Geometric and finite element modelling of the tibio-menisco-femoral contact under passive knee motion.

摘要

The meniscus is an important component of the knee joint. It transmits a large percentage of the load in the knee, and also helps to stabilize the joint. Several studies have investigated the material properties and mechanical functions of the normal meniscus. However, whether and how meniscal injuries affect the stress and strain distributions inside the meniscus, as well as the motion of the meniscus are not yet well understood. The major objectives of this dissertation were to develop a protocol for reconstructing a subject-specific knee joint from Magnetic Resonance (MR) images, and to use finite element (FE) method to study the biomechanical behavior of the meniscus under passive knee motions.;A three-dimensional FE model of the tibio-menisco-femoral contact area of the knee was developed using solid modeling and hexahedral mesh generation techniques. The geometry was reconstructed from the MR images of a volunteer's knee joint at full extension. Comparison study found that it is important to model the meniscus as a transversely isotropic (vs. isotropic) poroelastic: material to represent the much stiffer fibers in the circumferential direction. Comparison of an axisymmetric model of the contact area and the 3D model under equivalent amount of axial loading found considerable difference between their results.;Six sets of MR images of the knee were acquired from full extension to approximately 25 degrees of flexion without load bearing. The motion of the tibia relative to the femur at each imaging step was derived based on the automatic image processing data and applied to the 3-D FE model. The position of the meniscus predicted by the FE model was then compared to the MR Images and the anteriorsterior excursion of the menisci is around 2.5 mm ∼ 2.9 mm.;A circumferential and an anterior radial tear were created in the normal lateral meniscus model. Increased maximum principal stress around the tear was found in the radial tear model under both axial loading and passive knee flexion. Motion of the centroids of the torn meniscus models showed no difference compared with the centroid of the normal meniscus under passive knee flexion.