Paw pad pain: A review of corns in dogs - Veterinary Medicine
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Paw pad pain: A review of corns in dogs
In this overview, experts make the case that these painful lesions are likely caused by repetitive mechanical trauma and recommend a treatment and prevention plan.


VETERINARY MEDICINE



(GETTY IMAGES/ELKE VOGELSANG)
Sight hounds, especially greyhounds, often develop painful digital pad corn-type lesions. These well-demarcated, circumscribed hyperkeratotic lesions have a central core of keratin that is often conical. The lesions have the gross appearance of fibrous scar tissue and cause pain and local inflammation.1-4 They have been called corns,5-9 keratomas,3,4 and foot pad keratosis (orthokeratotic hyperkeratosis).10 The lesions are similar to the hard corn lesions seen on human feet (heloma durum), which are associated with chronic pressure or abrasion and overlie bony prominences where there is insufficient soft tissue between the skin and underlying bone.2,3

Corns can appear on the digital, metacarpal, or metatarsal paw pads, primarily in greyhounds, but most of the lesions occur on the digital paw pads. They are seen predominantly in active racing and retired middle-aged or older greyhounds.3,4,8-11

CLINICAL SIGNS

Clinical signs associated with corns include visible pain when palpation pressure is applied and a reluctance to walk on hard surfaces, both of which push the corn into subdermal tissues. It is important to apply pressure during palpation to elicit signs of pain.

There may be excessive nail growth on the affected paw, resulting from decreased wear as the dog tries to bear weight on the metacarpal or metatarsal pad rather than on the digital pads.3 When performing an orthopedic examination on a dog for lameness, especially a greyhound, a paw pad examination should be included.

ETIOPATHOGENESIS THEORIES

There are three theories as to the cause of corns:

1. Scar tissue and foreign bodies. One theory is that cuts or punctures of the pad result in an accumulation of scar tissue.6,7,9,12,13 The presence of a small foreign body in the pad is related to this theory. In this case, scar tissue accumulates at the lesion site as the body attempts to isolate the foreign body. This scar tissue develops into a thickened, hard corn on the pad.3,7,9,12,13


1. A corn lesion on a greyhound's digital pad.
2. Papilloma virus infection. A second theory is that a corn lesion is the result of a papilloma virus infection.3,6,7,9 Because of the pressure and abrasion associated with ambulation, the papilloma does not grow on the pad surface. Instead, the lesion is forced into the deeper pad layers, resulting in a flat, circular, painful area (corn-type lesion) that is visible on the pad surface (Figure 1).6

3. Pressure and abrasion. A third theory for corn development is that repetitive mechanical trauma in the form of pressure and abrasion leads to lesion development (Wright JC, Borghese IF, Swaim SF, College of Veterinary Medicine, Auburn University, Ala: Unpublished data, 2003).3,7,9,10 These traumatic forces would be present in racing greyhounds. It has been reported11 and has been our observation that corns occur quite commonly in racing or retired greyhounds. However, lesions are also seen in whippets and lurchers.3


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Source: VETERINARY MEDICINE,
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