About 2% and 6% of all racetrack fatalities in Thoroughbreds and Quarter Horses, respectively, are the result of scapular fractures, according to Stuart A. Vallance, BVSc (Hons), who, with Susan Stover, DVM, PhD, Dipl. ACVS, and a research team at the JD Wheat Veterinary Orthopedic Research Laboratory at the University of California, Davis, has investigated the risk factors for this fracture so that prevention strategies can be developed. Vallance reported his results at the 2010 American Association of Equine Practitioners Annual Meeting, held Dec. 4-8 in Baltimore, Md.

Vallance and his colleagues examined the necropsy reports of 73 Thoroughbreds and 28 Quarter Horses, as reported by the California Horse Racing Board postmortem program. These animals were euthanized after suffering a fractured scapula on a racing surface between 1990 and 2008.

The team discovered, through visual and CT examinations, that fractured scapulas showed signs of stress fractures that resulted in a region of weakness within the bone. Such weakness can predispose the bone to complete fracture when a horse is racing or working at high speed.

They reported that when the exercise histories were compared to those of live matched control horses, Thoroughbreds and Quarter Horses sustaining a scapula fracture had fewer races and works, fewer days in active training, less total distance schooled, and longer layup periods