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首页> 外文期刊>Journal of Biomechanics >Fatigue microcracks that initiate fracture are located near elevated intracortical porosity but not elevated mineralization
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Fatigue microcracks that initiate fracture are located near elevated intracortical porosity but not elevated mineralization

机译：引发断裂的疲劳微裂纹位于皮质内孔隙度升高附近，但矿化度未升高

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摘要

In vivo microcracks in cortical bone are typically observed within more highly mineralized interstitial tissue, but postmortem investigations are inherently limited to cracks that did not lead to fracture which may be misleading with respect to understanding fracture mechanisms. We hypothesized that the one fatigue microcrack which initiates fracture is located spatially adjacent to elevated intracortical porosity but not elevated mineralization. Therefore, the spatial correlation between intracortical porosity, elevated mineralization, and fatigue microdamage was investigated by combining, for the first time, sequential, nondestructive, three-dimensional micro-computed tomography (micro-CT) measurements of each in cortical bone specimens subjected to compressive fatigue loading followed by a tensile overload to fracture. Fatigue loading resulted in significant microdamage accumulation and compromised mechanical properties upon tensile overload compared to control specimens. The microdamage that initiated fracture upon tensile overload was able to be identified in all fatigue-loaded specimens using contrast-enhanced micro-CT and registered images. Two-point (or pair) correlation functions revealed a spatial correlation between microdamage at the fracture initiation site and intracortical porosity, but not highly mineralized tissue, confirming the hypothesis. This difference was unique to the fracture initiation site. Intracortical porosity and highly mineralized tissue exhibited a significantly lower and higher probability, respectively, of being located spatially adjacent to all sites of microdamage compared to the fracture initiation site. Therefore, the results of this study suggest that human cortical bone is tolerant of most microcracks, which are generally compartmentalized within the more highly mineralized interstitial tissue, but a single microcrack of sufficient size located in spatial proximity to intracortical porosity can compromise fracture resistance.
机译：皮质骨中的体内微裂纹通常在矿化程度更高的间隙组织中观察到，但是验尸研究固有地限于不导致骨折的裂缝，这在理解骨折机理方面可能会产生误导。我们假设一个引起破裂的疲劳微裂纹在空间上与升高的皮层内孔隙度相邻，但与升高的矿化度不相邻。因此，首次通过结合连续的，无损的，三维显微计算机断层扫描（micro-CT）测量对皮质骨标本中的每个进行了研究，从而研究了皮质内孔隙率，矿化度升高和疲劳微损伤之间的空间相关性。压缩疲劳载荷，接着是拉伸过载断裂。与对照样品相比，疲劳载荷会在拉伸过载时导致显着的微损伤积累和受损的机械性能。使用对比度增强的微CT和配准图像，可以在所有疲劳载荷的样品中识别出由拉伸过载引起的断裂的微损伤。两点（或成对）的相关函数揭示了骨折起始部位的微损伤与皮质内孔隙度之间的空间相关性，但没有高度矿化的组织，从而证实了这一假设。这种差异是骨折起始部位所独有的。与骨折起始部位相比，皮质内孔隙度和高度矿化的组织分别在空间上邻近所有微损伤部位显着降低和提高概率。因此，这项研究的结果表明，人类皮质骨可耐受大多数微裂纹，这些微裂纹通常在矿化程度更高的间隙组织中分隔开，但是位于皮质内孔隙空间附近的足够大的单个微裂纹会损害抗断裂性。

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