Popped Splints

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The bony lumps called splints turn up at the most inconvenient times. After 2005 Kentucky Derby favorite Bellamy Road finished a disappointing seventh in the race, for example, his trainers discovered a freshly popped splint in his left front leg. Bad timing, to say the least—but not a long-term threat to the horse’s career.

Injuries like Bellamy Road’s are common but rarely turn out to be serious. With rest and good care, says Steve Adams, DVM, of the Purdue University Veterinary Teaching Hospital, “Most splints resolve on their own, although they may keep a horse out of training for a while.” Occasionally, however, splints cause ongoing trouble. Here’s what you need to know to cope with these injuries and avoid the problems.

What Happens

Splints form after trauma to the splint bones—thin, tapering bones that run down each side of the cannon bone from the knee (or hock) to a point about two-thirds of the way to the fetlock. These bones are actually leftovers from prehistoric days, when the ancestors of today’s horses ran around on three toes. In modern horses, the vestigial splint bones still play a role—the upper, wider end of the bone takes a bit of the weight from the joint above and transfers it to the cannon.

A classic popped splint starts with injury to the membrane that covers the bone (the periosteum) or to the interosseous ligament, which fastens the splint bone to the cannon. The trigger may be a blow or, more often, abnormal weight loading. The injury causes inflammation, and the horse’s body responds to the inflammation by laying down a lump of new bone at the site.

Splints can appear on any leg, but they’re most common on the inside of the front legs because the bones in this location bear more weight. Horses that toe out or have offset knees are prone to splints because their conformation causes them to overload their splint bones. Improper hoof trimming can have the same result. But young horses—even those with good conformation and perfectly trimmed feet—can pop splints just by training or playing too hard. A young horse’s interosseous ligaments are still elastic, so they stretch and tear under stress. As the horse ages, the ligaments gradually calcify and fuse the splint bones to the cannon, making injury far less likely.

“These bones are actually leftovers from prehistoric days, when the ancestors of today’s horses ran around on three toes.”

Splint bones also commonly fracture as the result of a blow (a kick or interference, for example) or extreme stress (as in racing). As the break tries to mend, it forms a lump that may look superficially like a run-of-the-mill popped splint. X-rays can distinguish a fracture.

In both cases the horse will typically be lame, although the lameness may vary in degree or even come and go. If you feel along the splint bones, you’ll find an area that’s warm and sensitive to pressure. There may be a large, firm swelling if new bone is already forming. A so-called blind splint occurs between the splint bone and the cannon, making the lump hard to see or feel.

What to Do

Prompt treatment of a new splint can help limit the size of the lump that ultimately forms. “The usual approach is to provide rest and anti-inflammatory medication, and give the splint time to heal,” says Adams. The idea is to let the injured area finish calcifying on its own, which usually results in a strong union between the splint bone and the cannon. In most cases, further treatment isn’t necessary.

The first step is to cool the injury down. Cold hose or apply an ice pack to the area two or three times a day, for about 20 minutes at a time. Follow those sessions with a cold poultice or alcohol and standing wraps. (Don’t use liniments, sweats, or any poultice that generates heat at this point.) Your vet may prescribe phenylbutazone or another non­steroidal anti-inflammatory (NSAID), such as the topical Surpass, for the cool-down phase.

Cool down usually takes about a week, and the horse should be on stall rest with hand-walking during that time. If the leg is still warm and sore after a week, the vet may suggest x-rays or other diagnostic steps to rule out a fracture or injuries to other structures in the leg.

Successful cool down is usually followed by three weeks or more of rest, during which time the horse may be hand-walked, tack-walked, or turned out in a small paddock on soft ground (if you can be sure he won’t go nuts and re-injure himself). Then you can gradually ease the horse back into work, staying alert for signs of heat and soreness that indicate re-injury.

“Shock-wave therapy may be an option for a horse that must stay in training while a splint finishes healing, although we rarely use it for this,” Adams says. In this treatment, high-energy sound waves are transmitted to the injured area. Shock waves have been shown to stimulate bone formation, but the treatment’s main benefit for splint victims seems to be its analgesic effect, Adams says. The time to do it is after the splint has cooled down, perhaps 10 to 14 days out.

Problems

Splints don’t always heal trouble-free. Sometimes, for example, a splint keeps reoccurring each time the horse goes back into training. The location of the splint can be a factor in this problem—splints that are lower on the bone seem to recur more often. A solution devised by surgeons at Rood and Riddle Equine Hospital in Lexington, Kentucky, is to simply remove the lump and the section of bone below it. The surgery can be done if the splint is in the lower two-thirds of the bone. Particularly on the inside of the foreleg, the upper part of the splint bone is needed for weight bearing and can’t be removed. “It’s important to realize that this is basically a final effort to solve the problem,” notes Larry Bramlage, DVM, of Rood and Riddle. “The first line of treatment should always be in providing the horse with rest and perhaps some other therapy, such as anti-inflammatory agents.”

Fractures in the lower part of the bone can be troublesome, too. If the natural healing process doesn’t produce a union at the fracture site, the small piece of bone below the site can be surgically removed. This was once done routinely. However, Adams says, “Now it’s more common to treat closed, simple fractures conservatively”—with rest, wraps, and anti-inflammatory medication. He adds that a more serious injury, such as a kick resulting in multiple breaks, still requires surgery. If necessary, a fracture in the upper, weight-bearing part of the bone can be fixed by surgically implanting a plate.

Like classic popped splints, healed fractures typically leave hard, bony lumps. Once these lumps form (from either cause) they mostly remain as blemishes, usually without affecting the horse’s soundness.

But that’s not always the case. An “active” splint causes irritation, usually of the suspensory ligament, which runs along the splint bone. If a splint is large enough to interfere with and irritate the ligament, it may become a chronic problem. Blisters and other old-fashioned remedies aimed at reducing large splints don’t have much, if any, effect. The lumps can be surgically pared down, but they may reform. Thus the surgery is usually done only if the old splints seriously hinder the horse’s career.

While not a major injury, splints can be bothersome for both horse and rider. With immediate care and a lot of patience, the aftereffects of most of these injuries can be minimized.