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Should we start pre-racing screening?
Equine Veterinary Journal 2025
Obi Veterinary Education
October 05, 2025
Catherine Beck, Peta L. Hitchens, R. Christopher Whitton
Background
Fetlock joint fractures are a leading cause of catastrophic musculoskeletal injuries in Thoroughbred racehorses. Previous post-mortem studies suggest that such fractures result from the accumulation of microdamage in the metacarpophalangeal/metatarsophalangeal joint. This study aimed to identify post-mortem computed tomography (CT) features associated with fetlock fractures, potentially aiding in early detection of horses at risk of injury.
Methods
A retrospective cohort study analyzed post-mortem CT images of 367 limbs from 157 Thoroughbred racehorses that died or were euthanized on Victorian racetracks between 2017 and 2022. The images were graded for specific CT features, including subchondral/trabecular bone lysis, sclerosis patterns, and proximal sesamoid bone (PSB) density. Multivariable logistic regression models were used to identify features associated with condylar and PSB fractures. Intra- and inter-rater reliability of key CT features was assessed using intraclass correlation coefficients.
Results
Condylar fractures were significantly associated with lysis within the subchondral/trabecular bone of the parasagittal groove (PSG) of the distal third metacarpus/tarsus (odds ratio [OR] 9.6, p < 0.001). Sclerosis extending proximoaxially from the palmar condyle was also linked to condylar fractures (OR 4.6, p = 0.03). PSB fractures were associated with the presence of PSB lytic lesions (OR 5.3, p = 0.03) and increased medial PSB density (OR 1.02, p < 0.001). However, palmar osteochondral disease (POD) grade was not significantly associated with either condylar (p = 0.8) or PSB fractures (p = 0.09). Inter-rater reliability for PSG lysis detection was moderate (ICC 0.7), and the shape of sclerosis in the lateral condyle had moderate agreement (ICC 0.6).
Limitations
The study was limited by the inability to accurately measure PSG lysis and PSB volume in limbs with multiple fracture fragments. Additionally, horses that sustained condylar fractures amenable to surgery were not included, potentially affecting generalizability. Right limbs were not routinely imaged due to logistical constraints.
Conclusions
Post-mortem CT imaging identified key structural changes in the fetlock joint associated with condylar and PSB fractures. The findings suggest that pre-race CT screening could help reduce fracture rates by identifying horses at risk. Further research is needed to refine imaging protocols and validate the predictive value of these CT features in live horses.
Dorsal oblique plane images of the left forelimb from three different horses with PS lysis (A–C). The PS lysis (white arrows) has a variable size and shape between the three horses and is surrounded by sclerosis of the SCB and TB (black arrows). Horse B has POD (white arrowhead) in the lateral condyle, adjacent to the PS lysis. Lateral is to the left.
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