Tendon contracture and laxity problems in foals common, but still serious

Tendon contracture and laxity in foals is not an uncommon problem and one that most equine practitioners routinely deal with just about every foaling season.

There always seems to be at least one foal that is born with one of its parts too tight, too loose or somehow out of place.

Contracted tendons are the most potentially serious problem while excessively loose or lax ligaments are probably more commonly seen. These conditions usually involve the ligaments and tendons of the lower limbs, but potentially any such structures in the body can be affected. Occasionally foals are born with such a collection of contractures through their legs and upper bodies that they literally resemble rubber Gumby horses hit by a stiff wind.

This foal, born with tendon contracture, has the typical "windswept" appearance with curvature of the back, hips, stifles and hocks.

These twisted foals are in fact referred to as "windswept" and, though most grow out of the condition, their early management can be complicated by their problems.

Ears, noses, tongues and tails have also all been reported to have suffered some degree of contracture or laxity in young foals. Most owners are quite concerned about the abnormal appearance of their recent arrivals and an explanation and treatment options are usually sought.

Uterine malposition

Uterine malposition is the most common reason given for these congenital contractures and laxities. There is restricted space in the uterus, and some foals become twisted or "stuck" in awkward positions that do not allow them to stretch their limbs and move about. These abnormally positioned legs develop tightened or shortened ligaments and tendons.

Contracture of the front carpi (knees) in this foal was severe enough at birth that it could not stand and nurse. Additionally this foal had severe laxity to the hind fetlocks. The foal was bottle fed for the first week of its life. It was treated medically with intravenous oxytetracycline and splints were applied to the front legs. Within 10 days, the foal had responded well, and the front legs were almost normal. Resolution of the forelimb contracture allowed the foal to begin vigorous exercise which helped the hind fetlock laxity disappear.

This explanation is reasonable for contracture, but does little to explain laxity. Occasionally, some foals may be born with both contracture and laxity, which makes the pathogenesis of these conditions even harder to explain.

"Uterine malposition is the most plausible explanation, and the one most readily accepted by clients," says Dr. Andrew Parks, professor of surgery at the University of Georgia College of Veterinary Medicine. "However," adds Dr. Parks, "it is the explanation that is probably the most difficult to support from a research standpoint." Many veterinarians now believe that there are a host of factors, many probably interactive, that all contribute to cases of congenital contracture and laxity. Veterinarians seeking to assist their clients in determining the causes of these problems and in reducing the chances of reccurrence in breeding programs, need to be complete in their investigation of other possible factors.

Plants and toxins

Numerous case reports in the literature describe tendon contracture in foals born to mares that were exposed to various plants and toxins. Locoweed, Sudan grass and other plants have been reported.

Various infectious agents have been implicated, but much more research needs to be done before a definitive link can be made to any particular disease. Contracture and laxity problems have been suggested to be caused by depletions and excesses in various vitamins and minerals in the diet of pregnant mares. Again, no definitive correlation has yet been made. Pathologic bone problems leading to abnormal tendon development is believed likely as well as the existence of various defects in elastin and collagen production.

Though this foal had some difficulty initially, it stood and nursed unassisted. The foal was managed conservatively with simple exercise, and the condition resolved within one week.

Genetics may be more of a factor than was previously thought, and there is hope that new advances in gene mapping will shed some light on the exact reasons for the development of contracture and laxity. Until then, it is important to control those factors that have already been identified and to aggressively treat these twisted foals when they occur.

Weak flexor tendons

Many foals are born with flaccid or weak flexor tendons. The hind feet of these foals are usually affected, though the front feet can be involved as well.

The typical foal is bright and alert, but when it stands it places the palmar (plantar) surface of the hoof on the ground and the toe does not bear weight. In severe cases, the caudal surface of the fetlock may actually contact the ground.

The majority of these foals self-correct in a few days. Exercise is important and is often directly correlated to tightening of these affected tendons and a return to normal alignment of the fetlock and the bearing surface of the hoof. Trimming, to provide a flat bearing surface on the foal's heels, may be necessary in prolonged cases.

This foal is wearing a PVC toe extension that has been shaped for the foot and applied with acrylic glue. The extension will force stretch the ligaments and tendons and can help resolve many cases of contracture. These extensions are easy to fashion and apply with some experience.

There is a relatively rare condition of extreme laxity in the interphalangeal joints of young foals. The cause of this condition is unknown, and these foals do not respond to treatment. Dr. Ted Stashak, professor of surgery at Colorado State University College of Veterinary Medicine, advises that the only way to differentiate this rare condition from the more commonly seen laxity is to monitor improvement in each foal. Digital photos allow an accurate measurement of angulation changes so that even very slow positive improvement can be noted.

