Size and geometry of apical sesamoid fracture fragments as a determinant of prognosis in Thoroughbred racehorses

Summary Reason for performing study: Analysis was performed to examine a method for refining the preoperative prognosis for horses that had surgery to remove apical fractures of the proximal sesamoid bones (PSBs). Objectives: To determine if: 1) there was a difference in size or configuration of apical fractures between the different anatomical locations of the PSBs, which have been shown to affect the prognosis; and 2) the size or configuration could predict the prognosis for racehorses with these fractures. Methods: The study included 110 weanlings and yearlings and 56 training racehorses that underwent surgery to remove apical PSB fractures. Radiographs of the fractures were used for measurement of the abaxial and axial proportion and the abaxial to axial ratio, and race records were used to determine average earnings per start (AEPS) and total post operative starts. Analysis of variance and regression statistics were used to compare the fragment sizes between the specific PSBs on each of the limbs and compare size and configuration of the fractures to prognosis. Results: There was a significantly larger abaxial to axial ratio (more transverse fracture) for the forelimb medial sesamoids than for all other sesamoids in untrained racehorses (P = 0.03). There were no other significant differences in size. There was no relationship between fracture size or configuration and AEPS nor total post operative starts. Conclusions: Apical fractures in weanlings and yearlings tend to be more transverse in the forelimb medial PSBs than the other PSBs. Apical fracture size and geometry does not determine prognosis for apical sesamoid fractures. Potential relevance: Horses that undergo surgery to remove larger apical fractures of the PSBs do not have a worse outcome than those horses with smaller fractures.