Speirs Andrew D, Heller Markus O, Duda Georg N, Taylor William R
Center for Musculoskeletal Surgery Charité, Universitätsmedizin-Berlin, Free and Humboldt, University of Berlin, Augustenburger Platz 1, D-13353 Berlin, Germany.
J Biomech. 2007;40(10):2318-23. doi: 10.1016/j.jbiomech.2006.10.038. Epub 2006 Dec 12.
Finite element analysis has been used extensively in the study of bone loading and implant performance, such as in the femur. The boundary conditions applied vary widely, generally producing excessive femoral deformation, and although it has been shown that the muscle forces influence femoral deflections and loading, little consideration has been given to the displacement constraints. It is hypothesised that careful application of physiologically based constraints can produce physiological deformation, and therefore straining, of the femur. Joint contact forces and a complete set of muscle forces were calculated based on the geometry of the Standardised Femur using previously validated musculoskeletal models. Five boundary condition cases were applied to a finite element model of the Standardised Femur: (A) diaphyseally constrained with hip contact and abductor forces; (B) case A plus vasti forces; (C) case A with complete set of muscle forces; (D) distally constrained with all muscle forces; (E) physiological constraints with all muscle forces. It was seen that only the physiological boundary conditions, case E, produced physiological deflections (< 2.0mm) of the femoral head in both the coronal and sagittal planes, which resulted in minimal reaction forces at the constrained nodes. Strains in the mid-diaphysis varied by up to 600 micro-strain under walking loads and 1000 micro-strain under stair climbing loads. The mode of loading, as indicated by the strain profiles on the cortex also varied substantially under these boundary conditions, which has important consequences for studies that examine localised bone loading such as fracture or bone remodelling simulations.
有限元分析已广泛应用于骨骼负荷和植入物性能的研究，例如在股骨研究中。所应用的边界条件差异很大，通常会导致股骨过度变形，尽管已经表明肌肉力会影响股骨的挠度和负荷，但对位移约束的考虑却很少。据推测，仔细应用基于生理学的约束条件可以使股骨产生生理变形，进而产生应变。基于标准化股骨的几何形状，使用先前经过验证的肌肉骨骼模型计算了关节接触力和完整的肌肉力集。将五种边界条件情况应用于标准化股骨的有限元模型：(A) 骨干受约束，有髋关节接触力和外展肌力；(B) 情况A加上股四头肌肌力；(C) 情况A加上完整的肌肉力集；(D) 远端受约束，有所有肌肉力；(E) 有所有肌肉力的生理约束。可以看出，只有生理边界条件（情况E）在冠状面和矢状面都产生了股骨头的生理挠度（<2.0毫米），这导致约束节点处的反作用力最小。在行走负荷下，骨干中部的应变变化高达600微应变，在爬楼梯负荷下变化高达1000微应变。在这些边界条件下，皮质上的应变曲线所表明的加载模式也有很大变化，这对研究局部骨骼负荷（如骨折或骨重塑模拟）具有重要影响。