Young foals

The more serious problem in young foals is tendon contracture. This problem can vary from severe and almost arthrogryposis-like to relatively mild. In severe cases these foals may precipitate dystocias. Contracture occurs most commonly at the carpas or fetlock. These foals will stand knuckled over to varying degrees. If the contracture is severe enough, the foal may have difficulty positioning itself to nurse. Extreme care must be taken to be sure that these foals receive adequate colostrum and nutrition in the first few days of life or until their condition improves. Treatment for these foals is aimed at forcing flexion of the affected limb(s). If the foal's leg can be manually forced into normal position, its prognosis is very good. When normal alignment cannot be achieved by forced extension, the prognosis is not as favorable but many of these foals will respond to more aggressive methods.

Treatment

The use of systemic oxytetracycline is beneficial to many foals. While the exact mechanism of action is unknown, it is believed that this drug binds calcium and has an effect on the musculotendinous junctions in the leg.

An initial dose of 44 mg/kg is diluted in 250 to 500 cc saline and given slowly intravenously. This dose can be repeated in 12 to 24 hours if necessary. Many times a rapid improvement can be seen following this treatment. Some practitioners have recommended treating these foals with probiotics during this period, but adverse responses to oxytetracycline in foals is not commonly reported.

Splinted

Foals that do not respond to this treatment should next be splinted to force extension. "Correctly applied splints are the next best step and are usually very helpful in most cases," Stashak says. Heavy paper mailing tubes can be used on very small foals, but Stashak favors PVC pipe that is sized, cut and heat-bent to the appropriate angle. Correct application of splints in small foals is sometimes a difficult chore.

Adequate extension force is balanced against splint pressure and rubs. Constant observation of these splints is necessary and, since foals grow quickly and angles should change as improvement occurs, they must be continually adjusted.

Thermography or infrared camera use has been proven to be very beneficial in locating very early areas of pressure. These cameras will identify a "hot" area where the splint is causing skin damage and steps can be made to reduce pressure at the specific point. This early detection can help avoid a painful rub or blister that will slowly progress.

Toe extensions

Some practitioners favor the use of toe extensions in cases of mild to moderate tendon contracture.

In this treatment approach, a half-hoof shaped extension is fashioned out of PVC pipe. This piece should fit tightly over the dorsal surface of the foal's hoof and encompass a bit more than half of the surface area of the hoof. This piece is cut to extend forward and below the level of the foal's hoof. Holes are drilled in the PVC piece, and it is attached to the dorsal surface of the hoof with a strong acrylic. The space between the extension and the foal's sole surface is also filled with acrylic.

The correct application of such a toe extension causes the foal to place extra weight on its toe and to thereby stretch its flexor tendons. The length of the extension can be reduced, as the foal's angles become more and more normal. Care must be taken to ensure that toe bruising or abscessation does not occur.

Surgical correction

Severe cases that do not respond to exercise, oxytetracycline, splints or extensions may need to be surgically corrected. Carpal (inferior) check ligament desmotomies and flexor tenotomies have been successfully used to correct these foals. Many cases can avoid surgery though, if appropriate and aggressive treatments are instituted quickly. Clients need to know that contractures and laxities are potentially serious problems and veterinarians should treat these conditions with the urgency they deserve. It is easy to become complacent because the vast majority of cases, even initially severe ones, usually improve in a few days. Those that do not resolve in this time period, should not be overlooked.

Ears, noses and tails

Contracture of ears, noses and tails is more difficult to treat, but fortunately is less commonly seen. Many of these cases occur because of nerve irritation or trauma at the time of birth. The majority of such cases will spontaneously resolve.

Some practitioners have treated foals with intravenous DMSO if severe nerve irritation was suspected and acupuncture treatments and chiropractic adjustments have been helpful to some foals born with torticollis, scoliosis or wry face or tail that has been caused by muscle or other soft tissue trauma and spasm.

Many foals are born with swollen, floppy tongues. This laxity is again believed to be caused by trauma at the time of birth. Head compression during delivery can result in a flaccid tongue that hangs from the foal's mouth. This can sometimes make nursing difficult. Attention to colostrum absorption and nutrition will ensure that the foal does well until its problem resolves.

Nutrition

If a farm is experiencing contracture or laxity problems, then an evaluation of the farm environment and the nutritional program should be made.

Toxins, unusual plants, chemicals and possible pasture, hay or water contaminants should be investigated. Nutritionally, broodmares should be receiving a balanced diet with neither excessive protein nor calories. Vitamins and minerals should also be available in a balanced formulation that avoids excesses.

"Well-managed programs seem to do an excellent job of controlling diet and environmental factors," Parks says. He adds that it is these programs where possible genetic factors may actually come into play more noticeably. Certainly past foalings and the development and outcome of those foals should factor heavily into future breeding decisions.

New research may help identify more causes for laxity and contracture in foals, but that information is still on the horizon. Rapid identification of foals with problems and aggressive treatment is still the best method of straightening out these crooked foals.

Dr. Marcella, a 1983 graduate of Cornell University's veterinary college, was a professor of comparative medicine at the University of Virginia. His interests include muscle problems in sport horses, rehabilitation and other performance issues.