Page 213 - Canine Lameness

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13.5 Deformities of the Carpal Region

Deformities of the distal aspect of the antebrachium are the most common limb deformities, with
a reported prevalence of 0.74% of all orthopedic problems (Marcellin-Little et al. 1998). These
deformities result from genetic problems, most commonly chondrodystrophy and chondrodyspla-
sia (Parker et al. 2009; Brown et al. 2017). They can also result from developmental skeletal disor-
ders or inflammatory bone diseases including hypertrophic osteodystrophy (HOD) or multiple
epiphyseal dysplasia or premature growth plate closure.
Carpus valgus, a term used to describe lateral angulation originating in the distal portion of the
antebrachium, is the most common antebrachial deformity. The lateral deviation of the manus is
generally associated with excessive external rotation of the radius, and a loss of carpal flexion.
Carpus valgus can also be associated with subluxation of the elbow joint, particularly distal CARPAL REGION
humero-ulnar subluxation, and with a varus angulation of the proximal portion of the radius,
resulting in biapical antebrachial deformity (Kwan et al. 2014).
Carpus varus, the medial deviation of the carpus, is much less common than carpus valgus and is
most often the result of an injury to the distal radial physis.

13.5.1 Signalment and History
Deformities of the carpal region are common in chondrodystrophic and chondrodysplastic
dog breeds (Parker et al. 2009; Brown et al. 2017). Genetically driven deformities are bilat -
eral. However, one thoracic limb can be more severely affected than the contralateral tho -
racic limb (Kwan et al. 2014). Trauma to a radial or ulnar physis can lead to premature
closure and result in antebrachial deformity. In one study, 7% of physeal injuries led to a
limb deformity (Marretta and Schrader 1983). Antebrachial deformities secondary to trauma
are generally unilateral.

13.5.2 Physical Examination
Antebrachial deformities are diagnosed by observation and palpation and are confirmed by use of
radiographs. The deviation of the manus will vary when measured while standing, while sedated,
and on radiographs (Kwan et al. 2014). The examination of a patient with antebrachial deformity
includes the evaluation of varus or valgus; the presence of effusion, crepitus, and pain response to
joint motion in the carpus and elbow; and the range of motion of the carpus and elbow measured
using a goniometer (Chapter 5).

13.5.3 Diagnostics

Palpation and goniometry under sedation may be the most accurate way to evaluate valgus
or varus deformities; standing measurements appear to overestimate it and radiographs
appear to underestimate it. Radiographs should include the entire limb distal to the elbow.
It is easiest to evaluate deformities if an attempt is made to provide a true lateral and cranio -
caudal view of the elbow, without attempting to correct the position of the distal limb
(Figure 13.9). Complex deformities can be assessed using CT (Kwan et al. 2014), which
allows the objective assessment of radial rotation, length deficit, and subluxation of the
elbow and carpus.