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Off Track Thoroughbred Help and Answers Blog for OTTB Owners

Equine Splints

Equine Splints: Causes and Cures

Learn how to keep splints (bony lower leg swellings) from becoming permanent blemishes or problems that interfere with a horse’s athletic career.

Radiograph of a broken splint bone

Your 2 1/2-year-old horse has been in training for a few months, but even though you’re taking it slowly and steadily and not pushing too hard, he sometimes comes up lame during or after a workout. The lameness isn’t always present and rarely occurs at a walk, but it does show up when he trots and canters.

During the veterinary exam your horse flinched when his leg was touched. Your veterinarian suggested radiographs, suspecting the splint area is the problem.

Splints 101

An inflammatory condition of the splint bones, “splints” occur primarily in growing horses involved in heavy training. Splint bones are located on each side of the cannon bone. Between the splint bones and the cannon bone is the interosseous ligament, which is made of a dense connective tissue that ossifies into bone as the horse grows into adulthood. The ossified ligament fuses together with the cannon bone and splint bones; bony fusion is usually complete in most horses by 3-4 years of age.

Splints are caused by injury to the interosseous ligament or to the periosteum of the splint bones or adjacent bones. (The periosteum is the soft tissue covering bone.) “Splints are initially soft tissue swellings which progress to bony swellings,” says Julie Dechant, DVM, MS, Dipl. ACVS, assistant professor of Clinical Equine Surgical Emergency & Critical Care at the University of California, Davis. “Splints can originate from tearing of the interosseous ligament, external trauma to the bone, or secondary to healing of a fracture.”

Most splints pop on the inside of the leg.

Splints commonly occur in 2- to 3-year-old horses, occasionally in horses 4 years of age and older, and are usually associated with training and subsequent injury, Dechant says. Splints usually occur in the medial (inside) forelimb splint, about 3 inches below the carpus (knee), although they can occur in the lateral (outside) splint of the front or rear legs (see diagrams of the four splint types on page 40).

FOUR TYPES OF SPLINTS

  1. True splint This is a fibrous and bony enlargement at the interosseous space secondary to inflammation or tearing of the interosseous ligament.
  2. Blind splint The inflammation this causes results in a fibrous and bony enlargement between the splint bones and the suspensory ligament (i.e., little to no external swelling).
  3. Periostitis This inflammation and bony reaction is secondary to trauma to the periosteum (the soft tissue covering bone).
  4. Knee splint This type of splint involves swelling located very proximally (toward the upper part of the splint bone, closer to the knee) and involving the lower joint in the knee, resulting in osteoarthritis.

Risk Factors

The primary contributor to splints is training: “Two-year-old horses in heavy training have an increased frequency of splints,” notes Steve Adair, MS, DVM, Dipl. ACVS, associate professor of Equine Surgery at the University of Tennessee.

Other potential causes include conformational abnormalities such as offset carpi, base narrow (feet close together), toe-out conformation; improper hoof balance; mineral imbalances; and overnutrition. “Conformation and improper hoof balance can also lead to interference and superficial trauma and periostitis,” Adair adds.

“Working on hard ground can increase the risk of splints,” says Dechant. “Also, racehorses (Thoroughbreds and Standardbreds) may develop distal (farther away from the body, i.e., closer to the foot) splints relative to fracture of the distal splint bone due to tension from the suspensory ligaments. Reiners and cutting horses should be at greater risk, due to their quick movements and direction changes increasing the potential for inadvertent gait interference between limbs.”

Signs and Diagnosis

Heat, pain, and swelling along a splint bone in a 2- to 4-year old horse suggests a splint. “The swelling may be painful to palpation initially, but as the inflammation subsides, the swelling becomes firm and nonpainful,” says Adair. “Lameness is usually mild and most evident at the trot. Exercise on hard ground will accentuate the lameness. In mild cases no lameness may be evident at the walk.” Lameness might come and go or be continuous.

