Accuracy of acetabular cup placement during anterolateral supine total hip arthroplasty using intraoperative fluoroscopy: a retrospective study

Background: In our institution, total hip arthroplasty (THA) is performed using the anterolateral supine (ALS) approach with intraoperative fluoroscopy. This study aimed to investigate and review the accuracy of acetabular cup placement in ALS-THA using intraoperative fluoroscopy. Methods: A total of 142 patients with 154 joints (mean age 64.3 years, 30 males and 112 females) underwent ALSTHA with intraoperative fluoroscopy at the same institution. The target angle of the cup position was set at 40 degrees for radiographic inclination (RI) and 5 degrees-25 degrees for radiographic anteversion (RA) based on the functional pelvic plane according to the pelvic motion during individual postural changes. The cup position angle was measured using postoperative computed tomography, and the error in the target angle was investigated. Results: The target angle of RI was 40 degrees, and the postoperative RI was 39.3 degrees +/- 4.3 degrees. The target angle of the RA was 17 degrees +/- 2.6 degrees, and the postoperative RA was 20.6 degrees +/- 3.7 degrees. The absolute values of the error from the target angle were 3.6 degrees +/- 2.5 degrees for RI and 4.2 degrees +/- 3.3 degrees for RA. For RI and RA, 67.5% (104/154 joints) were within +/- 5 degrees of the target and 96.1% (148/154 joints) were within +/- 10 degrees. Conclusions: The accuracy of cup positioning in ALS-THA using intraoperative fluoroscopy was good and appeared comparable to that of various navigation systems.