Postmortem Human Subjects Research Articles

Biomechanical Responses and Injury Assessment of Post Mortem Human Subjects in Various Rear-facing Seating Configurations.

The objective of this study was to generate biomechanical corridors from post-mortem human subjects (PMHS) in two different seatback recline angles in 56 km/h sled tests simulating a rear-facing occupant during a frontal vehicle impact. PMHS were placed in a production seat which included an integrated seat belt. To achieve a repeatable configuration, the seat was rigidized in the rearward direction using a reinforcing frame that allowed for adjustability in both seatback recline angle and head restraint position. The frame contained instrumentation to measure occupant loads applied to the head restraint and seatback. To measure PMHS kinematics, the head, spine, pelvis, and lower extremities were instrumented with accelerometers and angular rate sensors. Strain gages were attached to anterior and posterior aspects of the ribs, as well as the mid-shaft of the femora and tibiae, to determine fracture timing. A chestband was installed at the mid sternum to quantify chest deformation. Biomechanical corridors for each body and seat location were generated for each recline angle to provide data for quantitatively evaluating the biofidelity of ATDs and HBMs. Injuries included upper extremity injuries, rib fractures, pelvis fractures, and lower extremity injuries. More injuries were documented in the 45-degree recline case than in the 25-degree recline case. These injuries are likely due to the excessive ramping up and corresponding kinematics of the PMHS. Biomechanical corridors and injury information presented in this study could guide the design of HBMs and ATDs in rigid, reclined, rear-facing seating configurations during a high-speed frontal impact.

Fracture Injury Risk of the Restrained Mandible to Anterior-Posterior Blunt Impacts.

This study describes the results of anterior-posterior impacts conducted on the mandibles of 22 male postmortem human subjects (PMHSs). The objective of this study was to develop an injury criterion for the mandible based on blunt impact while the jaw was restrained. Previous studies have attempted to characterize the injury risk of blunt impact to the mandible; however, due to the translation of the mandible during impact and a limited number of fractured specimens, previous studies were not able to produce an injury criterion. Blunt impact to a restrained mandible is relevant to a wide array of helmeted individuals, including the military population and sports that require helmets with chinstraps. Therefore, in this study, specimens were positioned with restrained jaws and impacted using a monorail drop tower with a gravity-driven cylindrical impactor. Nineteen of 22 specimens sustained at least one fracture during testing. Injury cases had an average impact energy of 15.0 ± 5.7 J (11.1 ± 4.2 ft-lb) and a fracture force of 2684 ± 726 N (603 ± 163 lbf). Results were used to generate an impactor force based injury criterion through survival analysis. Risk of injury was modeled using a Weibull distribution and a 50% risk of injury was found to occur at approximately 2834 N (637 lbf). The developed injury risk curve can be used to characterize injury to the restrained mandible for future testing and research studies, especially in the development of maxillofacial protective equipment.

THE INFLUENCE OF IMPACT SPEED ON CHEST INJURY OUTCOME IN WHOLE BODY FRONTAL SLED IMPACTS

While the seatbelt restraint has significantly improved occupant safety, the protection efficiency still needs further enhance to reduce the consequence of the crash. Influence of seatbelt restraint loading on chest injury under 40 km/h has been tested and documented. However, a comprehensive profiling of the efficiency of restraint systems with various impact speeds has not yet been sufficiently reported. The purpose of this study is to analyse the effect of the seatbelt loadings on chest injuries at different impact speeds utilizing a high bio-fidelity human body Finite Element (FE) model. Based on the whole-body frontal sled test configuration, the current simulation is setup using a substitute of Post-Mortem Human Subjects (PMHS). Chest injury outcomes from simulations are analysed in terms of design variables, such as seatbelt position parameters and collision speed in a full factorial experimental design. These outcomes are specifically referred to strain-based injury probabilities and four-point chest deflections caused by the change of the parameters. The results indicate that impact speed does influence chest injury outcome. The ribcage injury risk for more than 3 fractured ribs will increase from around 40 to nearly 100% when the impact speed change from 20 to 40 km/h if the seatbelt positioned at the middle-sternum of this study. Great injuries to the chest are mainly caused by the change of inertia, which indicates that chest injuries are greatly affected by the impact speed. Furthermore, the rib fracture risk and chest deflection are nonlinearly correlated with the change of the seatbelt position parameters. The study approach can serve as a reference for seatbelt virtual design. Meanwhile, it also provides basis for the research of chest injury mechanism.

