Identification of a previously unreported site of subchondral bone injury in the dorsodistolateral calcaneus in Thoroughbred racehorses.
Authors: Melly Virginia, Ortved Kyla F, Manzi Timothy J, Richardson Dean W, Stefanovski Darko, Wulster Kathryn B
Journal: Equine veterinary journal
Summary
# Editorial Summary Computed tomography imaging has revealed a previously uncharacterised site of subchondral bone injury (SBI) affecting the dorsodistolateral calcaneus in Thoroughbred racehorses—a lesion not previously documented in the veterinary literature. Researchers retrospectively analysed tarsal CT scans from 108 horses and cross-referenced nuclear scintigraphic studies from over 1,600 Thoroughbreds between 2007 and 2022, finding SBI at this location in 7.3% of all horses scanned, but exclusively in racing Thoroughbreds (affecting 20% of this cohort). The injury proved to be the primary cause of lameness in three cases and appeared alongside other significant tarsal pathology in a further three animals; notably, scintigraphy detected increased radiopharmaceutical uptake suggestive of this lesion in only 0.9% of Thoroughbred scans, suggesting the condition may be substantially underdiagnosed using nuclear imaging alone. The clinical significance of this lesion remains unclear—it may be incidental or contribute meaningfully to poor performance—and practitioners should be aware that dorsodistolateral calcaneal SBI may account for some cases of tarsal lameness previously attributed to other structures. Further prospective research examining the prevalence, prognostic factors, and response to treatment is essential before firm recommendations regarding management and career longevity can be established.
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Practical Takeaways
- •Consider DDLC SBI as a differential diagnosis in lame racing Thoroughbreds, particularly those with tarsal region pain, as it may be an underrecognized source of poor performance
- •CT imaging is superior to nuclear scintigraphy for identifying these lesions; lameness cases in racehorses warrant tarsal CT to avoid missing this injury
- •Be aware that DDLC SBI can coexist with other tarsal pathology (such as third tarsal bone fractures), so comprehensive imaging evaluation is essential for accurate diagnosis and prognosis
Key Findings
- •DDLC SBI was identified in 8/108 horses (7.3%), exclusively in racing Thoroughbreds (p=0.002)
- •20% of racing Thoroughbreds undergoing tarsal CT showed DDLC SBI
- •DDLC SBI was the primary cause of lameness in 3/8 affected horses
- •Nuclear scintigraphy showed increased radiopharmaceutical uptake in DDLC in only 0.9% (13/1663 scans), suggesting potential underestimation of lesion prevalence