Osteoporosis (OP), a skeletal disease making bone mechanically deteriorate and easily fracture, is a global public health issue due to its high prevalence. It has been well recognized that besides bone loss, microarchitecture degradation plays a crucial role in the mechanical deterioration of OP bones, but the specific role of microarchitecture in OP has not been well clarified and quantified from mechanics perspective. Here, we successfully decoupled and identified the specific roles of microarchitecture, bone mass and tissue property in the failure properties of cancellous bones, through μCT-based digital modeling and finite element method simulations on bone samples from healthy and ovariectomy-induced osteoporotic mice. The results show that the microarchitecture of healthy bones exhibits longitudinal superiority in mechanical properties such as the effective stiffness, strength and toughness, which fits them well to bearing loads along their longitudinal direction. OP does not only reduce bone mass but also impair the microarchitecture topology. The former is mainly responsible for the mechanical degradation of bones in magnitude, wherever the latter accounts for the breakdown of their function-favorable anisotropy, the longitudinal superiority. Hence, we identified the microarchitecture-deterioration-induced directional mismatch between material and loading as a hazardous feature of OP and defined a longitudinal superiority index as measurement of the health status of bone microarchitecture. These findings provide useful insights and guidelines for OP diagnosis and treat assessment.

中文翻译：

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纵向优势的丧失标志着骨质疏松松质骨的微结构恶化。

骨质疏松症（OP）是一种使骨骼机械性恶化并容易骨折的骨骼疾病，由于其高发病率而成为全球公共卫生问题。众所周知，除了骨丢失外，微结构退化在 OP 骨骼的机械退化中起着至关重要的作用，但微结构在 OP 中的具体作用尚未从力学角度得到很好的阐明和量化。在这里，我们通过基于 μCT 的数字建模和有限元方法对来自健康和卵巢切除术诱导的骨质疏松小鼠的骨骼样本进行模拟，成功地解耦并确定了微结构、骨量和组织特性在松质骨失效特性中的具体作用。结果表明，健康骨骼的微结构在有效刚度、强度和韧性等力学性能方面表现出纵向优势，使其能够很好地承受沿其纵向方向的载荷。OP 不仅会减少骨量，还会损害微架构拓扑。前者主要负责骨骼的机械退化，而后者则解释了它们的功能有利的各向异性的破坏，即纵向优势。因此，我们将材料和负载之间的微结构退化引起的方向不匹配确定为 OP 的危险特征，并将纵向优势指数定义为骨微结构健康状况的测量。