Acetabular index is the best predictor of late residual acetabular dysplasia after closed reduction in developmental dysplasia of the hip

Purpose Our objective was to find the best predictor of late residual acetabular dysplasia in developmental dysplasia of the hip (DDH) after closed reduction (CR) and discuss the indications for secondary surgery. Methods We retrospectively reviewed the records of 89 patients with DDH (mean age 16.1 ± 4.6 months; 99 hips) who were treated by CR. Hips were divided into three groups according to final outcomes: satisfactory, unsatisfactory and operation. The changes in the acetabular index (AI), centre-edge angle of Wiberg (CEA), Reimer’s index (RI) and centre-head distance discrepancy (CHDD) over time among groups were compared. The power of predictors for late residual acetabular dysplasia of AI, CEA, RI and CHDD at different time points was analysed by logistic regression analysis. Receiver operating characteristics (ROC) curve analysis was used to determine cutoff values and corresponding sensitivity, specificity and diagnostic accuracy for these parameters. Results Both AI and CEA improved in all groups of patients following CR. In the satisfactory group, AI progressively decreased until seven to eight years, while CEA increased until nine to ten years ( P