In this study, researchers at The Children’s Hospital of Philadelphia look at the natural progression of acetabular retroversion in children with Perthes disease. The acetabulum is the hip socket. Retroversion refers to the angle and position of the hip socket.
Perthes disease is a condition that affects the hip in children.
In this condition, the blood supply to the growth center of the hip (the capital femoral epiphysis) is disturbed. Loss of blood to this area causing the head of the femur (upper leg bone) to die.
The blood supply eventually returns, and the femoral head heals. How the bone heals determines how much problem the condition will cause in later life. A more deformed femoral head may result in greater acetabular retroversion. This condition can lead to serious problems in the hip joint later in life.
Radiologists rely on the presence of the crossover sign to diagnose acetabular retroversion. The crossover sign is seen as a change in the position of a line drawn on the X-ray. Normally, the edges of the anterior (front) and posterior (back) walls of the acetabulum appear to intersect at the top and along the side. In cases of acetabular retroversion, this crossover of the anterior and posterior acetabular wall outlines is down farther than normal.
But acetabular retroversion doesn’t show up on X-rays in children. So CT scans were used to measure this angle. X-rays were used to see when children reached skeletal maturity. Everyone in the study was followed until after skeletal maturation.
The results showed that acetabular retroversion was rare in children with Perthes disease. Retroversion was more likely to be seen in severe cases of Perthes. After skeletal maturity, the rate of retroversion was much higher (31 per cent).
This was the first study to show a cause and effect relationship between the deformed femoral head in Perthes disease and changes in the acetabulum. Surgeons address the changes observed in the femoral head. But they may not be as aware of the changes in the hip socket. More studies are needed to find ways to prevent this extra deformity from occurring.