膝关节三维有限元模型的建立

目的运用三维有限元技术建立人膝关节三维有限元模型,通过模型对膝关节应力进行分析,以了解人膝关节应力分布特点及生物力学机制。方法选取1名正常男性青年膝关节直立位横断CT扫描片一套,扫描范围包括膝关节上、下10 cm。图像经计算机处理后,按三维有限元网格划分原则,划分2 120个节点,1 382个单元,运用Super-Sap有限元计算程序,建立正常膝关节三维有限元模型。按双腿直立位时膝部实际受力大小和方向对模型加载相同载荷,计算得出模型中各节点及单元的应力值。结果正常膝关节外侧关节面应力分布较内侧均匀,内、外侧关节面应力均未见明显集中。内、外侧关节面峰值应力均位于关节面前部,内侧峰值应力为外侧的1.59倍;内侧关节面平均应力为外侧的1.03倍,内侧关节面较外侧承受更大的应力。结论①本实验所建模型属三维人膝关节解剖基静力模型,与人膝关节解剖实际相符,能很好地用来分析膝关节的应力情况。②半月板具有传导载荷,扩大股胫关节接触面,减少单位面积上的应力,并使应力平均分布于整个关节面的作用。

The three-dimensional finite element model of knee joint

Objective To understand stress distribution,knee joints model was studied using three-dimensional finite element method.Methods A set of consecutive transectional computerized tomography images of normal male knee joint in upright weight-bearing position(scan range,10 cm superior and inferior to the joint) was selected and image was divided into 2 120 nodes and 1 382 units as per the principle of three-dimensional finite element.The three-dimensional finite element model of the normal knee joint was then established through the Super-Sap finite element calculation procedure.Appropriate pressure mimicking the virtual magnitude and orientation of load on articular surfaces of upright weight-borne knees was applied to the model,to calculate the stress values of all nodes and units of each model.Results The stress on the lateral side of normal knee joint is more even-distributed than that on the medial side.No obvious stress centralization was seen on both lateral and medial side but front parts of articular surfaces were found to bear the most stress.The maximal and mean stresses on the medial side of articular surfaces were 1.59 and 1.03 times more than those on the lateral side,respectively.More stress was distributed on the medial side of articular surface compared with the opposite.Conclusion ①The model set up in this project belongs to three-dimensional human knee joint basic dissection models,which matches the virtual anatomy of human knees so that it can be reliably used to analyze the stress distribution condition of human knee joints.②Menisci functionally conduct stress load,broaden the contact area of femoro-tibial joint,lessen the stress per unit area and distribute stress evenly to the articular surface.