Phillips A T M
Department of Civil and Environment Engineering, Imperial College London, Structural Engineering Section, Skempton Building, London SW7 2AZ, UK.
Med Eng Phys. 2009 Jul;31(6):673-80. doi: 10.1016/j.medengphy.2008.12.008. Epub 2009 Feb 6.
Previous finite element studies of the femur have made simplifications to varying extents with regard to the boundary conditions used during analysis. Fixed boundary conditions are generally applied to the distal femur when examining the proximal behaviour at the hip joint, while the same can be said for the proximal femur when examining the distal behaviour at the knee joint. While fixed boundary condition analyses have been validated against in vitro experiments it remains a matter of debate as to whether the numerical and experimental models are indicative of the in vivo situation. This study presents a finite element model in which the femur is treated as a complete musculo-skeletal construct, spanning between the hip and knee joints. Linear and non-linear implementations of a free boundary condition modelling approach are applied to the bone through the explicit inclusion of muscles and ligaments spanning both the hip joint and the knee joint. A non-linear force regulated, muscle strain based activation strategy was found to result in lower observed principal strains in the cortex of the femur, compared to a linear activation strategy. The non-linear implementation of the model in particular, was found to produce hip and knee joint reaction forces consistent with in vivo data from instrumented implants.
以往对股骨的有限元研究在分析过程中使用的边界条件方面都有不同程度的简化。在研究髋关节近端行为时，通常对股骨远端施加固定边界条件，而在研究膝关节远端行为时，对股骨近端也采用同样的做法。虽然固定边界条件分析已通过体外实验得到验证，但数值模型和实验模型是否能代表体内情况仍存在争议。本研究提出了一个有限元模型，其中将股骨视为一个完整的肌肉骨骼结构，跨越髋关节和膝关节。通过明确纳入跨越髋关节和膝关节的肌肉和韧带，将自由边界条件建模方法的线性和非线性实现应用于骨骼。与线性激活策略相比，发现基于肌肉应变的非线性力调节激活策略会使股骨皮质中观察到的主应变更低。特别是，该模型的非线性实现产生的髋关节和膝关节反作用力与来自仪器植入物的体内数据一致。
