When to Combine Acetabular Osteotomy in Patients With Proximal Femoral Deformity Causing Residual Hip Dysplasia/Subluxation After Reduction of Developmental Dysplasia of the Hip.

BACKGROUND

After the successful reduction of developmental dysplasia of the hip, residual hip dysplasia may persist and lead to early osteoarthritis. Femoral and/or acetabular osteotomy has been used to address this problem. The purpose of this study is to determine the indication of femoral versus combined femoral-acetabular osteotomy in the management of residual hip dysplasia.

METHODS

Fifty-five patients with unilateral dislocated-type dysplasia of the hip, who had residual hip dysplasia after reduction, underwent femoral osteotomy with or without acetabular osteotomy before 8 years of age, and were followed for more than 2 years and over 8 years of age, were the subjects of this retrospective study. Twenty-eight patients underwent femoral osteotomy only at a median age of 34 months (group F), and 27 underwent combined femoral-Dega osteotomy at a median age of 49 months (group C). Seventeen patients in group F and 4 in group C had an additional osteotomy due to persistent hip dysplasia. Acetabular index (AI), lateral center-edge angle, and center-head distance difference were measured on serial radiographs. The z-value of AI (Z AI ) was calculated. At the latest follow-up, patients in group F with Severin I/II who did not have an additional osteotomy were considered satisfactory, and patients with Severin III/IV or those who had an additional osteotomy were considered unsatisfactory. Preoperative variables were tested for the difference between satisfactory and unsatisfactory cases. Receiver operating characteristic analysis was performed to delineate a cutoff value of a significant parameter dividing the outcome.

RESULTS

AI and Z AI before index osteotomy were significant parameters predicting a satisfactory outcome in group F. Receiver operating characteristic analysis returned a cutoff value of Z AI 2.6 (Area Under the Curve=0.86, P =0.001). Eight of 12 cases (66.7%) with Z AI <2.6 in group F achieved a satisfactory outcome, whereas only 2 of 14 cases with Z AI ≥2.6 in group F did ( P =0.02).

CONCLUSION

Z AI 2.6 may serve as a threshold to combine acetabular osteotomy with femoral osteotomy in the management of residual hip dysplasia before 8 years of age.

LEVEL OF EVIDENCE: Therapeutic III.