Post Mortem Human Surrogate Research Articles

Effect of data censoring on thoracic injury risk curves

Objective The first objective was to evaluate the effect of using less censored (i.e., exact and interval-censored) data on thoracic injury risk curves and the resulting injury probabilities. The second objective was to generate new injury risk curves to predict Abbreviated Injury Scale (AIS) 3+ rib fractures based on chest deflection. Methods Two data sets consisting of postmortem human surrogate (PMHS) tests with multipoint chest deflection measurements were compiled: A less censored data set consisting of exact and interval-censored data and a doubly censored data set consisting of left- and right-censored data. Chest deflection data from both data sets were processed in a consistent manner to calculate the maximum deflections at different locations across the chest. Survival analysis methods were used to generate nonparametric and parametric injury risk curves for serious skeletal injury. The total sample sizes and proportions of less censored data used to generate the risk curves were varied for each curve to evaluate the effects of sample size and less censored data on risk curve shape and predicted injury thresholds. Results Increasing the proportion of less censored data resulted in steeper injury risk curves and a higher predicted risk for a given amount of deflection. Differences in injury risk were more pronounced in the upper half of the injury risk curves. Introducing less censored data also produced narrower confidence intervals. At a total sample size of 79, increasing the percentage of less censored data from 0 to 30 had minimal effect on the shape of the risk curve. Conclusions Doubly censored chest deflection data have historically been used to generate thoracic injury risk curves for frontal motor vehicle crash events. This study found that incorporating less censored data into thoracic injury risk curves meaningfully affected the shape of the injury risk curves and their resulting injury risk predictions. All of the injury risk curves generated in the study predicted a lower threshold for serious rib fracture injury compared to previously developed injury risks curves that are currently in use in the field. Based on the results of this study, adding less censored data to injury risk curves should be strongly considered to improve thoracic injury risk curve prediction and confidence, especially for smaller sample sizes.

Determination of distal fibula fracture for prediction of ankle injuries

Objective This study quantified the local fracture tolerance of the distal fibula. The purpose of this data is to refine the understanding of ankle fracture tolerance in the population and enhance injury prediction by computational tools. Methods Fracture patterns of the fibula were obtained from the US National Highway Traffic Safety Administration (NHTSA) Crash Injury Research Engineering Network (CIREN). Of 143 cases of ankle injury, 120 included fibula fracture, many of which accompanied by radiology images. The most common fibula fracture type was a Weber C fracture, which was then used as the testing target to replicate with postmortem human surrogates. Isolated distal fibulae (male and female, across a wide anthropometric range) were subjected to quasi-static lateral-medial four-point bending superimposed on axial precompression. Results Of the 20 specimens tested, 17 fractured in compression and bending, two fractured in compression, bending, and shear, and one did not fracture upon the imposed displacement. Fractures occurring outside of the target testing span were treated as right-censored data points. Fracture patterns varied among specimens, with oblique fractures being most common, followed by segmental fractures. At failure, compressive force ranged from 77 N to 370 N and bending moment from 17 Nm to 47 Nm. Conclusions From the 19 fractured specimens, the variety of fracture patterns observed were generally consistent with the range of fibula fracture types and locations commonly observed in the field. While comparative studies with fibula specimens are largely absent from literature, comparison of this study to other long bones (radius and ulna) show that bending moment at fracture is similar. To the author’s knowledge, this is the first study to quantify the fracture tolerance of isolated distal fibulae under loading conditions representative of ankle injury mechanisms in motor vehicle collisions. By combining the results of this study with complementary results from parallel tibia-focused experiments (currently in-press), these results will aid development of tissue-level lower leg fracture prediction of human body models, thus enhancing prediction of ankle injury during safety assessment simulations. Specifically, the fracture tolerance information might generate an injury risk function to guide tissue-level injury prediction with human body models.

Comparison of Adult Female and Male PMHS Pelvis and Lumbar Response to Underbody Blast.

