Tissue Mechanics Laboratory, Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556, USA.
J Biomech. 2010 Sep 17;43(13):2460-6. doi: 10.1016/j.jbiomech.2010.05.032. Epub 2010 Jun 15.
Trabecular architecture plays a major role in bone mechanics. Osteoporosis leads to a transition from a plate-like to a more rod-like trabecular morphology, which may contribute to fracture risk beyond that predicted by changes in density. In this study, microstructural finite element analysis results were analyzed using individual trabeculae segmentation (ITS) to identify the type and orientation of trabeculae where tissue yielded during compressive overloads in two orthogonal directions. For both apparent loading conditions, most of the yielded tissue was found in longitudinally oriented plates. However, the primary loading mode of yielded trabeculae was axial compression with superposed bending for on-axis loading in contrast to bending for transverse loading. For either loading direction, most plate-like trabeculae yielded in the same loading mode, regardless of their orientation. In contrast, rods oriented parallel to the loading axis yielded in compression, while rods oblique or perpendicular to the loading axis yielded in combined bending and tension. The predominance of tissue yielding in plates during both on-axis and transverse overloading explains why on-axis overloading is detrimental to the off-axis mechanical properties. At the same time, a large fraction of the tissue in rod-like trabeculae parallel to the loading direction yielded in both on-axis and transverse loading. Hence, rods may be more likely to be damaged and potentially resorbed by damage mediated remodeling.
小梁结构在骨骼力学中起着重要作用。骨质疏松症导致从板状到更杆状小梁形态的转变，这可能导致骨折风险超出密度变化所预测的风险。在这项研究中，使用个体小梁分割（ITS）分析了微观结构有限元分析结果，以确定在两个正交方向上的压缩过载期间组织屈服的小梁的类型和方向。对于两种明显的加载情况，大多数屈服组织都存在于纵向定向的板中。然而，与横向加载相比，轴向加载的主要加载模式是轴向压缩与叠加弯曲。对于任一加载方向，大多数板状小梁都以相同的加载模式屈服，而与它们的方向无关。相比之下，与加载轴平行的杆在压缩下屈服，而与加载轴斜交或垂直的杆在弯曲和拉伸的组合下屈服。在轴向和横向过载期间，板中组织屈服的优势解释了为什么轴向过载对离轴机械性能有害。同时，在轴向和横向加载中，与加载方向平行的杆状小梁中的大量组织都发生了屈服。因此，杆可能更容易受到损坏，并可能通过介导损伤的重塑而被吸收。
