Yeni Yener N, Zelman Eric A, Divine George W, Kim Do-Gyoon, Fyhrie David P
Bone and Joint Center, Henry Ford Hospital, Detroit, MI, USA.
Bone. 2008 Mar;42(3):591-6. doi: 10.1016/j.bone.2007.11.011. Epub 2007 Dec 4.
Trabecular shear stress magnitude and variability have been implicated in damage formation and reduced bone strength associated with bone loss for human vertebral bone. This study addresses the issue of whether these parameters change with age, gender or anatomical location, and if so whether this is independent of bone mass. Additionally, 3D-stereology-based architectural parameters were examined in order to establish the relationship between stress distribution parameters and trabecular architecture. Eighty cancellous bone specimens were cored from the anterior region of thoracic 12 and donor-matched lumbar 1 vertebrae from a randomly selected population of 40 cadavers. The specimens were scanned at 21-microm voxel size using microcomputed tomography (microCT) and reconstructed at 50microm. Bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), bone surface-to-volume ratio (BS/BV), degree of anisotropy (MIL1/MIL3), and connectivity density (-#Euler/Vol) were calculated directly from micro-CT images. Large-scale finite element models were constructed and superoinferior compressive loading was simulated. Apparent cancellous modulus (EFEM) was calculated. The average trabecular von Mises stress generated per uniaxial apparent stress (sigma (-)VM / sigmaapp) and coefficient of variation of trabecular von Mises stresses (COV) were calculated as measures of the magnitude and variability of shear stresses in the trabeculae. Mixed-models and regression were used for analysis. sigma(-)VM / sigmaapp and COV were not different between genders and vertebrae. Both sigma(-)VM / sigmaapp and COV increased with age accompanied by a decrease in BV/TV. Strong relationship of sigma(-)VM / sigmaapp with BV/TV was found whereas COV was strongly related to EFEM/(BV/TV). The results from T12 and L1 were not different and highly correlated with each other. The relationship of sigma(-)VM / sigmaapp with COV was observed to be different between males and females. This difference could not be explained by architectural parameters considered in this study. Our results support the relevance of trabecular shear stress amplification and variability in age-related vertebral bone fragility. The relationships found are expected to help understand the micro-mechanisms by which cancellous bone mass and mechanical properties are modulated through a collection of local stress parameters.
小梁剪切应力大小和变异性与人类椎体骨丢失相关的损伤形成及骨强度降低有关。本研究探讨这些参数是否随年龄、性别或解剖位置而变化，若如此，这种变化是否独立于骨量。此外，研究了基于三维体视学的结构参数，以确定应力分布参数与小梁结构之间的关系。从40具尸体的随机样本中，取第12胸椎前部和与之供体匹配的第1腰椎椎体的80个松质骨标本。使用微型计算机断层扫描（microCT）以21微米的体素大小对标本进行扫描，并以50微米的分辨率进行重建。直接从microCT图像计算骨体积分数（BV/TV）、小梁数量（Tb.N）、小梁厚度（Tb.Th）、小梁间距（Tb.Sp）、骨表面积与体积比（BS/BV）以及各向异性程度（MIL1/MIL3）和连通性密度（-#Euler/Vol）。构建大规模有限元模型并模拟上下方向的压缩载荷。计算表观松质骨模量（EFEM）。计算每单位单轴表观应力产生的平均小梁von Mises应力（σ(-)VM / σapp）和小梁von Mises应力的变异系数（COV），作为小梁中剪切应力大小和变异性的度量。采用混合模型和回归分析。σ(-)VM / σapp和COV在性别和椎体之间无差异。σ(-)VM / σapp和COV均随年龄增加而增加，同时BV/TV降低。发现σ(-)VM / σapp与BV/TV有很强的相关性，而COV与EFEM/(BV/TV)密切相关。T12和L1的结果无差异且彼此高度相关。观察到σ(-)VM / σapp与COV的关系在男性和女性之间存在差异。这种差异无法用本研究中考虑的结构参数来解释。我们的结果支持小梁剪切应力放大和变异性与年龄相关的椎体骨脆性的相关性。所发现的关系有望有助于理解通过一组局部应力参数调节松质骨量和力学性能的微观机制。
