EFFECT OF MUSCLES ACTIVATION ON HEAD-NECK COMPLEX UNDER SIMULATED EJECTION

A detailed three-dimensional head-neck (C0–C7) finite element (FE) model developed based on the actual geometry of an embalmed human cadaver specimen was exercised to dictate the motions of the cervical spine under dynamic loadings. The predicted results analyzed under vertex drop impact were compared against experimental study to validate the FE model. The validated C0–C7 FE model was then further analyzed to investigate the response of the whole head-neck complex under 10G-ejection condition. From the simulation of ejection process, obvious hyper-flexion of the head-neck complex could be found. The peak flexion angles of all the lower motion segments were beyond physiological tolerance indicating a potential injury in these regions. Furthermore, the stress values in the spine were also related to the magnitudes of rotation of the motion segments. During the acceleration onset stage, the maximum stresses in the bone components were low. After that, the stress values increased sharply into the dangerous range with increased rotational angles. The effect of muscles in alleviating the potential damage in the neck is significant. It was implied that it is important for pilots to stiffen the neck before ejection to avoid severe cervical injury.