BIPARTITE PROXIMAL SESAMOID BONES IN YOUNG THOROUGHBRED HORSES

Twelve foals with unusual sesamoid development were found in a population of 107 Thoroughbred foals (60 males, 47 females) over a three year period. Radiographic examination was done at 14 days of age and at 42 day intervals thereafter. The routine administration was of a dorsopalmar view of the proximal sesamoid bones in the left forelimb. Changes of the proximal sesamoid bones were found in 11% of the foals between 14 and 56 days of age. The change was a radiolucent line at the junction of the middle and proximal third of the sesamoid bone. Of those which were observed with sesamoid bone changes, 8 had a normal radiographic appearance at 60 days. In most foals at least 2 or 3 sesamoid bones of the forelegs were affected. In some only 1 sesamoid bone was affected. The changes did not correlate with a clinical joint disorder. However, females seemed to be affected more than males. This condition may be similar to bipartite sesamoid bones described by others and probably a manifestation of secondary ossification centers.