Original Article

Accuracy and functional outcomes of robot-assisted total knee arthroplasty combined with inverse kinematic alignment: a 500-case cohort study

CHU Saint-Étienne, Avenue Albert Raimond, 42270 Saint-Priest-en-Jarez, France

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Received: 28 May 2026
Accepted: 7 June 2026

Abstract

Background: Robot-assisted techniques combined with inverse kinematic alignment in knee arthroplasty allow for improved intraoperative management of lower limb alignment, particularly regarding the Hip–Knee–Ankle (HKA) angle. Postoperative HKA outliers, associated with mechanical and functional complications, may be reduced. Our study aims at determining the incidence rate of HKA outliers at 12 months postoperatively in patients who underwent Robot-Assisted Total Knee Arthroplasty (RA-TKA). Secondary objectives were to evaluate functional outcomes, postoperative HKA deviation, and complication rates at 12 months. Methods: We conducted a retrospective cohort study including all RA-TKA procedures performed in our center between 2020 and 2022. The arthroplasty technique was assisted by the Stryker MAKO™ robotic system combined with inverse kinematic alignment. Patients underwent clinical follow-up for 12 months, enabling the collection of radiological, clinical, and functional data. An HKA outlier was defined as a deviation greater than 3° at 12 months compared to the target HKA obtained immediately postoperatively, measured by the Stryker MAKO™ system. Results: The cohort included 500 arthroplasties, of which 487 provided complete data. The outlier rate obtained with RA-TKA was 2.05%. The mean difference between immediate postoperative HKA (HKA-D0) and HKA at 12 months (HKA-M12) was 1.3° (SD ± 1.2°). At follow-up, mean functional scores were 214 (SD ± 31) for KSS-2011 and 82 (SD ± 14) for KOOS. Mean range of flexion was 127° (SD ± 11°). Regarding safety outcomes, 1.2% of patients experienced sepsis, and 2.3% developed joint stiffness requiring mobilization under general anesthesia. Conclusions: This large cohort study demonstrates a low incidence of HKA outliers (only 2.05%) at 12 months postoperatively. Functional scores and range of motion indicate good recovery. Although this observational and non-comparative study does not allow definitive conclusions, the findings provide encouraging insights into alignment and functional outcomes following the combination of robot-assisted surgery and inverse kinematic alignment. Level of Evidence: III. Retrospective Cohort.