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13

Carpal Region

1
Denis J. Marcellin-Little and Dirsko J.F. von Pfeil 2,3
1 Department of Veterinary Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA, USA CARPAL REGION
2 Small Animal Surgery Locum PLLC, Dallas, TX, USA
3 Sirius Veterinary Orthopedic Center, Omaha, NE, USA

13.1 Introduction and Common Differential Diagnoses

The carpus connects the antebrachium to the manus. Overall in dogs, carpal region pathology is
less common than elbow or shoulder pathology. The carpus is prone to instability, particularly
excessive extension secondary to damage to the palmar ligaments. The carpus is also a common
site of inflammation (e.g. immune-mediated polyarthritis [IMPA]). Carpal osteoarthritis is com-
mon and may occur as primary osteoarthritis (i.e. without an underlying disease) or secondary
osteoarthritis (e.g. secondary to carpal hyperextension or other primary conditions). The identifi-
cation of carpal problems most commonly relies on palpation, radiographs, and computed tomog-
raphy (CT); MRI and ultrasound are helpful if soft tissue pathology is suspected. Figure 13.1 and
Table 13.1 outline common differential diagnoses and diagnostic steps for this region.

13.2 Normal Anatomy and Osteoarthritis

The carpus is a complex joint that allows motion at three levels: antebrachiocarpal, middle carpal,
and carpometacarpal (Figure 13.2). The carpus includes 14 bones: the distal aspect of the radius and
ulna, proximal carpal row (intermedioradial carpal bone, ulnar carpal bone, and accessory carpal
bone), distal carpal row (first, second, third, and fourth carpal bones), and the proximal aspect of the
five metacarpal bones. The intermedioradial carpal bone (frequently referred to as radial carpal bone)
is the largest of the carpal bones. The carpus functions mostly in flexion and extension, with approxi-
mately 170° of sagittal plane motion. The carpus is the only limb joint that functions past a straight
line (i.e. 180°). All other joints extend to approximately 165° and stop short of a straight line. By
comparison, the carpus extends 15–20° past a straight line to almost 200° (Jaegger et al. 2002).
Extension is limited by the palmar fibrocartilage, by the radiocarpal and ulnocarpal ligaments, and,
to a lesser extent, by the medial and the lateral collateral ligaments (Slocum and Devine 1982;
Milgram et al. 2012). Approximately 70% of carpal motion occurs at the antebrachiocarpal joint level,
25% at the middle carpal joint level, and 5% at the carpometacarpal joint level (Yalden 1970).

Canine Lameness, First Edition. Edited by Felix Michael Duerr.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/duerr/lameness