Bone Chips: When the Chips Are Down

In the case of bone chips, sometimes bigger is better. In a study performed in 2006, researchers from the University of Pennsylvania's New Bolton Center theorized that bone chip characteristics in a horse's knees were an indicator of the severity of the horse's injury. They were right.

Liberty Getman, DVM, a surgical resident at the university, and her colleagues examined data from 31 Thoroughbred racehorses with palmar carpal (knee) osteochondral fragments. They found the size of the fragments can be used to predict the severity of joint damage, and the horse's prognosis.

These injuries usually occur when a horse's knee is overloaded or is twisted in an unusual direction (possibly caused by improper shoeing, poor limb conformation, and/or uneven footing).

"There is considerable hope that the Polytrack surfaces may decrease the prevalence of chip fractures in racehorses," Getman said.

According to Getman, immediate ramifications of bone chips are lameness, swelling, and pain. "If these fragments are left in the joint (not removed arthroscopically), the horse is at greater risk for developing arthritis in the joint over time, leading to decreased performance and continued lameness," she explained.

Researchers found multiple chips in 58% of the study horses, and half (52%) of those were smaller fragments (less than 3 mm in diameter).

The researchers noted, "Overall, 51.6% of the horses in the present study returned to racing (at least one start), and 48% earned money after surgery. Interestingly, the researchers noted that horses with multiple small bone fragments were less likely to successfully return to racing than horses with one or two large fragments.

Getman said, "It is most likely that the smaller chips originated from larger chips that were crushed into smaller pieces. This crushing of the larger chips and the movement of the multiple pieces through the joint resulted in more severe damage to the rest of the joint surfaces. Less damage occurred throughout the joint if the larger fragments were in locations that did not result in their being crushed. The larger chips only caused a problem in the specific location from which they arose."

The researchers also noted, "Horses in which palmar fragments were removed had more starts and higher earnings after the surgery than those in which fragments were not removed."

However, they were unable to distinguish if the improved prognosis was related to the removal of the chips or the size of the chips (surgeons were more apt to remove larger fragments than the smaller fragments).

Researchers for the study published in the May 15 issue of the Journal of the American Veterinary Medical Association included Getman, Louise Southwood, BVSc, PhD, Dipl. ACVS, and Dean Richardson, DVM, Dipl. ACVS.

About the Author

Chad Mendell

Chad Mendell is the former Managing Editor for TheHorse.com .

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