made PMMA spacer regarding radiological disturbance. From the clinical point of view, we found no difference between TLIF using preformed PEEK spacer or custom made PMMA spacer. However, in demanding situations like narrow window for cage insertion, irregular endplates or high degree wedge shaped intervertebral space when a preformed spacer is hardly possible to insert it is still possible to perform a custom-made spacer from PMMA which on the other hand is always available and cheap material. Introduction: In adult spinal deformity (ASD) surgery, multirod constructs (MRC) have recently gained favor to reduce instrumentation-related complications in areas of high mechanical stress, such as the lumbosacral junction or across 3-column osteotomy sites. We describe here MRCs in primary and revision cases, characteristics of MRC failures, and risk factors for failure in these constructs. Material and Methods: 57 ASD patients with at least 1.7 year follow-up, at least 10 levels instrumented, fusion to pelvis, and a MRC were retrospectively reviewed. Both primary and revision cases were included and the following variables were analyzed: age, gender, diagnosis, osteotomy type, radiographic parameters (coronal alignment, SVA, PI, LL, PT, PJA), number of rods, and interbody implantation. Mechanical failure was described as any rod or screw breakage postoperatively. Details of each failure were documented. Results: 57 ASD patients, average age 60 years, were included. Average follow-up was 2.4 ± 0.6 years. Average levels fused were 17, with 10 3CO. 6 patients had instrumentation failure with subsequent revision. The average sagittal vertical axis (SVA) correction in MRC without failure vs. MRC with failure were 52.1 mm and 77.2 mm, respectively, while coronal alignment correction was 29.6 mm vs. 47.9 mm. Coronal correction > 30 mm was significantly correlated with rod failure (p = 0.02) while SVA > 50 mm was not (p = 0.44). Odds ratio for instrumentation failure with coronal correction > 30 mm was 6.4. All 6 constructs that failed were 3-rod constructs and occurred just above the lumbosacral junction between L3-S1, in the presence of transforaminal interbody fusions (TLIF) caudally. Conclusion: Our study of MRCs in ASD surgery found that a greater amount of coronal correction obtained was a risk factor for instrumentation failurethe amount of sagittal correction obtained however was not statistically significant. Instrumentation failure occurred at levels above low lumbar TLIFs, and all cases had fewer than 4 rods. Thus we suggest considering at least 4-rod constructs for the lumbosacral region and extending up the lumbar spine 1 or 2 levels cephalad to where interbody fusions have been performed to avoid implant failure in these high demand constructs.

A328: The orientation and morphology of osteotomized vertebrae in two-level pedicle subtraction osteotomy play a crucial role in the remodeling of harmonious physiological curvature for severe thoracolumbar kyphotic deformity caused by ankylosing spondylitis Introduction: Long segment spinal fusion constructs are rigid and induce high stresses at the transitional vertebrae, possibly resulting in proximal junctional kyphosis (PJK) and proximal junctional failure (PJF). PJK is a radiographic observation which often manifests within the first 6-8 weeks following surgical correction of adult spinal deformity (ASD), with reported rates ranging from 20%-40%. PJF is defined in various ways, including: a fracture of the upper instrumented vertebra (UIV) or the vertebra above (UIV+1), the need for proximal extension of the fusion, and/or pullout or failure of the UIV fixation. Incidence rates reported in literature vary widely (1%-35%), possibly due to lack of a standardized definition. Instrumentation techniques aiming to prevent PJK and PJF have been developed, utilizing a semi-rigid fixation at the proximal end of a rigid spinal construct to create a more gradual transition of motion or by increasing the load carrying capacity of the anterior column. This systematic review summarizes the results of clinical studies investigating spinal instrumentation techniques aiming to reduce the postoperative incidence of PJK and/or PJF in ASD patients undergoing spinal fusion. Materials and Methods: EMBASE and Medline ® were searched for articles dating from January 2000 onward. Two researchers independently screened the titles and abstracts applying the following inclusion criteria: clinical study, ≥ 6 months follow up, degenerative/adult (≥ 18 years) spinal deformity, upper instrumented vertebrae in the thoracic spine, >4 segments fused or prophylactic technique for PJK and/or PJF. Exclusion criteria were: case reports, case series with <5 patients, fusion constructs ending proximally in the cervical spine, tuberculous spine, adolescent idiopathic scoliosis (<18 years), spinal trauma, spinal tumor or congenital spinal deformities. Full-text analysis was performed using the same criteria. Likewise, data was extracted by two independent authors and methodological quality was assessed using ROBINS-I. Results: 18 retrospective-and prospective cohort studies with a severe or critical risk of bias were included. Different techniques were applied at the upper instrumented vertebra (UIV): tethers in various configurations, 2-level prophylactic vertebroplasty (2-PVP), transverse process hooks (TPH), flexible rods (FR), sublaminar tapes (ST) and multilevel stabilization screws (MLSS). Compared to a pedicle screw (PS) group, significant differences in PJK incidence were found using tethers in various configurations (18% versus 45%, p = 0.001, 15% versus 38%, p = 0.045), 2-PVP (24% vs 36%, p = 0.020), TPH (0% vs. 30%, p = 0.023) Introduction: Achieving coronal alignment is crucial for successful spine deformity surgery. However, there is a paucity of literature demonstrating a reliable relationship between radiographic coronal malalignment and patient reported outcome (PROs) scores, potentially due to the inadequacy of CSVL to appropriately represent the coronal spinal alignment. CSPL is a novel radiographic parameter that portrays coronal alignment after spine deformity surgery. Material and Methods: We reviewed 93 deformity patients from 2015-2018. The CSPL bisects the sacrum and is perpendicular to the line connecting the superior aspects of the acetabuli. We derived two metrics describing coronal alignment from each radiograph: (1) the horizontal distance between the C7 plumb line and the CSPL at C7 (C7-CSPL) and (2) the horizontal distance between the C7 plumb line and the CSVL (C7-CSVL). We divided patients into coronally aligned (CA) and coronally malaligned (CM) groups based on a) CM defined as C7-CSVL > 4 cm and b) CM defined as C7-CSPL > 4 cm. Logistic regression and Chi-square analyses evaluated the relationship between the postop C7-CSVL and C7-CSPL with ΔODI/SRS (difference between pre and postop) scores. Results: Of the 93 patients, there were 7 patients with CM when it was defined as C7-CSVL > 4 cm. There were statically insignificant and minimal differences between the ΔODI scores (-10.0 vs -4.0, p = 0.45) and the ΔSRS total scores (18.0 vs 5.0, p = 0.03) in the CA and CM group when it was defined based on CSVL. When CM was defined as C7-CSPL > 4 cm, there were 10 patients with CM. There were statistically significant differences between the CA and CM group for both ΔODI (-12.0 vs -2.0, p = 0.03) and ΔSRS total scores (19.0 vs 5.0, p = 0.0015) when CM was defined as CSPL > 4 cm. Conclusion: The CSPL is a superior radiographic representation of coronal alignment after spine deformity surgery that directly correlates with ΔSRS and ΔODI scores. C7-CSPL > 4 cm is the critical distance that corresponds with clinical coronal malalignment.

