Inertia Effect of the Heart as a Contributing Factor in Aortic Injuries in Near-Side Impacts Open Access
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Blunt trauma aortic injuries are one of the leading causes of fatalities in side-impact crashes. The blunt trauma that occurs in side-impacts can cause partial or total rupture of the aorta, resulting in excessive blood loss and, potentially, death. Previous studies (Steps 2004) (Bertrand, et al., 2008) have established crash factors that could be used to predict aortic injury using real-world cases. Other studies have attempted to establish the injury mechanisms for aortic injury. This study attempts to further investigate the proposed injury mechanisms for aortic injury such as Viscous Criterion, Chest Compression and the inertial effect of the heart in the thoracic cavity. Criteria that use Chest Compression and compression velocity (Hardy, et al., 2008) have demonstrated that the aorta is very weak in resisting tension loading that may be caused by the motion of the heart relative to the aortic arch. Other studies, with cadavers subjected to side-impact conditions, suggested that aortic injury was influenced by the magnitude of the upward acceleration acting parallel to the spine (Cavanaugh, et al., 2005). One purpose of this study is to further evaluate the forces that act on the aorta, including those produced by the heart as a consequence of upward acceleration. Several scenarios were modeled using LS-DYNA and MADYMO to reproduce currently available tests. These tests include the NCAP, NCAP Y-Damage and IIHS Side-impact test. These scenarios were varied by adding airbags to determine the degree to which these safety systems reduced the risk of aortic injury. Sled tests were also modeled with and without a six inch pelvic offset in order to reproduce Cavanaugh's cadaver sled tests (Cavanaugh, et al., 2005). The effect of Spinal Acceleration is studied by adding a spring mass model within the Human Facet MADYMO Model, and exposing the resulting model to the selected crash environments. The inertia of the heart causing the aorta to stretch in the longitudinal direction is proposed as a possible injury mechanism. Results conclude that the inertia effect is a possible factor in the injury mechanisms of aortic rupture.