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Biomechanical Responses of PMHS Subjected to Abdominal Seatbelt Loading
Abstract
Past studies have found that a pressure based injury risk function was the best predictor of liver injuries due to blunt impacts. In an effort to expand upon these findings, this study investigated the biomechanical responses of the abdomen of post mortem human surrogates (PMHS) to high-speed seatbelt loading and developed external response targets in conjunction with proposing an abdominal injury criterion. A total of seven unembalmed PMHS, with an average mass and stature of 71 kg and 174 cm respectively were subjected to belt loading using a seatbelt pull mechanism, with the PMHS seated upright in a free-back configuration. A pneumatic piston pulled a seatbelt into the abdomen at the level of the umbilicus with a nominal peak penetration speed of 4.0 m/s. Pressure transducers were placed in the re-pressurized abdominal vasculature, including the inferior vena cava (IVC) and abdominal aorta, to measure internal pressure variation during the event. Jejunum tear, colon hemorrhage, omentum tear, splenic fracture and transverse processes fracture were identified during post-test anatomical dissection. Peak abdominal forces ranged from 2.8 to 4.7 kN. Peak abdominal penetrations ranged from 110 to 177 mm. A force-penetration corridor was developed from the PMHS tests in an effort to benchmark ATD biofidelity. Peak aortic pressures ranged from 30 to 104 kPa and peak IVC pressures ranged from 36 to 65 kPa. Updated pressure based abdominal injury risk functions were developed for vascular Ṗmax and Pmax*Ṗmax.
... The biofidelity and the repeatability of the ABISUP abdomen was assessed by reproducing Post Mortem Human Surrogates (PMHS) tests of Lamielle [17], Ramachandra [18] and Foster [19]. The sensitivity of the ABISUP abdomen was evaluated by varying the seatbelt belt loading height in Foster [19] and Kent's [7] test setups. ...
... Seatbelt pull tests with free back under Ramachandra's setup [18] were carried out at Transportation Research Center (TRC). The dummy was seated on a table with its back free to move ( Figure 4). ...
... The displacement of the dummy spine was subtracted from the belt displacement. The ABISUP abdomen response was compared with the PMHS responses from Ramachandra et al. [18]. ...
The standard THOR-50M dummy is equipped with sensors to measure the abdomen deflection and assess the risk of abdominal injuries. Since 2016, the "ABdominal Injury and SUbmarining Prediction" (ABISUP) consortium has developed a pressure-measuring abdomen for the THOR-50M to predict abdominal injuries and submarining as a potential alternative to the current THOR-50M abdomen design. A new lower abdomen including Abdominal Pressure Twin Sensor (APTS) was designed and four identical prototypes were built and shipped to consortium member test houses. Numerous abdominal belt loadings replicating tests from the literature were carried-out to check the prototype biofidelity, sensitivity and define a pressure-based AIS3+ injury risk functions (IRFs). Two compression-based IRFs were defined using porcine test results from the literature[7]. Compressions were defined as the ratios between the abdomen deflection and the full abdominal depth, or between the abdomen deflection and the abdominal depth in front of the spine. The abdominal depth in front of the spine was used in an attempt to minimize possible differences between species. It was estimated using simple assumptions and led to compressions exceeding 100% in a few cases. Then transfer functions between THOR abdominal compressions Beillas 2 and pressures were applied to obtain the pressure-based IRFs. Twenty-five sled tests were performed to assess the new abdomen under various restraint conditions and to evaluate the relevance of the IRFs. The THOR-50M new abdomen showed similar or better biofidelity than the standard abdomen without modifying the dummy kinematics. The abdomen was sensitive to loading height and no damage to the APTS was encountered during tests. Relationships between THOR-50M mean APTS pressure and abdominal compressions were modelled using a 3 rd degree polynomial with 0.98 R². The IRF with a log-logistic distribution obtained the lowest Akaike Information Criterion. For the compression based on the full abdomen depth, the AIS3+ injury risks of 25%, 50% and 75% corresponded to APTS pressures of 133, 201 and 304 kPa, respectively. For the compression based on the abdomen in front the spine, the AIS3+ injury risks of 25%, 50% and 75% corresponded to APTS pressures of 108, 197 and 361 kPa, respectively. The new abdomen discriminated between the restraint conditions: lower pressures (between 90 and 190 kPa) were obtained when the lap belt remained below or on the ASIS and higher pressures (170 to 450 kPa) were obtained when the lap belt loaded the abdomen. Using the IRF, a risk up to 50% could be obtained without submarining, i.e. with the lap belt still engaging the ASIS. This is not consistent with a risk expected to be low for a proper restraint. Possible adjustments are discussed in the paper to decrease APTS sensitivity when the lap belt is positioned below or on the ASIS.
