The Difference of Acetabular Cup Orientation Between Two Surgical Sides After Primary Total Hip Arthroplasty by Right-handed Surgeons

Abstract Background: We performed the retrospective cohort study to compare the acetabular cup orientation, including anteversion angle (AA) and inclination angle (IA), of dominant hand side and non-dominant hand side after primary total hip arthroplasty (THA) by right-handed orthopedic surgeons. Methods: Between January 2018 and December 2018, 290 patients who aged below 60 years and underwent primary THA were retrospective screened. Patients who had hemiarthroplasty, previous hip surgery, ankylosing spondylitis, developmental dysplasia of hip (DDH, Crowe type-Ⅲ and type-Ⅳ), severe comorbidity, missing information, inferior quality radiographs were excluded. According to the surgery side, all patients were divided into left group and right group. Postoperative plain radiographs were analyzed to compare the AA and IA between left and right side. Univariate and stepwise multivariable linear regression to control included confounding factors. Stratified analysis was performed to identify whether the operation approach can affect the result, including anterolateral (ALA) and posterolateral approach (PLA). Results: The mean AA was 17.7° (range 6.0° to 30.0°) and 21.0° (range 9.5° to 35.0°) for the left and right side respectively. The mean difference was 3.28° (95% CI: 1.92 – 4.64; P<0.001). The mean IA was 41.1° (range 24.0° to 59.0°) and 40.1° (range 20.5° to 56.0°) for the left and right side respectively (P=0.314). 113 patients' AA within the “safe zone” in the left (93.4 %), while the right was 93 patients (82.3 %) (P=0.009). 95 patients' IA within the “safe zone” in the left (78.5 %), while the right was 97 patients (85.8 %) (P=0.144). The IA of ALA group was smaller than PLA group in both sides. The mean difference was 3.98° (95% CI: 1.22 - 6.74; P=0.005). Conclusions: We concluded that AA in left side may be more accurate than right side after primary THA by right-handed surgeons. The IA was no difference between the two sides, while it was smaller in ALA than in PLA. The results are still needed to be verified in future.