MILITARY MEDICINE, 186, S1:424, 2021 Pelvic Injury Risk Curves for the Military Populations From Lateral Impact Narayan Yoganandan PhD * ; Tyler F. Rooks MS † ; Valeta Carol Chancey PhD † ; Frank A. Pintar PhD * ; Anjishnu Banerjee PhD ‡ ABSTRACT Introduction: Current methods for transporting military troops include nonstandard seating orientations, which may result in novel injuries because of different types/directions of loading impact. The objective of this study is to develop pelvic injury risk curves (IRCs) under lateral impacts from human cadaver tests using survival analysis for application to military populations. Methods: Published data from lateral impacts applied to whole-body cadaver specimens were analyzed. Forces were treated as response variables. Demographics and body mass index (BMI) were covariates. Injury risk curves were developed for forces without covariates, for males, females, 83 kg body mass, and 25 kg/m 2 BMI. Mean and ± 95% confdence interval IRCs, normalized confdence interval sizes at discrete risk levels, and quality indices were obtained for each metric- covariate combination curve. Results: Mean age, stature, total body mass, and BMI were 70.1 ± 8.6 years, 1.67 ± 0.1 m, 67.0 ± 14.4 kg, and 23.9 ± 3.97 kg/m 2 , respectively. For a total body mass of 83 kg, peak forces at 10%, 25%, and 50% probability levels were 5.7 kN, 7.4 kN, and 9.6 kN, respectively. For males, peak forces at the 10%, 25%, and 50% probability levels were 4.8 kN, 6.4 kN, and 8.4 kN, respectively. For females, peak forces at the 10%, 25%, and 50% probability levels were 3.0 kN, 4.0 kN, and 5.2 kN, respectively. Other data and risk curves are given. Conclusions: The IRCs developed in this study can be used as injury criteria for the crashworthiness of future generation military vehicles. The introduction of BMI, sex, and total body mass as covariates quantifed their contributions. These IRCs can be used with fnite element models to assess and predict injury in impact environments to advance Soldier safety. Manikins specifc to relevant military anthropometry may be designed and/or evaluated with the present IRCs to assess and mitigate musculoskeletal injuries associated with this posture and impact direction. INTRODUCTION Current methods for transporting troops in the military include many nonstandard seating orientations. 1, 2 For exam- ple, seats in the rear of the H-46 and H-47 platforms are side-facing seats with troops facing into the fuselage, which is in contrast to the more conventional forward- facing or rear-facing seats with fore-aft orientations. Seats in the rear of many ground vehicle platforms are also oriented with troops facing inward. 1, 2 Military occupants * Center for NeuroTrauma Research, Department of Neurosurgery, Med- ical College of Wisconsin, Milwaukee, WI, 53226, USA † Injury Biomechanics and Protection Group, U.S. Army Aeromedical Research Laboratory, Fort Rucker, AL, 36362, USA ‡ Division of Biostatistics, Medical College of Wisconsin, Milwaukee, WI, 53226, USA Presented as an oral talk at the 2019 Military Health System Research Symposium, Kissimmee, FL; MHSRS-19-00482 The views expressed are solely those of the authors and do not necessarily represent the offcial position or policy of the sponsors of the research study. doi:10.1093/milmed/usaa303 © The Association of Military Surgeons of the United States 2021. All rights reserved. For permissions, please e-mail: journals. permissions@oup.com. seated orthogonally to the line of travel may sustain lat- eral impact loading to the pelvis during crash events. 1, 2 Additionally, ground and aviation platforms and troop trans- port methods currently under development through the Next- Generation Combat Vehicle and future vertical lift cross- functional teams may also include nonstandard seating orientations. During impact events, current and future passengers trans- ported in military vehicles may be exposed to types of impacts and directions or vectors that are different from the civil- ian automotive experience. In principle, military occupant exposure to trauma as well as the mitigation of impacts par- allel many of the exposures encountered in and follow the research practice used in the civilian automotive feld. A military unique exposure has recently lead to military-based studies that focused on vertical loading from underbody blast- type impacts, and human tolerances have been derived in the form of injury risk curves for the pelvis-thoracolumbar com- plex from human cadaver tests. 3 There is, however, a paucity of data in the other loading directions. Therefore, the objec- tive of this study is to develop military-relevant pelvic injury risk curves for the pelvis under lateral impacts from available 424 MILITARY MEDICINE, Vol. 186, January/February Supplement 2021 Downloaded from https://academic.oup.com/milmed/article/186/Supplement_1/424/6119460 by guest on 16 October 2021