... The purpose of the current study was to compare the responses of different ATD abdominal inserts that are at various stages of development or implementation, to the responses from PMHS tests under identical test conditions [16]. Adult size ATDs evaluated included the Hybrid III 50 th percentile male (HIII-50M) with standard abdomen, HIII-50M retrofitted with RRSA, and THOR-K. ...
... The seatbelt loading device described in [16] was used to test the ATDs. The device used a pneumatic piston to pull a seatbelt into the abdomen of the ATDs in a controlled, dynamic scenario. ...
... For all the ATD tests, the chest jacket was used for accurate ATD representation and to take into account the influence of outer flesh/skin on the abdominal response. In terms of input, all six ATDs were tested using an accumulator pressure of 620 kPa, which is the same pressure as Test Condition A for the PMHS tests in [16]. Fig. 2 shows the pre-test positions of the HIII-50M, THOR-K, HIII 10yo, Q10, and LODC on the test apparatus. ...
This study investigated the biofidelity of anthropomorphic test device (ATD) abdomens subjected to a belt loading test condition. A total of six ATD/abdomen insert combinations were subjected to belt loading using a seatbelt pull mechanism, with the ATDs seated upright in a free‐back configuration. Three 50th percentile male ATDs were tested, including THOR‐K, Hybrid III 50th percentile male with reusable rate‐sensitive abdomen (HIII‐50M RRSA), and Hybrid III 50th percentile male with standard abdominal insert (HIII‐50M). Additionally, three 10‐year‐old (10yo) size child ATDs including Large Omni‐directional Child (LODC), Q10, and HIII 10yo were tested and evaluated. Force‐penetration results of the 50 th percentile male ATDs were compared directly to a belt loading corridor derived from post‐mortem human subject (PMHS) testing in this test configuration, while 10yo ATD responses were compared to a scaled version of the corridor. Biofidelity of the ATD abdomen responses under free‐back seatbelt loading condition were quantified using the NHTSA Biofidelity Ranking System (BioRank). Among the adult ATDs, HIII‐50M, HIII‐50M RRSA and THOR‐K scored 1.99, 1.71 and 1.33 respectively, indicating that the THOR‐K has a response closest to PMHS. All three child ATDs displayed responses that were outside of the scaled PMHS corridor. The child ATDs showed surprisingly similar responses even though their abdominal area structures are quite different.
... It is easier to measure pressure in such a component because pressure is a non-directional, full system measurement where two relative positions in the abdomen do not have to be accurately tracked in three-dimensional space. Internal pressures were collected in studies with adult PMHS, during either an impact or belt loading event, with resulting injuries documented [7][8][9]. A pressure-based IRF was developed from that work. ...
... Both peak rate of pressure change (Ṗ max ) multiplied by the peak pressure, P max *Ṗ max , (50% risk = 710 kPa 2 /ms) and peak rate of pressure change, Ṗ max , (50% risk = 10.2 kPa/ms) were better correlated with injury than peak pressure alone in PMHS testing [7,8,9]. A similar set of rate-dependent pressure variables were derived from the LODC sled tests shown in Figure 3 (Table VI). ...
The objective of this study was to develop injury risk functions for the Large Omni-directional Child (LODC) ATD abdomen and thorax. Paediatric specimen biomechanical data were gathered from literature, and thorax deflection and abdomen pressure were collected when the LODC was tested in the same conditions. Using the assumption of biofidelity and the measured relationships between various LODC responses, abdomen pressure and thorax deflection, compression, and velocity were estimated for paediatric specimen tests and used with the paediatric injury outcomes to construct risk functions. The maximum abdomen pressure associated with 50% risk of AIS3+ injury was found to be 114.5 kPa. LODC sled test data in various restraint conditions associated with low (e.g. 5-point harness) and high (e.g. submarining in lap belt only) probability of abdominal injury aligned well with the injury risk function. For the thorax, V max *C max was found to be the strongest predictor of thoracic injury, with a 50% risk of AIS2+ injury of 0.45 m/s. The accuracy of the thorax risk function was evaluated using LODC data from several restraint conditions, real-world cases using LODC response relationships, and literature-reported V max *C max injury thresholds for adult specimens.
