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Whiplash Mechanics in Low Speed Rear-End Automobile Collisions

Objectives: To develop a biomechanical model that can help determine the exposure to potential physical injury based on the rebound flexion moment [acceleration load] of the head and neck. Methods: By review of the biomechanical literature on rear-end collisions, to determine the impact force and the resulting acceleration to which the victim[s] had been exposed, and to determine the rebound flexion load acting on the cervical spine. To compare the developed formulation of the flexion load to measures taken from a staged rear-end impact experiment. To make adjustments to the injury threshold based on the above formulation, based on age, gender, and head position. Results: In target vehicle velocity changes of 4.9 mph [7.8 kph] with peak vehicle acceleration of 3.0 g, the peak linear head acceleration was predicted to be 5.9 g, with peak rotational acceleration of 237 rad/sec2. The resulting flexion moment about the occipital condyles was calculated to be about 20 ft-1bs [34 Nm], which was comparatively about 46% of the tolerance for a normal adult male, 53% of the tolerance for an elderly male, 68% of the tolerance of a young female, and 101% of the tolerance for an elderly female. Non-normal population groups were not calculated. Conclusions: Low velocity rear-end collisions should not likely expose a normal adult male or female to potential physical injury due to rebound flexion loading, but may expose an elderly female to injury.