Correlation between center-edge angle and acetabulum-head index in developmental dysplasia of the hip with avascular necrosis of the femoral head.

In order to clarify the relationship between the center-edge angle and the acetabulum-head index, we reviewed 97 hips in 86 patients suffering from developmental dysplasia of the hip. We measured the center edge angle and the acetabulum-head index, and evaluated avascular necrosis of the femoral head according to Kalamchi classification. The center-edge angle correlated highly with the acetabulum-head index in non-avascular necrosis, and in Kalamchi groups I and II, but not in Kalamchi groups III and IV. Because of difficulties in measurement, it is possible that the center-edge angle does not precisely indicate acetabular coverage of developmental dysplasia of the hip with avascular necrosis.