The goal of this study was to gather and compare kinematic response and injury data on both female and male whole-body Post-mortem Human Surrogates (PMHS) responses to Underbody Blast (UBB) loading. Midsized males (50th percentile, MM) have historically been most used in biomechanical testing and were the focus of the Warrior Injury Assessment Manikin (WIAMan) program, thus this population subgroup was selected to be the baseline for female comparison. Both small female (5th percentile, SF) and large female (75th percentile, LF) PMHS were included in the test series to attempt to discern whether differences between male and female responses were predominantly driven by sex or size. Eleven tests, using 20 whole-body PMHS, were conducted by the research team. Preparation of the rig and execution of the tests took place at the Aberdeen Proving Grounds (APG) in Aberdeen, MD. Two PMHS were used in each test. The Accelerative Loading Fixture (ALF) version 2, located at APG's Bear Point range was used for all male and female whole-body tests in this series. The ALF was an outdoor test rig that was driven by a buried explosive charge, to accelerate a platform holding two symmetrically mounted seats. The platform was designed as a large, rigid frame with a deformable center section that could be tuned to simulate the floor deformation of a vehicle during a UBB event. PMHS were restrained with a 5-point harness, common in military vehicle seats. Six-degree-of-freedom motion blocks were fixed to L3, the sacrum, and the left and right iliac wings. A three-degree-of freedom block was fixed to T12. Strain gages were placed on L4 and multiple locations on the pelvis. Accelerometers on the floor and seat of the ALF provided input data for each PMHS' feet and pelvis. Time histories and mean peak responses in z-axis acceleration were similar among the three PMHS groups in this body region. Injury outcomes were different and seemed to be influenced by both sex and size contributions. Small females incurred pelvis injuries in absence of lumbar injures. Midsized males had lumbar vertebral body fractures without pelvis injuries. And large females with injuries had both pelvis and lumbar VB fractures. This study provides evidence supporting the need for female biomechanical testing to generate female response and injury thresholds. Without the inclusion of female PMHS, the differences in the injury patterns between the small female and midsized male groups would not have been recognized. Standard scaling methods assume equivalent injury patterns between the experimental and scaled data. In this study, small female damage occurred in a different anatomical structure than for the midsized males. This is an important discovery for the development of anthropomorphic test devices, injury criteria, and injury mitigating technologies. The clear separation of small female damage results, in combination with seat speeds, suggest that the small female pelvis injury threshold in UBB events lies between 4 - 5 m/s seat speed. No inference can be made about the small female lumbar threshold, other than it is likely at higher speeds and/or over longer duration. Male lumbar spine damage occurred in both the higher- and lower lower-rate tests, indicating the injury threshold would be below the seat pulses tested in these experiments. Large females exhibited injury patterns that reflected both the small female and midsized male groups - with damaged PMHS having fractures in both pelvis and lumbar, and in both higher- and lower- rate tests. The difference in damage patterns between the sex and size groups should be considered in the development of injury mitigation strategies to protect across the full population.

Frontal-Crash Occupant Protection in the Rear Seat: Submarining and Abdomen/Pelvis Response in Midsized Male Surrogates.

Frontal-crash sled tests were conducted to assess submarining protection and abdominal injury risk for midsized male occupants in the rear seat of modern vehicles. Twelve sled tests were conducted in four rear-seat vehicle-bucks with twelve post-mortem human surrogates (PMHS). Select kinematic responses and submarining incidence were compared to previously observed performance of the Hybrid III 50th-percentile male and THOR-50M ATDs (Anthropomorphic Test Devices) in matched sled tests conducted as part of a previous study. Abdominal pressure was measured in the PMHS near each ASIS (Anterior Superior Iliac Spine), in the inferior vena cava, and in the abdominal aorta. Damage to the abdomen, pelvis, and lumbar spine of the PMHS was also identified. In total, five PMHS underwent submarining. Four PMHS, none of which submarined, sustained pelvis fractures and represented the heaviest of the PMHS tested. Submarining of the PMHS occurred in two out of four vehicles. In the matched tests, the Hybrid III never underwent submarining while the THOR-50M submarined in three out of four vehicles. Submarining occurred in vehicles having both conventional and advanced (pretensioner and load limiter) restraints. The dominant factors associated with submarining were related to seat pan geometry. While the THOR-50M was not always an accurate tool for predicting submarining in the PMHS, the Hybrid III could not predict submarining at all. The results of this study identify substantive gaps in frontal-crash occupant protection in the rear seat for midsized males and elucidates the need for additional research for rear-seat occupant protection for all occupants.

