Robotic total knee arthroplasty. The accuracy of CT-based component placement

Accurate alignment of the components in total knee arthroplasty is important. By use of postoperative CT controls, we studied the ability of a robotic effector to accurately place and align total knee arthroplasty (TKA) components according to a purely CT-based preoperative plan. Robotic TKA was performed in 13 patients (6 men) with primary gonarthrosis. Locator screws were placed into femur and tibia under spinal anesthesia. A CT-scan including the femoral head, knee and ankle was performed. In the preoperative planning software, virtual components were positioned into the CT volume. In a second operation, the robot milled femur and tibia with a high-speed milling tool according to the preoperative plan. On the 10th day, CT controls were performed following the same protocol as preoperatively. The mean deviation of the postoperative from the preoperatively planned mechanical axis was 0.2 degrees (95% CI: -0.1 degrees to 0.5 degrees ). The accuracy of angular component placement in frontal, sagittal and transverse planes was within +/-1.2 degrees , and the accuracy of linear component placement in mediolateral, dorsoventral and caudocranial directions was within +/-1.1 mm. Robotic TKA allows placement of components with unparalleled accuracy, but further development is mandatory to integrate soft-tissue balancing into the procedure and make it faster, easier and cheaper.