The Mechanical Response and Tolerance of the Anteriorly-Tilted Human Pelvis Under Vertical Loading
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Annals of Biomedical Engineering (Ó 2020) https://doi.org/10.1007/s10439-020-02634-6
WIAMan Biomechanics
The Mechanical Response and Tolerance of the Anteriorly-Tilted Human Pelvis Under Vertical Loading R. S. SALZAR ,1 E. M. SPRATLEY,1 K. A. HENDERSON,1 P. C. GREENHALGH,1 J. Z. ZHANG,2 B. J. PERRY,1 and J. A. MCMAHON1 1
Center for Applied Biomechanics, University of Virginia, Charlottesville, VA, USA; and 2Johns Hopkins Applied Physics Laboratory, Laurel, MD, USA (Received 7 May 2020; accepted 19 September 2020) Associate Editor Stefan M. Duma oversaw the review of this article.
Abstract—Military vehicle underbody blast (UBB) is the cause of many serious injuries in theatre today; however, the effects of these chaotic events on the human body are not well understood. The purpose of this research was to replicate UBB loading conditions on the human pelvis and investigate the resulting response in a controlled laboratory setting. In addition to better understanding the response of the human pelvis to high rate vertical loading, this test series also aimed to identify high rate injury thresholds. Twentyseven post mortem human surrogate (PMHS) component pelvis tests were completed using the University of Virginia’s (UVa) simulated blast rig under a range of loading conditions and postures. Of those tests, 17 were in the anteriorlytilted posture and used to construct the human injury probability curve. Average seat pan (rigid) accelerations for this subset of tests ranged from 300 to 2400 g over 2 to 3 ms of positive phase duration. Post-test computed tomography (CT) scans and necropsies were performed to determine injuries and revealed a frequent occurrence of anterior and posterior injuries, resulting in unstable pelvis ring fractures. The resulting Human Injury Probability Curve (HIPC) yielded mean forces of 5529, 8516, and 12431 N as measured by mass compensated seat platen loadcells applied through the rigid seat to the bilateral ischium are associated with a 10, 25, and 50% risk for unstable pelvic ring sacrum fractures in an anteriorly-tilted pelvis (28° from vertical), respectively. Keywords—Pelvis, Risk, Blast, Survival, Regression, Fracture, High-rate, Acceleration.
Address correspondence to R. S. Salzar, Center for Applied Biomechanics, University of Virginia, Charlottesville, VA, USA. Electronic mail: [email protected]
INTRODUCTION Underbody blasts (UBB) are high-energy events characterized by very high accelerations and short duration loads on the underside of a vehicle. These events typically occur from a bomb, mine, or improvised explosive device (IED).21 The occupants are subjected to a primarily vertical load by the seat which has transmitted the explosive energy of the blast through the vehicle structure to the seated occupants. Injuries from the vertical loading are considered tertiary, as mine-resistant ambush protected (MRAP) vehicles are specifically designed to shield occupants against the blast shock wave and ejected fragments—the source of primary and secondary injuries, respectively. The
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