Development of Adult and Elderly FE Thorax Skeletal Models 2009-01-0381

Accident statistics show that the thorax is one of the most frequently injured body regions in drivers who sustain severe injuries in frontal car crashes. Thoracic injuries are more significant for the elderly than for adults. However, there are no injury assessment tools accounting for differences in anatomical features and material properties between adults and the elderly.

The current study developed adult and elderly FE thorax models for investigating thoracic injury mechanisms for each generation. The ages represented by these models were defined as 35 and 75 years old (y.o.), respectively, based on the age distribution from accident statistics. The FE meshes representing the external shapes of the thoracic skeleton were first created based on the thorax CT images of the individuals with approximately average body sizes of males in their 30’s and 70’s. Since the geometry of the created mesh of the 35 y.o. appeared significantly different from the average statistically generated in the literature while that of the 75 y.o. was very close, the mesh of the 35 y.o. was recreated by morphing the mesh of the 75 y.o. targeting the geometry of this average geometry of the 35 y.o. The cortical thickness of the sternum and other bones were determined from the literature supplemented by the CT data. The average material property of the ribs, clavicles, costal cartilages and sternum for each age was estimated from the literature.

Due to the limited amount of available response data, the models for each age were validated by predicting the upper and lower limits of responses using individual variation of material parameters estimated from the literature. The average material parameters were considered valid when published response data fell within the predicted response limits. This procedure was applied to the validation of rib and thorax at the component level.

Isolated rib models were validated against quasi-static and dynamic bending tests from the literature. Then, the thoracic skeleton model incorporating the ribs, clavicles, sternum, costal cartilages and thoracic spine was validated against dynamic chest loading tests from the literature which were performed by four different types of loading - hub loading, single diagonal belt loading, double diagonal belt loading, and distributed loading.