Mechanisms and timing of injury to the thoracic, lumbar and sacral spine in simulated underbody blast PMHS impact tests

During an underbody blast (UBB) event, mounted occupants are exposed to high rate loading of the spine via the pelvis. The objective of this study was to simulate UBB loading conditions and examine mechanisms of injury in the thoracic, lumbar and sacral spine. Fourteen instrumented, whole-body, postmortem human subject (PMHS) experiments were performed using the WSU-decelerative horizontal sled system. The specimens were positioned supine on a decelerative sled, which then impacted an energy absorbing system mounted to a concrete barrier. Variables included the peak velocity and time-to-peak velocity for seat and floor, and the presence or absence of personal protective equipment (PPE) and seat padding. Post-test CT scans and autopsies were performed to identify the presence and severity of injuries. Acceleration and angular rate data collected at vertebra T1, T5, T8, T12, and S1 were used to assess injury timing and mechanisms. Additionally, joint time-frequency analysis (JTFA) of the spinal Z acceleration of the sacrum and vertebrae was developed with the aim of verifying spinal fracture timing. Injuries observed in the spine were attributed to axial compression applied through the pelvis, together with flexion moment due to the offset in the center of gravity of the torso, and are consistent with UBB-induced combat injuries reported in the literature. The injury timing estimation techniques discussed in this study provide a time interval when the fractures are predicted to have occurred. Furthermore, this approach serves as an alternative to the estimation methods using acoustic sensors, force and acceleration traces, and strain gauges.

Gender dimorphism in serotonin dopamine and norepinephrine neurons of isodendritc core in postmortem human and nonhuman primate control subjects

AbstractBackgroundComorbidity of depression in bMets, NPSs and NDDs is resource demanding clinical area considering treatment challenges and patient care. NPSs represent prodromal symptoms of dementia results of neurobiological changes in specific subcortical region. Dynamic cascade of Aβ shifts from nonamyloidogenic is implicated in early cognitive impairment and depressive symptoms. Serotonergic system is implicated in Aβ pathology and NE is important to compensatory in Aβ degradation. Although the role of DA is not investigated in AD pathology. Overall neuromodulation in IDC of midbrain is imperative and intriguing aspect of monoaminergic association in AD and other NDDs pathology.Here we present genetic dimorphism of key area of the brain (5HT: dorsal raphe, DA:substantia nigra, Noradrenaline: locus ceruleous).Method4males and 4 females midbrain of control subject were collected from Neurobiobank (NIH) and ONPRC. Brain sections were collected 20‐micron sections on cover glass plain slides. 4mm tissue punches were used to collect RNA from tissues. Enough tissues used to generate 10ug‐20 ug average quality RNA. 4ug RNA from Raphe, substantia nigra and locus ceruleous was isolated using trizol isolation and sent to UTSW microarray core. The RNA was hybridized to Clariom D Human chip and CEL chip data obtained from UTSW core. CEL files were uploaded in Transcriptome Analysis Console (TAC4.0). Statistically significant data in Excel file is uploaded in Ingenuity Pathway analysis software to find biological pathways dominate female and male brains. Microarray analysis of adult serotonin neurons in human and NHP dorsal raphe, Substantia nigra and Locus ceruleous (DR/SN/LC) Chip has expression of 500.000 known and unknown RNA species transcript encoding 135,000 RNAResultHuman DR/SNC/LC have 6643/13475/9194 number of probe set and 850/896//501 pathways, and Rhesus DR/SNC/LC have 7261/2157/1938 probe sets and 872/218/198 pathways altered respectively with one or more genes. Major dominated pathways: electron transport chain. Oxidative phosphorylation, miRNA, mitochondria dysfunction, apoptosis signaling, will be presented in the posterConclusionMajor energy metabolism pathway dominates in all three area in male DR/SN/LC area clearly state female brain having lower energy metabolism may results in reduce homeostasis in Isodendritc core midbrain area. Although compensatory mechanism may still yet investigate.

