Department of Aerospace and Mechanical Engineering, Bioengineering Graduate Program, University of Notre Dame, Notre Dame, IN 46556, USA.
J Biomech. 2011 Sep 2;44(13):2395-400. doi: 10.1016/j.jbiomech.2011.06.032. Epub 2011 Jul 20.
Microdamage in bone tissue is typically studied using destructive, two-dimensional histological techniques. Contrast-enhanced micro-computed tomography (micro-CT) was recently demonstrated to enable non-destructive, three-dimensional (3-D) detection of microdamage in machined cortical and trabecular bone specimens in vitro. However, the accumulation of microdamage in whole bones is influenced by variations in the magnitude and mode of loading due to the complex whole bone morphology. Therefore, the objective of this study was to detect the presence, spatial location, and accumulation of fatigue microdamage in whole rat femora in vitro using micro-CT with a BaSO(4) contrast agent. Microdamage was detected and observed to accumulate at specific spatial locations within the cortex of femora loaded in cyclic three-point bending to a 5% or 10% reduction in secant modulus. The ratio of the segmented BaSO(4) stain volume (SV) to the total volume (TV) of cortical bone was adopted as a measure of damage. The amount of microdamage measured by micro-CT (SV/TV) was significantly greater for both loaded groups compared to the control group (p<0.05), but the difference between loaded groups was not statistically significant. At least one distinct region of microdamage, as indicated by the segmented SV, was observed in 85% of loaded specimens. A specimen-specific finite element model confirmed elevated tensile principal strains localized in regions of tissue corresponding to the accumulated microdamage. These regions were not always located where one might expect a priori based upon Euler-Bernoulli beam theory, demonstrating the utility of contrast-enhanced micro-CT for non-destructive, 3-D detection of fatigue microdamage in whole bones in vitro.
骨组织中的微损伤通常使用破坏性的二维组织学技术进行研究。最近的研究表明，对比增强的微计算机断层扫描（micro-CT）可用于非破坏性的、三维（3-D）检测体外加工皮质骨和松质骨标本中的微损伤。然而，由于整个骨骼形态的复杂性，整个骨骼中微损伤的积累受到加载幅度和模式变化的影响。因此，本研究的目的是使用带有 BaSO4 对比剂的 micro-CT 检测体外大鼠股骨中疲劳微损伤的存在、空间位置和积累。通过在循环三点弯曲中对股骨施加 5%或 10%的割线模量减少来加载，检测到微损伤并观察到其在皮质骨的特定空间位置处积累。将分段的 BaSO4 染色体积（SV）与皮质骨的总体积（TV）的比值作为损伤的度量。与对照组相比，两种加载组的 micro-CT 测量的微损伤量（SV/TV）显著增加（p<0.05），但加载组之间的差异无统计学意义。至少在 85%的加载样本中观察到一个由分段 SV 指示的微损伤的独特区域。基于个体的有限元模型证实，在与累积微损伤相对应的组织区域中存在局部的拉伸主应变。这些区域并不总是位于根据欧拉-伯努利梁理论预先预期的位置，这证明了对比增强的 micro-CT 对于体外整个骨骼中疲劳微损伤的非破坏性、3-D 检测是有用的。
