Noncatastrophic and catastrophic fractures in racing Thoroughbreds at the Hong Kong Jockey Club

Abstract

Background: Reports of fractures in racehorses have predominantly focused on catastrophic injuries, and there are limited data identifying the location and incidence of fractures that did not result in a fatal outcome.

Objective: To describe the nature and the incidence of noncatastrophic and catastrophic fractures in Thoroughbreds racing at the Hong Kong Jockey Club (HKJC) over seven racing seasons.

Study design: Retrospective cohort study.

Methods: Data of fractures sustained in horses while racing and of race characteristics were extracted from the HKJC Veterinary Management Information System (VMIS) and Racing Information System (RIS), respectively. The fracture event was determined from the first clinical entry for each specific injury. The incidence rates of noncatastrophic and catastrophic fractures were calculated per 1000 racing starts for racetrack, age, racing season, sex and trainer.

Results: One hundred and seventy-nine first fracture events occurred in 64,807 racing starts. The incidence rate of noncatastrophic fractures was 2.2 per 1000 racing starts and of catastrophic fractures was 0.6 per 1000 racing starts. Fractures of the proximal sesamoid bones represented 55% of all catastrophic fractures, while the most common noncatastrophic fractures involved the carpus and the first phalanx. Significant associations were detected between the incidence of noncatastrophic fractures and sex, trainer and racing season.

Main limitations: The first fracture event was used to calculate the incidence rate in this study and may have resulted in underestimation of the true incidence rate of fractures in this population. However, given the low number of recorded fracture events compared with the size of the study population, this underestimation is likely to be small.

Conclusions: There were 3.6 times as many noncatastrophic fractures as catastrophic fractures in Thoroughbreds racing in Hong Kong between 2004 and 2011. Noncatastrophic fractures interfere with race training schedules and may predispose to catastrophic fracture. Future analytical studies on noncatastrophic racing fractures should be a priority for the racing industry.

Keywords: catastrophic fracture; epidemiology; horse; incidence rate; noncatastrophic fracture; racing.