An Improved Method for Developing Injury Risk Curves Using the Brier Metric Score.

Many injury metrics are routinely proposed from measured or derived quantities from biomechanical experiments using post mortem human subjects (PMHS). The existing literature did not provide guidance on deciding between parameters collected in an experiment that would be best to use for the development of human injury probability curves (HIPC). The objective of this study was to use the Brier Metric Score (BMS) to identify the most appropriate metric from an experiment that predicts injury outcomes. The Brier Metric Score assesses how well a metric predicts the outcome for a censored data point (a lower BMS is better). Survival analysis was then conducted with the selected metric and the best distribution was selected using Akaike information criterion (AIC). Confidence intervals (CIs) and the normalized confidence interval width (NCIS) were calculated for the injury probability curve. The testing and validation of the methods described were performed using biomechanics data in the open literature. The methods for the HIPC development procedure detailed herein have been rigorously tested and used in the generation of WIAMan HIPCs and Injury Assessment Reference Curves (IARCs) for the WIAMan ATD, but can also be used in other ATD or PMHS injury risk curve development.

Thoracolumbar spine kinematics and injuries in frontal impacts with reclined occupants

Objective Highly automated vehicles may permit alternative seating postures, which could alter occupant kinematics and challenge current restraint designs. One predicted posture is a reclined seated position. While the spine of upright occupants is subjected to flexion during frontal crashes, the orientation of reclined occupants tends to subject the spine to high compressive loads followed by high flexion loads. This study aims to investigate kinematics and mechanisms of loading in the thoracolumbar spine for a reclined seated posture through the use of postmortem human subjects (PMHS). Methods Frontal impact sled tests (50 kph delta-v) were conducted on five adult midsize male PMHS seated with the torso reclined to 50 degrees with respect to the vertical. The PMHS were seated on a semi-rigid seat and restrained by a seat-integrated three-point belt with dual lap-belt pretensioners and a shoulder-belt pretensioner with a 3 kN load-limiter. 3-D kinematic trajectories of five chosen vertebrae, and the pelvis were measured relative to the vehicle buck. Intervertebral pressure transducers were installed at three locations in the lumbar column to detect load timing. Results Three PMHS suffered fractures at L1. Combined compression and flexion of the thoracolumbar spine occurred in all tests, but the magnitude of peak flexion varied across the PMHS. During the PMHS' forward excursion, the pelvis rotated anteriorly in two tests and posteriorly in two tests (lap-belt submarining occurred in one). In one test, the pelvis mount interacted with the seat, but did not affect kinematics. Conclusions Anterior rotation of the pelvis caused increased extension of the lumbar spine, which exacerbated lumbar compression in two of the PMHS; the one subject whose pelvis kinematic tracking was lost exhibited similar compression kinematics. Posterior rotation of the pelvis enabled lumbar flexion, which decreased lumbar compression, but lead to lap-belt submarining in one case. Lumbar kinematics for these reclined frontal impacts were sensitive to changes in initial posture of the spine (magnitude of lordosis or kyphosis) and pelvis (pitch angle). To our knowledge, this study is the first to analyze thoracolumbar kinematics and resulting injuries of a reclined seating posture using PMHS.

Multilevel Validation of a Male Neck Finite Element Model With Active Musculature.

