Perthes disease is a childhood form of avascular necrosis of the hip. To learn more about treating Perthes disease, watch this video about a young girl's experience at the ICLL.
For reasons yet unknown, the head of the femur (ball of the hip) loses part or all of its blood circulation. Like any tissue that loses circulation, the bone of the hip dies. The normal reaction of the body to dead tissue is to remove it and replace it with living tissue. Gradually, the dead bone of the femoral head is removed by special cells in the bone called osteoclasts. At the same time, new bone is added by special cells called osteoblasts. If this demolition and reconstruction occurred in a completely coordinated fashion, there would be no problem. Unfortunately, the removal of bone weakens the femoral head and the bone in the femoral head cartilage (the outer coating of the joint) becomes deformed because of lack of bony support underneath. This is analogous to the removal of the support beams of a building by one construction crew and the subsequent replacement with new support beams the next day by another crew. In the interim, the roof of the building collapses. Fortunately, the cartilage on the outside of the femoral head is alive and able to grow. It has been observed that it is stimulated to grow outside the acetabulum (socket) where there is no load on the hip.
The treatment of Perthes disease is controversial. We know that the older the child is, the worse the prognosis. Most agree that children younger than 6 years do not require surgical treatment or even treatment with a brace. For patients of all ages, the most important concern in the treatment of Perthes disease is to maintain range of motion (ROM) of the hip. The other agreed upon treatment concern is containment. This means getting the femoral head more covered by the socket. Normally, approximately one-third of the diameter of the femoral head is uncovered by the acetabulum. By spreading the legs apart (abduction), the entire femoral head becomes covered by the socket. This is called containment. There are several ways to achieve containment. Nonsurgically, this is done by means of an abduction brace. The brace keeps the legs apart. Surgically, we can achieve the same thing by cutting the bone of the upper femur and bending it in (varus osteotomy) or of the pelvis to reorient the socket. Both of these methods lead to containment of the femoral head. Even with containment, there is a high failure rate, especially in children older than 8 years. In children older than 10 years, these treatments have very poor results.
In January 1990, a patient presented to us with a very severe case of Perthes disease that was not treatable with bracing or osteotomy. As in many cases, the femoral head was collapsed and consequently subluxed (displaced partially out of joint -- the femoral head moves up, out, and forward relative to the socket). Because the child was 11 years old, the prognosis was very poor. The hip was completely stiff and painful and stuck in a deformed position. We decided to treat this case by using distraction. This involved pulling the hip back to its normal position in the joint, using an external fixator between the pelvis and the femur that permits hip motion while it moves the bones apart. To our amazement, the shape of the deformed femoral head began to change from a flattened ball to a round ball. The device was in place for 4 months. After it was removed, the boy continued to receive physical therapy. The hip remained in place, and all of the motion of the hip was regained. This included flexion, extension, abduction, adduction, and internal and external rotation. Nearly 12 years after surgery, the patient has a painless, fully mobile hip and is fully active, working in construction. He is 6'4" tall.
Based on our experience from this first case, we began to treat with distraction of the hip joint other cases of Perthes disease that would have been considered for osteotomy and those that were either too severe for osteotomy or for which previous osteotomy had failed. The success rate to date in more than 20 cases treated with this method is greater than 90% in the most difficult cases. We now believe that hip distraction is as good as or better than osteotomy for treatment for Perthes disease. It offers the advantage that it does not deform the pelvis or femur to treat the disease. It is the method of last resort when other methods fail. It also seems to work in the treatment of children with avascular necrosis caused by other conditions such as slipped capital femoral epiphysis.
As part of the preoperative as well as postoperative treatment, we recommend aggressive ROM stretching exercises, which we call the Perthes exercises.