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Clues to Preventing Injuries Among Race Horses

In an anatomical comparison of the cannon bone among 3 horse breeds, researchers found that fostering adaptations in these bones through training might help prevent breakdown.

About 70% of leg fractures during racing occur in the third metacarpal bone between the horse's knee and pastern. Deanna Goldstein, a doctoral candidate in the Center for Functional Anatomy and Evolution at Johns Hopkins Medicine, compared the sizes, densities and abilities to bend without breaking of canon bones from Thoroughbreds, American Quarter Horses and Assateague Island ponies. She and her colleagues wanted to know how each breed's lifestyle and training affected the bone. Assateague Island ponies, which live in the wild, offered an untrained comparator group.

They studied bones from horses that died or were euthanized for reasons unrelated to a broken or injured third metacarpal bone. Although the size of the third metacarpal bone varied among the 3 breeds, Ms. Goldstein was surprised to find that the bone's strength and structure relative to body size were remarkably similar across the 3 types of horses.

“If Thoroughbreds are racing and training around turns, you would expect certain areas of their bones to be a lot stronger to reflect that,” she said. “However, since the Thoroughbred third metacarpals are not more dense or stronger than the other 2 breeds, it indicates that the Thoroughbreds' bones are just not prepared for those forces.”

Exposure to the stresses of racing around turns should create anatomical differences between Thoroughbred horses and other breeds. This bone remodeling would prepare their bones to resist fracturing.

Ms. Goldstein suggested that adding training around tighter turns at higher speeds could give Thoroughbred horses' bones time to adapt to the extreme forces and be more resistant to breaks on the track.

Scientifically backed interventions in how racehorses are managed and trained could better protect them from stress-related breakdowns on the track.

For more information:

Goldstein DM, Engiles JB, Rezabek GB, et al. Locomotion on the edge: Structural properties of the third metacarpal in Thoroughbred and Quarter Horse racehorses and feral Assateague Island ponies. Anat Rec. 2020 DOI: 10.1002/ar.24485. https://anatomypubs.onlinelibrary.wiley.com/doi/full/10.1002/ar.24485