Activity type, sex, season, and number of prior starts are associated with proximal sesamoid bone fractures in Thoroughbred racehorses in South Korea

Objective: To identify risk factors associated with proximal sesamoid bone fractures in Thoroughbreds in South Korea. Methods: A retrospective case-control design with multivariable logistic regression was used. This study included 138 Thoroughbreds diagnosed with proximal sesamoid bone fractures following racetrack activity between 2020 and 2025. Additionally, 580 healthy Thoroughbreds (635 observations) with at least 1 racetrack activity during the same period were included as controls. Results: A total of 7 risk factors were identified. Races or trials had markedly higher fracture risk than racetrack training (OR, 17.41; 95% CI, 10.48 to 28.92). Intact males (OR, 2.07; 95% CI, 1.09 to 3.93) and females (OR, 2.14; 95% CI, 1.09 to 4.18) had higher risk than geldings. Horses with 4 or more starts in the prior 360 days, 6 or more gallop training days in the prior 120 to 180 days (OR, 3.73; 95% CI, 1.50 to 9.27), and 37 or more racetrack training days in the prior 180 days (OR, 2.36; 95% CI, 1.08 to 5.14) were at higher risk. Higher cumulative starts and gallop training days were protective, and spring and summer were associated with increased risk (OR, 1.74; 95% CI, 1.10 to 2.74). Conclusions: Activity type, sex, season, and exercise-related variables were identified as risk factors for proximal sesamoid bone fractures in Thoroughbred racehorses in South Korea. Clinical Relevance: Profiling racetrack activity may help identify at-risk horses; managing each horse's cumulative workload may reduce the incidence of proximal sesamoid bone fractures.