Acetabular development after reduction in developmental dislocation of the hip.

A radiologic study was conducted on 56 patients with developmental dislocation of the hip (63 hips). Fifty hips in which neither acetabular nor femoral osteotomy was performed were classified as satisfactory (Severin Groups I and II) or unsatisfactory (Severin Groups III and IV) based on radiographs when growth was completed. The sequential changes in the center edge angle and the acetabular index were compared when the patients were ages of 5, 10, and 15 years. There was a significant relationship between the center edge angle and the acetabular index when the patients were 5 years of age and at final outcome. Most (85.7%) patients with a center edge angle less than 8 degrees and an acetabular index greater than 26 degrees at 5 years of age eventually were classified as Severin Groups III and IV at skeletal maturity. These findings suggest that radiologic results at the time when growth is completed can be predicted based on the center edge angle and the acetabular index in radiologic measurements at 5 years of age. The authors recommend that if at 5 years of age the center edge angle is less than 8 degrees and the acetabular index is greater than 26 degrees, consideration be given to an osteotomy to bring these values to a more normal range to improve final outcome.