Predicting acetabular growth in developmental dysplasia of the hip following open reduction after walking age

Background: Acetabular dysplasia of the hip following open reduction can complicate the treatment of developmental dysplasia of the hip (DDH). The purposes of this retrospective study were to investigate the long-term results of open reduction performed via an extensive anterolateral approach for DDH after walking age and to predict acetabular development using postoperative radiographs and arthrograms. Methods: From 1973 to 2001, we performed open reduction for 131 hips in 119 pediatric patients with DDH after failed closed reduction. Of these, 85 hips of 73 patients who underwent arthrography at 5 years old were followed-up radiologically until skeletal maturity. Mean age at the time of surgery was 17 ± 4.6 months (range, 10–33 months), and mean age at final survey was 19 ± 5.7 years (range, 14–33 years). Mean follow-up time was 17.7 ± 5.8 years (range, 13–32 years). Groups with satisfactory outcomes (66 hips) and unsatisfactory outcomes (19 hips) according to the Severin classification were compared. Factors predicting acetabular development were identified using univariate and multiple logistic analyses. Results: Univariate analysis showed a significant between-group difference in acetabular index (AI) at 2 months postoperatively, and in center-edge (CE) angle, cartilaginous AI (CAI), and cartilaginous CE angle at 5 years old (p < 0.05 each). In multiple logistic regression analysis, CAI at 5 years old represented a predictor of acetabular development after open reduction for DDH (odds ratio, 1.81; 95% confidence interval (CI), 1.04–3.13; p < 0.05). Area under the receiver operating characteristic curve for CAI at 5 years old was 0.93 (95%CI, 0.85–1.0), and the optimal cut-off was 10° (81.8% sensitivity, 92% specificity). Conclusions: A CAI ≥10° on hip arthrograms at 5 years old may offer a useful indicator of the need for corrective surgery following open reduction after walking age.