Revision of Unicompartmental Knee Arthroplasty to Total Knee Arthroplasty Using the CORI

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.