Legg-Perthes disease was described early in the 20th century following the invention of x-ray. Dr. Legg from Boston, Dr. Perthes from Germany, and Dr. Calve from France described the condition almost simultaneously. Thus, the odd name for the disorder. By custom in North America the name is shortened to Legg-Perthes disease. Despite careful studies we still do not know the exact cause of the condition. The reason for the xray changes and hip symptoms is an unexplained, temporary loss of blood supply to the ball (femoral head) of the hip joint. This ball is known as the femoral head.
The reason for the temporary loss of blood supply is unclear. It appears that some children, age 3 to 10 years, have a sensitive blood supply to the hip and that blood flow is somehow temporarily blocked. With loss of blood supply, the bone in the ball (femoral head), actually dies. This is followed by inflammation and irritation of the hip, with softening of the bone. This causes the limp and pain which leads to hip x-rays being performed and clarification of the diagnosis.
Once diagnosed, Legg-Perthes disease requires careful orthopedic evaluation. Some very young children with very minimal involvement do not require treatment and simply can be observed. In more serious cases vigorous treatment is required to prevent a change in the shape of the ball during the one to two year healing period in which the bone is soft and pliable and at risk for deformation.
Fortunately the blood supply always returns to the femoral head with slow but certain bone healing. However, the hip usually requires treatment during the healing phase so that the ball maintains a relatively round shape. This minimizes the risk for premature arthritis in the hip joint.
The affected hip is usually studied further by having a hip arthrogram that involves injecting an x-ray dye (contrast media) into the joint to allow careful study of the femoral head shape. This is done under general anesthesia at Rady Children’s Hospital-San Diego. While under the same anesthesia, the child is placed into a pair of special leg casts (Petrie casts) that hold the hip in a healing position. Special props (sticks) are placed between the two leg casts to hold the legs in a wide spread position. This position “contains” the femoral head deeply within the socket. A rental wheelchair is arranged since many children cannot walk very well with these casts.
Following this initial study and treatment, the parents then have a choice: cast or brace treatment can be continued, however, the child must wear the cast or brace full time for a year to a year and a half.
We generally recommend a more practical approach, which allows the child to be more normal during this healing phase. This involves surgically changing the angle of the socket so that the ball is more deeply centered (contained) in the hip joint while the child is in a normal standing posture. This requires a formal surgical procedure. The procedure that we commonly use is known as a triple pelvic osteotomy, which is performed four to six weeks after the initial arthrogram study.