Metacarpophalangeal Joint Pathology and Bone Mineral Density Increase with Exercise but Not with Incidence of Proximal Sesamoid Bone Fracture in Thoroughbred Racehorses.
Authors: Noordwijk Kira J, Chen Leyi, Ruspi Bianca D, Schurer Sydney, Papa Brittany, Fasanello Diana C, McDonough Sean P, Palmer Scott E, Porter Ian R, Basran Parminder S, Donnelly Eve, Reesink Heidi L
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Proximal sesamoid bone fractures remain the leading cause of fatal musculoskeletal injury in racing Thoroughbreds, yet identifying at-risk horses before catastrophic failure has proven elusive. Noordwijk and colleagues examined forelimbs from 29 racehorses (14 with PSB fractures, 15 controls) using dual-energy X-ray absorptiometry, computed tomography, Raman spectroscopy, and ash fraction analysis to determine whether differences in bone density, mineralisation, or quality distinguished horses that had fractured from those that had not. The key finding was paradoxical: horses exposed to greater high-speed exercise accumulated significantly higher bone mineral density in both the third metacarpal and proximal sesamoid bones, alongside increased metacarpophalangeal joint pathology including palmar osteochondral disease and subchondral changes, yet bone quality metrics (mineralisation ratios and tissue composition) did not differ between fracture and non-fracture groups. These results suggest that exercise-induced bone remodelling and joint degeneration may be adaptive responses to loading rather than direct fracture risk factors, implying that increased density alone cannot serve as a screening tool for identifying susceptible individuals. Clinically, this challenges assumptions linking higher BMD to greater safety and indicates that understanding fracture risk will require investigation of other biomechanical, genetic, or structural variables beyond mineral accumulation.
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Practical Takeaways
- •High-speed racing workload increases bone density but paradoxically increases joint pathology and fracture risk, suggesting that protective adaptations may be insufficient to prevent injury under intense racing demands
- •Current bone mineral density measurements alone cannot reliably predict which racehorses will suffer proximal sesamoid fractures, indicating that fracture risk involves factors beyond simple bone density
- •Regional variations in sesamoid bone composition suggest that localized areas of weakness may be more important for fracture risk than overall bone density
Key Findings
- •Bone mineral density in MC3 condyles and PSBs increased with high-speed furlongs (exercise intensity), but did not differ between fracture and control groups
- •Metacarpophalangeal joint pathology including POD, MC3 condylar sclerosis, and subchondral lysis were significantly greater in horses with more high-speed furlongs
- •Raman spectroscopy and ash fraction analysis revealed regional differences in PSB bone mineral density and tissue composition between anatomical regions
- •No significant differences in bone mineral density or Raman spectroscopy parameters were found between horses with PSB fracture history and control horses