In Greyhounds with paw pad corns, is surgical excision more effective at resolving lameness than extirpation?

a Knowledge Summary by

Dan Kenny BVSc MRCVS^1*

¹Paragon Veterinary Referrals, Red Hall Crescent, Wakefield, West Yorkshire, WF1 2DF
^*Corresponding Author (dan-kenny@hotmail.co.uk)

Clinical scenario

A 9-year-old ex-racing Greyhound presents with a 3 week history of right thoracic limb lameness which worsens when walking on hard surfaces. The dog has a firm well circumscribed, circular lesion on the pad surface of digit three of the right thoracic limb which is painful on palpation. You suspect that the lesion is a corn however you have never treated one before. You can recall that a previous colleague used to manage them by hulling them out with a dental elevator, your current colleagues suggest surgical excision of the lesion. As you have never treated this condition before you decide to look for higher level evidence.

The evidence

There is limited evidence to suggest that one technique is superior to the other with regards to outcome as none of the cited studies directly compare these techniques. All cited studies are either opinion pieces or case series with no statistical analysis performed and are therefore low on the hierarchy of evidence.

Summary of the evidence

Appraisal, application and reflection

Numerous treatments have been described for digital pad corns in Sighthounds but currently none of these appear to result in a predictable and satisfactory long-term resolution of lameness. Two of the most commonly used treatment methods in veterinary practice are extirpation (‘hulling’) or deep surgical excision of the lesions. Extirpation involves removing the hard, central core of the corn. An instrument such as a dental elevator is used to work around the junction of the hard centre of the corn and the soft tissue of the pad. A twisting or rocking motion is used to separate the lateral edges of the corn from the pad. Once the sides are free, the base of the corn is released by angling the instrument parallel to the footpad surface at the base of the corn, scissors may be required to remove any remaining attachment. There should be no pain or bleeding. Surgical excision of a whole corn involves making an incision through the dermis around the periphery of the corn. This can be performed with a scalpel blade or punch biopsy instrument. The underlying soft tissues are then dissected away, and the corn removed. The pad is sutured, and the foot can be placed in a protective dressing.

There are no studies directly comparing these two techniques so papers assessing individual techniques were reviewed. The only article to discuss extirpation or hulling of corns in relative detail, described the use of a dental elevator to remove corns in conscious dogs. Although the author reports that lameness initially improves, recurrence was reported to occur in as little as 3 weeks post-procedure (Macherey & Freeman, 2006). Unfortunately, this article was a narrative review and stated outcomes were not supported with scientific evidence. Case 3 in the case series by Görtz et al. (2003) underwent superficial excision of corns which may also refer to a procedure similar to the extirpation described by Macherey & Freeman (2006). The details of the procedure, however, were not available making this conclusion impossible to draw.

Surgical excision was the treatment modality used in two papers for which the outcomes were recorded Görtz et al., 2003; and Guilliard et al., 2010). No recurrence was reported at 4 months and 5 years post-surgical excision of corns in two Whippets (Görtz et al., 2003). Guilliard et al. (2010) reported a 1 year success rate of 74% in surgically excised corns but in the long-term, up to 5 years, 52% had regrowth of the lesions. Out of 27 dogs which had initial surgical excision one dog remained lame, two dogs had improved lameness and 11 dogs had recurrence of lameness. Three dogs had the procedure repeated once and one dog had the procedure repeated four times at a mean period of 20 months between surgeries. Balara et al. (2009a) reported that 10/18 (55%) Greyhounds with corns treated in the study had recurrence of the original lesion or developed novel lesions. Unfortunately, the treatment modality was not linked to recurrence as an outcome measure and therefore it is impossible to ascertain what rate of recurrence was present amongst dogs treated by debridement or by deep surgical excision. However, in an opinion-based article the authors of this study recommend that single corns are treated by surgical excision with postoperative splinting or bandaging, they also acknowledge that although extirpation can be associated with reduction or resolution of lameness, recurrence is inevitable (Balara et al., 2009b).

Retrospective case series, case reports and opinion articles are very low on the hierarchy of evidence therefore drawing accurate conclusions regarding the superiority of either technique is challenging. The highest level of evidence regarding extirpation is based on opinion and regarding surgical excision, although the evidence is of a higher level, it is scarce and generally retrospective. It is clear that there is requirement for higher level evidence and studies involving larger number of dogs to accurately assess the two treatment modalities. Until this evidence is available veterinary surgeons should consider that the current literature, although low quality suggests that extirpation appears to be a palliative treatment with recurrence invariably occurring following the procedure. Deep excision of the lesion may lead to a potential resolution however there is a moderate rate of long-term recurrence alongside the occurrence of novel lesions.  