Comparative biofidelity of the Hybrid III and THOR 50th male ATDs under three restraint conditions during frontal sled tests

Objective The purpose of this study was to provide a whole-body biofidelity assessment of the Hybrid III (HIII) and THOR 50th percentile male anthropomorphic test devices (ATDs) during frontal sled tests, incorporating data from kinematics, chest deflection, and test buck reaction load cells. Additionally, the accuracy of the injury risk prediction capabilities for each ATD was evaluated against injuries observed in matched postmortem human surrogate (PMHS) tests. Methods Sled tests, designed to simulate a United States New Car Assessment Program (US-NCAP) frontal test, were conducted using the HIII, THOR, and 8 approximately 50th percentile male PMHS under 3 restraint conditions. The test buck was instrumented with load cells on the steering column, knee bolster supports, and foot supports. ATD and PMHS reaction force–time histories were quantitatively compared using the ISO/TS-18571 objective rating metric. Previously published biofidelity analyses of kinematic and chest deflection data from the same tests were combined with the reaction force analyses to perform an overall assessment of the comparative biofidelity of each ATD. Injury risk predictions from existing HIII and proposed THOR injury risk curves for the US-NCAP were compared to observed injuries. Results For the reaction forces, the HIII and THOR had similar levels of biofidelity on average, except for 2 locations. The HIII produced more biofidelic knee bolster support forces, and the THOR lap belt forces were more biofidelic. The comparative biofidelity of the ATDs also varied by body region. The THOR head response was more biofidelic, whereas the HIII thorax and lower extremity responses had higher biofidelity. When all body regions were pooled, the HIII was more biofidelic, but differences between ATDs were generally small. Both ATDs were able to predict the observed injuries, except for the HIII chest, HIII neck, and THOR neck, all of which underpredicted PMHS injury outcomes. Conclusions This study revealed that biofidelity assessed through response time histories and accuracy of injury risk predictions do not always align. Specifically, the HIII had marginally better time history biofidelity, whereas the THOR had better injury prediction. However, not all THOR responses could be fully assessed, so more work is needed to assess the THOR in complex loading environments.

Effect of axial compression on stiffness and deformation of human lumbar spine in flexion-extension

Objective The goal of this study was to evaluate the effect of axial compression, employed with a follower-load mechanism, on the response of the lumbar spine in flexion and extension bending. Additional goals include measurement of both the kinetic (stiffness) and kinematic (deformation distribution) responses, evaluating how the responses vary across specimens, and to develop response corridors that can be used to evaluate human body models (HBMs) and anthropomorphic test devices (ATDs). Methods Seven mid-sized male adult lumbar spines (T12-S1) from postmortem human surrogates were tested in subinjurious flexion and extension bending with 0, 900, and 1800 N of superimposed axial compression. Tests were performed in load-control with a 6-DOF robotic test system that applied pure flexion and extension moments to the specimens, and axial compression was directed along the spine’s curvature via a follower load mechanism powered by force-controlled linear actuators. Load-deformation response data were captured and used to characterize the kinetic response of the lumbar spine in flexion/extension, and how it varies with axial compression. Individual vertebral kinematics were captured using 3D motion capture and the data was used to illustrate the distribution of bending deformation across each intervertebral joint of the spine, as well has how that distribution changes with axial compression. These response data were used to develop elliptical path-length parameterized response corridors for surrogate biofidelity evaluation. Results The lumbar spine was found to be generally stiffer in extension than in flexion, but this difference decreased with increasing axial compression. The lumbar spine exhibited a nonlinear kinetic (moment vs. angle) response in flexion that became more linear and stiffer with the addition of axial compression. In flexion without axial load, the majority of the bending deformation occurred at the L5-S1 joint, whereas in extension, deformation was more evenly distributed across the different intervertebral levels, but the locus of deformation was located in the mid-proximal lumbar at L2-L3. Conclusions The superposition of axial compression in the lumbar spine affects the kinetic and kinematic response of the lumbar spine in flexion and extension. The response data and approach detailed in this study permit better assessment of ATD and HBM biofidelity.

Biofidelity Assessment of the WIAMan Thorax by a Comparative Study With Hybrid III, THOR, and PMHS in Frontal Sled Testing.

