Revision of Unicompartmental Knee Arthroplasty to Total Knee Arthroplasty Using the CORITM Imageless System: A Step-By-Step Surgical Technique

Abstract

Conversion of unicompartmental knee arthroplasty (UKA) to total knee arthroplasty (TKA) is technically demanding due to altered anatomy, asymmetric bone loss, and soft-tissue imbalance, often necessitating stems or augments. Robotic-assisted TKA may enhance the accuracy of bone resection and ligament balancing, potentially facilitating bone preservation in this complex setting. This article describes a step-by-step surgical technique for imageless robotic-assisted conversion of a failed medial UKA to TKA using the CORI™ system in a case of early aseptic loosening. The workflow is based on intraoperative surface mapping and dynamic kinematic assessment. The knee is initially registered as a native joint to capture global alignment and soft-tissue behavior, followed by additional reference point acquisition after implant removal to accurately quantify bone loss. This strategy enables patient-specific planning of femoral and tibial resections, real-time adjustment of component positioning, and controlled gap balancing throughout the range of motion. The principal innovation of this technique is the dual-stage imageless robotic workflow, combining pre-explant native kinematic registration with post-explant defect mapping and iterative re-planning. In the presented case, conversion was successfully achieved without the use of stems or augments. Imageless robotic-assisted UKA-to-TKA conversion using this technique appears feasible and reproducible. By combining native kinematic mapping with quantitative defect assessment, this workflow may facilitate accurate implant positioning, controlled gap balancing, and bone-preserving reconstruction in selected cases.