Surgeons from Israel tracked 40 patients with Legg-Calvé-Perthes disease over a period of 30 years to see the long-term results of surgery. This is their report of the results for children who had a proximal femoral varus derotational osteotomy (see explanation below).
Perthes disease is a condition that affects the hip in children between the ages of four and eight. The condition is also referred to as Legg-Calvé-Perthes disease in honor of the three physicians who each separately described the disease.
In this condition, the blood supply to the capital femoral epiphysis (growth center of the hip) is disturbed. The bone in this area becomes necrotic (starts to die) without blood. The blood supply eventually returns, and the bone heals. How the bone heals determines how much problem the condition will cause in later life. This condition can lead to joint deformity and a poorly functioning hip.
The primary goal of treatment for Perthes disease is to help the femoral head recover and grow to a normal shape. All treatment options for Perthes disease try to position and hold the hip in the acetabulum as much as possible (referred to as containment). This healing process can take several years. If conservative (nonoperative) care is not successful, then surgery may be needed.
Surgical treatment for containment usually consists of procedures that realign either the femur (thighbone), the acetabulum (hip socket), or both. Realignment of the femur is the operation being reviewed in this study (femoral osteotomy). This procedure changes the angle of the femoral neck so that the femoral head points more towards the socket.
To perform this procedure, an incision is made in the side of the thigh. The bone of the femur is cut and realigned in a new position. A large metal plate and screws are then inserted to hold the bones in the new position until the bone has healed. The plate and screws may need to be removed once the bone has healed.
The advantages of this operation are that it contains or keeps the hip in the socket and molded into the round shape needed for movement. The idea is to prevent future hip joint deformities. This treatment method also eliminates the need for long periods of bracing and immobilization.
The surgeons used three types of classifications to describe the condition. The first classification scheme (Catterall classification) grouped the patients according to the percentage of changes seen on X-rays of the femoral head before surgery. There were four groups. Group one: only the front part of the growth plate was affected. Group two: 50 per cent of the femoral head was affected. Group three: 75 per cent of the head was involved and group four: the entire epiphysis was affected.
The second classification (Stulberg classification) rated the hip joint anatomy as I (normal hip joint), II (round but larger than normal femoral head), III oval or mushroom-shaped (but not flat) femoral head, IV (flat femoral head, abnormal femoral neck and hip socket), and V (flat femoral head with normal neck and socket).
The third classification model (Tönnis Classification) was used after surgery to identify and describe the development of osteoarthritis. A grade of zero means no sign of osteoarthritis. Grades one, two, and three describe mild, moderate, and severe arthritic changes.
All classifications were made using X-rays. Patients were also examined before and after surgery. Any differences in limb- length were measured and recorded. Pain was used as an additional measure of long-term outcomes.
Overall results were good-to-excellent for about half the group. Mild hip pain, slight limp, and leg length difference were commonly reported. Signs of osteoarthritis were present in about 25 per cent of the group. The Stulberg classification of anatomy (shape of femoral head) was a good predictor of function and development of osteoarthritis later.
As the longest follow-up on record for patients with Perthes who had a femoral osteotomy, this study was able to compare the shape of the femoral head with long-term function and the development of arthritis in later years. The authors report that most of the patients had a favorable result. Only one person had to have a total hip replacement (25 years after the osteotomy). Everyone was gainfully employed. The hip problem did not determine the type of job chosen.
The authors comment that with today’s new tests and knowledge of Perthes disease, some of the children in their study would not have needed surgery. And there was no control group (children matched by severity of condition who didn’t have surgery). These two factors may skew the results a bit. Relying on clinical signs (hip pain, limp) to diagnose arthritis is not advised. X-rays are needed to know for sure as many patients with osteoarthritis have no (or only mild) symptoms.
The authors also address one other criticism of the femoral osteotomy procedure. And that is the leg length shortening that occurs. Although there were mild limb length differences seen in this group, it wasn’t any more or any worse than differences reported in other studies using other forms of treatment. Function was not reduced by the limb-length discrepancy. Another study to look at the effect of limb length difference on the development of osteoarthritis later in life may be helpful.