Is Kalamchi and MacEwen Group I avascular necrosis of the femoral head harmless in developmental dysplasia of the hip?

The aim of this clinical study was to evaluate the influence of Kalamchi and MacEwen group I avascular necrosis of the femoral head (AVN) on the radiographic and clinical outcomes in developmental dysplasia of the hip (DDH). Preoperative and follow-up (at 2-3, 4-6, 7-9 and 10-15 years of age) Sharp's acetabular angles (AA) and the final Wiberg's center-edge angles (CEA) and proximal femoral center-trochanter distances (CTD) of 13 hips with group I AVN (AVN group) were compared with measurements of 22 hips without AVN (control group). All hips were initially treated by the same soft tissue surgical procedure (posteromedial limited surgery) under the age of 18 months and were completely followed up to at least 10 years of age. Radiographic diagnosis of group I AVN was made between 6 and 12 months postoperatively. The period for complete radiographic recovery of group I ischemic changes was between 2 to 4.5 years. Preoperative mean AA values of both groups were similar. However, the mean AA was found to be worse in the AVN group than in the control group during follow-up. Control group hips had a better mean CEA and higher number of hips having normal CTD than the AVN group, at latest follow-up. In conclusion, when compared with uncomplicated hips, group I ischemic changes retard acetabular development and have quantitative unfavorable effects on lateral femoral head coverage and proximal femoral anatomy in DDH. In addition, the healing process in group I AVN patients is extended.