Investigation of anteroposterior head-neck responses during severe frontal impacts using a brain-spinal cord complex FE model.

Injuries of the human brain and spinal cord associated with the central nervous system (CNS) are seen in automotive accidents. CNS injuries are generally categorized into severe injuries (AIS 3+). However, it is not clear how the restraint conditions affect the CNS injuries. This paper presents a newly developed three-dimensional (3D) finite element head-neck model in order to investigate the biomechanical responses of the brain-spinal cord complex. The head model consists of the scalp, skull, and a detailed description of the brain including the cerebrum, cerebellum, brainstem with distinct white and gray matter, cerebral spinal fluid (CSF), sagittal sinus, dura, pia, arachnoid, meninx, falx cerebri, and tentorium. Additionally, the neck model consists of the cervical vertebral bodies, intervertebral discs, muscles, ligaments, spinal cord with white and gray matter, cervical pia, and CSF. The two models were linked together to construct a finite element (FE) model of the brain-spinal cord complex. The material stiffness and failure properties of porcine cervical pia mater were measured from uniaxial tensile tests with various strain rates at Yamaguchi University. The head-neck model was validated against three sets of brain test data obtained by Nahum et al. (1977), Trosseille et al. (1992), and Hardy et al. (2001) and two sets of neck test data obtained from Thunnissen et al. (1995) and Pintar et al. (1995). Additionally, a series of parametric studies were conducted to investigate the effects of restraint conditions on CNS injuries. The injury criteria for brain injuries were based on Cumulative Strain Damage Measure, while those for spinal cord injuries were based on the ultimate strains of the spinal cord and pia mater. It was found that the brain-spinal cord model was useful to investigate the relationship between the restraint conditions and CNS injuries.