Analysis of horse race videos to identify intra-race risk factors for fatal distal limb fracture.

The objective of this study was to identify risk factors, during racing, associated with imminent fatal distal limb fracture in Thoroughbreds. One hundred and nine cases of fatal distal limb fracture were identified from all 59 UK racecourses over a 2-year period (February 1999-January 2001). Three uninjured control horses were randomly selected from the same race as the case horse. Videos of races in which fractures occurred were viewed using a defined protocol. Fractures in flat races occurred at any time during the race, whereas 74% (45/61) of cases in national hunt type races occurred in the second half of races. More than 75% (79/103) of cases were spontaneous, i.e. there was no obvious external influence such as a fall at a fence or collision with another horse. Sixty-six percent (44/67) of horses, sustaining a forelimb fracture, fractured the forelimb they were using as lead leg at the time of fracture. When case and control horses were compared, horses that were: (a) making good progress through the race, (b) reluctant to start and (c) received encouragement in the final 10s before the time of fracture, were more likely to sustain a fracture.