Incorrect resection of the patella during total knee arthroplasty (TKA) can lead to anterior knee pain (AKP), patellar maltracking, patellofemoral impingement, patellar fracture, component loosening, and reduced range of motion. Computer-assisted surgery (CAS) systems for the tibia and femur improve cut accuracy, but no CAS system is available for patellar resection. We developed a system that included an optoelectronic localizer, marker arrays on the patella and instruments, and navigation software. Three users performed resections on artificial patellae mounted in a simulated surgical setup using five techniques (two CAS, three conventional), each repeated at least three times in randomized order. Computer-assisted patellar resection produced better or equal cut symmetry compared to conventional techniques, particularly superoinferiorly. Using CAS with a sawguide produced better results than using CAS freehand with an oscillating saw. This study showed the feasibility of computer-assisted patellar resection, which could lead to reduced pain and complications after TKA. The feedback provided could also make patellar CAS a valuable training tool. ß

Incorrect patellar resection during total knee arthroplasty can lead to anterior knee pain, patellar maltracking, patellofemoral impingement, patellar fracture, component loosening and reduced range of motion. A computer-assisted surgery (CAS) system was developed to improve the accuracy of the patellar cut. Twelve cadaveric knee specimens (6 pairs) were surgically prepared and the patella resected by two senior orthopaedic residents using either a conventional sawguide technique (right knee) or a computer-assisted sawguide technique (left knee). Multiple cuts and measurements were permitted for the conventional technique, to reflect the clinical situation, whereas only a single cut was permitted for the CAS technique. Prior training had been provided on artificial bones for both techniques. Custom marker arrays were mounted on the sawguide and patella. The user positioned the sawguide based on a real-time display that compared the current sawguide plane to the ideal resection. The resulting mediolateral and superoinferior resection angles and central thickness were measured from CT scans of the specimens, relative to the anterior surface of the patella. Both techniques resulted in symmetric cuts (<7 ). Repeatability in the mediolateral direction was better for the CAS technique than for the conventional technique ( p < 0.01). This study demonstrated that computer-assisted patellar resection is a feasible approach that can produce results equal to or better than those obtained with conventional techniques, even when the experimental conditions favor the conventional technique. Improvements in the CAS hardware could further improve the accuracy and usability of the system, resulting in reductions in postoperative complications. Patellar CAS could also serve as a valuable tool for feedback and training.