Original Article

Image-based robotic-assisted conversion from partial to total knee arthroplasty under functional alignment: Comparable outcomes to primary total knee arthroplasty

¹ School of Rehabilitation Health Sciences, University of Patras, Rio, 26504 Patras, Greece
² Department of Orthopaedic Surgery, “Hygeia” General Hospital of Athens, 151 23, Athens, Greece
³ Ankara Bilkent City Hospital, Department of Orthopedics and Traumatology, 06800 Ankara, Turkey
⁴ Univ Lyon, Claude Bernard Lyon 1 University, IFSTTAR, LBMC UMR_T9406, 25 Avenue François Mitterand, 69622 Lyon, Turkey
⁵ Orthopaedics Surgery and Sports Medicine Department, FIFA Medical Center of Excellence, Croix Rousse Hospital, Hospices Civils de Lyon, Lyon North University Hospital, 103 Grande Rue de la Croix Rousse, 69004 Lyon, France
⁶ Ortoklinik & Çankaya Hospital, 06700 Ankara, Turkey

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 2 September 2025
Accepted: 28 September 2025

Abstract

Introduction: Image-based robotic systems in total knee arthroplasty (TKA) allow for precise implant positioning and soft tissue balance through patient-specific preoperative planning. Functional alignment (FA) leverages the native soft tissue envelope to guide implant placement. However, its application in partial TKA conversion remains limited. This study evaluates the outcomes of image-based robotic-assisted partial-to-TKA conversion under FA principles, comparing them to a cohort of primary robotic TKAs. Methods: This retrospective study analyzed eight partial-to-TKA conversions performed using the image-based robotic system, with a minimum follow-up of 12 months. Demographics, implant constraints, intraoperative positioning, and postoperative outcomes were assessed. The mean age of the revision cohort was 73.3 ± 9.0 years, with a mean follow-up of 39.0 ± 11.5 months. A control group of 50 primary robotic TKAs was used for comparison. Results: Osteoarthritis progression (75%) and aseptic loosening (25%) were the primary reasons for revision. No stems were used, and only one patient (12.5%) required a tibial augment. Postoperative coronal alignment was 1.1° ± 1.9°, and functional outcomes (Knee Society Score-Knee: 84.5 ± 6.7, Knee Society Score-Function: 83.0 ± 7.1, Forgotten Joint Score: 72.8 ± 8.2) were comparable to the primary TKA cohort. No complications or revisions were recorded. Conclusion: FA-based robotic-assisted partial-to-TKA conversion yields functional and implant positioning outcomes comparable to primary robotic TKA while minimizing the need for stems, augments, or constrained implants. Further studies with larger cohorts are needed to confirm these findings. Level of evidence: III.