Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46556, United States.
J Biomech. 2011 Jun 3;44(9):1817-20. doi: 10.1016/j.jbiomech.2011.04.009. Epub 2011 May 2.
Numerical models commonly account for elastic inhomogeneity in cortical bone using power-law scaling relationships with various measures of tissue density, but limited experimental data exists for anatomic variation in elastic anisotropy. A recent study revealed anatomic variation in the magnitude and anisotropy of elastic constants along the entire femoral diaphysis of a single human femur (Espinoza Orías et al., 2009). The objective of this study was to confirm these trends across multiple donors while also considering possible confounding effects of the anatomic quadrant, apparent tissue density, donor age, and gender. Cortical bone specimens were sampled from the whole femora of 9 human donors at 20%, 50%, and 80% of the total femur length. Elastic constants from the main diagonal of the reduced fourth-order tensor were measured on hydrated specimens using ultrasonic wave propagation. The tissue exhibited orthotropy overall and at each location along the length of the diaphysis (p < 0.0001). Elastic anisotropy increased from the mid-diaphysis toward the epiphyses (p < 0.05). The increased elastic anisotropy was primarily caused by a decreased radial elastic constant (C(11)) from the mid-diaphysis toward the epiphyses (p < 0.05), since differences in the circumferential (C(22)) and longitudinal (C(33)) elastic constants were not statistically significant (p > 0.29). Anatomic variation in intracortical porosity may account for these trends, but requires further investigation. The apparent tissue density was positively correlated with the magnitude of each elastic constant (p < 0.0001, R(2) > 0.46), as expected, but was only weakly correlated with C(33)/C(11) (p < 0.05, R(2) = 0.04) and not significantly correlated with C(33)/C(22) and C(11)/C(22).
数值模型通常使用幂律标度关系来考虑皮质骨的弹性各向异性，该关系与组织密度的各种指标相关联，但关于弹性各向异性的解剖学变异性的实验数据有限。最近的一项研究揭示了单个人类股骨骨干整个长度上弹性常数的大小和各向异性的解剖学变异性（Espinoza Orías 等人，2009 年）。本研究的目的是在多个供体中证实这些趋势，同时考虑解剖象限、表观组织密度、供体年龄和性别等可能的混杂效应。皮质骨标本取自 9 名人类供体的整个股骨，在股骨总长度的 20%、50%和 80%处取样。在水合标本上使用超声波传播测量从简化的四阶张量主对角线得到的弹性常数。组织在整个方向和骨干长度上的每个位置均表现出各向异性（p < 0.0001）。弹性各向异性从骨干中部向骨骺增加（p < 0.05）。弹性各向异性的增加主要是由于骨干中部向骨骺处的径向弹性常数（C(11)）降低（p < 0.05），因为周向（C(22)）和纵向（C(33)）弹性常数的差异在统计学上无显著差异（p > 0.29）。皮质内孔隙率的解剖学变异性可能导致了这些趋势，但需要进一步研究。表观组织密度与每个弹性常数的大小呈正相关（p < 0.0001，R(2) > 0.46），这是预期的，但与 C(33)/C(11)的相关性较弱（p < 0.05，R(2) = 0.04），与 C(33)/C(22)和 C(11)/C(22)无显著相关性。
