POSNA Information for Parents
Legg-Calvé-Perthes Disease
Dr. Elizabeth Pickvance

Legg-Calvé-Perthes disease, often shortened to just Perthes disease, was described by Drs. Legg, Calvé and Perthes in the early 1900’s.  It is a disease affecting the hip in children.

The hip joint consists of a spherical ball (femoral head) at the top of the thigh bone (femur) and the spherical socket (acetabulum).  The femoral head moves inside the acetabulum, thus the whole leg moves at the hip.  The femoral head and acetabulum bones have a coating of cartilage (like the shiny end of a chicken bone).

In Perthes disease, the bone of the femoral head dies and then it collapses.  The femoral head is no longer spherical and does not fit in the acetabulum very well.  This causes changes in the possible movement of the joint and thus the leg.  When a joint is not a perfect fit, the cartilage will wear out and then bone is rubbing on bone, this is arthritis and can be painful.  The worse the joint fit, the faster the cartilage will wear out.

The cause of Perthes disease is unknown.  It is believed that the blood supply to the femoral head is somehow interrupted.  Because the bone does not get blood, it dies, becomes soft and then collapses.  The femoral head eventually heals itself.  Blood  vessels re-grow into the femoral head, bringing in blood and new bone cells.  Hopefully, this is done before the head collapses and changes shape.

After the causative event occurs, the femoral head goes through four (some people say five) stages of the disease.  The entire course of the disease can take 1.5 to 3 years.  At first, the femoral head appears smaller on xrays.  This can be difficult to see.  Because of this difficulty, making the diagnosis in the early stages can be difficult.. Then the ball appears to fragment and it collapses.  The pain and limp are worse during this stage and the movement of the hip joint is decreased.  Most of this is due to the irritability of the hip during this stage of the disease.  The healing phase starts when new bone formation begins.  The pain decreases but the hip movement depends on the shape of the head.  Finally the head is completely healed and the dead bone is now replaced with new bone.

Not only is the femoral head involved but also the underlying growth plate.  This may cause growth disturbances during the course of the disease.  Frequently, the femoral neck (between the femoral head and the femur) becomes wider and shorter.  The femoral head may grow into a tilted position on the femoral neck.  When the femoral neck is short, the patient will have a shifting type of limp.

The outcomes of patients vary considerably.  An individual’s outcome is probably based on age and amount of femoral head involvement.  We do know that the younger the patient is at the on-set of complaints or limping (younger than 8 years), the better the final outcome will be.  The smaller the amount of head involvement, the better the person’s outcome will be.

The treatment of Perthes involves trying to change the results of those patients thought to have the potential for poor outcome.  The key word is “containment”.  This means trying to keep the soft and malleable femoral head in the spherical acetabulum during the healing phase so that the acetabulum can keep the femoral head spherical also.  There are several ways to accomplish this.  If a patient has good movement of the hip joint, then no active treatment may be needed.  Some physicians treat Perthes disease with casts or braces to keep the legs apart, this keeps the femoral head deep inside the acetabulum.  Some patients may need to have surgery.  Two surgical approaches are usually taken, either the femur is cut to put the femoral head deeper inside the acetabulum or the acetabulum is cut to make it cover the femoral head better.  Rarely, both the femur and the acetabulum will need to be cut.  Surgery does not guarantee good outcome.

Perthes disease varies from patient to patient.  No two cases are identical.  Physicians vary in the way they take care of patients with Perthes disease.  Radiographic monitoring during the stages of Perthes disease is necessary.  With appropriate radiographic follow-up, the physician and the family can make appropriate decisions about the treatment.

E.A. Pickvance, M.D.
Assistant Professor
Orthopaedic Surgery
University of Pittsburgh
Children's Hospital of Pittsburgh
Pittsburgh, PA