from the Vet Corner Archives

Part of Horse Previews Magazine website. Posted on 05/07/2001; 2:00:00PM.

Veterinary Corner 05/01: Angular Limb Deformities

by Frosty Franklin, DVM
Edgecliff Equine Hospital
S. 1322 Park Road, Spokane, WA 99212 * 509/924-6069

Crooked legs are a common problem of foals. They are usually classified into two main categories. "Knocked knees" or a valgal deformity indicates the lower limb is deviated away from or lateral to the midline. "Bowlegged" or varal deformity indicates the lower limb is deviated toward the midline or medial to the midline. These angulation deformities occur most commonly at the knee (or carpus), ankle (or fetlock), and the hock (or tarsus). The causes of these deformities are many; under developed bones of the knee, laxity of joint ligaments, in utero postioning, and the most common cause is related to uneven growth at each side of the growth plate.

Newborn foals usually have a slight carpal valgus deformity (knocked kneed) appearance of approximately 2-5 degrees. As the foal grows and matures the chest widens, the limbs rotate and straighten producing an individual of good conformation.

Fetlock angular deformities need much earlier assessment than most carpal angular deformities. Mild valgus angulation of the fetlock is common and usually responds and straightens with conservative therapy such as 30 days stall rest and frequent trimming. Varus fetlock deformities (pigeon toed) are usually more severe, especially of the hind limb. The growth plates of the fetlock close much earlier in life (approximaterly 3 months) than do the growth plates of the carpus. If surgery is to be attempted to correct the angulation of the fetlock it should be done before 4 weeks of age to get the best results.

Carpal angular deformities are the deformities most often noticed by horseman. Many newborn foals have carpal valgar (knocked kneed) angulation, usually less than 15 degrees, that resolves spontaneously within the first few weeks of life. My approach is to be patient with carpal vagus angulation, stall rest, frequent rasping the lateral aspect of the hoof to keep the foot balanced and time. More severe carpal angulation needs early evaluation by an experienced professional. Radiographs (xrays) are critical in evaluating angulation deformities. Moderate angulations (greater than 15 degrees) are candidates for surgery to correct the angulation. Surgery can be helpful in many individuals even up to a year of age. But early assessment and diagnosis of the underlying problem is paramount to good result.

Conservative therapy of angular limb deformities is my preferred line of treatment. It involves early evaluation, restricted exercise, rasping or trimming the foot into balance, and application of extended shoes, if necessary.

In those cases in which the angulation is too great or the conservative therapy is not getting results then manipulation of the growth at the growth plate should be considered. There are two common methods of manipulating the growth plate. The first and easiest method is called periosteal transection. The principle behind this method is releasing the tension in the periosteum (covering of the bone) stimulating rapid growth at the concave side of the growth plate thereby straightening the leg. This procedure does not cause an over correction. The advantages of this procedure are there is no risk of metal implants, less expensive, easier, and no need of a second surgery to remove implants. The disadvantage is the corrections are not as dramatic as with transphyseal bridging.

In cases where severe angulation or there is little time until growth plate closure a more difficult more expensive surgery called temporary transphyseal bridging maybe attempted. In this technique the idea is to retard the growth on the convex or more rapid growing side of the growth plate. A staple across the growth plate or, more commonly, a small screw placed on each side of the growth plate is bridged with a tightened figure eight wire used to retard the growth of that side of the growth plate. As the opposite side of the growth plate grows the limb straightens. The results are usually dramatic.

However, it is critical to monitor these foals closely. Over correction occurs easily. Follow up radiographs at monthly intervals and removal of the implants at just the right time is important for a cosmetic result. This procedure is costly, requiring specialized training, surgical equipment and a second surgery to remove the implants.

The take home message here is that foals having many mild to moderate angular limb deformities that are stalled or have restricted exercise will correct themselves. The fetlocks represent a challenge and all limb angular deformities need early assessment. An early, proper approach can have a dramatic pleasing cosmetic result.

Happy Trails!, Dr. Frosty Franklin

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