Abstract
Purpose The purpose of this study was to evaluate the approach of using an electromagnetic tracking (EMT) system for measuring the effects of stepwise, simulated knee injuries on patellofemoral (PF) and tibiofemoral (TF) kinematics. Methods Three cadaver knees were placed in a motion rig. EMT sensors were mounted on the patella, the medial/lateral femoral epicondyles, the tibial condyle, and the tibial tuberosity (TT). After determining the motion of an intact knee, three injuries were simulated and the resulting bony motion was tracked. Results Starting with the intact knee fully extended (0° flexion) and bending it to approximately 20°, the patella shifted slightly in the medial direction. Then, while bending the knee to the flexed position (90° flexion), the patella shifted progressively more laterally. After transecting the anterior cruciate ligament (ACL), the base of the medial menisci (MM) at the pars intermedia, and the medial collateral ligament (MCL), individual changes were observed. For example, the medial femoral epicondyle displayed a medial lift-off in all knees. Conclusion We demonstrated that our EMT approach is an acceptable method to accurately measure PF joint motion. This method could also enable visualization and in-depth analysis of in vivo patellar function in total knee arthroplasty, if it is established for routine clinical use.
Highlights
The knee joint, which can be divided into the patellofemoral (PF) joint and tibiofemoral (TF) joint, is one of the most complex joints of the human body
The effectiveness of the PF joint depends on the bone and soft tissue balance as well as the anatomy of the trochlear groove [1, 2]
Patients often present symptoms related to instability or maltracking because the PF joint is incongruent and the patella shows a large amount of movement during overall knee flexion and extension [5, 6]
Summary
The knee joint, which can be divided into the patellofemoral (PF) joint and tibiofemoral (TF) joint, is one of the most complex joints of the human body. Since a healthy knee has a valgus alignment, the tension of the quadriceps muscle produces a lateral patella movement [3]. An imbalance of the muscle tension can lead to PF pain syndrome and joint instability [3]. Patients often present symptoms related to instability or maltracking because the PF joint is incongruent and the patella shows a large amount of movement during overall knee flexion and extension [5, 6]. Abnormal patellar tracking and motion, respectively, which may progress with the onset of osteoarthritis, alter the mechanical interaction between patella and femur [4]. An imbalance of bony and soft tissue structures (e.g., quadriceps muscle) can lead to PF pain syndrome and instability.
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