Page 212 - Canine Lameness

184 13 Carpal Region

13.4.3 Diagnostics
Radiographs should be acquired in every patient as the first diagnostic step. When the problem is uni-
lateral, orthogonal views of the unaffected, contralateral side are obtained for comparison purposes.
Standing or stress views mimicking weight-bearing are imperative to identify the location of injury
within the carpal joint (Figure 13.7). Stress views can be safely acquired using adhesive tape or ties
to extend the carpus. Otherwise a wooden spoon can be used to provide counterpressure. This ensures
a safe distance of the examiner’s hands from the radiation beam, while simultaneously being able to
provide the necessary amount of pressure needed to achieve appropriate stress view imaging. In addi-
tion to regional soft tissue swelling, based on the level of subluxation and associated supportive
CARPAL REGION pal level results from damage to the short oblique radial carpal, palmar radiocarpal, and palmar
structures, injuries occur at three levels (Slocum and Devine 1982). Subluxation of the antebrachiocar-

ulnarcarpal ligaments. Injuries to the intercarpal level result from rupture of the metacarpal accessory
ligaments and the short intercarpal ligament between the accessory and ulnar carpal bones.
Carpometacarpal joint injuries include rupture of the ligaments of the middle carpal- the carpometa-
carpal joints and the palmar fibrocartilage. In addition to flexed and hyperextended views, views
with mediolateral stress (Figure 13.8) are also acquired to evaluate the medial and lateral collateral liga-
ments. Finally, oblique views acquired at 45° angles can help identify carpal bone fractures.
CT can be considered if there is concern for additional fractures of the carpal bones that may not
be visible on radiographs or if stress views do not reveal a subluxation of any joint. MRI may reveal
very subtle lesions and allow for evaluation of all periarticular soft tissue structures of clinical
interest. Advanced imaging can aid in treatment decision and increase the success for each specific
treatment, which depending on the damaged structures involved, may include partial or pancarpal
arthrodesis. Ultrasound has also been used, albeit its value for the diagnosis of these injuries has
not yet been established.
Arthrocentesis should be performed if infectious or inflammatory etiologies are possible. While
infrequently reported in the literature, IMPA should be considered as a possible cause for carpal
lameness (Lotsikas and Radasch 2006). With chronicity, affected dogs can progress to palmigrade
stance, mimicking a traumatic hyperextension injury. Based on the authors’ experience, Shelties
and Welsh Corgies may be at increased risk of IMPA affecting the carpus, although other breeds
are also affected. Arthroscopy of the carpus has also been suggested as a potential additional
imaging technique, to aid in the diagnosis of hyperextension, infection, and IMPA (Warnock and
Beale 2004).

13.4.4 Other Carpal Ligamentous Injuries
No ligament crosses the entire carpus. Rather, ligaments cross one or two carpal rows. The main
carpal ligaments are the medial collateral ligament, the short radial lateral collateral ligament and
the short oblique lateral collateral ligament. Medial collateral ligaments sprains can result from
severe trauma or, more seldomly, from athletic activities. Lateral collateral injuries have been
reported in racing Greyhounds and other dogs (Roe and Dee 1986; Guilliard and Mayo 2000).
Dorsal carpal ligament sprains have also been reported in a series comprising two racing
Greyhounds, one working Pointer, one working Border Collie, and one working Labrador Retriever
(Guilliard 1997). Injuries to collateral and dorsal ligaments result in focal swelling in the short
term and in focal fibrosis over time. Collateral injuries are detected by placing varus or valgus
stress on the carpus with the joint extended and are confirmed by use of stress radiography
(Figure 13.8) or diagnostic ultrasonography.