A333: Should length of construct influence our alignment goals in adult spinal deformity corrective surgery?Introduction: The impact of construct length on radiographic alignment goals in surgical adult spinal deformity patients has yet to be investigated. This study sought to determine the influence of fusion construct length on radiographic and clinical outcomes in adult spinal deformity (ASD) patients. Material and Methods: Included: operative ASD patients with fusion to S1/pelvis and with full baseline (BL) and 2-year (2Y) data. Patients were further stratified by UIV: L2 or below [Short Construct; SC], between T7 and L2 [Medium Construct; MC], or to T7 or above [Long Construct; LC]. Demographics, radiographic parameters, surgical descriptors, complications, and age-adjusted alignment goals for these groups were assessed by univariate analysis. An optimal outcome was defined as 1) 2Y postoperative SRS-22 Total score ≥ 4.5 or 2Y ODI ≤ 15 [Best Clinical Outcome targets as defined by Smith et al.] and 2) no PJF or mechanical failure with reoperation. Patients with an optimal outcome were assessed in terms of actual vs. ideal [age-adjusted] postoperative realignment by construct length. Results: 600 adult spinal deformity patients were included (64.0 ± 9.6 years, 78% female, 28.2 ± 5.6 kg/m 2 , CCI: 2.0 ± 1.7), and underwent surgical correction (levels fused 11.6 ± 4.1, EBL: 1921mL, operative time: 397min). 60% underwent a decompression, while 67% had an osteotomy. By approach, 65% posterioronly procedures and 35% combined. SRS-Schwab modifiers assessment found 49.3% ++ PI-LL, 34.3% ++ SVA, 35.1% ++ PT. At 2Y, 57.3% of the cohort had ≥ 1 age-adjusted match.Breakdown by fusion length: 8.0% (n = 48) UIV L2 or below [SC], 55.3% (n = 332) UIV between T7 and L2 [MC], and 36.7% (n = 220) with UIV T7 or above [LC] . Overall, 171 patients (28.5%) had an optimal outcome. By Chi-square, the likelihood of achieving an optimal outcome did not differ by construct length (p > 0.05). For patients with optimal outcome, mean BL and 2Y radiographic parameters, age-adjusted alignment targets, as well as actual and absolute differences (offset) between measured and ideal age-adjusted values were calculated and then stratified by fusion length. Among the patients with optimal outcome, those with long construct length had significantly lower 2Y minus age-adjusted target values for both PI-LL (SC 5.2°, MC -4.4°, LC -8.1°, p = 0.006) and SVA (SC -0.1°, MC -9.8°, LC -45.3°, p < 0.001). This indicated a higher proportion of overcorrection for those parameters in patients with a long fusion. However, in terms of offset (absolute value of the difference between 2Y radiographic measurement and age-adjusted target) there was a significant difference only in SVA by fusion construct length (SC 41.4°, MC 33.7°, LC 52.0°, p < 0.001). Conclusion: There are subtle variations in optimal alignment based on length of construct, with longer constructs extending above the thoracic apex of kyphosis demonstrating moderate but significantly greater offset from age-adjusted alignment goals, in the direction of overcorrection, in order to achieve optimal clinical outcomes and minimize junctional failure.OP38: Degenerative Lumbar: Radiologic 838 A334: Is preoperativ supine MRI a predicto for reduction and final lumbar sagittal alignment following one or two level transforaminal interbody fusion?Carlos Manuel Aguilar Escalante 1 1 Spine Surgery, Instituto Nacional de Rehabilitacion, Mexico, Mexico Purpose: The final postoperative reduction of degenerative spondylolisthesis, lumbar lordosis, and lumbar sagittal alignment cannot be determined in the preoperative period, those measures depend on several factors, however, supine MRI establish dynamic instability in patients with degenerative spondylolisthesis and it can be considered an option to predict postoperative results. The purpose of this study is to determine if the preoperative supine MRI parameters can predict the final lumbar sagittal alignment in the postoperative period. Methods: We conducted a retrospective review of adult patients diagnoses with spondylolisthesis who underwent TLIF for whom the required imaging was available for analysis in a single institution from 2018 to 2020. Radiographs and MRI were reviewed and measured. Linear regression analysis provided correlation and significance between variables to assess the radiographic outcomes. Results: Sevetyseven patients with 91 fused segments were included in the study. The average age was 59 years, and 63.3% were men. The average preoperative spondylolisthesis was 8.02 ± 6.78 mm, which was reduced to 3.41 ± 3.23 mm (p = 0.0001) six months after surgery. There were statistically significant changes in all radiographic parameters between the neutral radiographs and the six-month follow-up except for the TLL and SS. There were no statistically significant changes in terms of displacement and percentage of displacement between preoperative magnetic resonance and radiographs at six months (3.44 ± 4.41 vs 3.41 ± 3.23, p = 0.953) and (8.86 ± 8.22 vs 9.13 ± 8.68, p = 0.748). Conclusion: There was a significant correlation between the difference in translation on neutral standing radiograph and supine MRI with the amount of spondylolisthesis reduction Sagittal T2 MRI has a predictive value of spondylolisthesis reduction in 6 months X-rays in degenerative spondylolisthesis patients. The presence of an interbody cage modifies final disc height but do not influence the pelvic parameters in a significant way. Introduction: Adjacent segment disease (ASD) is a