The Warrior Injury Assessment Manikin (WIAMan) anthropomorphic test device (ATD) has been originally developed to predict and prevent injuries for occupants in military vehicles, in an underbody blast environment. However, its crash performance and biofidelity of the thoracic region have not been explored. The aim of this study was to determine and evaluate the WIAMan thoracic responses in a typical frontal sled test. The 40 kph frontal sled tests were conducted to quantify the WIAMan thoracic kinematics, chest deflection, and belt loads. Comparative biofidelities of the WIAMan thorax and other surrogates, including postmortem human surrogates (PMHSs), Hybrid III, and test device for human occupant restraint (THOR) ATDs, were assessed under comparable testing conditions. The similarities and differences between WIAMan and the other surrogates were compared and analyzed, including the motion of bilateral shoulders and T1, time histories of chest deflections, and belt loads. The CORrelation and Analysis (CORA) ratings were used to evaluate the correlations of thoracic responses between the ATDs and PMHS. Compared to the PMHS and THOR, the WIAMan experienced a similar level of left shoulder forward excursions. Larger chest deflection was exhibited in WIAMan throughout the whole duration of belt compression. Differences were found in belt loads between subject types. Overall, WIAMan had slightly lower CORA scores but showed comparable overall performance. The overall thoracic responses of WIAMan under the frontal sled test were more compliant than HIII, but still reasonable compared with PMHS and THOR. Comprehensive systematic studies on comparative biofidelity of WIAMan and other surrogates under different impact conditions are expected in future research.

A current assessment of the THOR 50M in rear impacts

Objective This study presents a comparison of the Test Device for Human Occupant Restraint (THOR) 50M and Hybrid III (HIII) 50M anthropomorphic test device (ATD) geometries and rear impact head and neck biofidelity to each other and to postmortem human surrogate (PMHS) data to evaluate the usefulness of the THOR in rear impact testing. Methods Both ATDs were scanned in a seated position on a rigid bench seat. A series of rear impact sled tests with the rigid bench seat with no head restraint support were conducted with a HIII-50M at 16 and 24 kph. Tests at each speed were performed twice with the THOR-50M to allow an assessment of the repeatability of the THOR-50M. A comparison of the test results from THOR-50M testing were made to the results of a previous study that included PMHS. Rear impact sled tests with both ATDs in a modern seat were then conducted at 40 kph. Results The THOR-50M head was 48.4 mm rearward and 60.1 mm higher than the HIII-50M head when seated in the rigid bench seat. In the repeated rigid bench testing at 16 and 24 kph, the THOR-50M head longitudinal and vertical accelerations, upper neck moment, and overall kinematics showed good test-to-test repeatability. In the rigid bench tests, the THOR-50M neck experienced flexion prior to extension in the 16 kph tests, where the neck of the HIII only experienced extension. At 24 kph both ATDs only experienced extension. The THOR-50M head displaced more rearward at both test velocities. The rigid bench tests show that the THOR-50M neck allows for more extension motion or articulation than the HIII-50M neck. The rigid bench test also shows that the head longitudinal and vertical accelerations, angular head kinematics, and upper neck moments were reasonably comparable between the ATDs. The THOR-50M results were closer to the average of the PMHS results than the HIII-50-M results, with the exception of the upper neck. In the 40 kph tests, with a modern seat design, the THOR-50M resulted in more deformation of the seatback with greater head restraint loading than the HIII-50M. The THOR-50M head backset distance was less. Conclusion This study provides insight into the differences and similarities between the THOR and the HIII-50M ATD geometries, instrumentation responses, and kinematics, as well as the repeatability of the THOR-50M in rear impacts testing. The overall geometries of the THOR-50M and the HIII-50M are similar. The seated head position of the THOR-50M is slightly further rearward and higher than the HIII-50M. The results indicate that the THOR-50M matches the PMHS results more closely than the HIII-50M and may have improved neck biofidelity in rear impact testing. The results indicate that the studied THOR-50M responses are repeatable within expected test-to-test variations in rear impacts. Early data suggest that the THOR-50M can be used in rear impact testing, though a more complete understanding of the THOR-50M differences to the HIII ATDs will allow for better correlation to the existing body of HIII rear impact testing.

Behind Shield Blunt Trauma: Characterizing the Back-Face Deformation of Shields with a Focus on Upper Limb Loading.

