Bone Mineral Density and Metacarpophalangeal Joint Pathology are Associated with Exercise but not Proximal Sesamoid Bone Fracture in Thoroughbred Racehorses

Introduction: Proximal sesamoid bone (PSB) fracture is the leading cause of fatal limb fracture in Thoroughbred racehorses in the United States and Hong Kong. Efforts are underway to investigate diagnostic modalities that could help identify racehorses at increased risk of fracture; however, features associated with PSB fracture risk are still poorly understood.

Materials and Methods: A cross-sectional cadaver morphologic study design was employed. Forelimbs were collected from 29 Thoroughbred racehorse cadavers (n = 14 PSB fracture, n = 15 control), and both metacarpophalangeal joints (MCPJ) were imaged using dual energy X-ray absorptiometry (DXA) and computed tomography (CT). An axial parasagittal section of one intact medial PSB was analysed by Raman spectroscopy, and a sagittal section of the same PSB was utilized for ash fraction measurements.

Results: Bone mineral density (BMD) was greater in the third metacarpal (MC3) condyles and PSBs in horses with more accrued furlongs. MCPJ pathology, including palmar osteochondral disease scores, MC3 condylar sclerosis, and MC3 subchondral lysis was greater in horses with more accrued total furlongs. While there were no significant differences in BMD, Raman parameters and most types of MCPJ pathology between fracture and control groups, bone volume fraction was increased in the MC3 condyle of both fracture cases and in horses with more accrued total furlongs. Raman and ash fraction measurements revealed regional differences in PSB tissue composition in fracture cases.

Discussion/Conclusion: DXA, CT, and Raman revealed few differences between fractures and controls; however, many parameters, including MC3 and PSB bone mineral density, were strongly correlated with total accrued furlongs.

Acknowledgements: Funding was provided by the Harry M. Zweig Memorial Fund for Equine Research. The authors thank the New York State Gaming Commission (NYSGC) for making the cadaver tissues available as part of the requirement for necropsy and Erica Bender for providing training and access to the DXA equipment.

Publication History

Article published online:
26 October 2022