Computational models of the human neck have been developed to assess human response in impact scenarios; however, the assessment and validation of such models is often limited to a small number of experimental data sets despite being used to evaluate the efficacy of safety systems and potential for injury risk in motor vehicle collisions. In this study, a full neck model (NM) with active musculature was developed from previously validated motion segment models of the cervical spine. Tissue mechanical properties were implemented from experimental studies, and were not calibrated. The neck model was assessed with experimental studies at three levels of increasing complexity: ligamentous cervical spine in axial rotation, axial tension, frontal impact, and rear impact; postmortem human subject (PMHS) rear sled impact; and human volunteer frontal and lateral sled tests using an open-loop muscle control strategy. The neck model demonstrated good correlation with the experiments ranging from quasi-static to dynamic, assessed using kinematics, kinetics, and tissue-level response. The contributions of soft tissues, neck curvature, and muscle activation were associated with higher stiffness neck response, particularly for low severity frontal impact. Experiments presenting single-value data limited assessment of the model, while complete load history data and cross-correlation enabled improved evaluation of the model over the full loading history. Tissue-level metrics demonstrated higher variability and therefore lower correlation relative to gross kinematics, and also demonstrated a dependence on the local tissue geometry. Thus, it is critical to assess models at the gross kinematic and the tissue levels.

Occupant Restraint in Far-Side Impacts: Cadaveric and WorldSID Responses to a Far-Side Airbag

Previous studies indicate that seatbelts may require supplementary restraints to increase their effectiveness in far-side impacts. This study aimed to evaluate the effectiveness of a novel, far-side-specific airbag in restraining and preventing injuries in far-side impacts, and to evaluate the WorldSID's response to the presence of a far-side airbag. A series of tests with three Post-Mortem Human Subjects and the WorldSID was conducted in a vehicle-based sled environment equipped with a far-side airbag. Results of these tests were evaluated and compared to a previous test series conducted without the airbag. All of the PMHS retained the shoulder belt on the shoulder. The airbag significantly reduced PMHS injury severity and maximum lateral head excursion. While the WorldSID exhibited a similar decrease in lateral excursion, it was unable to represent PMHS thoracic deflection or injury probability, and it consistently slipped out of the shoulder belt. This indicates that the WorldSID is limited both in its ability to evaluate the effect of changes in the seatbelt system and in its ability to predict thoracic injury risk and assess airbag-related injury mitigation countermeasures.

Trabecular bone mineral density correlations using QCT: Central and peripheral human skeleton

Musculoskeletal injuries to the lower leg and foot-ankle joint are associated with external mechanical loads resulting from motor vehicle crashes, under body blasts, falls from height, or sports. As an intrinsic material property, the bone mineral density (BMD) is related to bone strength. The clinically recognized biological sites for BMD evaluation are the hip and spine. The focus of this study was to define the correlation between BMD from standard clinical sites (hip and lumbar spine) compared to BMD from non-standard sites (foot-ankle-distal tibia bones). Twenty-one post-mortem human subjects (PMHS) with mean age, height, and mass of 63 ± 11 years, 179 ± 7 cm, and 86 ± 13 kg, respectively were used for analysis. Clinical BMD software (Mindways Software, Inc.) was used for trabecular BMD quantification using quantitative computed tomography (QCT). In quantification of BMD of the foot-ankle-distal tibia (hind foot), the trabecular BMD of the talus (316 ± 86mg/cc) was highest followed by the distal tibia (238 ± 72 mg/cc) and then calcaneus (147 ± 51 mg/cc). To correlate BMD values from foot bone regions with the central skeleton BMD values within the same PMHS, there were 18 lumbar spine and 12 hip BMDs available. The BMD of the distal tibia correlated best with the hip intertrochanter BMD (R2 of 0.72). Calcaneus BMD best correlated with the hip femoral neck BMD (R2 = 0.64). In summary, the hind foot bone BMD values correlated better with the hip as compared to the lumbar spine BMD from the same PMHS. These findings indicate that, in the absence of a direct measure of foot-bone BMD, hip BMD might be a better predictor of injury risk to hind foot rather than lumbar spine BMD, or alternatively, calcaneal trabecular BMD can be used to predict the risk of injury to hip. Further, these relationships between central and peripheral regions can also be implemented in finite element models for improved failure predictions.

