Objective:To investigate the mid-and long-term clinical efficacy of modified Colonna arthroplasty in the treatment of unilateral dislocation type developmental dysplasia of hip (DDH) in adolescents.Methods:A total of 28 adolescent DDH patients with unilateral dislocation who underwent modified Colonna capsular arthroplasty from January 2016 to January 2018 in the 920th Hospital of Joint Logistics Support Force of People's Liberation Army were retrospectively analyzed. There were 4 males and 24 females, aged 16.5±5.0 years (range, 10-25 years). The mean body mass index was 21.2±1.1 kg/m 2 (range, 18.7-24.1 kg/m 2). According to DDH classification, 10 cases were Tonnis type III and 18 cases were Tonnis type IV. The postoperative lateral center-edge angle, acetabular coverage, femoral anteversion angle and leg length discrepancy were measured. The operation time, intraoperative blood loss, visual analogue scale (VAS) of hip pain, Harris hip score (HHS) and congenital dislocation of the hip score were recorded. Results:All patients successfully completed the operation and were followed up for 72.1±5.2 months (range, 60-84 months). The operation time was 81.6±4.3 min (range, 70-90 min), the intraoperative blood loss was 177.5±12.6 ml (range, 160-200 ml), and the hospital stay was 6.8±0.7 days (range, 6-9 days). The VAS score of the hip joint was 1.8±0.6 before operation and 2.3±0.6 at the last follow-up, and the difference was not statistically significant ( t=2.845, P=0.224). The preoperative HHS score was 57.1±5.9, and it increased to 87.3±4.0 at the last follow-up, and the difference was statistically significant ( t=-22.141, P=0.001). At the last follow-up, the femoral anteversion angle was 17.0°±1.5°, which was lower than that before operation 41.6°±2.4°, with a statistically significant difference ( t=-44.868, P=0.008). The leg length discrepancy was 10.2±2.3 mm, which was lower than that before operation (26.4±6.1 mm), with a statistically significant difference ( t=-12.892, P<0.001). The lateral center-edge angle was 28° (26°, 30°), and the acetabular coverage rate was 78% (76%, 79%). The curative effect evaluation standard score of congenital dislocation of the hip was 24 (16.7, 25.7) points, including 7 excellent cases, 14 good cases, 4 fair cases, and 3 poor cases. The excellent and good rate was 75% (21/28). Conclusion:The modified Colonna arthroplasty for the treatment of unilateral dislocation DDH in adolescents has good mid-and long-term hip function recovery and radiographic improvement.