major reason for late reoperations after lumbar spine fusion (LSF) surgery. Etiology of the condition is multifactorial. Sagittal alignment after LSF is generally considered relevant here, although the related literature is somewhat controversial. We aimed to find out whether poor postoperative sagittal balance, i.e. hypolordosis, increases revisions for ASD after LSF performed for degenerative spinal disease. Material and Methods: 215 consecutive patients who underwent elective LSF surgery for spinal stenosis w/out spondylolisthesis were prospectively followed-up for 10 years. Spinal reoperations were collected from the hospital records. Pre-and postoperative sagittal alignment were evaluated from standing radiographs. The risk of revisions for ASD was evaluated by Cox proportional hazards regression models. Results: We did not find postoperative hypolordosis (mismatch of pelvic incidence lumbar lordosis > 9°) significantly increase the risk of revisions for ASD: crude hazard ratio (HR) 1.5 (95% CI 0.8 -2.7), adjusted (by age, sex, pelvic incidence, fusion length, and the level of the caudal end of fusion) HR 1.7 (95% CI 0.9 -3.3). We found higher lumbar lordosis outside the fusion segment (LL -segmental lordosis) to decrease the risk of revisions for ASD: HR 0.9 (95% CI 0.9 -1.0). Conclusion: Poor sagittal balance has only a limited role as a risk factor for the revisions for ASD among patients with degenerative spinal disease. However, the risk for ASD might be the greatest among patients with reduced spinal mobility. Introduction: Osteoporosis is associated with higher rates of surgical complications in lumbar spine surgery. Various techniques to improve pedicle screw fixation in osteoporotic bone have been described. In particular, polymethylmethacrylate (PMMA) augmentation with a fenestrated pedicle screw can be used to increase screw pull-out strength in osteoporotic vertebrae. While many elderly patients undergoing transforaminal lumbar interbody fusion (TLIF) have comorbid osteoporosis, few studies have evaluated the clinical safety and efficacy of cement augmented pedicle screws in this growing subgroup. This study aimed to compare the perioperative complications, radiographic fusion rate and patientreported outcomes (PROs) of patients undergoing TLIF with cement augmented pedicle screws (CAPS) and noncemented pedicle screws (NCPS) at minimum 2-year follow-up. Material and Methods: Prospectively collected data of 80 patients who underwent TLIF for degenerative spondylolisthesis were reviewed. A total of 40 patients with CAPS were identified and matched in a 1:1 ratio with 40 patients with NCPS. Propensity score matching was based on age, sex, body mass index, number of levels and baseline PROs. Perioperative data including operative time, fluoroscopic time, blood loss, morphine use, time to ambulation and length of stay were recorded. PROs including the Oswestry Disability Index (ODI), Neurogenic Symptom Score (NSS), 36-Item Short-Form Health Survey (SF-36), Visual Analogue Scale (VAS) back and leg pain at 3, 6 and 12 months were compared using independentsamples t-tests. Fusion rates according to Bridwell classification were compared using Chi-square analysis. Results: In total, 80 patients were included. The two groups were closely matched in terms of demographics and preoperative PROs. The CAPS group had significantly longer operative time (334 ± 106 vs. 254 ± 98.1 mins, p < 0.001), a higher percentage that required blood transfusions (32.5% vs. 5.0%, p < 0.01), but less postoperative morphine use (7.13 ± 13.6 vs. 19.1 ± 21.3, p < 0.01). There was no difference in time to ambulation or length of stay. Asymptomatic PMMA leak occurred in 42.5% of patients in the CAPS group, although all cases were managed non-surgically. There was no difference in PROs between the groups at 3 months, 6 months or 1 year (p > 0.05 for all). Interbody fusion rates were also similar at 6 months (84.6% vs. 92.1%, p = 0.306) and 1 year (93.8% vs. 97.4%, p = 0.422). Conclusion: Clinical and radiological outcomes of TLIF performed with PMMA augmentation and fenestrated pedicle screws were comparable to that of conventional pedicle screw fixation over a 2-year follow-up period. These findings support its utility as a safe and effective alternative in patients with osteoporosis who may otherwise suffer screw-related complications due to poor bone quality, although continued surveillance of this cohort is necessary. (Mizuho ProAxis) were prospectively studied. Patients were positioned prone on the motorized hinged table and flexed to 10°for decompression and TLIF. The table was extended in 5°increments and radiographs taken until 10°of extension is achieved (Figure 1 ). Segmental lordosis change across the operative site for each 5°increment was measured. Results: 33 patients were available for analysis. Table extension from +10°to +5°yielded 2.3°segmental lordosis change (n = 33); +5°to 0°yielded 1.5°segmental lordosis change (n = 33); 0°to -5°yielded 1.5°segmental lordosis change (n = 29); -5°and -10°yielded 1.5°segmental lordosis change (n = 23). Rod placement yielded an additional 3.2°o f segmental lordosis. Conclusion: Intraoperative fluoroscopy showed correlation between table extension and segmental lordosis correction. Utilizing a motorized hinged table facilitates controlled osteotomy closure and decreases the need for cantilevering forces across spinal instrumentation. After the TLIF with SPO is performed, approximately 7°of additional segmental lordosis correction can be acquired from 20°of intraoperative table extension.

