| Summary: | 碩士 === 國立陽明大學 === 醫學工程研究所 === 95 === There were no further progress about tibio-femoral kinematics for last decade. The different pattern of knee between medial and lateral condylar kinematics is mainly due to the shapes of tibio-femoral articulating surfaces. The articulating surfaces have been changed after total knee arthroplasty (TKA). Early studies showed the different kinematics between native and TKA knee as well. It’s needed to understand the kinematics after TKA. High degrees of knee flexion ( >150° ) are necessary for daily activities. Nevertheless, the knee after TKA might be unstable in high flexion. It’s still the controversial issue for posterior cruciate ligament-retaining (CR) versus posterior-stabilized (PS) TKA. The purpose of this study was to develop three-dimensional dynamic knee model. It can predict and compare the knee kinematics between native and TKA knee while knee flexed.
Mechanical simulation package is used in this study to develop the model. The native knee model included femur, tibia, patella and fibula. In addition, the non-linear anterior cruciate ligament, posterior cruciate ligament, medial cruciate ligament, lateral cruciate ligament and patellar ligament, the forces of hamstrings and quadriceps, meniscus excursion were simulated. Making use of this setup at the functional axis of knee flexion to simulate the flexion motion from full extension to full flexion. After simulating native knee, the total knee arthroplasty with cruciate-retaining and posterior-stabilized prostheses was applied to native knee model, and used the same conditions to simulate and predict the kinematics of knee flexion after TKA. Furthermore, this study contained another three models as moving the tibial post 2 mm anteriorly, 2 mm posteriorly and 4 mm posteriorly, then we used these models to perform the simulation.
The results of native knee model showed that tibio-femoral contact was lost as knee flexed to 150 degrees, meanly, the maximum flexion angle. The lateral and medial femoral condyle of CR TKA translated 15 mm and 1 mm posteriorly, respectively. The lateral and medial femoral condyle of PS TKA translated 20 mm and 2 mm posteriorly, respectively. The amounts of lateral and medial femoral translation after TKA was not restored properly to native knee model, which showed 30 mm and 10 mm of lateral and medial femoral posterior translation. The model with PS TKA showed 23° of tibial internal rotation, and properly agreed with native knee model. However, The model with CR TKA showed only 17° of tibial internal rotation during knee flexion. Every tibial post was moved 2 mm posteriorly, earlier the post-cam engaged by 5° of knee flexion. Although it showed better restoration of knee kinematics when the post-cam mechanism engaged early, the insufficient space behind tibial post make the risk of femoral dislocation possibly. The model in this study predicted the knee motion in high flexion, and compared the difference of knee kinematics between native and TKA knee. It could be the way to predict the kinematics of knee joint with variety novel design of prosthesis after TKA.
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