基于CT影像动态膝关节有限元模型的构建及仿真力学分析

目的:基于CT影像资料构建动态性膝关节有限元模型,并进行模型的有效性验证和初步的有限元分析,为膝关节的生物力学研究提供仿真模型和基础数据。方法:选取1名健康男性膝关节CT资料,借助Mimics 19.0和Hypermesh 12.0等软件,从膝关节的三维模型构建入手,经几何重建、逆向工程、网格划分、材料定性等步骤,建立高仿真的有限元模型。通过确定边界条件和扭矩加载产生动态性的屈膝模型,并进行模型的有效性验证。予有限元模型施加近似屈膝活动时所承受的载荷(500 N),研究分析不同屈膝角度下胫股关节和髌股关节的生物力学变化。结果:基于CT影像并结合解剖特性建立了膝关节有限元模型,模型包括骨、韧带、软骨、半月板和髌骨支持带等三维单元,在确立边界条件后施加不同扭矩产生了不同屈膝状态下的有限元模型。根据等同工况(屈膝30°,股四头肌腱受200N牵张)加载显示髌骨的应力峰值为2.209 MPa,平均Mises应力为1.132 MPa;股骨滑车的应力峰值为1.405 MPa,平均Mises应力0.936 MPa,与既往研究比较差异性在1%～13.5%,证明模型的有效性。动态性的模型加载发现:胫股关节的Mises应力随屈膝角度增加而下降;而髌股关节的Mises应力与屈膝角度正相关,不同屈膝角度下各软骨应力面的Mises应力对比,差异均有统计学意义(P0.05)。结论:研究建立的有限元模型结构更趋完整,可有效模拟动态性膝关节的生物力学特性,为膝关节进一步的仿真力学研究提供了支撑。

Construction and simulation mechanical analysis of dynamic knee joint finite element model based on CT image

Objective: To construct a dynamic knee joint finite element model based on CT image data and verify the validity of the model. To provide a simulation model and basic data for biomechanical research of the knee joint by further finite element analysis.Methods: The CT data of a healthy male knee joint was selected. With the help of Mimics 19.0 and Hypermesh 12.0 software,a high simulation finite element model of knee joint was established following steps,including geometric reconstruction,reverse engineering,meshing and material characterization. The dynamic knee flexion model was generated by determining the boundary conditions and torque loading,and the validity of the model was confirmed. The biomechanical changes of the tibiofemoral and patellofemoral joints under different knee flexion angles were analyzed by applying the loads(500 N) to the finite element model during knee flexion.Results: A finite element model of knee joint was established based on CT images and anatomical characteristics. The model included three-dimensional elements such as bone,ligament,cartilage,meniscus and patellar retinaculum. The different finite element models of knee flexion states were produced by applying different torques after establishing boundary conditions. According to equivalent conditions (knee flexion 30 degrees,quadriceps tendon under 200 N stretch),the peak stress value of patella was 2.209 MPa and the average Mises stress was 1.132 MPa;the peak stress value of femoral trochlear was 1.405 MPa and the average Mises stress was 0.936 MPa. The validity of the model was proved by the difference between the model and previous studies of 1% to 13.5%. Dynamic model loading showed that the Mises stress of tibiofemoral joint decreased with the increase of knee flexion angle,while the Mises stress of patellofemoral joint was positively correlated with knee flexion angle. The Mises stress of cartilage stress planes at different knee flexion angles was significantly different(P<0.05).Conclusion: The finite element model established in this study is more comprehensive and can effectively simulate the biomechanical characteristics of dynamic knee joint,which provides support for further simulation mechanics researches of the knee joint.