Details about a surgical procedure to help young horses with limb abnormalities.

Question:

How successful is the “screws and wire” procedure that is so commonly performed on yearlings as it relates to preventing soundness issues? Why is this procedure so necessary and recommended by vets? How can you tell if the surgery was a success?

Answer:

Daily turned to the American Association of Equine Practitioners for advice.

Abnormal angle of the limb starting at the knee can lead to abnormal weight bearing during exercise. This can result in joint and foot problems that cause lameness later in life due the unequal load transmitted up one side of the limb.

If a foal, weanling or yearling has an abnormal limb deviation (the lower part of the limb angles in or out from a straight line from the shoulder to the ground), which does not respond to normal foot trimming and restricted exercise, use of periosteal stripping may be helpful in mild deformities. If there is a significant deformity, which most often occurs with the limb angling out from a straight line from the shoulder to the ground, surgically placing a wire across the growth plate between two screws to inhibit the growth plate on the inside of the affected leg at the end of the radius will allow lengthening of the radius on the outside of the limb, thereby straightening the leg back to normal. This is best done between 3 to 6 months of age when the growth plate is rapidly adding new bone to the radius. Once the legs are straight, the screws and wire are removed. A single screw is sometimes used to bridge the growth plate to accomplish the same limb straightening. This is usually done to correct deviation of the limb inside the straight line from the shoulder. This is usually done in weanlings or yearlings. The screw is removed once the leg is straight.

This type of surgery is very effective if completed early in the growth phase (3 to 6 months). Some adjustment in the angle can be made with this technique from 6 to 20 months, though the corrections take longer and, depending on the amount of limb angulation, may not result in total correction. The surgery is successful if it results in a straight leg. Often horses will have a slight angle to the outside of the straight line from the shoulder (0 to 5 degrees determined by radiographs of the knee). If this is the case, no correction is necessary.

Dr. Nat White, Leesburg, Virginia, member of the American Association of Equine Practitioners

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