Evaluation of cup placement accuracy in computer assisted total hip arthroplasty

Abstract

Background

Total hip arthroplasty (THA) accuracy has improved significantly with various advances in computer-assisted equipment (CAE), including robotic systems, computed tomography (CT) navigation, and portable navigation. However, no studies have directly compared the accuracy of acetabular cup placement and its impact on patient-reported outcome measures (PROMs) across these three CAE systems. In this study, we aimed to evaluate cup placement accuracy and PROMs in THA using different CAE systems.

Methods

This retrospective analysis included 196 patients (202 hip joints) who underwent THA with three CAE systems from May 2021 to August 2023. Patients were categorized into the robotic system (73 hips), CT navigation (83 hips), and portable navigation (46 hips). Postoperative CT scans measured cup placement angles—radiographic inclination (RI) and radiographic anteversion (RA) —and compared them with preoperative target angles. Anterior-posterior (AP) cup position differences were evaluated by measuring the distance between the acetabular and cup center in the axial view of the postoperative CT scans. PROMs were evaluated using the Japanese Orthopaedic Association Hip Disease Evaluation Questionnaire (JHEQ) at 3 and 12 months.

Results

Demographic characteristics, including age, sex, primary disease, and Body Mass Index, were similar across groups. The robotic system exhibited significantly smaller deviations in ΔRI and ΔRA compared to CT navigation and portable navigation. AP cup position differences were also smaller in the robotic system versus portable navigation; however, the difference between the robotic and CT navigation systems was not statistically significant. Despite the superior precision of cup placement in the robotic system, no significant differences in JHEQ scores were observed among the groups at 3 and 12 months.

Conclusion

Robotic systems demonstrated superior accuracy in cup placement. However, short-term PROMs did not significantly differ, suggesting that PROMs may not solely depend on accurate cup placement. Future research should investigate additional factors influencing PROMs.