Neck injuries that occur during automobile collisions may lead to chronic symptoms. The objectives of the present investigation were to experimentally determine cervical spine injuries that occur during simulated automotive impacts, and to investigate injury mechanisms.

Using a bench-top mini-sled, a biofidelic whole cervical spine model (occiput-Tl) with muscle force replication and surrogate head underwent simulated head-forward rear impacts (n=6), head-turned rear impacts (n=6) or side impacts at 3.5, 5, 6.5, and 8 g nominal maximum horizontal accelerations of the T1 vertebra, or frontal impacts (n=6) at 4, 6, 8, and 10 g. Ligament injury was defined as a significant increase (p<0.05) in intervertebral flexibility due to impact, above the physiological limit. The injury threshold was the lowest T1 peak acceleration that caused injury. Dynamic ligament strains, spinal canal and intervertebral foramen narrowing, vertebral artery elongation, intervertebral rotations, spinal curvature, spinal loads and the Intervertebral Neck Injury Criterion (IV-NIC) were determined during each impact as functions o f time.

The injury threshold acceleration was 5 g for head-forward and head-turned rear impacts, 6.5 g for side impact, and 8 g for frontal impact. Based upon the flexibility data and IV-NIC peaks, the highest injury potential was at the middle and lower cervical spine (C3/4 to C7/T1) for all impact configurations. During head-forward rear impact, the cervical spine was subjected to not only bending moments, but also large axial and shear forces. These combined loads caused both intervertebral rotations and translations. Significantly greater potential for ganglia com pression injury existed at C3/4 and C4/5 during head-turned rear impact, as compared to head-forw ard rear impact. During frontal impact, supraspinous and interspinous ligaments and ligam entum flavum were risk for injury due to excessive dynamic strains. Elongation-induced vertebral artery injury was more likely to occur during side and head-turned rear impacts, as compared to frontal and head-forward rear impacts.

The present results enhance our understanding of neck injury mechanisms during automobile collisions.