Rib Variation at Multiple Locations and Implications for Histological Age Estimation.

Existing histological age estimation methods using the rib were developed mainly from the midshaft; however, in forensic practice, uncertainty of sampling location often arises due to fragmented or previously sampled ribs. The potential for error increases when sampling location is uncertain and utilizing a section beyond the midshaft (either anterior or posterior) may result in erroneous age estimates. Additionally, there is debate within the field regarding the minimum number of sections needed for accurate age estimation. The aim of this research is to determine the importance of the midshaft distinction for age-at-death assessment and the necessity of analyzing serial sections by evaluating histological variables at sampling locations along the length of the rib. Three seriated histological sections at three sampling locations (anterior, midshaft, and posterior) were obtained from sixth ribs of ten postmortem human subjects. Cortical area (Ct.Ar) and osteon population density (OPD) were collected from each section (n=90). Significant differences were determined in Ct.Ar between sampling locations, demonstrating the variation present along the length of the rib. A comparison of OPD at sampling locations revealed significant differences, suggesting that sampling site is critical to accurate age estimates. When sampling location is uncertain, a more anterior section should be taken. Analysis of serial sections within locations revealed no significant differences in OPD or Ct.Ar, supporting the practice of collecting data from one section for age estimation. While an age estimate can be achieved through the analysis of one section, best practice suggests reading two sections to capture intraindividual variation.

Strain Assessment of Deep Fascia of the Thigh During Leg Movement: An in situ Study.

Fascia is a fibrous connective tissue present all over the body. At the lower limb level, the deep fascia that is overlying muscles of the outer thigh and sheathing them (fascia lata) is involved in various pathologies. However, the understanding and quantification of the mechanisms involved in these sheathing effects are still unclear. The aim of this study is to observe and quantify the strain field of the fascia lata, including the iliotibial tract (ITT), during a passive movement of the knee. Three fresh postmortem human subjects were studied. To measure hip and knee angles during knee flexion-extension, passive movements from 0° to around 120° were recorded with a motion analysis system and strain fields of the fascia were acquired using digital image correlation. Strains were computed for three areas of the fascia lata: anterior fascia, lateral fascia, and ITT. Mean principal strains showed different strain mechanisms depending on location on the fascia and knee angle. For the ITT, two strain mechanisms were observed depending on knee movement: compression is observed when the knee is extended relative to the reference position of 47°, however, tension and pure shear can be observed when the knee is flexed. For the anterior and lateral fascia, in most cases, minor strain is higher than major strain in absolute value, suggesting high tissue compression probably due to microstructural fiber rearrangements. This in situ study is the first attempt to quantify the superficial strain field of fascia lata during passive leg movement. The study presents some limitations but provides a step in understanding strain mechanism of the fascia lata during passive knee movement.

Comparison of Human Surrogate Responses in Underbody Blast Loading Conditions.

