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.
[Originally printed on HorseTalk.co.nz]
Closeup of Thoroughbred racehorses galloping on a dirt track.
Photographer unknown.
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.