Department of Mechanical and Aerospace Engineering, Carleton University, 3135 Mackenzie Building, 1125 Colonel By Dr, Ottawa, ON, K1S 5B6, Canada.
J Orthop Res. 2019 Oct;37(10):2197-2203. doi: 10.1002/jor.24383. Epub 2019 Jun 18.
To manage osteoporotic hip fracture risk, it is necessary to understand failure mechanisms of bone at both the material and organ level. The structural response of bone is dependent on load history. Repeated loading causes progressive microstructural cracking, resulting in reduced apparent-level stiffness and, if damage is significant, reductions to peak load bearing capability. However, the effect of previous damage accumulation has not been well explored at the organ level. It was hypothesized that femoral fracture load and fracture pattern may be sensitive to damage accumulation from previous loading events. Six cadaveric specimens were used to develop patient specific finite element (FE) models from quantitative tomographic (qCT) scans. Material properties were assigned from qCT intensity at each element location, and damage evolution was predicted using a previously validated quasi-brittle FE model. Three scenarios were investigated: stumble followed by another stumble (S-S), fall followed by another fall (F-F), and stumble followed by a fall (S-F). Fracture load and pattern were compared to FE predictions for a single stumble (S) or single fall (F) loading event. Most specimens were resilient to accumulated damage, showing little (<5%) change in fracture load from the multiple-load scenarios (S-S, F-F, and S-F) compared to an equivalent single load scenario (S or F). Only one specimen demonstrated moderate (5-15%) reductions in strength from all three multiple-load scenarios. However, two specimens experienced moderate (20-30%) increase in fracture load in some load cases. In these cases, initial damage caused the load to be more evenly distributed upon subsequent loading events. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:2197-2203, 2019.
为了管理骨质疏松性髋部骨折风险，有必要了解骨在材料和器官水平上的失效机制。骨的结构响应取决于载荷历史。重复加载会导致微结构逐渐开裂，从而导致表观刚度降低，如果损伤严重，则会降低峰值承载能力。但是，以前的损伤累积对器官水平的影响尚未得到很好的探索。有人假设股骨骨折载荷和骨折模式可能对以前的加载事件引起的损伤累积敏感。使用 6 个尸体标本，根据定量断层扫描（qCT）扫描为每个标本开发了特定患者的有限元（FE）模型。在每个元素位置处，根据 qCT 强度分配材料性能，并且使用先前验证的准脆性 FE 模型预测损伤演化。研究了三种情况：绊倒后再次绊倒（S-S），跌倒后再次跌倒（F-F）和绊倒后跌倒（S-F）。将骨折载荷和模式与单一绊倒（S）或单一跌倒（F）加载事件的 FE 预测进行了比较。大多数标本对累积损伤具有弹性，与等效的单一载荷情况（S 或 F）相比，来自多个载荷情况（S-S、F-F 和 S-F）的骨折载荷变化很小（<5％）。只有一个标本显示出从所有三种多重载荷情况中强度降低（5-15％）。但是，在某些情况下，两个标本的骨折载荷增加了中等（20-30％）。在这些情况下，初始损伤导致在随后的加载事件中负载分布更加均匀。 © 2019 矫形研究协会。由 Wiley Periodicals，Inc. 出版。J Orthop Res 37：2197-2203，2019。
