Understanding bone strength and fracture by multiscale modeling, testing and imaging: the role of chemical composition and hierarchical structure

我的研究项目是通过多尺度计算建模、力学测试和成像来研究骨强度和骨折。骨折是由骨强度和施加的力决定的，而骨强度又是由骨的化学成分和结构决定的。骨具有复杂的化学成分和分层的纳米微观结构。现有的理论和模型大多是在宏观尺度上使用整块骨头或骨标本进行的，我们仍然不知道在宏观尺度上骨强度是如何定量地受到化学成分和纳米微观结构的影响的，以及冲击力是如何导致骨的特定部位骨折的。为了更好地理解骨强度和骨折，人们必须了解这种迷人材料在分子、细胞、组织、器官和整个身体水平上的层次结构，并结合对身体周围机械环境的理解。生物力学和生物医学研究人员还有很长的路要走。多尺度建模是一种很有前途的理解骨力学行为的方法，但仍处于发展阶段。我的研究项目的长期目标是为骨强度和骨折的多尺度理论和模型的建立做出贡献。在我之前的发现基金（DG）期间，我在宏观尺度上建立了一个三级生物力学模型的层次结构，以了解跌倒引起的髋部骨折的生物力学。我下一个DG学期的短期目标是在更小的长度尺度上研究骨强度和骨折，即了解骨的化学成分（矿物质、有机物和水）和纳米微观结构（孔隙和晶体大小）如何影响骨强度和骨折。本研究将有助于：(1)在不同尺度上建立骨刚度/强度与化学成分/结构之间的关系；(2)骨强度和骨折的多尺度生物力学模型的发展。

My research program is to study bone strength and fracture by multiscale computational modeling, mechanical testing and imaging. Bone fracture is determined by bone strength and the applied force, and bone strength is in turn determined by bone chemical composition and architecture. Bone has complicated chemical compositions and hierarchical nano-micro-structures. With the existing theories and models established from previous studies that were mostly conducted at macroscale using whole bones or bone specimens, we still do not know how bone strength at macroscale are quantitatively affected by chemical compositions and nano-micro-structures, and how an impact force causes a fracture at a specific site of a bone. To better understand bone strength and fracture, one has to understand the hierarchical architecture of this fascinating material at the molecular, cellular, tissue, organ, and whole body levels, in conjunction with an understanding of the mechanical environment surrounding the body. It is still a long way for biomechanical and biomedical researchers to go. Multiscale modeling is a promising method to understand bone mechanical behavior, but it is still under development. The long-term objective of my research program is to contribute to the establishment of multiscale theories and models for bone strength and fracture. In my previous Discovery Grant (DG) term, I developed a hierarchy of three-level biomechanical models at macroscale to understand the biomechanics involved in fall-induced hip fracture. The short-term objective of my next DG term is to study bone strength and fracture at smaller length scales, i.e. to understand how bone chemical composition (mineral, organic matter and water) and nano-micro-structure (pores and crystal sizes) affect bone strength and fracture. The proposed research will contribute to: (1) the establishment of relationships between bone stiffness/strength and chemical compositions/structures across different scales; (2) the development of multiscale biomechanical models of bone strength and fracture. The proposed research would have a major impact on the communities of Biomechanical/Biomedical Engineering and Materials Engineering. For example, the multiscale models of bone strength and fracture would help biomechanical engineers improve the effectiveness of protective devices in manned vehicles. The relationships between bone stiffness/strength and chemical compositions/structures would help biomedical engineers improve evaluation of fracture risk and advance design of 3D printed bone crafts; it would also inspire material engineers to design novel and efficient composite materials. Highly qualified personnel trained in the proposed research would be equipped with cutting-edge knowledge and techniques of material multiscale modeling, which will be necessary for innovations in both Biomechanical/Biomedical and Materials Engineering.