Perthes disease was described independently by Drs. Legg, Calve, and Perthes in the first decade of the 20th century.

Causes of Legg Calve Perthes Disease

To the best of our knowledge, the cause of the disorder remains unknown; however, the most accepted theory is that for some reason (i.e., trauma or clotting abnormality) there is a temporary loss of the blood supply to the ball portion of the hip joint (femoral head). This causes a partial death of a portion of the femoral head. When the bone and cartilage lose its blood supply they eventually become soft and ultimately collapse. When the femoral head collapses it loses its circular and spherical shape and no longer fits well into the hip socket. This results in loss of motion of the hip joint and causes a limp. Over the long term, as the joint fit becomes less and less perfect, the cartilage wears out and eventually arthritis develops with bone rubbing on bone. The worse the joint fit, the earlier the onset of arthritis. Eventually the femoral head heals itself with in-growth of new blood vessels, delivering new bone cells to the joint. If this occurs before the femoral head collapses and changes shape then the hip has a better long-term prognosis.

Who does Legg Calve Perthes Disease Affect?

Perthes usually occurs between ages 4 to 8, but it can occur in children age 2 to teenager. The disease characteristically affects boys almost 5 times as frequently as girls; however, girls do not do as well as boys if they get it. Perthes can occur in both hips in up to 10-15 percent of the time. If both hips are involved it does not occur together in the exact same stage (see below). Children often have a slowly progressive painless limp and it usually takes several months before the child presents to the doctor. Pain is not usually present at rest but is more activity related. Due to the nerve supply of the hip joint, patients often complain of pain in the lower thigh or knee area.

Stages of Legg Calve Perthes Disease

Once the femoral head loses its blood supply it typically goes through four stages (seen by X-ray) over the course of 1.5 to 3 years. In the initial stage the femoral head appears smaller and more dense on X-ray and can be difficult to see. The second stage is fragmentation where the femoral head appears to fragment on X-ray. This is usually the stage that the diagnosis is made, as the pain and limp are worst in this stage and the movement of the hip is significantly less than normal. Treatment is most effective during this stage. Once the third stage of re-ossification starts, treatment can no longer effect the end result as new bone formation has begun. The final stage is the healed stage when the collapsed area of the femoral head has been completely replaced with new bone.

Important Factors Regarding Outcome

The two most important factors regarding outcome are age at onset of disease and the amount of femoral head involved. The younger the child at the onset of the disease, and the less amount of femoral head involved, the better the outcome. The younger child does better than the older one because there is more time to remodel and reshape the femoral head because there is simply more growth remaining to do so.

Treatment of Legg Calve Perthes Disease

The treatment of Perthes relies on two basic principles: preserving the motion of the hip joint and containing the femoral head in the socket. The longer that motion is preserved, the better the chance of keeping the femoral head contained in the socket. It is believed that by containing the soft femoral head in the spherical socket during the re-ossification and healing phases that the socket can keep the femoral head spherical and help prevent deformation of the femoral head. Initially, motion is preserved by decreasing the inflammation, pain, and muscle spasm around the hip joint. This is accomplished by anti-inflammatory medication, rest, and physical therapy. Sometimes home traction or hospitalization is required.

If it becomes increasingly difficult to preserve motion, the child may be admitted to the hospital to have dye injected into the hip joint (an arthrogram) in the operating room. This is done to determine the shape of the femoral head and to decide whether or not the femoral head can be contained. Methods of containment include plaster casts, bracing, and surgery. Surgical containment can be either on the femoral head or the socket side or both.

Whichever approach is chosen, the idea is to put the femoral head deeper into the socket and hope that the socket induces the femoral head to become more round when healing. If the femoral head is not containable, surgery may be suggested to put a more round portion of the femoral head within the socket and/or enlarge the socket to cover the larger more deformed femoral head. In addition, since the growth of the femoral head is affected during the growing years of the child, it is probable that there will be some leg length difference at the end of growth that may require additional treatment.

It is important to understand that Perthes disease is very variable and no two patients have an identical course. In addition, physicians vary in the way they treat patients with Perthes disease as there is not a great deal of established scientific fact in the treatment literature. Thus surgeons vary in their treatment according to local custom in the way they were trained. Surgery does not necessarily guarantee a good outcome and may not have an immediate effect on the symptoms that the child is exhibiting, but will hopefully improve the long term result of the hip. The rounder the hip is at skeletal maturity, the later arthritis is likely to occur. Due to the active growth of the child it is important to follow the patient throughout childhood and intermittently into adulthood.

Recently, long-term studies have been published suggesting that 30 to 40 years after the onset of Perthes disease, 80-90 percent of patients are active and pain free despite that their hips have and abnormal shape once healing is finished.

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