The Efficacy and Safety of a Novel Extramedullary Guide Coordinated with 3D Surgical Assistive Software for Total Knee Arthroplasty: an Open-Label Single-Arm Trial

To improve component-placement accuracy in total knee arthroplasty, we developed two devices: an original extramedullary patient-specific guide for the femur and an original extramedullary universal guide for the tibia (EM-TIBIA). We also developed a new function in ZedView, a three-dimensional surgical assistive software, that provides the parameters necessary to install the EM-TIBIA. Compared with conventional manual methods based on X-ray two-dimensional images or ZedView, these newly developed devices function as an extramedullary intraoperative support guide in conjunction with ZedView, simplifying surgical procedures. We conducted a study to evaluate the efficacy and safety of the surgery using the new guides and software function. Nineteen patients underwent surgery. On the femoral side, the mean absolute difference of the installation alignment was within 3° for all parameters. On the other hand, on the tibial side, the mean absolute difference from the preoperative plan for the rotation was 5.26±5.30°. The proportion of patients whose difference fell within ±3° was 52.6% (95% confi dence interval: 28.9 to 75.6%), and did not meet the pre-specified criteria for efficacy (P=0.261). No serious adverse events were reported, and no excessive bleeding, thrombosis, infections, or intraoperative or postoperative fractures were noted. The two new guides can easily reproduce the preoperative plan as 3D intraoperative support jigs, but errors can occur on the tibia side due to soft tissue that is not recognized by CT, creating problems in installation accuracy.