History and clinical findings (swelling that is painful to palpation) are usually sufficient for indicating splints, says Dechant, but radiographs are needed to confirm the diagnosis, to rule out a splint bone fracture, and to document the size and amount of bony proliferation of the swelling. “This establishes a baseline for monitoring for further bony reaction, predicts the degree of permanent cosmetic blemish (bony swelling), and helps determine the potential for impingement on the suspensory ligament, which could cause persistent lameness,” she notes.

“Occasionally, local infiltration of the area with local anesthetic may be needed to confirm the origin of lameness,” says Dechant. “Ultrasound may be needed if there is concern about injury or impingement on the suspensory ligament. In selected cases advanced diagnostic imaging, such as nuclear scintigraphy (bone scans) or computed tomography, may be needed to evaluate splints that are located between the splint bone and the suspensory ligament (i.e., blind splints).”

Treatment

There are various means of addressing splints, but rest is mandatory and is the most appropriate therapy. Veterinarians and horse owners might also utilize additional treatments adjunctive to rest.

The goal of conservative therapy is to eliminate the swelling or minimize its size, although often a small cosmetic blemish (bony swelling) remains. “Conservative management,” reports Dechant, “includes rest until the splint is no longer painful to palpation (usually six weeks, but it can range from two weeks to three months); topical cold therapy with icing, cold hosing, or similar therapy to decrease the swelling and local inflammatory response; pressure bandaging to reduce swelling; oral non-steroidal anti-inflammatory drugs to reduce inflammation; and topical anti-inflammatory drugs such as DMSO (dimethyl sulfoxide) or Surpass (1% diclofenac sodium). Perilesional (around a lesion) injections of corticosteroids may decrease inflammation and reduce the size of bony swelling.”

Adair adds, “Anti-inflammatory agents are primarily indicated for the acute phase, whereas intralesional injections of steroids may be used in the subacute case to further decrease inflammation and reduce swelling.”

For cases due to interference caused by improper trimming or shoeing, have the horse shod and trimmed to prevent further interference or stress on the area.

Some chronic or severe cases might require surgery to remove the bony swelling or to remove a portion of the splint bone. Says Dechant: “Surgical treatment may be considered later (once the inflammation and active bony proliferation has subsided) if the cosmetic blemish is unacceptable or if the bony reaction is impinging on the suspensory ligament and causing persistent lameness.”

The disadvantages of surgery are the risks and expense of performing surgery and that a bony reaction might recur after surgery.

“Lasers, ultrasound, and pulsed electromagnetic therapy may reduce inflammation and also speed healing,” Adair says. “Shock wave therapy will speed healing by stimulating new blood vessel ingrowth, but it will not reduce inflammation.”

Counter-irritation (pin firing, cryotherapy with liquid nitrogen, and blistering, for example) is sometimes used for chronic cases, but it is not recommended, says Adair. “The idea with counter-irritation is to change a chronic condition into an acute condition, thus increasing blood flow to the area and improving healing.”

Prognosis

After all inflammation has subsided, the horse can gradually return to work.

Prognosis is good to excellent except for those cases in which the bony growth is large and interferes with the knee joint or suspensory ligament. “Splints are curable,” reports Adair, “although most horses will have a knot on the splint. While it may not be visible in all cases, it will be palpable. Most performance horses that I have seen with them have visible knots on the medial splint.”

Prevention

You can minimize the risk of splints or prevent them altogether, says Adair, by slowing down the intensity and frequency of your young horse’s work, by providing proper nutrition, avoiding obesity, maintaining proper foot care, and, for cases with limb interference, using protective splint boots during training and turnout.

In choosing protective splint boots, look for padded boots that provide more reinforced or rigid protection, especially medially along the length of the cannon bone, Dechant suggests. “Boots can be synthetic or leather, but should have extra padding and material to absorb or dissipate the impact of hoof interference. Simple un-reinforced neoprene leg wraps, Vetrap, or cloth stable bandages don’t provide sufficient protection against splints.

Take-Home Message

“Don’t assume that a ‘splint’ is a benign problem,” Dechant says. Act promptly and treat aggressively: By quickly reducing the inflammation and the resulting bony reaction, you can minimize the risk of performance-limiting impact or the horse developing a long-term cosmetic blemish.

Reprint from theHorse.com

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