Impact biomechanics research in occupant safety predominantly focuses on the effects of loads applied to human subjects during automotive collisions. Characterization of the biomechanical response under such loading conditions is an active and important area of investigation. However, critical knowledge gaps remain in our understanding of human biomechanical response and injury tolerance under vertically accelerated loading conditions experienced due to underbody blast (UBB) events. This knowledge gap is reflected in anthropomorphic test devices (ATDs) used to assess occupant safety. Experiments are needed to characterize biomechanical response under UBB relevant loading conditions. Matched pair experiments in which an existing ATD is evaluated in the same conditions as a post mortem human subject (PMHS) may be utilized to evaluate biofidelity and injury prediction capabilities, as well as ATD durability, under vertical loading. To characterize whole body response in the vertical direction, six whole body PMHS tests were completed under two vertical loading conditions. A series of 50th percentile hybrid III ATD tests were completed under the same conditions. Ability of the hybrid III to represent the PMHS response was evaluated using a standard evaluation metric. Tibial accelerations were comparable in both response shape and magnitude, while other sensor locations had large variations in response. Posttest inspection of the hybrid III revealed damage to the pelvis foam and skin, which resulted in large variations in pelvis response. This work provides an initial characterization of the response of the seated hybrid III ATD and PMHS under high rate vertical accelerative loading.

Kinematics of inboard-leaning occupants in frontal impacts

Objective: Up to one-half of drivers swerve before a crash, which may cause vehicle motions that displace an occupant from a normal seated position. How these altered postures affect occupant restraint in a crash is unknown. The goal of this study was to quantify the effect of an initial inboard lean on occupant kinematics in a frontal impact.Methods: 30 km/h frontal impact tests were performed with three postmortem human subjects (PMHS) seated in a neutral, upright posture and in a 20° inboard-leaning posture identified from simulated swerving tests with human volunteers.Results: In comparison to the upright posture, the inboard-leaning posture increased the initial distance from the D-ring to the belted shoulder by 105-156 mm. In the inboard-leaning tests, the occupant’s head displaced 45-70 mm farther forward than in the upright tests and was also located 123-147 mm farther inboard at the time of maximum forward excursion. The peak resultant velocity of the occupant’s head relative to the vehicle interior increased 1.40-1.54 m/s in the inboard-leaning tests.Conclusions: The posture-induced increase in the distance between the D-ring and the shoulder permitted the increased maximum forward head displacement and increased maximum head resultant velocity relative to the vehicle interior. Thus, an initial inboard lean in a frontal impact may increase the risk and severity of a head strike to the vehicle interior, and alter the location, timing, and nature of airbag engagement.

Biofidelity of THOR 5th Percentile Female ATD in Ankle Eversion and Inversion

<div class="section abstract"><div class="htmlview paragraph">Females have higher frequency and risk of foot and ankle injuries in motor vehicle collisions than similar-sized males. Therefore, lower extremity biofidelity and accurate injury prediction of female ATDs is critical. This paper aims to compare the THOR 5th percentile female (THOR-05F) anthropomorphic test device (ATD) response with male and female PMHS data of various sizes under ankle inversion and eversion. The THOR-05F lower extremity was subjected to dynamic inversion and eversion ankle loading with a constant 2000N axial force applied through the tibia. Twelve THOR-05F tests (3 inversion and 3 eversion on both, left and right legs) were performed with boundary conditions consistent with previous post-mortem human subject (PMHS) lower extremity tests. The biofidelity of THOR-05F ankle stiffness was evaluated via comparison of measured and equal-stress equal-velocity scaled data (using mass-based scale factors) from previous PMHS datasets with mid-size males, small females and larger females. THOR-05F ankle moment-angle response falls within the range of previous mid-sized male and larger female PMHS test data for eversion, when scaled to a small female. However, when compared to PMHS response measured on small female subjects, the THOR-05F response was less stiff in both inversion and eversion. The THOR-05F moments were 65% and 90% less stiff in eversion and inversion respectively, when compared to the average of the measured small female PMHS dataset at 25<sup>°</sup> ankle rotation. Because ATD stiffness differs from measured PMHS ankle stiffness, care should be taken when applying PMHS-based injury risk functions (IRF) to the THOR-05F ankle.</div></div>

Far Side Impact Injury Threshold Recommendations Based on 6 Paired WorldSID / Post-Mortem Human Subjects Tests.