... Tomic et al reported that seat-belt abdominal aortic injury and rib fracture [35]. Ramachandra et al reported on seat belt-induced increase in abdominal pressure during an accident [36]. Abbas et al. reported that seatbelt-related injuries include spinal, abdominal or pelvic injuries and the presence of a seatbelt sign must raise the suspicion of an intra-abdominal injury due to seatbelt repositioning during traffic accidents. ...
Analysis using human body models has been performed to reduce the impact of accidents; however, no analysis has shown a relationship between lumbar and pelvic/spine angle and seat belts in reducing human damage from accidents. Lumbar and pelvic/spine angles were measured in 75 individuals and the measurements were used to create three different angles for the Total Human Model for Safety model. In the present study, we focused on lumber lordosis (LL) and pelvic angle (PA). A normal distribution and histogram were used for analysis of PA (01, 10, and 50). The Total Human Model for Safety, including LL and PA, was corrected using finite element software. Simulations were conducted under the conditions of the Japan New Car Assessment Programme (JNCAP) 56 kph full lap frontal impact. Using the results of the FEM, the amount of lap-belt cranial sliding-up, anterior movement of the pelvis, posterior tilt of the pelvis, head injury criterion (HIC), second cervical vertebrae (C2) compressive load, C2 moment, chest deflectiou (upper, middle, and lower), left and right femur load, and shoulder belt force were measured. The lap-belt cranial sliding-up was 1.91 and 2.37 for PA10 and PA01, respectively, compared to PA50; the anterior movement of the pelvis was 1.08 and 1.12 for PA10 and PA01, respectively; and the posterior tilt of the pelvis was 1.1 and 1.18 for PA10 and PA01, respectively. HIC was 1.13 for PA10 and 1.58 for PA01; there was no difference in C2 compressive load by PA, but C2 moment increased to 1.59 for PA10 and 2.72 for PA01. It was found that as LL increases and the PA decreases, the seat belt becomes likely to catch the iliac bone, making it harder to cause injury. This study could help to reconsider the safe seat and seatbelt position in the future.
... Lau and Viano [40] considered that there were two regions of biomechanical response to blunt hepatic injury at the impact speeds of >12 m/s or ≤12 m/s. Some studies considered that the abdomen pressure may be an ideal predictor of liver injuries from horizontal loading [41][42][43][44]. From the current experiment, at the impact speed of 10.69 ± 0.41 m/s, the abdomen internal pressure was up to 63.61 ± 65.83 kPa, while the subjects in group I and group II did not experience liver injury. ...
To know the caudocephalad impact- (CCI-) induced injuries more clearly, 21 adult minipigs, randomly divided into three groups: control group ( n=3 ), group I ( n=9 ), and group II ( n=9 ), were used to perform the CCI experiments on a modified deceleration sled. Configured impact velocity was 0 m/s in the control group, 8 m/s in group I, and 11 m/s in group II. The kinematics and mechanical responses of the subjects were recorded and investigated. The functional change examination and the autopsies were carried out, with which the injuries were evaluated from the Abbreviated Injury Scale (AIS) and the Injury Severity Score (ISS). The subjects in group I and group II experienced the caudocephalad loading at the peak pelvic accelerations of 108.92 ± 58.87 g and 139.13 g ± 78.54 g, with the peak abdomen pressures, 41.24 ± 16.89 kPa and 63.61 ± 65.83 kPa, respectively. The injuries of the spleen, lung, heart, and spine were detected frequently among the tested subjects. The maximal AIS (MAIS) of chest injuries was 4 in group I and 5 in group II, while both the MAIS of abdomen injuries in group I and group II were 5. The ISS in group II was 52.71 ± 6.13, significantly higher than in group I, 26.67 ± 5.02 ( p<0.05 ). The thoracoabdomen CCI injuries and the mechanical response addressed presently may be useful to conduct both the prevention studies against military or civilian injuries.