Shield back-face deformation (BFD) is the result of composite ballistic shields deflecting or absorbing a projectile's energy and deforming towards the user. BFD can result in localized loading to the upper extremity, where the shield is secured to the user. An augmented anthropomorphic test device upper extremity was used to quantify this applied load. Four locations along the upper extremity were tested-the hand, wrist, forearm, and elbow-for investigating differing boundary conditions and their effect on resultant load. Varying stand-off distances, the distance between the back of the shield and the force sensor, were investigated. Digital image correlation was also conducted to measure the dynamic displacement of the shield. The mean peak back-face velocity of the shield was 208.4 ± 38.8m/s, while the average affected area was 1505 ± 158.3 mm2. Impulse was not significantly affected by anatomical location for the same stand-off distance; however, as stand-off distance decreased, the measured force significantly increased (p < 0.05). Notably, impact duration did not differ significantly for any of the impact scenarios. This is the first step in developing injury criteria for this region resulting from behind shield blunt trauma, and these data will be used for developing injury thresholds in post-mortem human surrogates.

Research on Occupant Safety in Frontal Collision Based on Different Sitting Positions of Intelligent Vehicles

Abstract: To study the safety of drivers with different sitting positions in intelligent vehicle collision, the slide model of SUV was established and the precision of the model was verified by slide test. The simulation model of driver's attitude was established by THUMS. According to the results of post mortem human surrogate (PMHS), the sitting postures of THUMS at different seat backrest angles were adjusted and the drivers’ injuries of three sitting postures in frontal collision were analyzed. Simulation results show that when the driver was in semi-recumbent and reclining posture, the protective effect of the airbag on the head was obviously reduced in collisions, and the head and chest will be seriously damaged due to the large seat backrest angle, resulting in increased distance between the head and the wheel. Besides, the tilting sitting posture leads to the risk of sunken seat in the collision. Therefore, with the development of autonomous driving technology, not only should intelligent vehicles meet occupants’ comfort requirements, but the collision safety caused by the change of sitting postures should be considered.

Analysis of the spinal 3D motion of postmortem human surrogates in nearside oblique impacts

Objective: The objective of this study is to analyze the 6 degrees of freedom (DOF) motion of the spine using the finite helical axis (FHA) in three postmortem human surrogates (PMHS) sled tests. Methods: The sled test configurations corresponded to a 30° nearside oblique impact at 35 km/h. Two different restraint system versions (RSv) were used. RSv1 was used for PMHS A and B while RSv2 was used for PMHS C. The 6 DOF motion of the head and three selected vertebrae have been analyzed using the FHA which describes the 3 D motion of a rigid body between two instants of time as a rotation about and a translation along a unit vector. A minimal amount of rotation is necessary to the FHA calculation, thus the FHA components have been calculated based on a pre-defined interval of 8° of rotation. Results: The analysis of the FHA components demonstrated right lateral bending until around 100 ms, when the rebound phase was reached and the head and the lower spine undergoes left lateral bending. The three PMHS exhibited, in general, flexion movement of the whole body and torsion to the right side of the occupant. This general motion can be associated to the effect of the seatbelt acting as a fulcrum of the rotational movement of the bony landmarks. The interaction of the PMHS with the retention system can be noted by analyzing the time in which the head and the upper spine initiated the rotation and the sudden changes of rotational direction of the three PMHS’s head. Conclusions: The rotational analyses have shown to be more sensitive to experimental events than the trajectory analyses for the studied physical tests. Additionally, the results presented in the present study contributes to the analysis of the body kinematics during an oblique impact and adds new experimental data for Human Body Models (HBM) and Anthropometric Test Devices (ATD) benchmarking.

Quantifying the Effect of Pelvis Fracture on Lumbar Spine Compression during High-rate Vertical Loading.

Fracture to the lumbo-pelvis region is prevalent in warfighters seated in military vehicles exposed to under-body blast (UBB). Previous high-rate vertical loading experimentation using whole body post-mortem human surrogates (PMHS) indicated that pelvis fracture tends to occur earlier in events and under higher magnitude seat input conditions compared to lumbar spine fracture. The current study hypothesizes that fracture of the pelvis under high-rate vertical loading reduces load transfer to the lumbar spine, thus reducing the potential for spine fracture. PMHS lumbo-pelvis components (L4-pelvis) were tested under high-rate vertical loading and force and acceleration metrics were measured both inferior-to and superior-to the specimen. The ratio of inferior-tosuperior responses was significantly reduced by unstable pelvis fracture for all metrics and a trend of reduced ratio was observed with increased pelvis AIS severity. This study has established that pelvis fracture reduces compression forces at the lumbar spine during high-rate vertical loading, thus reducing the potential for fracture to the lumbar spine. Therefore, pelvis injury potential should be considered when implementing lumbar injury criteria specific to UBB.

