Objective:To investigate the clinical efficacy of preoperative three-dimensional (3D) reconstruction planning in total hip arthroplasty for development dysplasia of the hip secondary to osteoarthritis.Methods:A total of 80 patients with osteoarthritis secondary to Crowe I-III developmental dysplasia of the hip who underwent primary unilateral total hip arthroplasty from October 2019 to March 2021 were retrospectively analyzed, including 18 males and 62 females and the mean age was 55.7±10.4 years (range 41-72 years). Forty patients in the 3D group, the prosthesis type and installation angle were planed on the 3D reconstruction software based on the full-length CT scan data of the lower limbs, and the length difference of the lower limbs and hip offset were calculated. Forty patients in the control group underwent preoperative planning using conventional film measurement, and lower limb length was judged based on the preoperative measurement data and intraoperative comparison of both lower limbs. The difference of postoperative leg length, hip offset, hip function score, operating time, intraoperative blood loss, and incidence of complications were compared between the two groups.Results:All 80 patients completed the surgery successfully and the follow-up time was up to 3 months after operation. The 3D group was better than the control group in operation time (70.9±7.7 min vs. 81.6±13.3 min, t=-4.91, P<0.001), the difference of postoperative lower limb length (2.78±1.31 cm vs. 5.35±2.15 cm, t=-5.74, P<0.001), and hip function score at 1 week after operation (75.67±3.35 vs. 67.35±4.21, t=12.33, P=0.002), with statistically significant differences. In the 3D group, 95% of acetabular prosthesis and 90% of femoral stem components were consistent with the planned model, while the rate were only 75% and 68% in the control group, and the difference was statistically significant (χ 2=7.51, P=0.023; χ 2=14.92, P=0.005). There were no intraoperative complications such as vascular and nerve injury, and no postoperative complications such as dislocation or periprosthetic infection in all 80 patients. Conclusion:3D preoperative planning assisted total hip arthroplasty in the treatment of Crowe I-III developmental dysplasia of the hip secondary to osteoarthritis can improve the accuracy of the operation, and has a good clinical effect on restoring the leg length and hip offset.