192 Effect of Helmet on Cervical Spine Biomechanics in Rear Impact Scenario (Whiplash)

Abstract

INTRODUCTION: Rear impact (whiplash) is a common scenario has been studied previously by subjecting the head-neck complex under postero-anterior acceleration. There is a lack of studies investigating the effect of helmet on cervical spine biomechanics despite its common use in military and competitive automotive environments. METHODS: We developed a finite element model of the head-neck complex simulating the three spinal columns with layered intervetebral discs and ligaments. This was then validated against a cadaver (head to T1) model which was fixated to a sled on linear rails with a rear pendulum that simulated rear impact scenario. Standard-issue US Military Combat helmets in small, medium, large sizes were modeled and mounted on the finite element model. 1.8 m/s and 2.6 m/s velocity profiles were simulated and the range of motion at each functional spinal unit from C2-3 to C7-T1 was measured. RESULTS: Segmental motions were measured over 120 ms for all scenarios. 2.6 m/s vector resulted in peak acceleration of 3.5 g, and 1.8 m/s resulted in 2.5 g. Helmet use increased the range of motion at all segments from C2-3 to C7-T1. The greatest range of motion occurred at C5-6, followed by C6-7 and C7-T1. Greatest percentage increase in motion occurred at C2-3 followed by C5-6. Increasing helmet size resulted in increasing motion at all spinal segments. CONCLUSIONS: Helmet use, although protective for the cranium, significantly increases the motion at all spinal segments, especially C2-3 and C5-7, in a rear impact scenario (whiplash). Increasing helmet size results in greater motion change at all cervical spine segments. This is important to consider when designing the helmet and determining the need for additional head-mounted gear in both military and competitive automotive environments.