Human cancellous bone from T12-L1 vertebrae has unique microstructural and trabecular shear stress properties.
Human cancellous bone from T12-L1 vertebrae has unique microstructural and trabecular shear stress properties.
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DOI：
10.1016/j.bone.2008.09.002
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发表时间：
2009-01
期刊：
影响因子：
4.1
通讯作者：
Cody, Dianna D.
中科院分区：
文献类型：
--
作者：
Yeni, Yener N.;Kim, Do-Gyoon;Divine, George W.;Johnson, Evan M.;Cody, Dianna D.
随着年龄和疾病的增加，松质骨脆性增加的机制之一是骨小梁应力变异性随骨量的减少而增加。在目前的研究中，先前观察到的骨小梁剪应力估计值随人体脊柱变化而变化，使得来自胸椎12(T12)-腰椎1(L1)交界处的松质组织在给定载荷下经历最高的骨小梁应力，这一观察结果被作为正式假设使用多个人脊柱进行验证。对10具成人身体脊柱的胸椎4、T5、T7、T9、T10、T12、L1、L2、L4和L5椎体进行了观察。在中央前区的一个标本在上下(SI)方向取芯，在后外侧区域的另一个标本取材于每个椎体的横向(Tr)方向。对每个试件建立基于Micro-CT的大型有限元模型，模拟圆柱试件在长轴方向的受压情况。计算松质骨弹性系数和骨小梁von Mise应力的平均值、标准差、变异性和放大系数。采用三维体视学方法计算骨体积分数、骨小梁数目、骨小梁厚度、骨小梁间距、连接密度和各向异性程度。使用混合模型对结果进行分析，其中脊柱水平使用二次多项式进行建模。当取同一椎体标本的结果取平均值时，T12-L1部位的松质组织的骨小梁剪应力放大最大，骨体积分数最小。当组分开时，显微结构和骨小梁应力随着脊柱水平的不同而变化，最大值仅在T12-L1水平，仅对于TR标本。测量参数的SI/TR值与脊柱节段也存在二次曲线关系，大多数参数的极值位于T12-L1节段。对于显微结构参数，这些比率在T12-L1节段接近1，表明T12-L1椎体具有比其他节段更均匀的松质组织特性。骨小梁方向第二主方向的平均截距长度可以解释所有力学参数随脊柱水平的变化。我们的结果支持T12-L1节段的松质组织是独一无二的，这可能部分解释了这些节段脊柱骨折发生率较高的原因。
Increase of trabecular stress variability with loss of bone mass has been implicated as a mechanism for increased cancellous bone fragility with age and disease. In the current study, a previous observation that trabecular shear stress estimates vary along the human spine such that the cancellous tissue from the thoracic 12 (T12)-lumbar 1 (L1) junction experiences the highest trabecular stresses for a given load was tested as a formal hypothesis using multiple human spines. Thoracic 4, T5, T7, T9, T10, T12, L1, L2, L4 and L5 vertebrae from 10 human cadaver spines were examined. One specimen in the central anterior region was cored in the supero-inferior (SI) direction and another in the postero-lateral region was cored in the transverse (TR) direction from each vertebra. Micro-CT-based large-scale finite element models were constructed for each specimen and compression in the long axis of the cylindrical specimens was simulated. Cancellous bone modulus and the mean, the standard deviation, variability and amplification of trabecular von Mises stresses were computed. Bone volume fraction, trabecular number, trabecular thickness, trabecular separation, connectivity density and degree of anisotropy were calculated using 3D stereology. The results were analyzed using a mixed model in which spine level was modeled using a quadratic polynomial. The maximum of trabecular shear stress amplification and minimum of bone volume fraction were found in the cancellous tissue from the T12-L1 location when results from the samples of the same vertebra were averaged. When groups were separated, microstructure and trabecular stresses varied with spine level, extrema being at the T12-L1 levels, for the TR specimens only. SI/TR ratio of measured parameters also had quadratic relationships with spine level, the extrema being located at T12-L1 levels for most parameters. For microstructural parameters, these ratios approached to a value of one at the T12-L1 level, suggesting that T12-L1 vertebrae have more uniform cancellous tissue properties than other levels. The mean intercept length in the secondary principal direction of trabecular orientation could account for the variation of all mechanical parameters with spine level. Our results support that cancellous tissue from T12-L1 levels is unique and may explain, in part, the higher incidence of vertebral fractures at these levels.
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