ANGULAR LIMB CORRECTIONS AND LIMB LENGTHENING WITH RING FIXATORS

Treatment of angular growth deformities in growing dogs involves not only correction of the angular deformity but correction of current and future shortening of the limb. Ring fixators are especially adapted and useful for treating these cases.

Angular, rotational and mild length deformities can be treated very adequately with a other orthopedic implants and equipment. The same injuries or diseases in younger dogs around 3 to 4 months must be treated differently because the present and potential shortening of the leg become more important. As described earlier an injury to the growth plate of the ulna in the front leg with no angular deformity can be treated by simply cutting the slow growing bone. If there is already significant angular deformity a single procedure can be used to correct both angular and length problems. The angular and rotational deformity can be corrected either slowly or in one step at surgery (if not excessive) and then the bones can be slowly lengthened to correct and keep up with any continued growth of the pet.

Dr. Ilizarov a Russian physician developed the lengthening procedures called distraction osteogenesis. He also developed and modified an external fixator which is an apparatus that consists of pins or wires that are placed through the skin and bone and then attached to bars on the outside of the body that hold the bones together. This form of external fixator utilizes rings and thin connecting wires with numerous accessories to facilitate the procedure. The procedure is separate from the equipment and not totally dependent on any one type, but ring fixators lend themselves better to lengthening than classical fixators. The process entails cutting the bone, waiting a few days for the constituents of healing callus to gather in the area, and then slowly distracting or separating the ends 1 to 2 mm twice a day. Soft callus forms in the gap and is stretched by the distraction. The callus adjacent to the bone ends turns to bone first, and as long as the center ( 4 mm ) stays soft the lengthening can continue. When full length is obtained the center of the distraction callus is allowed to completely heal. The fixator is locked and left in place until the callus matures and strengthens and healing is complete.

This procedure has revolutionized the treatment of lengthening bones that was not available previously. Animals that would previously have a useless limb now can look forward to full function after a few months of treatment. This procedure can also be used when a large section of bone is lost from infection or cancer allowing Veterinarians to save a leg that previously would have had to be amputated.