Functional positioning in robotic medial unicompartmental knee arthroplasty: a step-by-step technique

Abstract

Unicompartmental knee arthroplasty (UKA) compared to total knee arthroplasty, offers several benefits, though it is associated with a higher revision rate, primarily due to suboptimal implant positioning. Recent advances in robotic-assisted techniques have contributed to more personalized and reproducible procedures. Functional Positioning (FP), a three-dimensional alignment concept, introduces a tailored approach based on a surgical technique that is both effective and reproducible. This article presents a step-by-step surgical technique for medial UKA using FP principles in combination with an image-based robotic system. The technique ensures accurate preoperative planning, real-time intraoperative adjustments, and precise component placement. The key steps of this surgical technique include achieving congruent contact points between the femur and tibia under load across the full range of motion, positioning the implant based on the compliance of the medial soft tissues, planning for a targeted laxity that results in an "eagle-wing" appearance, and the use of robotic tools to map cartilage for optimal resurfacing. Future studies will help refine FP strategies and further optimize outcomes in these patients.