Can Subchondral Bone Thickness Predict Catastrophic Injury?
Wouldn’t it be great to know a horse was about to break a bone before it tragically fractures on the racecourse? For one particular—and common—break, such premonition may now be possible. British researchers have determined that MRI images of bone thickness could provide critical information about fracture risk in the lateral condyle of the third metacarpal bone (MC3)—those that occur on the outer half of the bottom bulbous end of the cannon bone.
These long front leg bones are particularly susceptible to fracture starting from the joint surface within the fetlock. It’s a high-risk fracture area for racehorses—the No. 1 reason horses are euthanized on U.K. racetracks, said Tim Parkin, BSc, BVSc, PhD, Dipl. ECVPH, FHEA, MRCVS, dean of the Division of Equine Clinical Sciences and clinical director of the Weipers Equine Centre in the School of Veterinary Medicine at the University of Glasgow, in Scotland. In the United States, these fractures are the second most common site for catastrophic fracture, just behind fractures of the proximal sesamoid bones.
In their extensive five-year study, Parkin and his fellow researchers investigated 191 MC3 bones from 96 Thoroughbreds that had died or been euthanized while racing in Great Britain. This included 47 horses that had sustained MC3 lateral condylar fractures; the other horses died of cardiovascular failure, spinal injuries, or other causes. The scientists used MRI to measure the depth of dense subchondral bone (which is found below the cartilage and supports the cartilage of the joint surface) in several sites around the lower part of the bone.
They discovered “significant changes” in the lateral condyle’s bony makeup in horses that had sustained fractures at that site. The horses had these bony changes not only in the leg that ended up getting a fracture but also in the opposite leg. In contrast, the horses that had died for other reasons did not show these changes in their bone structure, Parkin said
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