Musculoskeletal injury is the most common cause of lost training days for Thoroughbred racehorses. This type of injury, particularly fractures, is also cited as a major reason horses leave the industry. But the incidence and characteristics of fractures in racing Thoroughbreds are not well understood.
Characterizing fractures was the aim of Kristien Verheyen, DVM, MSc, and James Wood, BSc, BVetMed, MSc, PhD, of the Animal Health Trust in the United Kingdom. These researchers set out to determine the incidence of fractures in British Thoroughbreds in race training and to describe the fracture types seen.
Due to the high level of cooperation required for this two-year study, 13 trainers were chosen on recommendations from veterinarians, rather than a typical random sample. A total of 1,178 horses were monitored daily, including their exercise regimens and any fracture occurrence. This provided 12,893 months of data, which was analyzed as the number of horses at risk of fracture per month, or "horse months."
Fractures totaled 148, a rate of 1.15 per 100 horse months. The majority of fractures (78%) occurred during training, not racing. Verheyen explains, "It is likely that the majority of fractures occurred during training because horses spend much more time training than racing. When you take time at risk into account, the fracture rate is actually 20 times higher in racing than training."
Another finding was that 57% of the fractures were stress fractures, with pelvic and tibial bones accounting for 49% of these. Stress fractures occur in bone that is subjected to repetitive loading forces, "much like material fatigue that could cause a paper clip to break after repeated bending," Verheyen explains. The authors suggest that the high number of stress fractures in this study support a need for training regimens designed to strengthen the skeleton and help prevent this type of injury.
Finally, 7% of the fractures that occurred during this study had a fatal outcome. Five occurred during training and six on the racecourse. The authors hope that alterations in training strategy can decrease fracture and mortality rate.
Verheyen is continuing research into training regimens in Thoroughbred racehorses to limit fractures and tendon injuries. For more information, visit www.aht.org.uk/sci_diag_disc_epidem_raceh.html
Verheyen, K.L.P.; Wood, J.L.N. Equine Veterinary Journal, 36 (2): 167-173, 2004.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.