Prevalence of abnormal radiographic findings in 2-year-old Thoroughbreds at in-training sales and associations with racing performance

Objective-To estimate the prevalence of radiographic abnormalities (lesions) in Thoroughbred racehorses at 2-year-old in-training sales and determine whether these lesions and 1-furlong presale workout times were associated with subsequent racing performance. Design-Retrospective cohort study. Animals-953 Thoroughbreds. Procedures-Repository radiographs of carpal, metacarpophalangeal and metatarsophalangeal (fetlock), stifle, and tarsal (hock) joints were examined. Horses with lesions were classified by lesion type and location. Race performance variables were compared between horses with and without lesions and between horses categorized by 1-furlong presale workout times (< or ≥ 11 seconds). Results-299 horses had ≥ 1 lesion, and 654 had no lesion detected. Odds of starting a race and of earning money racing were lower for horses with any lesion and lower for horses with proximal phalangeal dorsoproximal articular margin chip fracture, proximal sesamoid bone fracture or sesamoiditis, or wedge-shaped central or third tarsal bones, compared with horses that had no lesion. For horses that raced, proximal phalangeal dorsoproximal articular margin chip fractures were associated with lower lifetime earnings, and flattening of the medial femoral condyle was associated with fewer 3-year-old racing starts, compared with values for horses that had no lesion. Horses with workout times < 11 seconds had greater odds of having lifetime starts, lifetime earnings, and maximum purse above threshold (median) values than did horses with slower workout times. Conclusions and Clinical Relevance-No radiographic lesions prevented all affected horses from racing. Among horses that raced, few differences were found in performance for horses with and without lesions.