The aetiology of paw pad corns is currently poorly understood. Suggested causes include; chronic mechanical trauma or pressure, foreign bodies, scar tissue, deficiencies in the fatty layer in the pad and papillomavirus (Guilliard et al., 2010). In one study, canine papillomavirus was isolated from corn lesions in two Greyhounds (Anis et al., 2016). However, Balara et al. (2009a) found no evidence of papillomavirus on immunohistochemistry staining in six Greyhounds, but 3/5 dogs which were not Greyhounds were positive for papillomavirus. Given the paucity of reports assessing the involvement of papillomavirus in this condition, it is currently difficult to ascertain its significance. A greater understanding of the aetiology of the condition in Greyhounds may lead to the development of new treatment modalities and therefore better management of the condition. With such high recurrence rates and poor curative treatment options this condition is problematic for the veterinary surgeon.

Methodology Section

Search Strategy
Databases searched and dates covered:	CAB Abstracts on OVID interface [1973–2019 Week 45] PubMed accessed via the NCBI website – Veterinary Science filter [1910–current]
Search strategy:	CAB Abstracts: 1     (sighthound* or lurcher* or greyhound* or whippet* or dog or dogs or canine* or canis).mp. or exp dogs/ or exp canis/ or exp greyhound/ or exp racing animals/ 2     (corn or corns or hyperkerat* or keratoma* or keratinis* or keratiniz* or keratos* or "hard pad disease*").mp. or exp hyperkeratosis/ or exp keratosis/ or exp hyperkeratotic scabies/ or exp keratinization/ 3     (pedal* or foot or feet or paw* or digit* or heel* or sole* or footpad* or pad*).mp. or exp feet/ or exp digits/ or exp footpads/ or exp soles/ 4     1 and 2 and 3   PubMed: #1     (sighthound* OR lurcher* OR greyhound* OR whippet* OR dog OR dogs OR canine* OR canis) #2     (corn OR corns OR hyperkerat* OR keratoma* OR keratinis* OR keratiniz* OR keratos* OR "hard pad disease*") #3     (pedal* OR foot OR feet OR paw* OR digit* OR heel* OR sole* OR footpad* OR pad*) #4     #1 AND #2 AND #3
Dates searches performed:	22 Nov 2019

Exclusion / Inclusion Criteria
Exclusion:	Not relevant to PICO Wrong species Wrong breed Textbook chapters Review article with no detail of technique outcome
Inclusion:	Greyhounds or Sighthounds with pedal corns or keratomas Surgical excision of lesion performed Extirpation of lesion performed Outcome and recurrence of lesion reported

Search Outcome
Database	Number of results	Excluded – Not relevant to PICO question	Excluded – Wrong species	Excluded – Wrong breed	Excluded – Textbook chapter	Excluded – Review article	Total relevant papers
CAB Abstracts	186	177	1	1	2	1	4
PubMed	87	84	0	0	0	0	3
Total relevant papers when duplicates removed							5

The author declares no conflicts of interest.

1. Anis, E.A., Frank, L.A., Francisco R. & Kania, S.A. (2016). ‘Identification of canine papillomavirus by PCR in Greyhound dogs’. PeerJ 4:e2744. DOI: https://doi.org/10.7717/peerj.2744
2. Balara, J.M., McCarthy, R.J., Kiupel, M., Buote, M.A., Wise, A.G. & Maes, R.K. (2009a). ‘Clinical, histologic, and immunohistochemical characterization of wart-like lesions on the paw pads of dogs: 24 cases (2000–2007).’ Journal of the American Veterinary Medical Association 234(12), p. 1555–1558. DOI: https://doi.org/10.2460/javma.234.12.1555
3. Balara, J.M., McCarthy, R.J. & Buote, M.A. (2009b). ‘Comments on study of paw pad lesions in dogs.’ Journal of the American Veterinary Medical Association 235(6), p. 657–659. DOI: https://doi.org/10.2460/javma.235.6.620
4. Görtz, K., Rooster, H., Chiers, K., Kramer, M. & Declerq, J. (2003). ‘Digital hyperkeratosis as a cause of severe lameness in two Whippets and a Greyhound.’ Kleintierpraxis 48 p. 435–439.
5. Guilliard, M.J., Segboer, I. & Shearer, D.H. (2010). ‘Corns in dogs; signalment, possible aetiology and response to surgical treatment. .’ Journal of Small Animal Practice 51(3), p. 162–168. DOI: https://doi.org/10.1111/j.1748-5827.2010.00892.x
6. Macherey, C.L. & Feeman, W.E. (2006). ‘Using a dental root elevator to remove footpad corns in dogs: two practitioners’ experience.’ Veterinary Medicine 101 p. 778–781.