CHILD SAFETY IN AUTONOMOUS VEHICLES: "LIVING ROOM" LAYOUT

Autonomous vehicles start to be introduced on our roads and will soon become a reality. Although fatal traffic accidents will be significantly reduced, remaining fatal passenger car crashes should be taken into account to ensure the safety of users. The new highly adaptable interior designs, with totally different layouts from the current ones, may significantly impact occupant safety, especially child passenger safety. Analyzing how these new vehicles affect child safety is a challenge that needs to be addressed. The "living room" layout (face-to-face seating position) is one of the preferences of families traveling with children. Young children need further support and supervision so the possibility of rotating seats to be able to be in front of the small children is a valuable feature for parents. Therefore, new seating orientations away from the forward facing position should be taken into account to ensure children protection. The objective of this study is to evaluate child occupant safety in a "living room" seating position (a possible option in full autonomous vehicles) versus the current forward facing position. Virtual testing methodology was used to perform this study. The virtual PIPER child human body model (HBM) was used. This model is one of the only HBMs developed and validated from child PMHS data (Paediatric Post-Mortem Human Surrogate). The two configurations were defined according with the EuroNCAP child occupant protection test protocol. It was found that the "living room" layout presents worse results according to the child's head injury patterns than in forward facing position. In conclusion, attending to the new seating orientations away from the forward facing position, it is necessary to adapt the restraint systems; otherwise children could suffer potentially dangerous situations.

Analysis of the Spinal 3D Motion of Post-Mortem Human Surrogates in Nearside Oblique Impacts

Analysis of the Spinal 3D Motion of Post-Mortem Human Surrogates in Nearside Oblique Impacts

Deflection-based parametric survival analysis side impact chest injury risk curves AIS 2015

Objectives The objective of this study was to reanalyze lateral postmortem human surrogate (PMHS) sled test chestband data to construct updated lateral thoracic injury risk curves (IRCs) using survival analysis. Methods Chestband and injury data were gathered from 16 previously conducted PMHS sled tests. Briefly, 2 chestbands were wrapped around the thorax’s circumference at the levels of ribs 4 and 8. Tests were conducted at 6.7 m/s on a rigid and padded load wall fixed to the top of a rebound sled. The injuries were reclassified using the Abbreviated Injury Scale (AIS) 2015 coding scheme. Chestband signals were combined with pretest specimen measurements to calculate the chest deflection contour time history. Deflections were determined using updated processing techniques calculating the change in length of every point on the contour from the impacted side using the thorax’s midpoint as the origin. Four candidate metrics were selected: the deflection from rib 4, the deflection from rib 8, the greater of the deflections from ribs 4 and 8, and the average of the deflections from ribs 4 and 8. AIS 3+ IRCs were developed considering outcomes of AIS ≥3 injuries. All injury data were uncensored, and noninjury data were right-censored. Three specimen mass-based IRCs were determined using the IRC with the lowest Brier score metric (BSM): The first corresponded to the 5th percentile female mass (49 kg), the second to the 50th percentile male mass (77 kg), and the third to the average mass of the PMHS ensemble (65 kg). Results Sixteen PMHS were used in the current study. Six specimens were right-censored, and 10 were uncensored. The average metric had the lowest BSM, and mass was a significant covariate with 50% risk of AIS3+ injury at 72mm of chest deflection. The 50% risk deflection magnitudes for the 5th percentile female (49 kg), 50th percentile male (77 kg), and PMHS ensemble (PMHS-E) (65 kg) were 59, 81, and 71 mm. IRCs for the 4 metrics and the 3 occupant masses are given. Conclusions IRCs were developed using survival analysis, and the average of the peak deflections was found to best represent the thoracic chest deflection response. Mass-based side impact IRCs were calculated for occupants representing the WorldSID 5th percentile female and 50th percentile male anthropomorphic test device.