Far side has been identified in the literature as a potential cause of numerous injuries and fatalities. Euro NCAP developed a far side test protocol to be performed to assess adult protection. A monitoring phase was undertaken between January 2018 and December 2019, and the far side assessment will become part of the rating for all vehicles launched in 2020 onward. A test buck was developed and 6 paired WorldSID / Post Mortem Human Subjects (PMHS) were subjected to the test protocol proposed by Euro NCAP to contribute to the development of limits. The buck consisted of a rigid seat and a rigid central console covered with 50 mm of Ethafoam TM 180 with a density of 16 kg/m3. The buck was mounted on the sled with an angle of 75° between the X axis of the vehicle and the X axis of the sled. The peak head excursion was compared between PMHS and the WorldSID dummy. It was found reasonably similar. However, the dummy repeatability was found to be poor. Out of 6 tests conducted on 6 PMHS, 2 specimens sustained AIS3 and, 3 specimens AIS2 cervical spine injuries, 3 specimens sustained AIS3, 1 AIS2 and 1 AIS1 thoracic injuries, and 2 specimens sustained AIS2 abdominal injuries. The peak values recorded on the dummy according to the Euro NCAP protocol were compared with the injury assessments of the PMHS tests. In the configuration used, which includes a central console, the hard thorax injury prediction was found to be excellent. For the neck injury prediction, the data were merged with similar results available in the literature and an Injury Risk Curve was proposed as a derivative from the curve published by Mertz et al. (2003) for neck extension.

Assessment of Several THOR Thoracic Injury Criteria based on a New Post Mortem Human Subject Test Series and Recommendations.

Several studies, available in the literature, were conducted to establish the most relevant criterion for predicting the thoracic injury risk on the THOR dummy. The criteria, such as the maximum deflection or a combination of parameters including the difference between the chest right and left deflections, were all developed based on given samples of Post Mortem Human Subject (PMHS). However, they were not validated against independent data and they are not always consistent with the observations from field data analysis. For this reason, 8 additional PMHS and matching THOR tests were carried out to assess the ability of the criteria to predict risks. Accident investigations showed that a reduction of the belt loads reduces the risk of rib fractures. Two configurations with different levels of force limitation were therefore chosen. A configuration representing an average European vehicle was chosen as a reference. It consists of a 3-point belt with a 3.5 kN and then 2 kN digressive limiter, combined with a 54-liter airbag. For better reproducibility and durability, the tests were performed with a pre-inflated bag and a semi-rigid seat. In this first configuration, the THOR dummy had a maximum resulting deflection of 43 mm. To differentiate the criteria, the second configuration was chosen such that it resulted in about the same deflection on the THOR dummy, but with a 5 kN belt force limitation combined with a lower pressure airbag. To reach this target of 43 mm, the pulse severity was lowered. Some criteria were higher in this second configuration, which allows them to be distinguished from the maximum deflection criterion. Four tests on four PMHS were performed in each configuration. The injury assessments showed that the total number of fractures was almost the same in both configurations, but that the number of separated fractures was greater in the 5 kN configuration. 25% of the subjects sustained AIS >3 injuries related to the number of displaced fractures in the 3.5/2 kN load limitation configuration. The result increased to 75% in the 5kN configuration. In total, 8 PMHS and the matching THOR tests were performed and used to assess the ability of the thoracic criteria to predict rib fractures in 2 types of chest loading configurations. The test results did not allow to conclude on the relevance of the criteria measured on the THOR dummy for the total number of rib fractures identified at autopsy (NFR). However, clearly different assessments for separated rib fractures (NSFR), make it possible to differentiate the criteria. The maximum resultant deflection failed to properly predict separated rib fractures while other criteria that include the left-to-right rib deflection difference did.

PMHS and WorldSID Kinematic and Injury Response in Far-Side Events in a Vehicle-Based Test Environment.

