Legg-Calvé-Perthes or Perthes disease is a hip condition in growing children with osteonecrosis or death of bone. The femoral head (round top of the thigh bone) is affected when the blood supply to the growth center is disturbed. The blood supply eventually returns, and the bone heals. How the bone heals determines how much problem the condition will cause in later life.
In this study doctors at the duPont Hospital for Children in Delaware looked at changes in the shape of the acetabulum (hip socket) in 243 children with unilateral Perthes (one hip involved). They tracked these changes from the start of Perthes disease until bone maturity (growth stopped). They looked for any link between age, gender, and type of treatment with the final shape of the acetabulum.
The cup-shaped socket of the acetabulum helps hold the femoral head in place and keeps it from sliding out or dislocating. Subluxation (partial dislocation) or complete dislocation can occur when the bone starts to crumble after it loses its blood supply and dies. Without a normal femoral head inside the acetabulum, the shape of the socket starts to change, too.
X-rays were used to group the hips into one of three types according to the shape of the acetabulum. Type I was normal with a curved edge along the top of the acetabulum to hold the femoral head in place. Type II was flat. Type III sloped upwards. With types II and III less of the femoral head was covered.
The results showed there was no link between age when Perthes first started and the shape of the acetabulum at bone maturity. They did find there was less hip motion with Types II and III sockets. Only surgical treatment improved the shape of the acetabulum. Other forms of treatment such as bed rest, traction, or braces didn’t make a difference.
The authors conclude the shape of the acetabulum helps predict the final result of Perthes disease. Keeping the head of the femur centered inside the acetabulum is important to prevent dislocation. The best results were seen in patients who had surgery to rebuild the acetabulum.