Pankaj Kumar Sharma 1 1 Orthopaedics, All India Institute of Medical Sciences, Bathinda, India Introduction: The management of lumbar canal stenosis depends on the clinical severity and MRI findings but the correlation between the same still remains unclear. The study aims to evaluate that is there any correlation between the clinical severity and the MRI findings. The objective of study to assess the correlation between Magnetic resonance imaging features and clinical severity in patients with symptomatic lumbar canal stenosis. Material and Methods: A prospective observational study including 150 patients with lumbar canal stenosis. Data including demographic, anthropometric profile and clinical features, visual analogue score (VAS) score for back pain and leg pain, modified Oswestry disability index (mODI) scores were collected on initial visit. Schizas 7 grade classification system was used to classify the MRI severity of lumbar canal stenosis. AP diameter and crosssectional area of dural sac for central, diameter of the foramen for foraminal and height of lateral recess for lateral stenosis were the most commonly used criteria in the diagnosis of LCS. Results: 87 males and 63 females with a Introduction: Maintenance of sagittal balance is largely dependent upon lumbar lordosis, the majority of which is derived from the lower lumbar motion segments and specifically the segmental disc angles. Lumbar degenerative spondylolisthesis (LDS) with associated spinal stenosis is a common indication for spinal surgery, often treated with fusion surgery with or without the use of an interbody. It is important to understand the effects of spinal fusion on the index spinal segment prior to surgery so as not to induce iatrogenic deformity by changing previously lordotic disc spaces to kyphotic or failing to address a preoperatively kyphotic disc space. The objective of this study was to determine the effect of interbody cages inserted via posterior approach on segmental lordosis in the setting of preoperative lordotic versus kyphotic/neutral disc spaces in patients with LDS. Material and Methods: Five consecutive years of retrospective data from the Canadian Spine Outcomes and Research Network (CSORN) prospective study on the assessment and management of LDS patients was collected from two contributing centres of consecutively enrolled patients. Patients were analyzed preoperatively and at 12-month follow-up with standing lumbar radiographs. At the spondylolisthesis level, segmental lumbar lordosis (SLL) was measured from the upper end plate of the proximal vertebra to the lower end plate of the distal vertebra. Patients were stratified into four groups based on index level disc angle and the type of procedure performed: preoperative lordotic posterolateral fusion (PLF) (Group 1); preoperative neutral/ kyphotic PLF (Group 2); preoperative lordotic interbody fusion (IF) (Group 3); preoperative neutral/kyphotic IF (Group 4). Results: A total of 100/111 (90%) patients completed one-year follow-up. Twenty-three patients underwent PLF with 18 (18%) in group 1 and only five (5%) in group 2. Eighty-eight patients underwent IF, with 40 (40%) in group 3 and 48 in group 4 (48%). Among patients with preoperatively lordotic disc angles, group 3 had a greater magnitude of worsening in SLL than group 1 patients, with significant differences persisting at one-year (mean difference 2.3 0 , 95% CI, 0.3, 4.3, p = 0.029). Patients in group 4 were more likely to achieve improvement in SLL at one year than group 3 (67% vs. 44%, p = 0.046), with similar mean improvement magnitude between groups 3 and 4 (-1.1, 95% CI, -3.7, 1.6, p = 0.415). Conclusion: In the setting of an index-level preoperative lordotic disc angle, the magnitude of segmental lordosis worsening was more pronounced when an interbody cage was used versus PLF. Patients who have a kyphotic or neutral disc space preoperatively are more likely to gain lordosis when an interbody cage is used.

A340: Impact of interbody approach and lumbar level on segmental, adjacent, and saggital alignment in degenerative disease effectively treat lumbar degenerative pathology and provide spinopelvic balance. The objective of this study is to compare changes in spinopelvic parameters 6 months following 1-2 level TLIF, PLIF, ALIF, and LLIF. Material and Methods: This retrospective study included 18 centers of various practice settings across the USA. Patients were included in the study if they underwent a one-or two-level primary lumbar fusion for degenerative pathology. Measurements of the pre-operative and 6-month post-operative lumbar AP and lateral lumbar plain radiographs included: pelvic incidence (PI), pelvic tilt, lumbar lordosis from L1-S1 (LL), as well as segmental lordosis (SL) of each segment between L1-S1. Results: 474 patients underwent 632 levels of fusion. ALIF/LLIF resulted in significantly more segmental lordosis compared to TLIF/PLIF procedures at both L4-5 and L5-S1 (p < .001). Overall, ALIF/LLIF resulted in significantly more global lumbar lordotic alignment change compared to TLIF/PLIF (p = .01). Whether patients' alignment was preserved versus worsened was not significantly predicted by type of procedure. Similarly, whether patients' alignment was restored versus not corrected was not significantly predicted by type of procedure. Finally, anterior approaches resulted in decreased lordosis at both the supra and infra adjacent levels, thus resulting in a more neutral position. Conclusion: In this large-scale multicenter study of lumbar fusion patients presenting with degenerative lumbar pathology, we report that anteriorly-placed grafts (ALIF/LLIF) led to a greater likelihood of patients being preserved rather than worsened in their spinopelvic mismatch. Posteriorly-placed TLIF or PLF grafts tended to worsen lordosis both segmentally and globally, yet even the anterior grafts only modestly improved those two measurements. Therefore, A/LLIF procedures maintain preoperative segmental lordosis more effectively than T/PLIF procedures. Background: MRI is the gold standard investigation for lumbosacral degenerative disc disease. However, there is controversy regarding the clinical value of repeating an MRI scan within 12 months when a patient presents with recurring or changing symptoms. This study measures rates of radiological change in a real-world cohort to guide clinicians when deciding to repeat a scan. Methods: All patients over a ten-year window in one general hospital who underwent two lumbosacral MRI scans for degenerative disc disease within twelve months of each other were included in the study. All MRI reports were manually reviewed. Level of main vertebral pathology was recorded, along with location of a disc prolapse. Time intervals between the two scans were calculated, these were collated into 30-day intervals for analysis. The repeat scans were categorized into three groups: no change, radiological improvement, and radiological deterioration. Patients who had emergency intervention due to a radiological change on MRI scan were recorded. Results: 481 patients were included for analysis. 