The following information has been obtained from the extensive research and information provided by Michael Guilliard, DVM, Richard Doughty, DVM and Bill Freeman III, DVM. For more information or to contact one of these veterinarians, email firstname.lastname@example.org
A corn is a hard mass of keratin, the structural fibrous protein of skin, pads, horns, and hooves; and corns are found predominantly in the digital paw pads of sight hounds. It presents as a circular area of hard pad that can protrude from its surrounding and has a deep root that impinges on the underlying flexor tendon and its bony attachment. It does not occur in the large metacarpal and metatarsal pads. Approximately 80% are found in the central digits of the forelimbs and are a source of considerable lameness especially when exercising on hard ground.
The cause has been attributed to foreign body penetration, virus infection—notably papilloma virus found in warts, and repeated mechanical pressure. X-rays of the corn never show a foreign body and none has been found over the several hundred examined histologically by Richard Doughty. Extensive testing for the papilloma virus in the U.K. has been negative, however, a small study in Tennessee found papilloma virus in four corns. It would be difficult to determine why any virus would be selective to specific pads but additional research is needed. Inverted papillomatous warts have very rarely been found in the large foot pads but never in the digital pads.
It is now accepted that the cause is from repeated mechanical trauma focused on one area of the pad. In people, corns can be a result of tight footware or from an anatomical deformity, such as a hammer toe, and if the problem is corrected then the corn will disappear. In dogs, some form of toe or foot abnormality including flexor tendon damage, adjacent toe amputation and hyperflexed or very tight toes, has been reported in 40% of cases. The best evidence is that the corn will exfoliate and disappear if the pressure is taken off the pad.
There are many as is often the case when there is none that gives reliable results.
- Conservative management: the protruding hard tissue is regularly filed down and a protective boot fitted for exercise.
- Lotions and creams: these consist of chemicals that will dissolve, soften or burn the corn and again will need regular applications.
- Excision is a surgical procedure that removes the entire corn with suturing of the pad.
- Amputation of the last joint preserving the pad.
- Hulling is popular and involves digging out the corn with a dental elevator or Dremel drill.
5. Amputation of the entire digit.
6. Flexor Tenotomy
Any treatment that does not remove the entire corn will result in recurrence and this includes hulling and the various lotions.
Amputation of the last joint can produce a permanent resolution of the corn but in many cases this will be unsuccessful due to the difficulty in positioning the pad in an unnatural position over the stump of the toe.
Complete surgical excision has been shown to give the best long term results but about 50% of corns will have recurred in a year.
The reason for the failures is that the underlying anatomical cause has not been addressed and in many cases this will not be obvious as it can be a result of previous injury, degenerative change of possibly conformation as seen with corns appearing in the same digit on both fore feet.
The ultimate treatment is amputation of the entire digit permanently removing the problem and it usually has no untoward consequences.
The rationale for this novel surgical treatment is that by unloading the pad the lameness will immediately resolve and the corn will grow out and permanently disappear.
The flexor tendons run along the under side of the toe with the superficial tendon attaching to the bone just beyond the knuckle joint and the deep tendon attaching to the nail bone and when contracted they cause the toe to flex or curl. Cutting them prevents this action and the toe is then lifted by the action of the extensor tendon running along the top of the toe.
The surgery is relatively simple with a small cut under the toe that is closed with 2 or 3 small sutures. Post-operative pain does not seem to be an issue with many patients lameness free is just a few days. The toe becomes flattened and the nail protrudes from the front. If the toe is unweighted i.e. when the dog lies on its back, the toe will appear elevated by about 30 degrees.
These are the results of the preliminary study as of January 2019:
29 dogs with 36 corns were followed after surgery
Dogs: Whippet = 8; Retired racing greyhound = 17; Racing greyhound = 3; Lurcher = 1
Three dogs remained lame after surgery. All three had pre-existing conditions impacting recovery. Two of these had a digit missing on the affected foot and one had a twisted foot from a metacarpal fracture malunion. It would seem that the tenotomised digit requires support from its adjacent digits.
The remaining 26 dogs showed improvement at seven days.
At seven days, three were assessed as moderately improved and 23 as greatly improved in perceived lameness and well-being.
At the six- to eight-week follow up, 21 dogs with 26 corns were examined.Four dogs had slight lameness and the remaining 17 dogs showed no lameness.When reviewing owner satisfaction, all owners very satisfied with the outcome. The dogs were much happier and willing to exercise normally. All corns had grown out/disappeared by this time.
One racing greyhound with bilateral thoracic limb corns returned to the track in 25 days and raced very successfully.
In the three failures the corn disappeared in two cases but the resultant lameness was soreness on the underside of the dropped toe as there was no support from adjacent digits.
Long terms results are unknown but dropped toes are not uncommon in racing dogs and usually do not cause a clinical problem.
One question frequently asked is the possibility of further digits on the same foot developing corns and the answer is probably very unlikely but there is no evidence for that yet.
Flexor tenotomy has given excellent results to date and taken these dogs out of pain giving them back a great quality of life.
Additional resources and home treatments can be found on the Greyhounds with Corns Facebook page or veterinarians can join the Veterinary Greyhound Corn Yahoo Listserv page. Additional photos and research data have been published in Veterinary Practice News Canada.
We are currently working with Michael Guilliard, DVM and Richard Doughty, DVM to gather funding and start new research protocols to gain more insight in to what causes corns and what options exist for dogs with multiple corns. We will update this page as these research protocols get organized and samples are needed.
©The Greyhound Health Initiative. Reproduced with permission.