Cervical spine curvature during simulated rear crashes with energy-absorbing seat

BACKGROUND CONTEXT: Epidemiological studies indicate potential benefits of the Whiplash Protection System (WHIPS) for reducing neck injury risk. PURPOSE: Our goal was to evaluate cervical spine curvature during simulated rear crashes of a Human Model of the Neck (HUMON) within a WHIPS seat with fixed head restraint (HR). STUDY DESIGN: In vitro biomechanical study. METHODS: The HUMON consisted of a human neck specimen mounted to the torso of BioRID II (Denton ATD, Inc., Milan, OH, USA) and carrying a surrogate head stabilized with muscle force replication. The HUMON was subjected to simulated rear crashes in a WHIPS seat (n=6) at 9.9, 12.0, and 13.3 g and in a seat with no WHIPS or HR (n=6) at 11.5 g. Statistical tests (p <.05) determined significant increases in spinal motion peaks during the crashes with WHIPS relative to physiologic and significant differences in spinal curvature peaks between WHIPS (12.0 g) and no WHIPS or HR (11.5 g). RESULTS: The WHIPS absorbed crash energy during the initial 75 milliseconds, while peak lower cervical spine (LCS) extension occurred as late as 179 milliseconds. The average C7/T1 rotation peaks during the 13.3-g rear crashes with WHIPS significantly exceeded physiologic by 95% in flexion (4.3 degrees vs. 2.2 degrees) and more than 225% in extension (9.8 degrees vs. 3.0 degrees). The WHIPS caused a significant reduction in average peak normalized LCS extension as compared with no WHIPS or HR (1.2 vs. 3.7). CONCLUSIONS: Although the peak LCS extension was significantly reduced due to WHIPS as compared with no WHIPS or HR, it exceeded physiologic as the cervical spine maintained a prolonged S-shaped curvature. Nonphysiologic LCS motion may occur even if head/HR contact occurs early, and injury is possible before head/HR contact even with a modern energy-absorbing seat. Future whiplash-reduction systems will most likely integrate active injury prevention systems with advanced features such as accident avoidance technology. (C) 2011 Elsevier Inc. All rights reserved.