Institute for Biomechanics, ETH Zürich, Zürich, Switzerland.
Division of Orthopaedic Trauma, Department of Orthopaedics, University of British Columbia, Vancouver, BC, Canada.
J Bone Miner Res. 2019 Oct;34(10):1837-1850. doi: 10.1002/jbmr.3804. Epub 2019 Aug 14.
The majority of hip fractures in the elderly are the result of a fall from standing or from a lower height. Current injury models focus mostly on femur strength while neglecting subject-specific loading. This article presents an injury modeling strategy for hip fractures related to sideways falls that takes subject-specific impact loading into account. Finite element models (FEMs) of the human body were used to predict the experienced load and the femoral strength in a single model. We validated these models for their predicted peak force, effective pelvic stiffness, and fracture status against matching ex vivo sideways fall impacts (n = 11) with a trochanter velocity of 3.1 m/s. Furthermore, they were compared to sideways impacts of volunteers with lower impact velocities that were previously conducted by other groups. Good agreement was found between the ex vivo experiments and the FEMs with respect to peak force (root mean square error [RMSE] = 10.7%, R = 0.85) and effective pelvic stiffness (R = 0.92, RMSE = 12.9%). The FEMs were predictive of the fracture status for 10 out of 11 specimens. Compared to the volunteer experiments from low height, the FEMs overestimated the peak force by 25% for low BMI subjects and 8% for high BMI subjects. The effective pelvic stiffness values that were derived from the FEMs were comparable to those derived from impacts with volunteers. The force attenuation from the impact surface to the femur ranged between 27% and 54% and was highly dependent on soft tissue thickness (R = 0.86). The energy balance in the FEMS showed that at the time of peak force 79% to 93% of the total energy is either kinetic or was transformed to soft tissue deformation. The presented FEMs allow for direct discrimination between fracture and nonfracture outcome for sideways falls and bridge the gap between impact testing with volunteers and impact conditions representative of real life falls. © 2019 American Society for Bone and Mineral Research.
老年人的大多数髋部骨折是由站立或较低高度跌倒引起的。当前的损伤模型主要集中在股骨强度上，而忽略了特定于主体的加载。本文提出了一种与侧方跌倒相关的髋部骨折损伤建模策略，该策略考虑了特定于主体的冲击载荷。使用人体有限元模型（FEM）在单个模型中预测所经历的载荷和股骨强度。我们针对与匹配的侧向跌倒撞击（n = 11）的预测峰值力、有效骨盆刚度和骨折状态验证了这些模型，其具有 3.1 m/s 的转子速度。此外，它们与其他组先前进行的较低撞击速度的志愿者的侧向撞击进行了比较。在峰值力（均方根误差[RMSE] = 10.7%，R = 0.85）和有效骨盆刚度（R = 0.92，RMSE = 12.9%）方面，体外实验与 FEM 之间存在很好的一致性。对于 11 个标本中的 10 个，FEM 可预测骨折状态。与来自低高度的志愿者实验相比，对于低 BMI 受试者，FEM 高估了峰值力 25%，对于高 BMI 受试者高估了 8%。从 FEM 得出的有效骨盆刚度值与从志愿者撞击得出的有效骨盆刚度值相当。从撞击表面到股骨的力衰减范围在 27%到 54%之间，并且高度依赖于软组织厚度（R = 0.86）。FEMS 中的能量平衡表明，在峰值力时，总能量的 79%到 93%要么是动能，要么转化为软组织变形。所提出的 FEM 允许直接区分侧向跌倒的骨折和非骨折结果，并弥合志愿者冲击测试与代表真实生活跌倒的冲击条件之间的差距。 © 2019 美国骨与矿物质研究协会。
