Improved accuracy of functional alignment restoration with robotic-assisted total knee arthroplasty : A quasi-randomized controlled trial.

Background and objectives: This quasi-randomized controlled trial compared robotic-assisted and conventional total knee arthroplasty (TKA) in restoring patient-specific coronal alignment according to a functional alignment philosophy. Outcomes included preservation of the anatomical hip-knee-ankle angle (aHKA), mechanical axis deviation (MAD), and component positioning. Subgroup analyses assessed consistency in valgus and varus morphotypes.

Material and methods: A single-blind parallel group quasi-RCT was conducted at the Department of Orthopedic Surgery, Eifelklinik St. Brigida, Germany (2021-2025). Patients underwent TKA following identical perioperative pathways. All procedures used a medial parapatellar approach and Smith & Nephew Legion Genesis II implants.

Results: A total of 692 patients were enrolled (346 robotic, 346 freehand). Baseline characteristics were comparable. Postoperative HKA was similar between groups, but the robotic group achieved a significantly smaller aHKA delta (2.58° vs 4.49°, p = 0.002). Robotic-assisted TKA preserved joint line alignment more consistently in valgus (2.63° vs 5.72°, p = 0.03) and varus knees (2.56° vs 4.22°, p = 0.004). The MAD control was improved, while differences n the mechanical lateral distal femoral angle (mLDFA) and mechanical medial proximal tibial angle (mMPTA) were not significant.

Conclusion: Robotic-assisted TKA enhanced accuracy in reproducing native joint line orientation, offering more consistent preservation of joint line obliquity in both valgus and varus morphotypes, thus supporting its role in personalized alignment strategies.