Larsson Karl-Johan, Blennow Amanda, Iraeus Johan, Pipkorn Bengt, Lubbe Nils
Autoliv Research, Vårgårda, Sweden.
Division of Vehicle Safety, Department of Mechanics and Maritime Sciences, Chalmers University of Technology, Gothenburg, Sweden.
Front Bioeng Biotechnol. 2021 May 24;9:677768. doi: 10.3389/fbioe.2021.677768. eCollection 2021.
To evaluate vehicle occupant injury risk, finite element human body models (HBMs) can be used in vehicle crash simulations. HBMs can predict tissue loading levels, and the risk for fracture can be estimated based on a tissue-based risk curve. A probabilistic framework utilizing an age-adjusted rib strain-based risk function was proposed in 2012. However, the risk function was based on tests from only twelve human subjects. Further, the age adjustment was based on previous literature postulating a 5.1% decrease in failure strain for femur bone material per decade of aging. The primary aim of this study was to develop a new strain-based rib fracture risk function using material test data spanning a wide range of ages. A second aim was to update the probabilistic framework with the new risk function and compare the probabilistic risk predictions from HBM simulations to both previous HBM probabilistic risk predictions and to approximate real-world rib fracture outcomes. Tensile test data of human rib cortical bone from 58 individuals spanning 17-99 years of ages was used. Survival analysis with accelerated failure time was used to model the failure strain and age-dependent decrease for the tissue-based risk function. Stochastic HBM simulations with varied impact conditions and restraint system settings were performed and probabilistic rib fracture risks were calculated. In the resulting fracture risk function, sex was not a significant covariate-but a stronger age-dependent decrease than previously assumed for human rib cortical bone was evident, corresponding to a 12% decrease in failure strain per decade of aging. The main effect of this difference is a lowered risk prediction for younger individuals than that predicted in previous risk functions. For the stochastic analysis, the previous risk curve overestimated the approximate real-world rib fracture risk for 30-year-old occupants; the new risk function reduces the overestimation. Moreover, the new function can be used as a direct replacement of the previous one within the 2012 probabilistic framework.
为评估车辆驾乘人员的受伤风险，可在车辆碰撞模拟中使用有限元人体模型（HBMs）。HBMs能够预测组织受力水平，并且可以基于基于组织的风险曲线来估计骨折风险。2012年提出了一个利用基于年龄调整的肋骨应变风险函数的概率框架。然而，该风险函数仅基于12名人类受试者的测试。此外，年龄调整是基于先前的文献，该文献假定股骨骨材料的失效应变每十年下降5.1%。本研究的主要目的是利用涵盖广泛年龄范围的材料测试数据，开发一种新的基于应变的肋骨骨折风险函数。第二个目的是用新的风险函数更新概率框架，并将HBM模拟的概率风险预测与先前的HBM概率风险预测以及近似真实世界的肋骨骨折结果进行比较。使用了来自58名年龄在17 - 99岁之间个体的人类肋骨皮质骨拉伸测试数据。采用加速失效时间的生存分析来为基于组织的风险函数模拟失效应变和年龄依赖性下降。进行了具有不同碰撞条件和约束系统设置的随机HBM模拟，并计算了概率性肋骨骨折风险。在所得的骨折风险函数中，性别不是一个显著的协变量——但人类肋骨皮质骨明显呈现出比先前假设更强的年龄依赖性下降，相当于每十年失效应变下降12%。这种差异的主要影响是，与先前风险函数预测相比，年轻个体的风险预测降低。对于随机分析，先前的风险曲线高估了30岁驾乘人员近似真实世界的肋骨骨折风险；新的风险函数减少了这种高估。此外，新函数可以在2012年的概率框架内直接替代先前的函数。
