Department of Mechanical Engineering, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249, USA.
J Mech Behav Biomed Mater. 2012 Oct;14:101-12. doi: 10.1016/j.jmbbm.2012.05.003. Epub 2012 May 23.
It is of great interest to delineate the effect of orientation distribution of mineral crystals on the bulk mechanical behavior of bone. Using a unique synergistic approach combining a progressive loading scheme and synchrotron X-ray scattering techniques, human cortical bone specimens were tested in compression to examine the in situ mechanical behavior of mineral crystals aligned in different orientations. The orientation distribution was quantitatively estimated by measuring the X-ray diffraction intensity from the (002) plane in mineral crystals. In addition, the average longitudinal (c-axis), transverse (a-axis), and shear strains of the subset of mineral crystals aligned in each orientation were determined by measuring the lattice deformation normal to three distinct crystallographic planes (i.e. 002, 310, and 213) in the crystals. The experimental results indicated that the in situ strain and stress of mineral crystals varied with orientations. The normal strain and stress in the longitudinally aligned mineral crystals were markedly greater than those in the transversely oriented crystals, whereas the shear stress reached a maximum for the crystals aligned in ±30° with respect to the loading direction. The maximum principal strain and stress were observed in the mineral crystals oriented along the loading axis, with a similar trend observed in the maximum shear strain and stress. By examining the in situ behavior, the contribution of mineral crystals to load bearing and the bulk behavior of bone are discussed.
阐明矿物晶体取向分布对骨整体力学性能的影响具有重要意义。本研究采用独特的协同方法，结合渐进加载方案和同步辐射 X 射线散射技术，对人皮质骨标本进行压缩试验，以研究不同取向排列的矿物晶体的原位力学行为。通过测量矿物晶体（002）面上的 X 射线衍射强度，定量估计了取向分布。此外，通过测量晶体中三个不同晶面（即 002、310 和 213）上晶格的变形，确定了每个取向排列的矿物晶体子集的平均纵向（c 轴）、横向（a 轴）和剪切应变。实验结果表明，矿物晶体的原位应变和应力随取向而变化。纵向排列的矿物晶体的法向应变和应力明显大于横向排列的晶体，而剪切应力在相对于加载方向成±30°排列的晶体中达到最大值。在沿加载轴取向的矿物晶体中观察到最大主应变和应力，最大剪切应变和应力也呈现出类似的趋势。通过原位行为的研究，讨论了矿物晶体对承载和骨整体行为的贡献。