390 (81%) showed no change in MRI findings, 18 (3.7%) had improvements in their repeat scans and 73 (15.3%) demonstrated deterioration in their repeat scans. From the 73 patients with a radiological deterioration, 3 patients (0.62% of total) required urgent surgical intervention. Conclusions: Though there is no alternative to detailed clinical assessment in determining whether a repeat MRI scan is indicated, the findings demonstrate that repeating MRI within 12 months for patients with lumbosacral degenerative disc disease has a low chance of altering the management plan. Over the 10-year period, only three patients required an urgent change to their clinical management. We believe this data can help guide clinical decision making when considering a repeat scan. the first revision procedure were: adjacent segment disease (23.8%), herniated nucleus pulposus (28.3%), degenerative spondylolisthesis (42.3%), and pseudarthrosis (28.7%). Of the 455 patients, 39 patients (8.6%) went on to require multiple revisions surgeries for malpositioned instrumentation (17.9%), adjacent segment disease (18.0%), pseudarthrosis (15.4%), to receive additional direct decompression (10.2%), and mechanical failure (5.1%). Mechanical failure primarily consisted interbody cage retropulsion. Comparison of patients who were successfully treated with one revision surgery versus those that required multiple revision procedures demonstrated that multiple revision patients were more likely to have had an intra-or post-operative complication during their first revision, particularly intraoperative fracture or malpositioned instrumentation. Patients who required multiple revision surgeries more commonly had a diagnosis of iatrogenic or degenerative flatback deformity at the time of their first revision (7.9% vs 2.5%, p = 0.059). The most common pathologies requiring multiple revision surgeries were adjacent segment disease (42.8%) and pseudarthrosis (42.8%). Conclusion: We found that compared with patients who were treated successfully with a single revision surgery, patients who require multiple revision surgeries more commonly had an iatrogenic or degenerative flatback deformity at the first revision, and sustained an intra-or postoperative complications after the first revision. The most common indications for multiple revisions were adjacent segment disease and recurrent pseudarthrosis OP39: MISS: Outcomes 438 A343: Perioperative outcomes of minimally invasive sacroiliac joint fusion using hollow screws through a lateral approach: a single surgeon retrospective cohort study Hamid Abbasi 1 1 Neurosurgery, Inspired Spine Health, Burnsville, USA Introduction: Traditionally, SIJ fusion was performed using an open technique that required accessing the SI joint through a large incision with subsequent decortication of the joint, packing of bone graft, and fixation with screws or plates. Over time, minimally invasive approaches have become the standard of care for candidates of SIJ fusion due to the minimization of soft-tissue damage, reduced blood loss, lower operative times, and quicker recovery, with 85% of SIJ fusions being minimally invasive in 2012. There is no consensus on the preferred approach or technology for minimally invasive SIJ fusion, and several techniques are currently used. One technique involves the percutaneous implantation of triangular titanium implants with the goal of transarticular stabilization and long-term biological fixation and fusion. Another common type of fusion utilizes hollow or solid screws to achieve transarticular stabilization and promote fusion. Material and Methods: This study is a retrospective cohort study of 62 patients with SIJ disease who underwent 78 SIJ fixations. Procedures were performed by a single surgeon in 7 hospitals in Minnesota. Pearl Pathways IRB granted institutional review board (IRB) exemption. Inclusion criteria for this study were patients >18 years who underwent SIJ fixation between 1/1/2015 and 5/31/2020 by the study surgeon. Exclusion criteria were the presence of osteomyelitis, tumors, and the presence of severe lumbar pathology, traumatic injury before or after surgery, uncontrolled psychiatric comorbidities, and patients with possible secondary gain such as workers compensation. Patients who underwent unilateral SIJ fixation and underwent evaluation of the contralateral SIJ at the time of study conclusion were also excluded. Patients were candidates for surgery if they had SIJ pain diagnosed by the following clinical protocol. Clinical diagnostic criteria were a history of characteristic pain, typically unilateral caudal to the lumbar spine, and at least three positive provocation tests on clinical exam per Medicare criteria. Results: There were 78 operations involving 62 patients because 16 patients had a fusion of both SIJ in two separate operations. Mean operative time was 34 ± 9 minutes and blood loss was 22 ± 35 ml. Overnight hospitalization was required for six operations (8.6%) for ambulation or pain management. Preoperative Oswestry was available for 55 patients (87%), and postoperative Oswestry at the one-year follow up could be obtained for 44 patients (71%). Mean preoperative disability on the ODI was 52.2%, which improved to 34.9% at the one year follow up. Patients experienced significant improvements in each sub-category of the ODI. Conclusion: Minimally invasive SIJ fusion using hollow screws through a lateral to the medial trajectory is a safe and effective procedure in patients with SIJ pain who have failed conservative therapy. This procedure can routinely be performed on an outpatient basis, and patients report significant improvements in their Oswestry disability scores one year after the procedure. Given the significant burden caused by SIJ pain, more research is warranted to determine the best surgical treatment.

A344: Significantly shorter hospital stay is observed with endoscopic surgery compared with microscopic surgery for bilateral decompression in lumbar stenosis patients Nicholas Van Halm-Lutterodt 1 2 , Krishna Mandalia 3 , Ziyang Ye 4 , Wei-Cheng Chen 2 , Wei-Hsun Huang 2 , Wenju Jiang 2 5 , Xin Yuan Chen 6 , Mercy Bartels-Mensah 7 , and Yu Wang 2 Introduction: Lumbar radiculopathy patients are frequently referred to spine surgeons. A herniated lumbar disc impinging on a lumbar nerve root is the most typical cause of this issue. While most disc herniations recover within 6 weeks of conservative treatment, some patients have refractory neuropathic pain and paralysis in the dermatomal distribution and myotome of the affected nerve root, necessitating surgical decompression. Over time, spine surgeons have moved from open operations with substantial muscle dissection and laminectomy or laminotomy to minimally invasive treatments. The introduction of the microscope into the operating room cleared the path for microdiscectomy, allowing spine surgeons to operate more efficiently through a short surgical corridor with better visibility. Several studies have shown good results with microdiscectomy. Material and Methods: On a 5-year follow-up, 62 individuals with symptomatic lumbar disc herniation were reviewed. The study ran from 2014-2019, with a 1-year follow-up. The study included all patients who received minimally invasive lumbar tubular microdiscectomy for radiculopathy within the stated study period and were available for a 1-year post-operative follow-up session, either by phone or in person. Patients with cauda equina syndrome, conus medullaris syndrome, or spinal stenosis were excluded from the study. We used the grading system to assess patient satisfaction at 1-year follow-up. All statistical analyses were performed. Results: Only 62 subjects were enrolled for a year. It was 52.3. In terms of gender, 47% were female and 53% were male. 81% of patients had degenerative disc degeneration. 