Distal third metacarpal bone palmar cortical stress fractures in four Thoroughbred racehorses

Stress fractures of the third metacarpal bone (McIII) are a common cause of lameness in Thoroughbred racehorses. The most commonly described location is the mid-dorsolateral cortex (Copelan 1979; Richardson 1984, 1999; Stashak 1987; Stover et al. 1988; Cervantes et al. 1992; Pilsworth and Shepherd 1997; Stover 1998; Sullins 1998), but they also occur distally and proximally in the dorsal cortex (Richardson 1984, 1999; Stashak 1987; Stover et al. 1988; Cervantes et al. 1992). On the palmar aspect of McIII, stress fractures have been identified in the proximal cortex (Pleasant et al. 1992; Lloyd et al. 1988) and the distal condyle (Kawcak et al. 1995). Identification of stress fractures may require multiple views and sequential radiographs or nuclear scintigraphy to demonstrate the lesion. For this reason, knowledge of predilection sites and the optimal means of fracture identification are clinically valuable. In this report, the authors describe the clinical characteristics and outcome of horses having metacarpal stress fractures in a previously unreported location.