Risks arising from microdamage and tissue remodelling in a leg bone prone to fracture in racehorses have been highlighted in American research.
The recent University of California, Davis, study sought to characterize bone abnormalities that precede proximal sesamoid bone fractures and determine if pre-existing abnormalities are associated with these fractures.
Sarah Shaffer, Dr Susan Stover and colleagues at the J.D. Wheat Veterinary Orthopedic Research Laboratory at the university’s School of Veterinary Medicine studied cases from California Thoroughbred racehorses that died from such fractures, and controls that died for other reasons.
Proximal sesamoid bone fractures are the most common fatal injury in racehorses in the United States. They account for 45 to 50 percent of such injuries in Thoroughbreds, and 37 to 40 percent in racing Quarter Horses.
The proximal sesamoid bones are two comparatively small bones located in the fetlock that act as part of the suspensory apparatus. Fractures in these bones are likely due to the accumulation of repeated, stress-related processes.
This is supported by evidence that racehorses in intensive training are at higher risk for such fractures, but the exact causes are not well understood.
Other repetitive overuse injuries in horses are known to be bilateral in nature, meaning that they are similar on both sides of the horse, with the more severely affected limb usually incurring the fracture.
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Featured Image: Closeup of Thoroughbred racehorses galloping on a dirt track. Photographer unknown.