m zyxwvutsrqp radial rn carpal zy n bone in tour dogs A. Miller, S. Carmichael, T. J. Anderson and I. Brown zyxwvutsrq Department of Veterinary Surgery, Glasgow University Veteri- nary School, Bearsden Road, Bearsden, Glasgow G61 1QH zyxwvutsr lournal zyxwvutsrqpo of Small Animal Practice (1990131,148-154 ABSTRACT Four cases of radial carpal bone luxation in dogs seen at Glasgow University Veterinary School in a period of six years are described. Three were border collie types. Two of these were working sheepdogs and the third was an agility triallist. The fourth was a rough collie. All were adult, two were male and two were female. Three cases were of short duration and were managed by open reduction of the luxation and surgical stabilisation of the radial carpal bone. The other was of longer duration and was treated by pancarpal arthrodesis. In all cases the carpus was supported externally for one to two months following surgery. At the time of writing, the progress of only the three working dogs was known. Despite the presence of osteoarthritic changes in the carpi of these dogs, they all became sound and returned to work. A mecha- nism for the injury based upon the results of cadaver studies is proposed. 148 INTRODUCTION Luxation of the radial carpal bone in the dog is an uncommon injury and there is a paucity of information available in the literature (Pillet 1957, Punzet 1974, Early and Dee 1980, Vaughan 1985). Punzet (1974) stated that radial carpal bone luxation accounted for 1.45 per cent of trau- matic dislocations in dogs seen over a 13 year period. Those authors who described a patho- genesis (Punzet 1974, Brinker and others 1983) agreed that the luxation resulted from a fall and that the bone invariably dislocated in a palmaro- medial direction and rotated through 90’ around dorsopalmar and mediolateral axes so that the proximal articular surface came to lie facing palmar and medial. Punzet (1974) con- sidered that the injury was the result of carpal hyperextension. In man, a specific mechanism consisting of a combination of extension, ulnar deviation and intercarpal supination has been shown to reliably reproduce a variety of carpal injuries in human cadavers and is considered to be responsible for the range of clinical injuries recognised in the human wrist (Mayfield 1980). No description of a biomechanical mechanism for radial carpal bone luxation in the dog could be found in the literature. Comparative anatomy is illustrated in Figs l a and Ib, respectively. The anatomy of the canine and human carpus FIG 1. Diagram of volar aspect of canine carpus showing rele- vant anatomy. UCL Ulnar (lateral) collateral ligament, RCL Radial [medial) collateral ligament, PRL Palmar radiocarpal ligament, OPUL Oblique palmar ulnocarpal ligament