[Effect of the acetabular cup positioning and leg length restoration after total hip arthroplasty using...

Objective: To assess the improvement of the robotic-assisted total hip arthroplasty (rTHA) regarding the acetabular cup positioning and the leg length restoration. Methods: Clinical data of 246 patients undergoing primary unilateral THA from September 2019 to June 2021 in Peking University Third Hospital were retrospectively reviewed, including patients treated with rTHA (n=113) and conventional THA (cTHA) (n=133). Thirty-seven male patients along with 76 females were enrolled into the rTHA group with a mean age of (62±9) years. In comparison, the average age of cTHA group was (60±12) years with 59 males and 74 females. The postoperative inclination and anteversion of the acetabular cup and the rate of acetabular cup within the Lewinnek and Callanan "safe zone" were documented and analyzed. For the patient with normal or surgically restored contralateral hip, the leg length discrepancy was also measured and compared between the two groups. Results: The overall mean postoperative inclination and anteversion was 39.0°±5.5° and 14.1°±5.1°, respectively. No statistically significant difference was found between the rTHA and cTHA group regarding postoperative inclination (39.3°±2.9° vs 38.7°±7.0°, P=0.383) and anteversion (13.4°±4.3° vs 14.7°±5.6°, P=0.054). In rTHA group, 97.3%(110/113) of the cups were implanted within the Lewinnek"safe zone"(75.9%(101/133) in cTHA group) and 94.7%(107/113) were within the Callanan"safe zone"(66.2%(88/133) in cTHA group), and those were both higher in rTHA group (both P<0.01). There was no significant difference in postoperative leg length discrepancy between the two groups (P=0.445). Meanwhile, 29(23.0%) cases of cTHA group had leg length discrepancy more than 5 mm, and it was 9.7%(9/93) in rTHA group. Conclusion: It indicated the benefit of rTHA in acetabular cup positioning as well as the leg length restoration.