Assistant Professor of Large Animal Diagnostic Imaging University of Pennsylvania
Identification of a Previously Unreported Site of Tarsal Subchondral Injury in the Thoroughbred Racehorse. Wulster K1, Richardson DW2, Manzi TJ2, Ortved K2. 1University of Pennsylvania, Kennett Square, PA; 2University of Pennsylvania, New Bolton Center, Kennett Square, PA.
Increasing accessibility and advancements in standing tomographic imaging improve understanding of contributors to poor performance and lameness in Thoroughbred racehorses. This study characterizes a previously unreported site of dorsodistolateral calcaneal (DDLC) subchondral bone injury in this population. We hypothesized that DDLC lesions would be overrepresented in Thoroughbred racehorses and the lesion would be a primary cause of lameness. Retrospective analysis of 101 horses presented to a single equine referral center with tarsal lameness that underwent either standing or recumbent computed tomography (CT) was performed. Calcaneal lesion location and configuration were recorded. The likelihood of identifying DDLC subchondral injury in horses of different breeds and disciplines was explored using logistic regression. One hundred and three tarsal CT studies of 101 horses were analyzed. DDLC subchondral injury was identified in 6/101 (5.9%) of total cases and in 6/35 (17.1%) of racing Thoroughbreds. All lesions were found in racing Thoroughbreds, OR 29.30 (1.60–537.37 P < 0.023). DDLC subchondral injury was the primary cause of lameness in 3/6 horses. Third tarsal bone fracture was the primary cause of lameness in the remaining 3/6 horses. The dorsodistolateral calcaneus is a previously unreported site of subchondral bone injury in the Thoroughbred racehorse. The lesion can be a primary source of lameness but is also found incidentally in horses with other clinically relevant osteochondral injuries. Further study is required to determine the true prevalence, clinical relevance, and prognosis in Thoroughbred racehorses with this injury. Limitations include retrospective design and limited substantive follow-up information. DDLC subchondral injury is likely underestimated.