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

Amateurs playing an instrument have difficulty reaching a professional level without practice and training in the presence of a mentor. We show that the skill level of a person playing a French horn could be distinguished by differences in the tone shape displayed via a spectrogram produced using the short-term Fourier transform. The appropriateness of this approach for comparing amateur and professional timbre was unclear for our target audience: Junior High School musicians. Simpler statistical parameters used for characterizing normal and abnormal electro-encephalographic and vibroarthrographic signals were investigated. These parameters summarize the tone characteristics within a single number, opening up their use within an artificial intelligence context. It was discovered that using the kurtosis measure led to better differentiation of skill levels than the complexity measure, with skewness providing no differentiation.