Shi Xiutao, Wang Xiang, Niebur Glen L
Tissue Mechanics Laboratory, Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA.
Ann Biomed Eng. 2009 Feb;37(2):354-62. doi: 10.1007/s10439-008-9619-4. Epub 2008 Dec 12.
While the effects of bone mineral density and architecture in osteoporotic bone have been studied extensively, the micromechanics of yielding and failure have received less attention. However, understanding architectural features associated with failure should provide insight into assessing bone quality. In this study, microstructural finite element models were used to compute regions of tissue level yielding in ten bovine tibial trabecular bone samples. The morphology, number, and mean volume of the yielded regions were quantified for four apparent strains under two loading conditions. For on-axis loading, the mean aspect ratio of the tissue that yielded due to compressive strain increased with increasing apparent strain, expanding along the principal trabecular orientation. This suggests that tissue level yielding progresses along vertical trabeculae when a specimen is loaded on-axis. The number, but not the volume, of the regions yielded due to tensile strain increased with increasing applied load, consistent with relaxation and redistribution of stresses around the yielded regions. When the specimens were compressed perpendicular to the principal axis, the aspect ratio of the yielded regions was close to one, while the number, mean volume, and mean thickness of the yielded regions increased. This indicates that localized high strains consistent with bending rather than axial deformation of struts occur at the tissue level. Overall, the results provide new insight into trabecular bone failure, which is relevant to assessing diagnostic tests for fracture risk or evaluating osteoporosis treatments.
虽然骨质疏松性骨中骨矿物质密度和结构的影响已得到广泛研究，但屈服和破坏的微观力学受到的关注较少。然而，了解与破坏相关的结构特征应有助于深入评估骨质量。在本研究中，使用微观结构有限元模型来计算十个牛胫骨小梁骨样本中组织水平屈服的区域。在两种加载条件下，对四个表观应变下屈服区域的形态、数量和平均体积进行了量化。对于轴向加载，由于压缩应变而屈服的组织的平均纵横比随着表观应变的增加而增加，沿主要小梁方向扩展。这表明当样本进行轴向加载时，组织水平的屈服沿着垂直小梁发展。由于拉伸应变而屈服的区域的数量而非体积随着施加负荷的增加而增加，这与屈服区域周围应力的松弛和重新分布一致。当样本垂直于主轴压缩时，屈服区域的纵横比接近1，而屈服区域的数量、平均体积和平均厚度增加。这表明在组织水平上发生了与支柱弯曲而非轴向变形一致的局部高应变。总体而言，这些结果为小梁骨破坏提供了新的见解，这与评估骨折风险的诊断测试或评估骨质疏松症治疗方法相关。