19% had recent significant lumbar trauma with traumatic mechanism. (p = 0.73). Preoperative symptom duration was 8.7 (2.5) weeks, ranging from 5 to 15.11% patients achieved 4/ 10, while 11% individuals achieved 3/10. Acute postoperative back pain had no link with 1-year patient satisfaction (p = 0.41). The rest of the Demographic data is in. After a year, 79% were very or extremely satisfied, with 67% moderately satisfied. After a year, 95% of respondents said they were satisfied or very satisfied with the outcome. After a year, 5% were only moderately satisfied. Conclusion:After a year, 79% were very or extremely satisfied, 16% were satisfied, 5% were somewhat satisfied, and 0%. An annual follow-up found that 95% of respondents were satisfied to very satisfied with their outcomes. After a year, 5% were just partially satisfied. Introduction: Clinical outcomes amongst degenerative lumbar disease patients have shown satisfactory results being reported after minimal invasive lumbar surgery. Despite the transforaminal lumbar interbody fusion (TLIF) has been widely used in indirect decompression of the lumbar disease, adoption of the anterolateral interbody fusion technique, including anterior lumbar interbody fusion (ALIF) and oblique lumbar interbody fusion (OLIF), has increased due to a high fusion rate, less surgery time, blood loss, and less paraspinal muscle invasion whilst sufficiently relief clinical symptoms. However, the comparison of clinical and radiologic outcome between ALIF, OLIF, and TLIF has scarcely been addressed in the available literature. Material and Methods: Patients receiving interbody fusion including ALIF, OLIF, and TLIF with posterior instrumentation for single level degenerative lumbar disease were examined for patient-reported outcome, sagittal alignments (including SVA, PT, PI-LL, LL, TK), implant subsidence, revision rate, and fusion status at pre-OP, post-OP, and two-year follow-up. Results: After matching age and sex, we enrolled a total of 120 patients, including 30 patients in ALIF and OLIF, 60 patients in TLIF for single level degenerative lumbar disease for the study. All patients acquired substantial improvement in sagittal alignments after surgery whilst ALIF and OLIF showed greater extent at twoyear follow up comparing to TLIF group (p < 0.05). The OLIF group suffered from a higher subsidence rate (p < 0.05) with no significant difference in fusion rate when compared to ALIF and TLIF. The ALIF and OLIF showed significantly better patient-reported outcome in visual analogue scale of pain in total, Oswestry Disability Index comparing to TLIF group (p < 0.05), with no differences whilst comparing ALIF to OLIF. There was no difference in revision rate between ALIF, OLIF, and TLIF. Conclusion: We revealed the comparison of surgical outcomes in single level ALIF, OLIF, and TLIF towards symptomatic degenerative lumbar disease with good fusion outcome despite the relative high subsidence rate amongst the OLIF group. The anterolateral approach, including ALIF and OLIF technique provides superior outcome in restoring sagittal alignments and improving patientreported outcome whilst ALIF an OLIF showed no difference comparing to each other. However, patient selection remains crucial when considering the options between the methods. However, evidence on the efficiency of interlaminar fullendoscopic decompression (FED) versus conventional microsurgical decompression (MSD) in patients with lumbar spinal stenosis is still scarce. Specifically, the association between the surgical learning curve and perioperative complications in FED is scientifically under-investigated. Therefore, we conducted a case-matched comparison for treatment success with consideration of clinical, laboratory, and radiologic predictors, as well as the confounding factor "surgeon". Material and Methods: We included 88 consecutive patients (FED: 36/88, 40.9%; MSD: 52/88, 59.1%) presenting with lumbar central spinal stenosis. Surgery-related (operation time, complications, length of stay, American Society of Anesthesiologists Physical Status (ASA) score, Creactive protein (CRP), white blood cell count, side of approach (unilateral/bilateral), patient-related outcome measures (PROMs) (Oswestry Disability Index (ODI), Numeric Rating Scale of Pain (leg-, back pain), EuroQol questionnaire (eQ-5D), Core Outcome Measures Index (COMI)), and radiological (dural sack cross-sectional area, Schizas score (SC), left and right lateral recess heights, and facet angles, respectively) parameters were extracted at different time points. Associations between PROMs were analyzed with the Pearson correlation coefficient (r). Spearman rank correlation was utilized to examine the relationship between the number of surgeries and the operation time as indicators for surgical learning curve. Surgery-related outcome parameters were correlated with patient-centered and radiological outcomes utilizing a regression model to determine predictors for propensity score matching. Results: Complication (most often residual sensorimotor deficits and restenosis due to hematoma) rates were higher in the FED (33.3%) than MSD (13.5%) treatment group (p < 0.05). All complications were found within the first 20 FED patients. Operation time was higher in the FED group, whereas length of stay was higher in the MSD group. Higher Age, SC, and CRP revealed significant inverse associations with PROMs. We did not observe significant differences between FED and MSD when comparing PROMs. The correlation between ODI and COMI was significantly high, and both were inversely correlated with eQ-5D, whereas the correlations of these PROMs with NRS findings were less pronounced. Spearman's rho revealed a significant inverse relationship between the number of full-endoscopic surgeries and the operation time (rho = -0.4219; p = 0.0104), whereas there was no significant correlation for the microsurgical group. Conclusion: Endoscopic treatment of lumbar spinal stenosis was similarly successful as the conventional microsurgical approach when comparing PROMs, although it was associated with higher complication rates. The distribution of complications and the improvement in operation time indicated the surgical learning curve as the main factor of the present findings. Future long-term prospective studies considering the learning curves are warranted for reliable comparisons of these techniques. Introduction: Open spinal surgery comes with an approach related morbidity cost. The importance of reducing muscle damage, particularly to the multifidus muscle, has become well recognized. Transforaminal endoscopic surgery and tubular minimally invasive lumbar discectomy are both minimally invasive surgical procedures. Although they can achieve satisfactory results, which procedure has better clinical effects remains controversial. However there is a clearly need for high-quality clinical studies to determine whether transforaminal endoscopic surgery is as effective as tubular minimally invasive discectomy. The purpose of this study was to compare the clinical outcomes between transforaminal endoscopic lumbar discectomy versus tubular minimally lumbar microdiscectomy for symptomatic lumbar disc herniation treatment. Material and Methods: We retrospectively analyzed 49 patients who underwent discectomy surgery (group A: transforaminal endoscopic surgery, 23 cases; group B: tubular minimally invasive discectomy, 26 cases) for lumbar disk herniation between January 2017 and January 2020. All patients have a minimum follow up of 18 months. To evaluate outcomes, we checked the leg and back visual analog scale (VAS), Oswestry Disability Index (ODI), EQ-5D, MacNab criteria, complications and recurrence for all patients. Results: 49 patients, 49.3 ± 15 years (range: 19-70), 57.1% female were eligible, mean follow up time was 26.9 ± 14.3 (range 18-60) months and operation level (L3-L4: 2; L4-L5:10; L5-S1:11 for group A and L2-L3: 1; L4-L5:11; L5-S1:14; p = 0.72). The mean improvement of VAS for leg was 7.8 ± 2.4 for group A and 8.4 ± 1.1 for group B (p = 0.284). The mean improvement of VAS for back pain was 6.5 ± 2.3 for group A and 6.7 ± 2.2 for group B (p = 0.851). The mean improvement of ODI scores was 37.3 ± 8.7 for group A and 39.6 ± 7 for group B (p = 0.262). The mean improvement of EQ-5D score was 6.5 ± 2.4 for group A and 7.1 ± 1.1 for group B (p = 0.271). The pos-operative MacNab criteria for group A was 1.8 ± 0.83 and 1.4 ± 0.7 for group B (p = 0.11). There were only one complication in group A and four complications in group B (p = 0.106), they were all iatrogenic dural lesions. There were no recurrences in group A and two in group B (p = 0.16). Hospital stay was shorter following transforaminal endoscopic surgery (1. a surgical open decompression is not required. Delineation of the fracture classification and indication for each treatment approach has not been established. The objective of this study was to compare the direct operative and postoperative outcomes between these two treatment groups in patients with traumatic TL spine fractures. Material and Methods: Our single-center retrospective study analyzed all patients undergoing treatment for a traumatic TL spine fracture that did not require surgical decompression at a large level 1 trauma center from 2012 to 2017. Patients were treated with either percutaneous screw fixation or bracing. Variables collected included patient demographics, medical comorbidities, prior history of spine surgery, use of non-steroidal anti-inflammatory drugs (NSAIDs), use of anticoagulation, mechanism of injury, AOSpine Thoracolumbar Injury Classification, and level of the fracture. Results: A total of 147 patients were included in the study, with 58 treated with percutaneous fixation, and 89 with bracing. Percutaneous fixation patients sustained more AO classification B fractures (32.8% versus 1.1%, respectively, p < 0.0001). Additionally, 32.5% in the percutaneous fixation group had fractures to the L1 vertebra, compared to 18.0% in the bracing group (p = 0.0235). Preoperative sagittal Cobb angles were greater in the percutaneous fixation group compared to the bracing group (11.2°versus 4.5°, p = 0.0087), and postoperative sagittal Cobb angles were smaller in the percutaneous fixation group compared to bracing (2.6°versus 8.1°, p = 0.031). The percutaneous fixation group revealed significantly more documented healed fractures (53.4% versus 16.9% respectively, p < 0.0001) and significantly fewer patients lost to follow up compared to the bracing group (20.7% versus 51.7% respectively, p < 0.0002). Finally, percutaneous fixation patients were more likely to be taking anticoagulants (60.3% versus 30.3%, p = 0.0003) and have had prior spine surgery (p = 0.0308). Conclusion: In this study, injury characteristics and patient history varied significantly between treatment groups, with more at-risk presentations being treated by percutaneous fixation. While percutaneous fixation and bracing both remain valuable treatment options for thoracolumbar injury, selection of either therapy must take into consideration severity of injury and patient risk factors. Introduction: The purpose of this retrospective cohort study was to analyze the early complications and mortality associated with multilevel spine surgery for unstable fractures in patients with ankylosing spondylitis aged over 80 years and to compare the results with an age-and sex-matched cohort of patients with unstable osteoporotic fractures. Material and Methods: A retrospective review of the electronic medical records at our institution was conducted between January 2014 and December 2019. Patient demographics, surgical characteristics, complications, hospital course, and 90-day mortality were collected. Comorbidities were stratified using the age-adjusted Charlson Comorbidity Index (CCI). Results: Among 11,361 surgically treated patients, 22 patients with ankylosing spondylitis (AS group) and 24 patients with osteoporosis (OS group) were identified. Mean age was 83.1 ± 3.1 and 83.2 ± 2.6 years, respectively. A significant difference in mean CCI was found (7.6 vs 5.6; p < 0.05). Multilevel posterior fusion procedures were conducted in all patients, with 6.7 ± 1.4 fused levels in the AS group and 7.1 ± 1.1 levels fused in the OS group (p > 0.05). Major complications developed in 10 patients (45%) of the AS group compared to 4 patients (17%) in the OS group (p < 0.05). The 90-day mortality was 36% in the AS group compared to 0% in the OS group (p < 0.05). Conclusion: Patients over 80 years of age with ankylosing spondylitis bear a high risk of adverse events after multilevel spinal fusion procedures. The high morbidity and 90-day mortality should be clearly discussed and carefully weighed against surgical treatment.

A355: Does erector spinae plane block decrease amount of analgesia needed after minimal-invasive posterior transpedicular stabilization in patient with vertebral body fracture? A prospective double-blinded controlled study Introduction: The erector spinae plane (ESP) block is a simple ultrasound guided block. This technique was first described in 2010 as treatment option of pain associated with rib fractures and since 2016 used by anaesthesiologists for acute and chronic pain treatment. Many scientific articles have been published on the use of this technique for pain treatment in the immediate postoperative period since that time. There are only a few case reports published in the literature mentioned the use of ESP block in spinal surgery. Therefore, ESP block appears to be a promising technique that could be routinely used in spinal surgery. In our study, we examined the effect of ESP block on opioid consumption in the first 48 hours after minimally invasive posterior stabilization for vertebral fracture treatment, as well as it's effect on blood loss during surgery and on disability level. Material and Methods: This study was designed as a prospective double-blinded randomized cohort study. Adult patients with vertebral fracture in thoracic and lumbar region suitable for minimal invasive posterior stabilisation were included to the study. After the induction of general anaesthesia and positioning to prone position, the local anaesthetic is administered under ultrasound guidance under erector spinae muscles directly on transverse process of fractured vertebra bilaterally. The solution used for the block could contain 20ml of 0.25% levobupivacaine (ESP group) or saline solution (placebo group). During the surgery blood loss were determined. The opioid consumption was measured during the first 48 hours. Visual analogue score (VAS) was assessed on the second postoperative day. Modified Oswestry Disability Index (ODI) and modified Patient Reported Outcome Spine Trauma (PROST) were used to measure the disability after spine surgery. The results were subjected to statistical analysis. Results: Total 60 patients were included to this study. Follow up finished 56 of them, 28 in ESP group and 28 in placebo group. Both groups were consistent in terms of age, gender, level of fracture and AO Spine classification. Average morphine consumption during the 48 hours period after surgery was 5.357 mg in ESP group and 8.607 mg in placebo group (p = 0.059), whereas median of morphine consumption was 3.0 mg in ESP group and 10.0 mg in placebo group. Blood loss was 14.8 g per screw in ESP group and 14.8 g in placebo group. The value of the second day PROST was 33.9 in ESP group and 28.8 in placebo group (p = 0.008). The ODI score on the second day after surgery was 39.1 in ESP group and 48.6 in placebo group (p = 0.080). The second day after surgery VAS was 4.11 in ESP group, respectively 4.57 in placebo group (p = 0.557). Conclusion: The ESP block in minimal invasive spinal surgery leads to the reduction of opioid consumption in first 48 hours after surgery, with no effect on perioperative blood loss. It also improves the general disability of the patients on the second day after surgery measured with PROST and ODI. A statistically insignificant difference in VAS can be explained by adequate pain treatment protocol.

