Dynamic biaxial testing system for the fatigue and failure of bone

负重骨骼的机械疲劳是体力活动的必然结果。随着时间的推移，骨骼系统的习惯性负荷与微损伤积累有关，这会降低骨骼的整体质量，导致表观刚度降低和机械应变增加。如果没有足够的骨重塑和修复，微损伤的演变和积累最终可能导致骨衰竭或“疲劳性”骨折。人类的疲劳骨折已经有了很好的记录，但人们对其了解甚少。对文献的全面回顾表明，在体外测试的骨样本在加载比体内经历的大得多的应变量级之前不会显示疲劳骨折。这种异常可以用三种现象来解释，即：1)应变速率，2)混合模式相互作用，3)应力体积对骨机械疲劳响应的影响。在本提案中，要求为满足测试这些现象的苛刻要求的材料测试系统提供资金，其中分别包括：1)高频动态测试，2)双轴加载能力，以及3)使用生理波形的高强度全骨加载。校园或附近的机构没有符合上述确切规格的设备，具体引用的系统在加拿大任何地方都不存在。因此，拟议的制度将提供独特的培训机会和科学探究，这是目前其他机构的受训者所没有的。爱德华兹博士正在卡尔加里大学建立一个国际公认的骨力学和计算建模项目，他不知道国内还有其他实验室在研究疲劳断裂的潜在机制。这些机制不一定是骨所特有的，可能与其他具有分层组织的生物纤维基复合材料有关。如果拟议的技术基础设施没有获得，他的实验室就有可能把这个令人兴奋的机会拱手让给竞争的国际研究小组。拟议的设备将确保爱德华兹博士的陡峭的职业轨迹，几个研究小组共同代表70多个HQP的持续成功，以及卡尔加里大学人类表现实验室在生物力学方面的卓越和培训的长期传统。

Mechanical fatigue of load bearing bones is an inevitable consequence of physical activity. Over time, habitual loading of the skeletal system is associated with microdamage accumulation that reduces the overall quality of bone and leads to a reduction in apparent-level stiffness and an increase in mechanical strain. Without adequate bone remodeling and repair, the evolution and accumulation of microdamage may eventually lead to bone failure, or “fatigue” fracture. Fatigue fractures have been well documented in humans but are still poorly understood. A comprehensive review of the literature illustrates that bone samples tested ex vivo do not illustrate fatigue fractures until loaded at strain magnitudes much greater than experienced in vivo. This anomaly may be explained by three phenomena, namely: 1) strain rate, 2) mixed mode interaction, and 3) stress volume effects on the mechanical fatigue response of bone. In this proposal, funding is requested for a materials testing system that meets the demanding requirements to test these phenomena, which includes, respectively: 1) high-frequency dynamic testing, 2) biaxial loading capabilities, and 3) high-magnitude whole-bone loading using physiological waveforms. There is no equipment available on campus or at nearby institutions meeting the exact specifications described above, and the specific quoted systems do not exist anywhere in Canada. Thus, the proposed system will allow for unique training opportunities and scientific inquiry that are currently unavailable for trainees at other institutions. Dr. Edwards is working to establish an internationally recognized program in bone mechanics and computational modeling at the University of Calgary, and he is unaware of any other labs in the nation working to address the underlying mechanisms of fatigue fracture. These mechanisms are not necessarily specific to bone, and may be relevant to other biological fiber-based composite materials with hierarchical organization. If the proposed technical infrastructure is not acquired, his lab risks ceding this exciting opportunity to competing international research groups. The proposed equipment will ensure a steep career trajectory for Dr. Edwards, the continued success of several research groups collectively representing more than 70 HQP, and the longstanding tradition of excellence and training in biomechanics in the Human Performance Laboratory at the University of Calgary.