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

Overview

• This study investigated factors that increase the risk of proximal sesamoid bone fractures in Thoroughbred racehorses in South Korea.
• It analyzed activity types, sex, season, and exercise history to identify which horses are more likely to sustain these fractures.

Study Design and Population

• A retrospective case-control study design was used to analyze risk factors.
• The study included 138 Thoroughbred racehorses diagnosed with proximal sesamoid bone fractures from 2020 to 2025.
• As a control group, 580 healthy Thoroughbreds with at least one racetrack activity during the same period were included, totaling 635 observations.
• Multivariable logistic regression was employed to identify significant risk factors.

Key Risk Factors Identified

• Activity Type:
  • Participation in races or trials increased fracture risk substantially compared to racetrack training (Odds Ratio [OR] 17.41).
• Sex:
  • Intact males had about twice the risk compared to geldings (OR 2.07).
  • Females also had a higher risk than geldings (OR 2.14).
• Exercise History:
  • Horses with 4 or more starts in the prior 360 days showed increased risk.
  • Having 6 or more gallop training days between 120 to 180 days before was associated with higher risk (OR 3.73).
  • 37 or more racetrack training days in the prior 180 days also elevated risk (OR 2.36).
  • Interestingly, higher cumulative numbers of starts and gallop training days were found to have a protective effect, indicating a complex relationship between workload and fracture risk.
• Season:
  • Spring and summer seasons were linked to an increased risk of fractures (OR 1.74).

Interpretation and Implications

• Race or trial activities are substantially more hazardous in terms of proximal sesamoid bone fracture risk compared to routine training.
• Sex differences suggest intact males and females are more vulnerable than geldings, potentially due to hormonal or behavioral factors.
• The relationship between exercise variables and risk is nuanced:
  • Recent high-intensity workloads seem to increase fracture risk.
  • However, a higher overall cumulative workload may provide a protective effect, possibly due to adaptation or conditioning.
• Seasonal factors may influence fracture risk, suggesting environmental or management factors play a role.
• Profiling an individual horse’s racetrack activities and carefully managing cumulative workloads may help prevent fractures.

Conclusion

• The study identifies activity type, sex, season, and various exercise-related factors as important risk factors for proximal sesamoid bone fractures in Thoroughbred racehorses in South Korea.
• Using these findings, trainers and veterinarians can better identify at-risk horses and adjust training and racing schedules to reduce fracture incidence.