Recurring Splints

On the list of injuries a horse might acquire, "popping a splint" is considered, at most, an inconvenience that requires laying the affected horse off his normal routine. However, when it keeps happening, that little inconvenience can become a major nuisance and perhaps a surgical problem.

Where the "popped splint," or splint exostosis, occurs along the length of the bone is the key to the amount of concern it should cause the owner. The horse's splint bone is actually what is left of what was once one of his toes. The bone is still there, it just no longer reaches the ground. It still carries weight passed down to it by the carpus (knee).

A popped splint occurs where the splint bone attaches to the cannon bone. The load from weight bearing causes a tear of the ligamentous attachment between the splint bone and the cannon bone. Calcium then builds in the affected area--the body's repairing mechanism--and attaches the splint to the cannon bone by creating new bone in between. Problem solved naturally, if the injury is near the top of the bone.

If the splint "pops" and heals in the middle portion of the bone, it is more vulnerable to re-injury than a normal (higher) popped splint. Although the horse's body dutifully sets about repairing the area with calcium, the calcium is more brittle than the ligament attachments above and below the fracture. So, as the horse goes back to work after the lameness has subsided, the repairing calcium cracks and breaks. Then you're back to square one--or maybe even worse than the first time. In the normal splint exostosis, the healing attachment is high on the bone, very near the site of weight transfer to the splint bone, which is stronger. In the mid-splint exostosis, there is a long mobile piece of splint bone between the site of weight application and the site of attachment to the cannon bone, increasing the stress.

Sometimes the problem just keeps recurring each time the horse becomes sound and goes back to work, whether he is racing, chasing a calf, or jumping a fence. The problem occurs in all athletic horses. However, this type of splint will usually occur in an older horse. The higher splints are common in younger horses.

The first approach to any popped splint is always the same, which is to allow time to heal. Rest, or reduced exercise, is often accompanied by other treatments that are directed at reducing the size of the splint blemish or speeding the re-attachment. However, an approach developed by surgeons at Rood and Riddle Equine Hospital is useful for splints that tend to recur.

In splints that recur in the middle of the bone, instead of trying to get the splint to calcify to the cannon bone, we just take out the bottom part of the splint and the exostosis. This treatment is not applicable for the usual splint injury where you cannot remove that much splint bone. It only applies in splint injuries that occur in the unnecessary part of the splint bone (the bottom two-thirds).

Our team defined the process with work on Thoroughbred racehorses in the racehorse-rich Lexington, Ky., area, where our hospital is based. However, this process has been used on other types of athletic horses.

It's important to realize that this is used to solve a recurring problem. The first line of treatment should always be to provide the horse with less invasive therapy, such as anti-inflammatory agents. The best primary therapy depends on the horse's use and the degree of concern over the size of the proliferative bone lump that accompanies healing of the splint.

About the Author

Larry Bramlage, DVM, MS, Dipl. ACVS

Larry Bramlage, DVM, MS, Dipl. ACVS, practices at the Rood and Riddle Equine Hospital in Lexington, Ky.

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