In foals, restriction of a joint in a flexed position or the inability to extend a joint completely is termed a flexural limb deformity. Flexural limb deformities may be congenital (present at birth) or acquired (developed after birth). Suggested causes of congenital flexural deformities include malposition in the uterus, genetic predisposition, poor nutrition and exposure to toxins. Congenital flexural deformities usually involve the knee or fetlock joints and range in severity from mild flexion of one joint to extreme flexion of several joints. Although foals with severe flexion of the fetlock may respond to treatment, those with severe flexion of the knee are unlikely to improve and often are euthanatized.
It is important for the veterinarian that is examining a newborn foal with flexural limb deformities to determine if the foal can stand without assistance. If the foal can stand, specific treatment for flexural limb deformities is often unnecessary. These foals should have controlled exercise such as turnout in a small paddock with the mare for one hour daily. The goals of controlled exercise are to help lengthen or stretch the soft tissues on the back of the leg (tendons, ligaments, joint capsules) while protecting the limbs from overuse. Progress towards normal limb extension should be monitored daily. Some foals can bear weight on the limb with the fetlock joint knuckled forward (flexed). As a result, the tendons on the front of the leg become taut and the tendons on the back of the leg become lax. In these instances, the limb should be splinted to extend the fetlock joint and load the tendons on the back of the leg. If the foal cannot stand, splinting the limb in an extended position is necessary to allow the foal’s body weight to load and stretch the tendons and other soft tissues on the back of the leg. Your veterinarian will take care to apply the splints carefully as they can easily cause pressure sores due to the fragile nature of the foal’s skin and the pressure that is required to extend the limb. The splints are left on for a maximum of eight hours. If re-application of the splints is necessary, the limb should be unsplinted for several hours before the splints are applied again. Corrective shoeing in foals with congenital flexural deformities is usually limited to applying toe extensions. Toe extensions, most valuable in foals with fetlock flexion, can be difficult to keep on the foal’s foot. Hoof acrylic and aluminum plates may be used or commercial glue-on shoes are also available. Intravenous administration of oxytetracycline may be useful in treating foals with congenital flexural deformities to relax the tendons. Improvement is frequently observed after a single treatment but your veterinarian may need to administer up to three consecutive days of treatment. Oxytetracycline appears to be most effective if used in the first few days of life, especially with fetlock deformities, but it may be useful in older foals. Splints are often used in conjunction with oxytetracyline. Nonsteroidal anti-inflammatory drugs should be used in the treatment of congenital flexural deformities because the limbs are often painful from stretching of the soft tissues. These drugs may cause ulcers, however, reducing limb pain and promoting exercise will aid recovery.
Surgery to cut restrictive tendons, ligaments or joint capsules is often not necessary for treatment of foals with congenital flexural deformities, and should be reserved for foals that fail to respond to other treatments. Foals with acquired deformities are more likely to require surgery. Many horses can become successful athletes after the accessory (check) ligaments are cut. However cutting the tendons or the suspensory ligament in animals intended as athletes is not recommended. These animals can be used for breeding or in some instances for very light pleasure work. Fusion of the joint may be the treatment of choice for animals with severe fetlock deformities of marked flexion and abnormally-shaped bones. This procedure can result in a pasture-sound animal.
Although flexural limb deformities in foals are a common orthopedic problem, no single treatment regime is always successful because of the range of severity. Many congenital flexural limb deformities can be treated successfully without surgery. Controlled exercise, splinting, corrective shoeing, oxytetracycline and pain-killers may be components of successful treatment. Many horses requiring surgery of the accessory ligaments can be used for riding, racing, and competition.
Contributed By: Stephen Adams, DVM, MS (AAEP)