# MAKO Robotic-Arm-Assisted Versus Conventional Dual-Incision Total Hip Arthroplasty: A Propensity-Score-Matched Retrospective Study

## TL;DR

This study compares robotic-assisted and conventional hip replacement surgeries, finding that robotic assistance improves implant placement accuracy but not early patient recovery.

## Contribution

The study demonstrates that robotic-arm assistance in hip surgery improves radiographic precision and biomechanical restoration without enhancing short-term functional outcomes.

## Key findings

- Robotic assistance resulted in smaller deviations from planned acetabular orientation and higher proportion of cups within the Lewinnek safe zone.
- Functional outcomes like HHS and OHS were comparable between robotic and conventional groups at six months.
- Greater radiographic precision was independently linked to better patient-reported outcomes.

## Abstract

Background: This propensity-score-matched retrospective study compared radiographic accuracy and short-term functional outcomes between MAKO robotic-arm-assisted and conventional dual-incision minimally invasive total hip arthroplasty (THA). It was hypothesized that robotic assistance would provide superior radiographic accuracy, primarily smaller absolute deviations from the planned acetabular inclination and anteversion and a higher proportion of cups within the Lewinnek safe zone, without improving early functional outcomes. Methods: Consecutive patients who underwent dual-incision total hip arthroplasty were retrospectively analyzed at two affiliated institutions between March 2023 and March 2025. The study included 52 robotic-arm-assisted cases. The dual-incision technique used an anterolateral incision for acetabular preparation and cup implantation and a posterolateral incision for femoral preparation and stem implantation. Propensity score matching (1:1) generated 52 balanced pairs for age, sex, body mass index (BMI), preoperative Harris Hip Score (HHS), ASA class, and diagnosis. Operative time, blood loss, radiographic accuracy (acetabular anteversion, inclination, leg-length discrepancy [LLD], femoral and combined offsets, and stem subsidence), and functional outcomes (HHS, Oxford Hip Score [OHS], Forgotten Joint Score-12 [FJS-12]) were compared. Results: The robotic group achieved smaller deviations from the planned anteversion (1.15° vs. 3.0°, p < 0.001) and inclination (1.33° vs. 4.5°, p < 0.001), with a higher proportion of cups within the Lewinnek safe zone (98.1% vs. 82.7%, p = 0.016). Significant improvements were also seen in femoral stem subsidence (p = 0.006) and offset restoration, although the reduction in leg-length discrepancy did not reach statistical significance. Operative time was longer (77.8 vs. 65.0 min, p = 0.001), while blood loss and 6-month functional scores were comparable (HHS, p = 0.144; OHS, p = 0.328). Multivariable regression confirmed that greater deviations in acetabular orientation, higher LLD, and increased subsidence were independent predictors of poorer functional outcomes. Conclusions: MAKO robotic-arm assistance was associated with improved radiographic accuracy and biomechanical restoration in dual-incision THA, but no direct short-term functional advantage was observed. Greater radiographic precision was independently associated with better patient-reported outcomes, suggesting that technical precision is a key factor in optimizing early postoperative outcomes, highlighting the importance of technical accuracy in total hip arthroplasty.