Page 187 - Canine Lameness

12.6 ­ onDcD oe ofsctrs DeDcral rons raw rne 159

12.5.2.2 Deep Digital Flexor Muscle
Mechanisms of injury are similar to those of the superficial tendon. Both muscles and/or their
tendons may be affected concurrently. The deep digital flexor tendon is more commonly lacer -
ated than the superficial tendon, as it lies superficial to the latter, and so is more vulnerable to
injury. The clinical appearance is of the claw of one or more digits being elevated off the contact DISTAL LIMB REGION
surface, colloquially referred to as “kicked up” or “knocked up” toe. If there is concurrent
superficial flexor muscle injury, the digit becomes flattened as described above, but the claw is
cocked dorsally. Clinical assessment and diagnostic options are similar for those of the superfi-
cial digital muscle.

12.5.2.3 Flexor Tendon Strain: Bowed Tendon
A condition termed “bowed tendon” has been described in racing Greyhounds (Blythe et al. 2007).
This is a strain injury of one or more of the tendons of mainly the superficial and occasionally deep
digital flexors of the thoracic limbs. The condition manifests clinically as a swelling on the palmar
surface of the foot extending from the level of the accessory carpal bone to the level of the metacar-
pal footpad. Palpation of the affected tendon evokes pain and the tendon may feel thickened and
more prominent than the adjacent, unaffected tendons.

12.6 Conditions of the Digital and Paw Pads

12.6.1 Trauma
Laceration of the metacarpal pad has been ascribed to be the most common traumatic injury in
working dogs and pets. In one study, concurrent injuries were uncommon, and the prognosis
remained favorable even for full-thickness injuries, regardless of treatment (Hansen et al. 2015).
Diagnosis can generally be established by careful visual inspection and palpation. Concurrent
damage to underlying structures, such as the flexor tendons, needs to be investigated; this can be
accomplished by blunt probing through the laceration while extending the toes or through use of
ultrasound. Radiographs may be required to detect radiopaque foreign bodies and to investigate
the underlying osseous structures for osteomyelitis.
Aside from laceration, other traumatic injuries to the digital and paw pads include foreign bod-
ies, blistering from hot surfaces, chemical damage (e.g. walking through wet cement or undiluted
surface disinfectants), maceration when pads remain wet for extended periods, abrasions, and
ulcerations. Specifically, ulcerations (Figure 12.9F) often occur when dogs are exposed to hard
surfaces that they are not conditioned to, or through overuse in runs with cement floors such as
found in communities of highly active and driven dogs (e.g. police and military work dogs). In
such cases, the keratinized epidermis is worn away, leaving the sensitive dermis exposed (“hot
spots”) and can cause dogs to show a more pronounced lameness when walking on paved surfaces.
Therefore, establishing a diagnosis may require walking affected animals on soft surfaces or don-
ning paw covers to determine if the lameness disappears.

12.6.2 Corns
Corns are well-circumscribed hyperkeratotic lesions with a central, often conical core of kera-
tin. The validity of the term “corn” has been questioned since in people, corns are generally
non-painful. Other terminology suggested includes “wart-like lesion” or “Porokeratosis planta-
ris discreta” (Balara et al. 2009). The lesions appear as white, flat, and circular thickened areas