Hao Zhixiu, Wan Chao, Gao Xiangfei, Ji Tao
Division of Intelligent and Biomechanical Systems, State Key Laboratory of Tribology, Tsinghua University, Beijing 100084, China.
J Biomech Eng. 2011 Oct;133(10):101006. doi: 10.1115/1.4005223.
The finite element (FE) model of the pelvic joint is helpful for clinical diagnosis and treatment of pelvic injuries. However, the effect of an FE model boundary condition on the biomechanical behavior of a pelvic joint has not been well studied. The objective of this study was to study the effect of boundary condition on the pelvic biomechanics predictions. A 3D FE model of a pelvis using subject-specific estimates of intact bone structures, main ligaments and bone material anisotropy by computed tomography (CT) gray value was developed and validated by bone surface strains obtained from rosette strain gauges in an in vitro pelvic experiment. Then three FE pelvic models were constructed to analyze the effect of boundary condition, corresponding to an intact pelvic joint, a pelvic joint without sacroiliac ligaments and a pelvic joint without proximal femurs, respectively. Vertical load was applied to the same pelvis with a fixed prosthetic femoral stem and the same load was simulated in the FE model. A strong correlation coefficient (R(2)=0.9657) was calculated, which indicated a strong correlation between the FE analysis and experimental results. The effect of boundary condition changes on the biomechanical response depended on the anatomical location and structure of the pelvic joint. It was found that acetabulum fixed in all directions with the femur removed can increase the stress distribution on the acetabular inner plate (approximately double the original values) and decrease that on the superior of pubis (from 7 MPa to 0.6 MPa). Taking sacrum and ilium as a whole, instead of sacroiliac and iliolumber ligaments, can influence the stress distribution on ilium and pubis bone vastly. These findings suggest pelvic biomechanics is very dependent on the boundary condition in the FE model.
骨盆关节的有限元（FE）模型有助于骨盆损伤的临床诊断和治疗。然而，FE模型边界条件对骨盆关节生物力学行为的影响尚未得到充分研究。本研究的目的是研究边界条件对骨盆生物力学预测的影响。利用计算机断层扫描（CT）灰度值对完整骨结构、主要韧带和骨材料各向异性进行个体特异性估计，建立了骨盆的三维FE模型，并通过体外骨盆实验中从应变片获得的骨表面应变进行了验证。然后构建了三个FE骨盆模型，分别对应完整骨盆关节、无骶髂韧带的骨盆关节和无近端股骨的骨盆关节，以分析边界条件的影响。在固定假体股骨柄的同一骨盆上施加垂直载荷，并在FE模型中模拟相同载荷。计算得到了较强的相关系数（R(2)=0.9657），表明FE分析与实验结果之间存在较强的相关性。边界条件变化对生物力学响应的影响取决于骨盆关节的解剖位置和结构。研究发现，去除股骨后全方位固定髋臼可增加髋臼内板上的应力分布（约为原始值的两倍），并降低耻骨上部的应力分布（从7MPa降至0.6MPa）。将骶骨和髂骨视为一个整体，而不是骶髂韧带和髂腰韧带，会极大地影响髂骨和耻骨上的应力分布。这些发现表明，骨盆生物力学在很大程度上依赖于FE模型中的边界条件。
