Evaluation of the Kinematic Responses and Potential Injury Mechanisms of the Jejunum during Seatbelt Loading.

High-speed biplane x-ray was used to research the kinematics of the small intestine in response to seatbelt loading. Six driver-side 3-point seatbelt simulations were conducted with the lap belt routed superior to the pelvis of six unembalmed human cadavers. Testing was conducted with each cadaver perfused, ventilated, and positioned in a fixed-back configuration with the spine angled 30° from the vertical axis. Four tests were conducted with the cadavers in an inverted position, and two tests were conducted with the cadavers upright. The jejunum was instrumented with radiopaque markers using a minimally-invasive, intraluminal approach without inducing preparation-related damage to the small intestine. Tests were conducted at a target peak lap belt speed of 3 m/s, resulting in peak lap belt loads ranging from 5.4-7.9 kN. Displacement of the radiopaque markers was recorded using high-speed x-ray from two perspectives. Marker trajectories were tracked using motion analysis software and projected into calibrated three-dimensional coordinates to quantify the seatbelt and jejunum kinematics for each test. Five of the six tests resulted in jejunum damage. Based on the autopsy findings and the assessment of the belt and jejunum kinematics, it is likely that direct abdominal interactions with the seatbelt resulting in compression and stretch of the jejunum are components of the mechanisms of crash-induced jejunum injuries. In addition, the presence of fluid or air in the portion of the jejunum in the load path appears to be necessary to create jejunum damage in the cadaver model. Overall, the kinematics and damage data generated in this study may be useful for future restraint system development.

The effects of cadaver orientation on the relative position of the abdominal organs.

Biplane x-ray was used to image two cadavers in upright and inverted postures, and the three-dimensional variation in the relative abdominal organ position was quantified. The abdominal organs of each surrogate were instrumented with radiopaque markers using a minimally invasive approach. Imaging was performed with a known stomach volume, with residual air removed from the abdominal cavity, and with ventilation and perfusion. Marker positions were determined in two planar x-ray perspectives using target tracking software and projected into calibrated three-dimensional coordinates. Intuitive changes in organ position were observed with the effect of gravity in the upright orientation; in the superior-inferior direction, the separation between the most cranial and caudal diaphragm and liver markers was 95 mm to 169 mm. When inverted, the abdominal organs shifted cranially and fell within 66 to 81 mm in the superior-inferior direction. The relative change in position of the diaphragm markers, determined as the vector magnitude from the upright to the inverted position, was 99 to 121 mm. These data were scaled and compared to positional MRI data from nine human subjects in seated postures and the Global Human Body Models Consortium (GHBMC) model geometry. The overall shapes and relative positions of the inverted cadaver organs compared better to the human subjects and model geometry. These results give rise to several issues for consideration when interpreting cadaver test results and comparing them to finite element simulations and their associated injury prediction abilities.

Deflection measurement system for the hybrid iii six-year-old biofidelic abdomen.

Motor vehicle collisions are the leading cause of death for children ages 5 to 14. Enhancement of child occupant protection is partly dependent on the ability to accurately assess the interaction of child-size occupants with restraint systems. Booster seat design and belt fit are evaluated using child anthropomorphic test devices, such as the Hybrid III 6-year-old dummy., A biofidelic abdomen for the Hybrid III 6-year-old dummy is being developed by the Ford Motor Company to enhance the dummy’s ability to assess injury risk and further quantify submarining risk by measuring abdominal deflection. A practical measurement system for the biofidelic abdominal insert has been developed and demonstrated for three dimensional determination of abdominal deflection. Quantification of insert deflection is achieved via differential signal measurement using electrodes mounted within a conductive medium. Signal amplitude is proportional to the distance between the electrodes. A microcontroller is used to calculate distances between ventral electrodes and a dorsal electrode in three dimensions. This system has been calibrated statically, and its performance demonstrated in a series of sled tests. Deflection measurements from the instrumented abdominal insert indicate performance differences between two booster seat designs, yielding an average peak anterior to posterior displacement of the abdomen of 1.0 ± 3.4 mm and 31.2 ± 7.2 mm for the seats, respectively. Implementation of a 6-year-old abdominal insert with the ability to evaluate submarining potential will likely help safety researchers further enhance booster seat design and interaction with vehicle restraint systems , and help to further understand child occupant injury risk in automobile collisions.

Material properties of the post-mortem colon in high-rate equibiaxial elongation.

Crash-induced injuries of the colon that occur in motor vehicle collisions include perforations, serosal tears, and ischemic colon injuries. To characterize the biomechanical response of the colon associated with these failure modes, high-rate equibiaxial stretch was applied to cruciate tissue samples harvested from four post-mortem human surrogates. Sample arms were gripped in four low-mass tissue clamps and simultaneous motion of four carriages applied equibiaxial stretch in four orthogonal directions. Tests were conducted to failure at a target strain rate of 100s-1 to investigate failure at rates expected to be experienced in motor vehicle collisions. Overhead high-speed video captured at 2500fps provided optical marker displacement data in a central region of interest. Marker positions were tracked using motion analysis software. Displacement data were input into LS-DYNA and average Green-Lagrange strain was calculated at 0.05ms time intervals. All data were truncated at tear initiation determined from high-speed video analysis. This manuscript presents the results of 26 colon tests conducted at an average strain rate of 67.1±17.9s-1. Average failure strain was 0.164±0.046 and 0.139±0.042 in the circumferential and longitudinal directions. Average maximum principal failure strain was 0.211±0.064. Material property data acquired in this study contribute to the biomechanical dataset useful for human body finite element model validation.

Kinematics of the thoracoabdominal contents under various loading scenarios.

High-speed biplane x-ray was used to investigate relative kinematics of the thoracoabdominal organs in response to blunt loading. Four post-mortem human surrogates instrumented with radiopaque markers were subjected to eight crash- specific loading scenarios, including frontal chest and abdominal impacts, as well as driver-shoulder seatbelt loading. Testing was conducted with each surrogate perfused, ventilated, and positioned in an inverted, fixed-back configuration. Displacement of radiopaque markers recorded with high-speed x-ray in two perspectives was tracked using motion analysis software and projected into calibrated three-dimensional coordinates. Internal organ kinematics in response to blunt impact were quantified for the pericardium, lungs, diaphragm, liver, spleen, stomach, mesentery, and bony structures. These data can be used to better understand the interaction of anatomical structures during impact and the associated injury mechanisms, and for the development or validation of human body finite element models.