International Orthopaedics - 2026-04-14 - Journal Article
Robotic-assisted total knee arthroplasty reduces alignment variability and rotational outliers compared with conventional techniques.
Endara Urresta F, Peñaherrera-Carrillo C, Barros Castro A, Lustig Md PhD PS
Topics
Key Takeaway
Robotic-assisted TKA reduced coronal outliers (>3° from target) from 21.3% to 6.7% and rotational outliers from 24.0% to 8.7% compared with conventional technique, without changing mean HKA alignment.
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Summary
This retrospective comparative cohort asked whether robotic-assisted TKA improves surgical reproducibility beyond mean alignment accuracy versus conventional technique under identical mechanical alignment targets. Both groups achieved equivalent mean HKA (0.4° robotic vs. 0.6° conventional; p=0.41), but robotic assistance reduced SD from 2.8° to 1.6° (p<0.001), coronal outlier rate from 21.3% to 6.7%, and rotational outlier rate from 24.0% to 8.7%. Multivariable logistic regression identified conventional technique as an independent predictor of outlier status.
Key Limitation
The study reports no functional outcomes or patient-reported measures, so whether the demonstrated reduction in alignment outliers translates to improved clinical results or reduced revision rates remains unestablished.
Original Abstract
INTRODUCTION
Precise component positioning in total knee arthroplasty (TKA) influences tibiofemoral mechanics, patellofemoral tracking, and soft-tissue balance. Although robotic-assisted TKA improves alignment accuracy, most comparative studies emphasize mean alignment rather than surgical reproducibility. Variability and outlier rates may better reflect precision. This study compared alignment variability and the proportion of coronal and rotational outliers between robotic-assisted and conventional TKA performed under identical mechanical alignment targets.
METHODS
A retrospective comparative cohort included 300 primary TKAs (150 robotic-assisted, 150 conventional) performed by the same surgical team between 2022 and 2025. Postoperative hip-knee-ankle (HKA) alignment was measured on standardized long-leg radiographs. Rotational alignment was evaluated by computed tomography in a predefined subgroup. Variability was quantified using standard deviation and equality of variance tested with the Brown-Forsythe method. Outliers were defined as deviation > 3° from target alignment. Multivariable logistic regression identified predictors of outlier status.
RESULTS
Mean postoperative HKA did not differ between groups (0.4° ± 1.6° robotic vs. 0.6° ± 2.8° conventional; p = 0.41). Robotic-assisted TKA showed lower dispersion (SD 1.6° vs. 2.8°; p < 0.001). Coronal outliers occurred in 6.7% of robotic cases versus 21.3% of conventional cases (p < 0.001). Rotational mismatch > 3° was less frequent with robotic assistance (8.7% vs. 24.0%; p = 0.006).
CONCLUSIONS
Robotic-assisted TKA reduced alignment variability and outliers without altering mean alignment, suggesting improved surgical reproducibility.