Morphometrical variations of the carpal bones in thoroughbreds and ponies.

There is scant morphological data for equine carpal bones despite the frequent pathology in Thoroughbreds (TB). This study aimed to identify morphological and morphometrical variations and similarities in carpal bones between and within TB and Ponies (Po). Carpal bones from nine TB and 13 Po were prepared by boiling and drying. Lateromedial width, dorsopalmar depth, proximodistal height, relative density and volume of each bone were measured. Normalized measurements of the radial (Cr) and third (C3) carpal bones were significantly different in all dimensions, and there were significant variations in relative sizes of articular facets of the ulnar (Cu), C3 and fourth (C4) carpal bones between the groups. Bilaterally, the proportionate volume of the intermediate carpal bone (Ci) was significantly greater in Po while that of Cu and C4 were significantly greater in TB. Relative density of most bones was greater in Po. The palmar tuberosity of the proximal surface of Ci and palmar tubercle on the palmar surface of Cu were more prominent and relatively larger in TB. In the second carpal bone (C2), the distal extent of the proximal articular surface on the palmar surface was greater in Po. The inconsistent first carpal bone (C1) was relatively larger in Po. Morphometrical similarities and differences in carpal bones between TB and Po indicate potential effects of selection for body size or fast exercise.