Are there radiologically identifiable prodromal changes in Thoroughbred racehorses with parasagittal fractures of the proximal phalanx?
Authors: Smith M R W, Wright I M
Journal: Equine veterinary journal
Summary
# Parasagittal Fractures of the Proximal Phalanx: Evidence for Stress-Related Origins Whilst proximal phalangeal fractures in racing Thoroughbreds are typically attributed to acute, excessive loading events, clinical radiographs suggest a cumulative stress mechanism may underlie at least some cases. Smith and Wright retrospectively examined radiographs and case records from 110 Thoroughbreds with confirmed parasagittal proximal phalangeal fractures, measuring subchondral bone plate thickness in both affected and contralateral limbs and documenting additional radiological signs of prodromal pathology. The fractured limbs displayed significantly thickened subchondral bone plates compared to their contralateral counterparts, with 14% of affected limbs showing additional prodromal features such as bone remodelling or joint surface irregularities—a figure substantially higher than the 4% observed in unaffected contralateral limbs. These findings challenge the single-load failure model and instead implicate repetitive stress and maladaptive bone remodelling in fracture development, suggesting the thickened subchondral bone may represent unsuccessful compensatory responses to cumulative loading. For practitioners, this implies that management strategies targeting training loads, monitoring for early radiological changes, and addressing underlying biomechanical issues could potentially reduce fracture incidence in racing stock.
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Practical Takeaways
- •Parasagittal proximal phalanx fractures may result from repetitive stress rather than single traumatic events, suggesting training and workload management are important preventive strategies
- •Radiographic assessment of subchondral bone thickness changes in at-risk horses may help identify early pathology before fracture occurs
- •Early recognition of prodromal radiological signs could enable intervention to reduce fracture risk in racehorses
Key Findings
- •Subchondral bone plate thickness was significantly greater in fractured limbs compared to contralateral limbs
- •Prodromal fracture pathology was present in 15/110 (14%) limbs with parasagittal fractures versus 4% of contralateral limbs
- •Findings suggest stress-related aetiology rather than monotonic loading as the primary cause of fracture
- •Increased subchondral bone plate thickness may represent failed adaptive responses preceding fracture