Sagittal plane moment responses of the THOR-05F anthropomorphic test device

Objective Anthropomorphic test devices (ATD) are used in crashworthiness studies to advance safety in automotive, military, aviation, and other environments. The Test Device for Human Occupant Restraint (THOR) is an advancement over the widely used Hybrid III ATD. The female version THOR-05F is different from the male as it is not a scaled-down version of the male, and it is based on the recognition that the cervical spines (necks) of females have a different response than males. The objective of this study is to evaluate its response at dynamic rates of loading and compare it with previous postmortem human surrogate (PMHS) responses under sagittal plane bending. Methods The head/neck assembly was separated from the thorax, and a lower neck plate was attached to the head/neck assembly to mount the preparation to the frame of an electro-hydraulic testing device. A custom upper neck interface plate was attached to a novel angular displacement test device that converted the linear motion of the vertical electrohydraulic piston to moment loading at the occipital condyle joint. The neck was preconditioned by applying a sinusoidal 10-degree flexion-extension cycle for 90 s and then three repeat dynamic tests at a target rate of 90 Nm/s. Flexion and extension tests were performed with and without the front and rear neck cables of the THOR-05F neck. Targets were fixed to the upper neck adapter plate, occipital condyle joint, mid-spine aluminum puck, and lower neck adapter plate. The targets’ three-dimensional positions were measured using a seven-camera optical motion capture system. Upper neck load cell and occipital condyle potentiometer data were sampled at 20 kHz, and loading rates were determined by calculating the sagittal moment slope between 15% and 85% of the signal. Results The mean occipital condyle angle versus sagittal moment response from the 12 tests (three tests each with and without cables and under flexion and extension) are given in the body of the manuscript. With and without cables, the loading rates for flexion tests were 89.3 ± 0.5 Nm/s and 86.3 ± 0.4 Nm/s, and for extension tests they were 90.8 ± 1.2 Nm/s and 88.0 ± 1.5 Nm/s. The average peak sagittal moments were 34.2 ± 0.3 Nm and 30.3 ± 0.2 Nm for flexion and 50.6 ± 0.3 Nm and 47.0 ± 0.3 Nm for extension tests. The mean peak occipital condyle angles were 23.5 ± 0.2 deg and 25.3 ± 0.1 deg for flexion and 22.7 ± 0.2 deg and 25.8 ± 0.1 deg for extension. Conclusion Using the angular motion as a basis and comparing it with the previously conducted PMHS tests, the THOR-05F neck has approximately twice the stiffness of the human under sagittal plane bending.

Intracranial Displacement Measurements Within Targeted Anatomical Regions of a Postmortem Human Surrogate Brain Subjected to Impact

The dynamic response of the human brain subjected to impulsive loading conditions is of fundamental importance to the understanding of traumatic brain injuries. Due to the complexity of such measurements, the existing experimental datasets available to researchers are sparse. However, these measurements are used extensively in the validation of complex finite element models used in the design of protective equipment and the development of injury mitigation strategies. The primary objective of this study was to develop a comprehensive methodology to measure displacement in specific anatomical regions of the brain. A state-of-the-art high-speed cineradiography system was used to capture brain motion in post-mortem human surrogate specimens at a rate of 7500fps. This paper describes the methodology used to capture these data and presents measurements from these tests. Two-dimensional displacement fields are presented and analyzed based on anatomical regions of the brain. These data demonstrated a multi-modal displacement response in several regions of the brain. The full response of the brain consisted of an elastic superposition of a series of bulk rotations of the brain about its centre of gravity. The displacement field could be linked directly to specific anatomical regions. The methods presented mark an improvement in temporal and spatial resolution of data collection, which has implications for our developing understanding of brain trauma.

Lower Extremity Impact and Injury Responses of Male and Female PMHS to High-Rate Vertical Loading.

