Biomechanics and Mechanobiology, Institute for Bioengineering of Catalonia, C/ Baldiri Reixac 4, Barcelona, Spain.
Biomech Model Mechanobiol. 2011 Apr;10(2):203-19. doi: 10.1007/s10237-010-0227-5. Epub 2010 Jun 9.
In the human lumbar spine, annulus fibrosus fibres largely contribute to intervertebral disc stability. Detailed annulus models are therefore necessary to obtain reliable predictions of lumbar spine mechanics by finite element modelling. However, different definitions of collagen orientations coexist in the literature for healthy human lumbar annuli. Therefore, four annulus fibre-induced anisotropy models were built from reported anatomical descriptions, and inserted in a L3-L5 lumbar bi-segment finite element model. Annulus models were, respectively, characterized by radial, tangential, radial and tangential, and no fibre orientation gradients. The effect of rotational and axial compressive loadings was simulated and first, predictions were compared to experimental data. Then, intervertebral disc local biomechanics was studied under axial rotation and axial compression. A new parameter, i.e. the fibre contribution quality parameter, was computed in the anterior, lateral, postero-lateral, and posterior annuli of each model, in function of fibre stresses, radial load distributions, and matrix shear strains. Locally, each annulus model behaved differently, affecting intervertebral disc biomechanics and segmental motions. The fibre contribution quality parameter allowed establishing direct links between local annulus fibre organization and local annulus loadings, while other kinematical and biomechanical data did not. It was concluded that functional relations should exist between local annulus fibre orientations and overall segment morphology. The proposed fibre contribution quality parameter could be used to examine such relations and calibrate lumbar spine finite element models by locally adjusting the annulus bundle criss-cross angles. Conclusions of this study are particularly relevant to patient-specific models or artificial disc designs.
在人类的腰椎中，纤维环纤维在很大程度上有助于椎间盘的稳定性。因此，为了通过有限元建模获得可靠的腰椎力学预测，需要详细的纤维环模型。然而，在健康的人类腰椎纤维环的文献中，不同的胶原取向定义并存。因此，根据报道的解剖描述，构建了四个纤维环诱导各向异性模型，并将其插入到 L3-L5 腰椎双节段有限元模型中。模型分别以放射状、切线状、放射状和切线状以及无纤维取向梯度为特征。模拟了旋转和轴向压缩载荷的作用，首先将预测结果与实验数据进行了比较。然后，研究了轴向旋转和轴向压缩下椎间盘的局部生物力学。在每个模型的前、侧、后外侧和后纤维环中，计算了一个新参数，即纤维贡献质量参数，作为纤维应力、径向载荷分布和基质剪切应变的函数。局部上，每个纤维环模型的行为不同，影响椎间盘的生物力学和节段运动。纤维贡献质量参数允许在局部纤维环组织和局部纤维环载荷之间建立直接联系，而其他运动学和生物力学数据则没有。结论是，局部纤维环纤维取向和整体节段形态之间应该存在功能关系。所提出的纤维贡献质量参数可用于通过局部调整纤维环束交错角度来检查这些关系并校准腰椎有限元模型。本研究的结论特别适用于患者特定模型或人工椎间盘设计。
