Prediction of acetabular development after closed reduction by overhead traction in developmental dysplasia of the hip

Background The prediction of acetabular development after reduction of developmental dysplasia of the hip (DDH) is important to ensure optimal timing of acetabuloplasty and to avoid unnecessary surgery. The objective of this study was to find early and reliable predictors of future acetabular dysplasia in the hips reduced by overhead traction (OHT). Methods We retrospectively reviewed 45 hips in 40 patients treated by OHT for DDH without additional procedures. The average age at the time of closed reduction was 9.3 months, and the average age at the latest examination was 17.3 years. Residual hip dysplasia at skeletal maturity was defined according to Severin's classification. The following variables were evaluated as possible predictors of the final outcome: age at reduction, severity of the dislocation, serial measurements of acetabular index (AI), center-edge angle of Wiberg (CE), and the center-head discrepancy distance (CHDD). Results Sixty-two percent of the hips had satisfactory results in Severin I/II and 38% had unsatisfactory results in Severin III. Bilateral DDH showed significantly poorer outcome than unilateral DDH. The average AI of the unsatisfactory group was significantly greater than that of the satisfactory group at 4 years or more after reduction. Similarly, the average CE of the satisfactory group was greater than that of the unsatisfactory group at 5 years or more after reduction. In unilateral cases, the AI and the CE of the uninvolved hip at 1 year after reduction also correlated with the final outcome of the involved hip. Conclusions The AI of 4 years and the CE of 5 years after reduction were the earliest predictors of the final outcome. Careful consideration for the need of acetabuloplasty would be given at 4 or 5 years after reduction by OHT. Bilateral DDH and poor acetabular coverage of the uninvolved hip in unilateral DDH were the prognostic factors of unfavorable acetabular development of the dislocated hip. This work was done at the Department of Orthopaedic Surgery, Nagoya University School of Medicine, Nagoya, Japan.