Acetabular component placement accuracy and short-term outcomes in total hip arthroplasty : comparison of robotic...

Precise acetabular component positioning is critical to the success of total hip arthroplasty (THA). Mako uses CT-based robotic assistance, whereas AR-hip is an augmented reality-based portable navigation system operating without preoperative CT and at lower costs. Although both systems improve accuracy, direct comparative data are scarce. We compared cup placement accuracy and short-term outcomes between Mako robotic arm and AR navigation systems.

This single-centre retrospective cohort study included 192 primary THAs (Mako, 147; AR navigation, 45). Cup placement accuracy was assessed three-dimensionally using postoperative CT, evaluating cup alignment (radiological inclination (RI) and anteversion (RA)) and position (centre of rotation (COR)). Short-term outcomes were evaluated using the Harris Hip Score (HHS), Japanese Orthopaedic Association hip score (JOA), Japanese Hip-disease Evaluation Questionnaire (JHEQ), Timed Up and Go (TUG), and 10 m walk test (10MWT). Baseline differences were adjusted using propensity score overlap weighting.

Mako demonstrated significantly superior accuracy than AR navigation, with smaller absolute errors in cup angles (RI 2.0° vs 3.0°, p = 0.045; RA 1.7° vs 2.4°, p = 0.005) and COR errors in the superior-inferior direction (1.5 mm vs 3.7 mm, p < 0.001). More cases were within 5° of planned angles with Mako (92.3% vs 77.7%, p = 0.030), while Lewinnek safe zone rates were high in both groups (99.5% vs 95.2%, p = 0.202). Short-term clinical scores and functional recovery at discharge were similar between groups. Operating time and blood loss were greater with Mako (122.6 vs 103.5 mins; 242.5 vs 171.5 ml; both p < 0.001). Subgroup analyses showed greater advantages of Mako in complex cases, such as obesity and developmental dysplasia of the hip, although interactions were insignificant.

Mako demonstrated superior cup placement accuracy and COR reconstruction compared with AR navigation, with comparable short-term clinical outcomes, potentially offering advantages in complex cases. However, further research is warranted to clarify its long-term outcomes and cost-effectiveness.