Department of Mechanical Engineering, Villanova University, Villanova, PA, USA.
Sibley School of Mechanical and Aerospace Engineering, Cornell University, Ithaca, NY, USA.
J Mech Behav Biomed Mater. 2023 Sep;145:106034. doi: 10.1016/j.jmbbm.2023.106034. Epub 2023 Jul 18.
Microstructural and compositional changes that occur due to aging, pathological conditions, or pharmacological treatments alter cortical bone fracture resistance. However, the relative importance of these changes to the fracture resistance of cortical bone has not been quantified in detail. In this technical note, we developed an integrated experimental-computational framework utilizing human femoral cortical bone biopsies to advance the understanding of how fracture resistance of cortical bone is modulated due to modifications in its microstructure and material properties. Four human biopsy samples from individuals with varying fragility fracture history and osteoporosis treatment status were converted to finite element models incorporating specimen-specific material properties and were analyzed using fracture mechanics-based modeling. The results showed that cement line density and osteonal volume had a significant effect on crack volume. The removal of cement lines substantially increased the crack volume in the osteons and interstitial bone, representing straight crack growth, compared to models with cement lines due to the lack of crack deflection in the models without cement lines. Crack volume in the osteons and interstitial bone increased when mean elastic modulus and ultimate strength increased and mean fracture toughness decreased. Crack volume in the osteons and interstitial bone was reduced when material property heterogeneity was incorporated in the models. Although both the microstructure and the heterogeneity of the material properties of the cortical bone independently increased the fracture toughness, the relative contribution of the microstructure was more significant. The integrated experimental-computational framework developed here can identify the most critical microscale features of cortical bone modulated by pathological processes or pharmacological treatments that drive changes in fracture resistance and improve our understanding of the relative influence of microstructure and material properties on fracture resistance of cortical bone.
由于衰老、病理状况或药物治疗引起的微观结构和组成变化会改变皮质骨的骨折阻力。然而，这些变化对皮质骨骨折阻力的相对重要性尚未详细量化。在本技术说明中，我们开发了一个综合的实验计算框架，利用人类股骨皮质骨活检来深入了解微观结构和材料特性的改变如何调节皮质骨的骨折阻力。从具有不同脆性骨折史和骨质疏松症治疗状况的个体中获取了四个活检样本，将其转化为有限元模型，纳入了标本特异性的材料特性，并使用基于断裂力学的建模进行了分析。结果表明，水泥线密度和骨单位体积对裂纹体积有显著影响。与具有水泥线的模型相比，由于缺乏水泥线的模型中没有裂纹偏转，去除水泥线会大大增加骨单位和间质骨中的裂纹体积，代表直裂纹生长。当平均弹性模量和极限强度增加而平均断裂韧性降低时，骨单位和间质骨中的裂纹体积增加。当模型中纳入材料性能异质性时，骨单位和间质骨中的裂纹体积减少。尽管皮质骨的微观结构和材料性能的异质性都独立地增加了断裂韧性，但微观结构的相对贡献更为显著。这里开发的综合实验计算框架可以确定由病理过程或药物治疗调节的皮质骨的最关键的微观特征，这些特征会改变骨折阻力，并提高我们对微观结构和材料性能对皮质骨骨折阻力的相对影响的理解。
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