UPMC Univ Paris 06, UMR 7623, Laboratoire d'Imagerie Paramétrique, 75005 Paris, France.
Bone. 2011 Nov;49(5):1020-6. doi: 10.1016/j.bone.2011.08.002. Epub 2011 Aug 9.
At the mesoscale (i.e. over a few millimeters), cortical bone can be described as two-phase composite material consisting of pores and a dense mineralized matrix. The cortical porosity is known to influence the mesoscopic elasticity. Our objective was to determine whether the variations of porosity are sufficient to predict the variations of bone mesoscopic anisotropic elasticity or if change in bone matrix elasticity is an important factor to consider. We measured 21 cortical bone specimens prepared from the mid-diaphysis of 10 women donors (aged from 66 to 98 years). A 50-MHz scanning acoustic microscope (SAM) was used to evaluate the bone matrix elasticity (reflected in impedance values) and porosity. Porosity evaluation with SAM was validated against Synchrotron Radiation μCT measurements. A standard contact ultrasonic method was applied to determine the mesoscopic elastic coefficients. Only matrix impedance in the direction of the bone axis correlated to mesoscale elasticity (adjusted R(2)=[0.16-0.25], p<0.05). The mesoscopic elasticity was found to be highly correlated to the cortical porosity (adj-R(2)=[0.72-0.84], p<10(-5)). Multivariate analysis including both matrix impedance and porosity did not provide a better statistical model of mesoscopic elasticity variations. Our results indicate that, for the elderly population, the elastic properties of the mineralized matrix do not undergo large variations among different samples, as reflected in the low coefficients of variation of matrix impedance (less than 6%). This work suggests that change in the intracortical porosity accounts for most of the variations of mesoscopic elasticity, at least when the analyzed porosity range is large (3-27% in this study). The trend in the variation of mesoscale elasticity with porosity is consistent with the predictions of a micromechanical model consisting of an anisotropic matrix pervaded by cylindrical pores.
在介观尺度（即几毫米）上，皮质骨可以被描述为由孔隙和致密矿化基质组成的两相复合材料。皮质骨的孔隙率已知会影响介观弹性。我们的目的是确定孔隙率的变化是否足以预测骨介观各向异性弹性的变化，或者骨基质弹性的变化是否是一个需要考虑的重要因素。我们测量了 21 个从 10 位女性供体（年龄 66 至 98 岁）的骨干中段制备的皮质骨样本。使用 50MHz 扫描声学显微镜（SAM）评估骨基质弹性（反映在阻抗值上）和孔隙率。SAM 进行的孔隙率评估与同步辐射 μCT 测量结果进行了验证。标准接触超声法用于确定介观弹性系数。仅在骨轴方向的基质阻抗与介观弹性相关（调整后的 R(2)=[0.16-0.25]，p<0.05）。介观弹性与皮质骨孔隙率高度相关（adj-R(2)=[0.72-0.84]，p<10(-5)）。包括基质阻抗和孔隙率的多元分析并没有提供一个更好的介观弹性变化的统计模型。我们的结果表明，对于老年人群，矿化基质的弹性性质在不同样本之间没有发生很大的变化，这反映在基质阻抗的低变异系数（小于 6%）上。这项工作表明，在分析的孔隙率范围内较大（本研究中为 3-27%）时，皮质内孔隙率的变化解释了介观弹性变化的大部分原因。介观弹性随孔隙率的变化趋势与由各向异性基质和圆柱状孔隙组成的微观力学模型的预测一致。
