Chantarapanich Nattapon, Nanakorn Pruettha, Chernchujit Bancha, Sitthiseripratip Kriskrai
School of Manufacturing Systems and Mechanical Engineering, Sirindhorn International Institute of Technology, Thammasat University, Pathumthani, Thailand.
J Med Assoc Thai. 2009 Dec;92 Suppl 6:S97-103.
To study the stress distributions in normal and osteoarthritic knee joints using the finite element method (FEM).
Three normal and three varus knee joints are included in the study. Computed tomography (CT) images of the lower extremities are used to create 3D geometric models consisting of bones, articular cartilages, menisci, and knee ligaments. Each of the lower extremities includes the femur, tibia, fibula, and talus. Each 3D geometric model is adjusted to the normal standing configuration with the help of its corresponding 2D radiographic image. After that, 3D finite element (FE) models are created from the adjusted 3D geometric models. FEM is then used to obtain stress distributions on the articular cartilages. In the analysis, the displacements on the posterior calcaneal articular surface of the talus are fully fixed. A vertical concentrated force equal to the body weight is applied at the femoral head.
In the normal knee joints, the maximum normal stresses on the articular cartilages in the lateral compartments are always higher than those in the medial compartments. In the varus knee joints, the opposite results are observed. However, in each normal knee joint, the stress distribution on the whole articular cartilage is moderately uniform. On the contrary, in each varus knee joint, comparatively high magnitudes of the normal stress are found on a large area of the articular cartilage in the medial compartment.
Varus knee joints have higher stresses in the medial compartments while normal knee joints have higher stresses in the lateral compartments. This pilot study shows that FE studies are comparable to cadaveric studies. FEM can be used as an alternative method for studying and examining knee joints of patients.
使用有限元方法（FEM）研究正常和骨关节炎膝关节的应力分布。
本研究纳入三个正常膝关节和三个内翻膝关节。利用下肢计算机断层扫描（CT）图像创建由骨骼、关节软骨、半月板和膝关节韧带组成的三维几何模型。每个下肢包括股骨、胫骨、腓骨和距骨。借助其相应的二维放射图像将每个三维几何模型调整到正常站立姿势。之后，从调整后的三维几何模型创建三维有限元（FE）模型。然后使用有限元方法获取关节软骨上的应力分布。在分析中，距骨后关节面的位移完全固定。在股骨头处施加一个等于体重的垂直集中力。
在正常膝关节中，外侧间室关节软骨上的最大正应力总是高于内侧间室。在内翻膝关节中，观察到相反的结果。然而，在每个正常膝关节中，整个关节软骨上的应力分布较为均匀。相反，在每个内翻膝关节中，在内侧间室的大面积关节软骨上发现相对较高的正应力值。
内翻膝关节在内侧间室有较高应力，而正常膝关节在外侧间室有较高应力。这项初步研究表明有限元研究与尸体研究具有可比性。有限元方法可作为研究和检查患者膝关节的替代方法。