A356: Necessity of direct decompression for thoracolumbar junction burst fractures with neurological compromise Sarvdeep Dhatt 1 1 Orthopaedics, PGIMER, Chandigarh, IndiaBackground: Surgical management of burst fractures is controversial, with many different operative options. From a posterior approach, decompression of the spinal cord can be performed through both indirect and direct methods, the former relying on ligamentotaxis. It is unclear whether indirect decompression with ligamentotaxis is as effective as direct decompression. Methods: Prospective, randomized controlled data were retrospectively analyzed to include only burst fractures of the thoracolumbar junction. Patients were treated with either direct decompression, involving wide posterior decompression in addition to operative stabilization, or indirect decompression, where decompression was performed solely through ligamentotaxis. Patients were followed up at 6 months with clinical assessment and imaging. Additional clinical assessment was performed at 1 year. For all analyses, p < 0.05 was significant. Results: The study included 46 patients, with 18 patients in the direct decompression subgroup and 28 patients in the indirect decompression subgroup. The average age of the full cohort was 35.1 13.1 years (range, 16e60 years). Most patients had L1 fractures (21/46; 46%), with an AOSpine classification type A4 fracture morphology (17/46; 37%), and were American Spinal Injury Association grade B (18/46; 39%). Both treatments resulted in similar in-creases in canal diameter and decreases in dural sac compromise (p > 0.5) at 6-month follow-up. Both treatments resulted in similar grades of neurological improvement (p [ 0.575) at 1 year. Conclusions: There were no significant differences in clinical and imaging outcomes when comparing direct decompression with ligamentotaxis. Ligamentotaxis alone may be effective in carefully selected cases. Introduction: Previous studies have shown the AO Spine PROST (Patient Reported Outcome Spine Trauma) to be a valid and reliable tool to measure outcomes of spine trauma patients up to 12 months after their injury. However, it remains unclear whether the tool would also be applicable in the longer term. The primary aim of this cross-sectional study is to assess the validity of the AO Spine PROST for the long-term followup of spine trauma patients. The secondary aim is to evaluate patients' health-related quality of life (HRQoL) as compared to their demographic characteristics, types of spine fractures sustained, and received treatment. Material and Methods: All patients with a traumatic spine injury between 2003 and 2018 were recruited from an established database including patients from a level-1 trauma center in The Netherlands. Patients were divided in a cross-sectional or test-retest arm, and asked to complete several questionnaires, namely: AO Spine PROST, EuroQoL 5D-5L (EQ-5D-5L), and either Oswestry Disability Index (ODI) or Neck Disability Index (NDI) for concurrent validity. Patients within the test-retest arm were selected randomly and asked to fill out all questionnaires twice with a fourteen day interval. Internal consistency was assessed by calculating Cronbach's α and item-total correlation coefficients (ITCCs). Test-retest reliability was estimated using Intraclass Correlation Coefficients (ICCs). Spearman correlation tests were performed for the AO Spine PROST in correlation with the EQ-5D-5L, and ODI or NDI. Predicting factors were analyzed using multivariate regression models. Results: All 768 patients within the database were approached, of whom 299 initially responded in consent. Out of those, 224 patients were allocated to the cross-sectional arm and 75 to the test-retest arm. In the cross-sectional arm 175 patients (78.1%) were included because they filled out all questionnaires. In the test-retest arm 49 patients (65.3%) were included. Median duration of follow-up was 94.5 months (IQR: 56.6-131.7). Patients' mean age at the time of trauma was 50.8 years (SD:16.9) and 68.8% were male. Internal consistency (α = 0.98, ITCC 0.73-0.91) as well as test-retest reliability (ICC = 0.81) were excellent. Compared to the AO Spine PROST, satisfactory correlations were seen for the EQ-5D-5L (0.76; p < 0.001), ODI (0.69; p < 0.001) and NDI (0.68; p < 0.001). The strongest correlation (r s = 0.71) was seen for "Usual activities" domain of the EQ-5D-5L. Multivariate linear regression models showed several significant independent predictors for a worse AO Spine PROST score, i.e. ≥ 1 comorbidities, duration of return to work within the range of 7-43 months, and not being able to return to work. Conclusion: The AO Spine PROST showed very good reliability and validity results for long-term follow-up of traumatic spinal column injury patients. These results were comparable to the results of previous psychometric studies of the AO Spine PROST.Pre-existing comorbidities, increased duration of return to work within 7-43 months, and not being able to return to work may negatively influence HRQoL outcomes in spine trauma patients in the long-term. This study contributes to the long-term outcomes evaluation of spine trauma patients in a valid and reliable fashion using the AO Spine PROST.

A358: Robotic assisted pedicle screw placement for the treatment of unstable thoracolumbar spine fractures using the Mazor X Robot: Preliminary Experience At A Level 1 Trauma Center Kyle Holmberg 1 , Daniel Altman 1 , Ryan Sauber 1 , Alex Yu 2 , Jonathan Acosta 1 , Hareindra Jeyamohan 1 , and Boyle Cheng 3 1 Orthopaedic Surgery 2 Neurosurgery 3 Neuroscience, Allegheny Health Network, Pittsburgh, USA Introduction: Pedicle screw instrumentation has been used to treat a wide variety of conditions of the spine including degenerative disease, deformity, and trauma. In spine surgery, robotic platforms are primarily involved in the planning and insertion of pedicle screws in order to stabilize the vertebral column. The utility of robotic assisted placement of pedicle screws for the stabilization of thoracolumbar spine fractures has not been widely reported. At our institution thoracolumbar spine fractures are stabilized using pedicle screw fixation guided by fluoroscopy, computer navigation, or using robotic assistance. Surgeons using robotic assistance underwent extensive training in the procedure prior to initial use. We report our initial experience using the newest version of the Mazor X articulating surgical robot in the treatment of patients with traumatic spine fractures over a three-year period. Materials and Methods: A retrospective chart review was performed focusing on patients admitted to our Level 1 Trauma center with a diagnosis of traumatic thoracolumbar spine fracture. Our inclusion criteria consisted of patients eighteen years and over who underwent stabilization of traumatic fracture of the thoracolumbar spine using Mazor X robotic assisted pedicle screw and rod constructs. Results: Three surgeons treated 27 patients between 22-90 years old with robotic assisted pedicle screws for the stabilization of acute traumatic spine fractures between 2018 -2021. There was a total of 219 pedicle screws inserted in the thoracolumbar spine using the Mazor X articulating robotic arm. Zero screws required revision for malposition or loosening. Six screws were unable to be inserted with robotic assistance and were inserted manually utilizing navigation. Cumulative OR time was on average 227 min per case (Range = 95-641 min, SD = 102 min). Average estimated blood loss was 229 cc per case (Range = 25-750 cc,