Far-side kinematics and injury are influenced by the occupant environment. The goal of the present study was to evaluate in-vehicle human far-side kinematics, kinetics and injury and to assess the ability of the WorldSID to represent them. A series of tests with five Post-Mortem Human Subjects and the WorldSID were conducted in a vehicle-based sled test environment. The surrogates were subjected to a far-side pulse of 16.5 g in a 75-degree impact direction. The PMHS were instrumented with 6 degree-of-freedom sensors to the head, spine and pelvis, a chestband, strain gauge rosettes, a 3D tracking array mounted to the head and multiple single 3D tracking markers on the rest of the body. The WorldSID lateral head excursion was consistent with the PMHS. However, forward head excursion did not follow a PMHS-like trajectory after the point of maximum lateral excursion. All but one PMHS retained the shoulder belt on the shoulder during the entire test. However, the WorldSID consistently slipped out of the shoulder belt. The PMHS sustained an average of five rib fractures for which the seatbelt was observed to be the largest contributor. The WorldSID showed a maximum rib deflection of 25 mm. The first rib fracture occurred no later than 50 ms into the event. Anatomical differences between the WorldSID and the PMHS rib cage prevented the WorldSID from capturing the injury mechanisms related to interactions of the occupant with the seatbelt and the seat.

A Novel Approach to Scaling Age-, Sex-, and Body Size-Dependent Thoracic Responses using Structural Properties of Human Ribs.

Thoracic injuries are frequently observed in motor vehicle crashes, and rib fractures are the most common of those injuries. Thoracic response targets have previously been developed from data obtained from post-mortem human subject (PMHS) tests in frontal loading conditions, most commonly of mid-size males. Traditional scaling methods are employed to identify differences in thoracic response for various demographic groups, but it is often unknown if these applications are appropriate, especially considering the limited number of tested PMHS from which those scaling factors originate. Therefore, the objective of this study was to establish a new scaling approach for generating age-, sex-, and body size- dependent thoracic responses utilizing structural properties of human ribs from direct testing of various demographics. One-hundred forty-seven human ribs (140 adult; 7 pediatric) from 132 individuals (76 male; 52 female; 4 pediatric) ranging in age from 6 to 99 years were included in this study. Ribs were tested at 2 m/s to failure in a frontal impact scenario. Force and displacement for individual ribs were used to develop new scaling factors, with a traditional mid-size biomechanical target as a baseline response. This novel use of a large, varied dataset of dynamic whole rib responses offers vast possibilities to utilize existing biomechanical data in creative ways to reduce thoracic injuries in diverse vehicle occupants.

Kinematic and Biomechanical Response of Post-Mortem Human Subjects Under Various Pre-Impact Postures to High-Rate Vertical Loading Conditions.

Limited data exist on the injury tolerance and biomechanical response of humans to high-rate, under-body blast (UBB) loading conditions that are commonly seen in current military operations, and there are no data examining the influence of occupant posture on response. Additionally, no anthropomorphic test device (ATD) currently exists that can properly assess the response of humans to high-rate UBB loading. Therefore, the purpose of this research was to examine the response of post-mortem human surrogates (PMHS) in various seated postures to high-rate, vertical loading representative of those conditions seen in theater. In total, six PMHS tests were conducted using loading pulses applied directly to the pelvis and feet of the PMHS: three in an acute posture (foot, knee, and pelvis angles of 75°, 75°, and 36°, respectively), and three in an obtuse posture (15° reclined torso, and foot, knee, and pelvis angles of 105°, 105°, and 49.5°, respectively). Tests were conducted with a seat velocity pulse that peaked at ~4 m/s with a 30-40 ms time to peak velocity (TTP) and a floor velocity that peaked at 6.9-8.0 m/s (2-2.75 ms TTP). Posture condition had no influence on skeletal injuries sustained, but did result in altered leg kinematics, with leg entrapment under the seat occurring in the acute posture, and significant forward leg rotations occurring in the obtuse posture. These data will be used to validate a prototype ATD meant for use in high-rate UBB loading scenarios.