Post-mortem computed tomography features associated with fracture of the fetlock joint in racing Thoroughbreds.
Authors: Beck, Hitchens, Whitton
Journal: Equine veterinary journal
Summary
# Post-mortem CT Features Associated with Fetlock Fracture in Racing Thoroughbreds Beck, Hitchons and Whitton's retrospective analysis of 367 limbs from 157 racing Thoroughbreds identifies specific computed tomography (CT) features that correlate with catastrophic fetlock fractures, building on established evidence that these injuries are preceded by zones of microdamage within the joint. Using multivariable logistic regression on post-mortem imaging, the researchers found that lysis (bone loss) within the subchondral and trabecular bone beneath the parasagittal grooves of the distal metacarpus significantly increased fracture risk (odds ratio 9.6), whilst sclerosis in the palmar region and lytic lesions in the proximal sesamoid bones also demonstrated strong associations with fracture occurrence. Notably, the presence of palmar osteochondral disease showed no statistical relationship with either condylar or sesamoid bone fractures, suggesting that traditional osteoarthritic changes may not be reliable predictors of acute failure. Although inter-rater reliability was moderate for some features, these findings suggest that pre-race CT screening could identify high-risk individuals before catastrophic injury occurs—a significant development for injury prevention protocols in thoroughbred racing. The limitation that fragmented fractures themselves complicate accurate measurement of lesion extent indicates that CT assessment would be most useful as a prospective screening tool on intact joints rather than applied retrospectively.
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Practical Takeaways
- •Post-mortem CT can identify structural changes (lysis and sclerosis patterns) in fetlock joints that precede fracture, suggesting pre-race CT screening could identify at-risk horses and potentially reduce fracture rates in racing Thoroughbreds
- •Lytic lesions in the parasagittal groove region and increased density of proximal sesamoid bones are measurable CT markers worth evaluating in pre-purchase or pre-race screening protocols
- •Standard palmar osteochondral disease grading does not predict fracture risk, so practitioners should focus on lysis and sclerosis patterns rather than general degenerative changes when assessing fetlock fracture risk
Key Findings
- •Lysis in the subchondral bone under parasagittal grooves showed 9.6-fold increased odds of condylar fracture (95% CI 4.3-21.3, p<0.001)
- •Proximal sesamoid bone lytic lesions had 5.3-fold increased odds of PSB fracture (95% CI 1.2-23.6, p=0.03), and increasing medial PSB density was independently associated (OR 1.02 per unit, p<0.001)
- •Sclerosis of palmar subchondral bone underlying parasagittal grooves was associated with condylar fracture (OR 4.6, p=0.03)
- •Palmar osteochondral disease grade was not associated with either condylar or PSB fracture