Acetabular development after open reduction to treat dislocation of the hip after walking age

Abstract Background Treatment of hip dislocation diagnosed after walking age is often difficult. We report the surgical treatment of these patients by open reduction with a soft tissue surgical procedure without osteotomy. Methods Thirty-eight children (43 hips) diagnosed with complete dislocation of the hip after walking age were included in this study. We radiographically analysed postoperative hip joint development up to 6 years of age. To assess the predictors of acetabular development, we evaluated the radiographs, using an acetabular index of ≤35° and a centre-edge angle of >5° at 6 years of age as satisfactory outcomes, and evaluated the advance of acetabular development over time. Results AI on the affected side was improved with time after open reduction. The diameter of the capital femoral ossific nucleus on the affected side was almost equivalent to that on the unaffected side at 6–12 months after surgery, after which the centre-edge angle improved gradually from one year after surgery. We compared hips classified as satisfactory to unsatisfactory at 6 years of age, and found that the centre-edge angle at one year after open reduction was significantly associated with acetabular development ( P  = 0.044). The cut-off value was −2° with sensitivity of 0.909 and specificity of 0.677. Conclusions The results of the current study suggest that initial development of the capital femoral ossific nucleus after open reduction would be followed by improved joint congruity, and that this would facilitate acetabular development. The centre-edge angle at one year after surgery could be regarded as a potential predictor of acetabular development in open reduction surgery for late-diagnosed developmental dysplasia of the hip cases.