Robot-Assisted Total Knee Arthroplasty (RATKA) and its more Automated Versions: Active RATKA
Keywords:
Arthroplasty, Replacement, Knee; Robotic Surgical Procedures; Osteoarthritis, Knee; Postoperative Complications.Abstract
Background: Robotic-assisted total knee arthroplasty (RATKA) improves alignment accuracy over conventional instrumentation, but direct comparative evidence between fully autonomous (Active) and surgeon-guided (Semi-active) robotic platforms remains scarce despite their differing cost, workflow, and regulatory implications. This study compared post-operative alignment accuracy and secondary clinical, functional, and economic outcomes between Active and Semi-active RATKA.
Methods: In this prospective, multicentre study, 120 patients undergoing primary unilateral total knee arthroplasty were allocated to Active or Semi-active RATKA (60 per arm) by randomisation or propensity-matched cohort design across four centres from November 2025 to March 2026. The primary outcome was post-operative hip–knee–ankle (HKA) mechanical-axis deviation. Secondary outcomes included component positioning, intra-operative parameters, functional and patient-reported scores to one year, complications, inter-surgeon variability, and per-case direct cost.
Results: Active RATKA achieved significantly smaller mean HKA deviation and fewer alignment outliers than Semi-active RATKA. Component positioning was statistically equivalent across five of six planes, with Semi-active RATKA showing more accurate femoral rotational alignment. Active RATKA required longer operative time and higher direct cost. No significant between-group differences emerged in functional scores, complications, readmission, revision, or inter-surgeon variance at one year, and WOMAC scores were numerically worse with Active RATKA despite its alignment advantage.
Conclusion: Active RATKA improves mechanical-axis alignment precision over Semi-active RATKA, but this advantage did not translate into superior early functional, safety, or cost outcomes, and was accompanied by an isolated deficit in femoral rotational accuracy. Alignment gains alone do not currently justify preferential adoption of fully autonomous platforms; adequately powered trials with longer follow-up are needed before firm technology-adoption decisions can be made.