Whole-body PMHS (Post Mortem Human Surrogate) testing was conducted on the Accelerative Loading Fixture (ALF), which is designed to generate floor and seat loading conditions at the level, rate, location, direction, and extent seen in UBB (Underbody Blast). The overarching goal of this research effort was to examine potential differences in the lower extremity response of females and males under UBB conditions. The ALF consists of an occupant platform that is driven upward by the detonation of an explosive charge. The floor plate undergoes plastic deformation. The occupant platform supports two rigid seats for surrogates. Twenty un-embalmed PMHS were tested, including 50th-percentile males, 75th-percentile females, and 5th-percentile females. Two test series were conducted. Series A had a target floor speed of 8 m/s (2-ms time-to-peak) with a target seat speed of 5 m/s (4-ms time-to-peak). Series B had a target floor speed of 20 m/s (2-ms time-to-peak) with a target seat speed of 4 m/s (7-ms time-to-peak). Major damage occurred to the femur, tibia, fibula, talus, and calcaneus. Lower extremity damage type, incidence, and extent varied between the two sexes. Fifty-percent probability of calcaneus fracture for less than 3-ms time-to-peak is associated with a 781-g peak tibia vertical acceleration for 50th-percentile males, 650-g for 75th-percentile females, and 396-g for 5th-percentile females. Fifty-percent probability of calcaneus fracture, regardless of time-to-peak, is associated with a 368-g peak femur vertical acceleration for 50th-percentile males, 332-g for 75th-percentile females, and 218-g for 5th-percentile females. These results show differences in kinematics and damage outcome between female and male PMHS in UBB conditions. These findings will inform future decisions regarding the requirements for test capabilities that incorporate the female Warfighter. Ultimately, advancements can be made in injury assessment tools such as improved physical surrogates, injury assessment and prediction criteria, modeling and simulation capabilities, test methods, and the optimization of military ground vehicles, personal protective equipment, and injury countermeasures.

Comparison of Upper Neck Loading in Young Adult and Elderly Volunteers During Low Speed Frontal Impacts.

Cervical pain and injuries are a major health problem globally. Existing neck injury criteria are based on experimental studies that included sled tests performed with volunteers, post-mortem human surrogates and animals. However, none of these studies have addressed the differences between young adults and elderly volunteers to date. Thus, this work analyzed the estimated axial and shear forces, and the bending moment at the craniocervical junction of nine young volunteers (18–30 years old) and four elderly volunteers (>65 years old) in a low-speed frontal deceleration. Since the calculation of these loads required the use of the mass and moment of inertia of the volunteers' heads, this study proposed new methods to estimate the inertial properties of the head of the volunteers based on external measurements that reduced the error of previously published methods. The estimated mean peak axial force (Fz) was −164.38 ± 35.04 N in the young group and −170.62 ± 49.82 N in the elderly group. The average maximum shear force (Fx) was −224.42 ± 54.39 N and −232.41 ± 19.23 N in the young and elderly group, respectively. Last, the estimated peak bending moment (My) was 13.63 ± 1.09 Nm in the young group and 14.81 ± 1.36 Nm in the elderly group. The neck loads experienced by the elderly group were within the highest values in the present study. Nevertheless, for the group of volunteers included in this study, no substantial differences with age were observed.

Whole Body PMHS Response in Injurious Experimental Accelerative Loading Events.

Previous studies involving whole-body post-mortem human surrogates (PHMS) have generated biomechanical response specifications for physically simulated accelerative loading intended to reproduce seat and floor velocity histories occurring in under-body blast (UBB) events (e.g.,. References 10, 11, 21 These previous studies employed loading conditions that only rarely produced injuries to the foot/ankle and pelvis, which are body regions of interest for injury assessment in staged UBB testing using anthropomorphic test devices. To investigate more injurious whole-body conditions, three series of tests were conducted with PMHS that were equipped with military personal protective equipment and seated in an upright posture. These tests used higher velocity and shorter duration floor and seat inputs than were previously used with the goal of producing pelvis and foot/ankle fractures. A total of nine PMHS that were approximately midsize in stature and mass were equally allocated across three loading conditions, including a 15.5m/s, 2.5ms time-to-peak (TTP) floor velocity pulse with a 10m/s, 7.5ms TTP seat pulse; a 13m/s, 2.5ms TTP floor pulse with a 9.0m/s, 5ms TTP seat pulse; and a 10m/s, 2.5ms TTP floor pulse with a 6.5m/s, 7.5ms TTP seat pulse. In the first two conditions, the seat was padded with a ~ 120-mm-thick foam cushion to elongate the pulse experienced by the PMHS. Of the nine PMHS tests, five resulted in pelvic ring fractures, five resulted in a total of eight foot/ankle fractures (i.e.,two unilateral and three bilateral fractures), and one produced a femur fracture. Test results were used to develop corridors describing the variability in kinematics and in forces applied to the feet, forces applied to the pelvis and buttocks in rigid seat tests, and in forces applied to the seat foam in padded seat tests. These corridors and the body-region specific injury/no-injury response data can be used to assess the performance and predictive capability of anthropomorphic test devices and computational models used as human surrogates in simulated UBB testing.