Epidemiology of race-day distal limb fracture in flat racing Thoroughbreds in Great Britain (2000–2013)

Background: A key focus of the racing industry is to minimise the number of race-day distal limb fractures although no studies have identified risk factors for both fatal and non-fatal distal limb fractures. 
Objective: To determine risk factors for race-day distal limb fractures experienced by Thoroughbred racehorses participating in flat racing in Great Britain (GB). 
Study design: Retrospective cohort. 
Methods: Information was collected from all flat racing starts occurring on GB racecourses between 2000 and 2013, including horse, race, course, trainer and jockey data for each horse start and race-day injury data as reported by on-course veterinarians. Associations between exposure variables and cases of distal limb fracture were assessed using mixed-effects logistic regression analyses using data from all starts, and turf starts only. 
Results: A total of 806,764 starts and 624 cases of distal limb fracture were included, of which 548,571 starts and 379 cases of distal limb fracture occurred on turf surfaces. In both models, increasing firmness of the going, increasing racing distance and horses in their first year of racing were at a higher risk of distal limb fracture while increasing number of previous race starts were protective. Trainer performance was associated with distal limb fracture. Generally, the risk of distal limb fracture increased with increasing horse age. Starts in selling or claiming races or Group 1, Group 3 or claiming races were at higher odds of distal limb fracture in the all starts and turf models, respectively. 
Main limitations: Clinical diagnosis of distal limb fracture and all types of distal limb fracture considered as one outcome. 
Conclusions: This study confirmed previously identified risk factors for distal limb fracture including going, race distance and number of horse starts. Novel risk factors were related to trainer and horse performance, and race type. Identification of at risk groups will help inform interventions to reduce distal limb fracture occurrence in flat racing horses.