Fatigue-induced microdamage in cancellous bone occurs distant from resorption cavities and trabecular surfaces.
Fatigue-induced microdamage in cancellous bone occurs distant from resorption cavities and trabecular surfaces.
复制标题
DOI：
10.1016/j.bone.2015.05.020
复制
发表时间：
2015-10
期刊：
影响因子：
4.1
通讯作者：
Hernandez CJ
中科院分区：
文献类型：
--
作者：
Goff MG;Lambers FM;Nguyen TM;Sung J;Rimnac CM;Hernandez CJ
骨骼韧性受损越来越被认为是导致脆性骨折的一个因素。在组织层面上，韧性与骨组织抵抗微裂纹或其他组织损伤的能力有关。虽然我们对微损伤的大多数了解都来自于对皮质骨的研究，但大多数脆性骨折发生在以松质骨为主的骨骼区域。由于组织微结构和组织超微结构的不同，松质骨组织微损伤的发展可能与皮质骨不同。为了深入了解微损伤是如何在松质骨中积累的，我们测定了不同循环压缩载荷后微损伤部位的数量、大小和位置的变化。人椎体松质骨标本32例，男10例，女6例，年龄76±8.8岁，平均(±SD)。只有少数几个大的微损伤部位(最大的10%)占循环载荷引起的所有微损伤的70%。与整体损伤体积分数(DV/BV)相比，大的微损伤部位的数量更能预测循环载荷引起的杨氏模量的降低。大多数微损伤体积(69.12±7.04%)位于骨小梁表面>30μm(平均侵蚀深度)，提示微损伤主要发生在松质骨的间质区域。此外，与其他骨表面相比，微损伤发生在吸收腔附近的可能性较小(p<；0.05)，挑战了由吸收腔引起的应力上升会影响松质骨疲劳破坏的观点。综上所述，这些发现表明，疲劳加载过程中表观水平机械性能的降低只是几个大的微损伤部位的结果，疲劳中微损伤的积累可能是由组织材料特性的异质性而不是由微尺度几何形状引起的应力集中所主导的。
Impaired bone toughness is increasingly recognized as a contributor to fragility fractures. At the tissue level, toughness is related to the ability of bone tissue to resist the development of microscopic cracks or other tissue damage. While most of our understanding of microdamage is derived from studies of cortical bone, the majority of fragility fractures occur in regions of the skeleton dominated by cancellous bone. The development of tissue microdamage in cancellous bone may differ from that in cortical bone due to differences in microstructure and tissue ultrastructure. To gain insight into how microdamage accumulates in cancellous bone we determined the changes in number, size and location of microdamage sites following different amounts of cyclic compressive loading. Human vertebral cancellous bone specimens (n=32, 10 male donors, 6 female donors, age 76 ± 8.8, mean ± SD) were subjected to sub-failure cyclic compressive loading and microdamage was evaluated in three-dimensions. Only a few large microdamage sites (the largest 10%) accounted for 70% of all microdamage caused by cyclic loading. The number of large microdamage sites was a better predictor of reductions in Young’s modulus caused by cyclic loading than overall damage volume fraction (DV/BV). The majority of microdamage volume (69.12 ± 7.04%) was located more than 30 μm (the average erosion depth) from trabecular surfaces, suggesting that microdamage occurs primarily within interstitial regions of cancellous bone. Additionally, microdamage was less likely to be near resorption cavities than other bone surfaces (p<0.05), challenging the idea that stress risers caused by resorption cavities influence fatigue failure of cancellous bone. Together, these findings suggest that reductions in apparent level mechanical performance during fatigue loading are the result of only a few large microdamage sites and that microdamage accumulation in fatigue is likely dominated by heterogeneity in tissue material properties rather than stress concentrations caused by micro-scale geometry.