Spinal Curvature Update of the SAFER Human Body Model: A study on the effect of spinal curvature in frontal and run-off road crash scenarios

Sammanfattning

The human body is a complex system made of various tissues, making it a difficulttask to model in a biofidelic manner. It is of importance to be able to accuratelydo this in order to predict the risk of injury when exposed to large magnitudes ofacceleration, e.g. in car crashes. Prior research has found that force and momentwithin the spine have been significant predictors of vertebral body fracture risk.This thesis implemented a spinal curvature from a prediction model, derived fromvolunteer data, into the SAFER HBM and evaluated its influence on the spine’smechanical response. This was done in two ways: 1) implementing the curvatureof the prediction model in the sagittal plane, as well as 2) varying the curvaturein the coronal plane, to represent normal variations within the population with theassumption that the human body is not completely symmetrical.These two alternative models, together with the original SAFER HBM, were appliedin paired simulations of six different crash scenarios to investigate whether the mechanicalresponse of the vertebrae differed. The crash scenarios modelled were twofrontal crashes of different severity, two oblique crashes of different impact directionsas well as two run-off road scenarios with different vehicle roll motions.When reviewing the updated sagittal spinal curvature, it was seen that the predictedspinal curvature was more straight than the original SAFER HBM, showing reducedlordosis in the upper thoracic spine and reduced kyphosis in the thoracolumbarregion. Then, once the updates had been applied into crash simulations, it wasnoted that the vertebral body trabecular bone inferior-superior strain was affectedby the updated curvature, which in its own affects the vertebral body fracture risk.These differences were mainly observed in the run-off road impacts, whereas thevariations of frontal impacts did not support the same findings. For these run-offroad impacts, it was observed that the compressive forces exerted on the vertebraewere increased with the spinal curvature update. These compressive forces, as wellas the flexion of the spine were found to be related to the peak vertebral bodytrabecular bone inferior-superior strain, in multiple locations in the spine supportedby linear regression models. The results of the coronal plane curvature simulationssupported the relations between flexion of the spine and compressive strain, as wellas between the compressive force and compressive strain.