Objective To evaluate the effect of preoperative digital planning in acetabular reconstruction of total hip arthroplasty (THA) for development dysplasia of the hip (DDH). Methods A prospective study was performed on 42 patients with DDH undergoing primary THA between January 2009 and December 2011. The patients were divided into 2 groups according to whether preoperative digital planning was made or not; before operation, conventional imaging method was used in 23 cases (group A), and TraumaCad software was used for preoperative digital planning in 19 cases (group B). There was no significant difference in gender, age, body mass index, DDH classification, and preoperative Harris score between 2 groups (P gt; 0.05). The operation time, amount of bleeding, and postoperative complication were observed. After 7 days of operation, X-ray films were done to measure the vertical location, horizontal location, radiographic anteversion angle, radiographic inclination angle, and prosthesis size by TraumaCad software. The qualified rate of cup placement was compared between 2 groups. Coincidence rate of cup size between preoperative predicted by the digital planning and actually implanted in group B also was calculated. Results The operation time and the amount of bleeding were (119.25 ± 47.16) minutes and (410.00 ± 200.39) mL in group A and were (155.31 ± 84.03) minutes and (387.50 ± 251.99) mL in group B respectively, showing no significant difference between 2 groups (P gt; 0.05). Incision infection and prosthetic anterior dislocation occurred in 1 case of group A respectively, prosthetic posterior dislocation in 1 case of group B. The patients were followed up 1 year and 1 month to 4 years and 1 month (mean, 2 years and 8 months ) in group A, and 1 year and 3 months to 4 years (mean, 2 years and 7 months) in group B. At last follow-up, the Harris scores were 91.09 ± 5.35 in group A and 91.72 ± 3.48 in group B, which were significantly increased when compared with preoperative scores (P lt; 0.05), but no significant difference was found between 2 groups (t=0.41, P=0.69). The qualified rate of cup placement of group B (78.95%, 15/19) was significantly higher than that of group A (43.48%, 10/23) (χ2=5.43, P=0.02); the coincidence rate of the cup size between preoperative predicted by the digital planning and actually implanted was 68.42% (13/19). ConclusionPreoperative digital planning can further optimize the acetabular reconstruction in THA for DDH.