Long‐Term Efficacy of Restricted Quantitative Superior Placement Technique in Total Hip Arthroplasty for Severe Developmental Dysplasia of the Hip: An 8‐ to 10‐Year Follow‐Up of a Prospective Randomized Controlled Trial

Objective Total hip arthroplasty (THA) in patients with developmental dysplasia of the hip (DDH), particularly those with Crowe II or III dysplasia, is challenging because of abnormal acetabular morphology and deficient bone stock. This study aims to compare the long‐term outcomes of true anatomic versus restricted quantitative superior placement of the acetabular component. Methods This prospective, patient‐ and assessor‐blinded randomized controlled trial was conducted from August 1, 2013, to July 31, 2024. Forty‐four hips were allocated 1:1 to true anatomic center placement or restricted quantitative superior placement. Restricted quantitative superior placement was defined as positioning the cup center no more than 15 mm superior to the true anatomic center. Harris Hip Score (HHS), 36‐Item Short Form Health Survey (SF‐36), complications, perioperative outcomes, and radiographic parameters were assessed. The mean final follow‐up was 8.94 years. Independent‐samples t‐ test, Mann–Whitney U test, Chi‐square test, and Fisher's exact test were used for statistical analysis. Results No statistically significant between‐group difference was observed in prosthetic complications. No revisions were recorded among the 36 hips that completed the 8–10‐year follow‐up. At the 8–10‐year follow‐up, the restricted quantitative superior placement group had a higher HHS than the true anatomic center group (93.70 ± 5.20 vs. 86.73 ± 11.62, p = 0.024); multiple imputation analysis showed a mean difference of 5.79 points (95% CI, 0.46–11.13; p = 0.034). Significant between‐group differences were also observed at 2 and 7 years. SF‐36 scores did not differ significantly between groups. Morselized bone grafting was required in 45.5% of the anatomic center group and 40.9% of the restricted quantitative superior center group. Structural grafting was used in 18.2% and 9.1%, respectively. Radiographic analysis showed higher center of rotation height and less limb lengthening in the restricted quantitative superior center group. Conclusions Restricted quantitative superior placement within 15 mm above the true anatomic center was associated with higher long‐term HHS, with no significant difference in prosthetic complications and no revisions recorded among the 36 hips that completed the 8–10‐year follow‐up. It may represent a potential reconstructive option for patients with DDH. Trial Registration : Chictr.org , ChiCTR‐TRC‐1404388; https://www.chictr.org.cn/showproj.html?proj=5182