Understanding Bone Strength Is Not Enough.
Understanding Bone Strength Is Not Enough.
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DOI：
10.1002/jbmr.3078
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发表时间：
2017-06
期刊：
影响因子：
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通讯作者：
van der Meulen MC
中科院分区：
文献类型：
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作者：
Hernandez CJ;van der Meulen MC
骨折风险的增加超出了骨密度（BMD）的预期，通常归因于较差的“骨质量”，如骨组织强度受损。然而，最近的研究强调了组织材料性能的重要性，而不是强度，例如断裂韧性。在这里，我们回顾了除强度和导致机械失效的物理机制之外的失效特性背后的概念：强度描述了单次过载的失效；断裂韧性描述的是由适度载荷和预先存在的缺陷或损伤引起的失效；疲劳强度描述的是小载荷数千到数百万次循环的失效。在骨中，这些不同的失效机制似乎在一些临床骨折中比其他骨折更常见。例如，手腕骨折通常是单一超载的结果，其破坏机制主要是骨强度，而脊柱骨折很少是单一超载的结果，这意味着多次加载循环和疲劳强度的重要性增加。导致断裂的组织材料特性和失效机制的结合代表了不同的机制途径，类似于用于描述细胞信号传导的分子途径。了解这些不同的机制途径是必要的，因为骨组织的一些特征可以通过损害断裂韧性或疲劳强度而增加骨折风险，而不损害骨组织强度。此外，与断裂韧性和疲劳相关的断裂机制途径涉及多种加载事件，这增加了在骨骼明显破坏之前检测和中断正在发生的骨折的可能性。在过去的二十年里，通过了解骨强度和单次载荷引起的骨折，在骨折预防方面取得了实质性的进展，但如果我们要提高骨折风险预防，我们必须考虑强度以外的材料特性。
Increases in fracture risk beyond what are expected from bone mineral density (BMD) are often attributed to poor “bone quality” such as impaired bone tissue strength. Recent studies, however, have highlighted the importance of tissue material properties other than strength, such as fracture toughness. Here we review the concepts behind failure properties other than strength and the physical mechanisms through which they cause mechanical failure: strength describes failure from a single overload; fracture toughness describes failure from a modest load combined with a pre-existing flaw or damage; and fatigue strength describes failure from thousands to millions of cycles of small loads. In bone, these distinct failure mechanisms appear to be more common in some clinical fractures than others. For example, wrist fractures are usually the result of a single overload, the failure mechanism dominated by bone strength, while spinal fractures are rarely the result of a single overload, implicating multiple loading cycles and increased importance of fatigue strength. The combination of tissue material properties and failure mechanisms that lead to fracture represent distinct mechanistic pathways, analogous to molecular pathways used to describe cell signaling. Understanding these distinct mechanistic pathways is necessary because some characteristics of bone tissue can increase fracture risk by impairing fracture toughness or fatigue strength without impairing bone tissue strength. Additionally, mechanistic pathways to failure associated with fracture toughness and fatigue involve multiple loading events over time, raising the possibility that a developing fracture could be detected and interrupted before overt failure of a bone. Over the past two decades there have been substantial advancements in fracture prevention by understanding bone strength and fractures caused by a single load, but if we are to improve fracture risk prevention beyond what is possible now, we must consider material properties other than strength.