In vitro motions of the medial and lateral proximal sesamoid bones under mid-stance load conditions are consistent with racehorse fracture configurations.

This research explores the movement of proximal sesamoid bones (PSBs) in horses under various load conditions, to understand how these movements can lead to bone fractures commonly found in racehorses. The findings suggest that the motion of these bones under certain conditions are consistent with common fracture configurations in racehorses, paving the way towards better preventative measures.

Objective of the Research

• The main objective of this study was to understand the three-dimensional movements of the proximal sesamoid bones (PSBs) in relation to the third metacarpal condyle under different load conditions that typically occur during horse racing. This could help to explain why certain types of fractures commonly occur in racehorses.

Methods Used in the Research

• The researchers used seven equine cadaveric forelimbs and subjected them to axial loading at different conditions that mimic those experienced during standing, walking, trotting, and galloping (1.8-10.5 kN).
• The team tracked the positions of bone-fixed kinematic markers to determine joint angles.
• The researchers conducted an analysis of variance (ANOVA) with Tukey-Kramer post hoc tests for pairwise comparisons to compare the rotation and abduction-adduction and flexion-extension of each PSB relative to the third metacarpal condyle across different loads.

Key Findings of the Research

• Findings highlighted that the medial PSB rotated externally while the lateral PSB apex abducted during limb loading. Notably, the medial PSB external rotation was significantly greater during galloping than during walking or trotting.
• The motions observed in the medial and lateral PSBs under different loads were found to align with the locations of fatigue damage and fracture configurations commonly seen in thoroughbred racehorses.
• Specifically, medial PSB external rotation seems to lead to a certain type of lesion associated with medial PSB transverse fracture. Moreover, lateral PSB abduction appears to lead to axial longitudinal fractures of the lateral PSB.

Significance of the Study

• This study’s results are crucial as they shed light on how the repetitive loads and consequent internal movements of the bones in a horse’s leg during racing could lead to common fracture configurations. Understanding these mechanisms could pave the way for preventative measures to reduce fracture risk in racing horses in the future.