Bone mineral density (BMD) is often used for injury prediction and fracture risk evaluation. This study aims to determine the breadth and depth of BMD utilization in injury biomechanics research and evaluate the appropriateness of these approaches by assessing BMD sensitivity and variability throughout the human body. A scoping review was conducted examining post-mortem human subject (PMHS) experimental studies that utilized dual-energy x-ray absorptiometry (DXA) and/or quantitative computed tomography (QCT) for bone quality assessment. Subsequently, areal BMD (aBMD) and volumetric BMD (vBMD) of 76 male PMHS were assessed throughout the body using DXA and QCT. Results indicated that methods and applications of BMD in injury biomechanics are largely inconsistent, and that only 40% of studies assessed bone quality with injurious PMHS testing. aBMD differed between almost every skeletal site (p<0.05) and, similarly, vBMD was different between most sites (p<0.05). Further, no singular measure from DXA or QCT represented global BMD throughout the body. Few relationships in BMD were found between DXA and QCT (p<0.05) at comparable sites. Variability in bone quality assessment methods may limit comparability of data within the field. Overall, assessing BMD for PMHS biomechanical testing requires standardized methods and comprehensive understanding of variability between/within skeletal elements of interest.
Currently, neither abdominal injury risk nor rear seat passenger safety is assessed in European frontal crash testing. The objective of this study was to provide real world in-depth analysis of the factors related to abdominal injury for belted front and rear seat occupants in frontal crashes. Rear occupants were significantly more at risk of AIS 2+ and 3+ abdominal injury, followed by front seat passengers and then drivers. This was still the case even after controlling for occupant age. Increasing age was separately identified as a factor related to increased abdominal injury risk in all seating positions. One exception to this trend concerned rear seated 15 to 19 year olds who sustained moderate to serious abdominal injury at almost the same rate as rear occupants aged 65+.No strong association was seen between AIS 2+ abdominal injury rates and gender. The majority of occupant body mass indices ranged from underweight to obese. Across that range, the AIS 2+ abdominal injury rates were very similar but a small number of very obese and extremely obese occupants outside of the range did exhibit noticeably higher rates. An analysis of variance in the rate of AIS 2+ abdominal injury with different restraint systems showed that simple belt systems, as used by most rear seat passengers, were the least protective. Increasing sophistication of the restraint system was related to lower rates of injury. The ANOVA also confirmed occupant age and crash severity as highly associated with abdominal injury risk. The most frequently injured abdominal organs for front seat occupants were the liver and spleen. Abdominal injury patterns for rear seat passengers were very different. While they also sustained significant injuries to solid organs, their rates of injury to the hollow organs (jejunum-ileum, mesentary, colon) were far higher even though the rate of fracture of two or more ribs did not differ significantly between seat positions. These results have implications for the design of restraint systems, particularly in relation to the occurrence of abdominal injury. They also raise issues of crash protection for older occupants as well as the protection afforded in different seating positions.
Public awareness for safety and vehicle improvements has contributed to significant reduction in injuries secondary to motor vehicle crashes. The spectrum of trauma has shifted from one region of the body to another with varying consequences. For example, airbags have minimized head and neck injuries for adults while emphasizing the lower regions of the human body. Studies have concentrated on the changing patterns of these injuries in frontal impacts. However, there is almost a paucity of data with regard to the characterization of abdominal injuries. Consequently, this study was conducted to determine the patterns of abdominal injuries in frontal and side impacts with an emphasis on more recent crashes. In particular, the frequency and severity of trauma were investigated with a focus on the various abdominal organs (e.g., spleen and liver). Results indicate that side crashes contribute to a large percentage of injuries to the abdomen. The liver and spleen organs are most vulnerable; therefore, it may be beneficial to apply concerted efforts to focus on injury biomechanics research and prioritization activities in these areas of the abdomen. These data may be of benefit to develop anthropomorphic dummies with improved biofidelity.
An in-depth study was conducted through the analysis of medical reports and crash data from real world accidents. The objective was to investigate the abdominal injury patterns among car occupants in frontal crashes. The influence of the type of restraint system, the occupant seat, the age and the crash severity was investigated. The results indicate that the risk of abdominal AIS 3+ injuries increased with crash severity and decreased with the introduction of belt retractors. Rear belted passengers were observed to be more likely injured than front belted occupants. The organs injured in frontal crashes for belted occupants were mainly hollow organs especially jejunum, ileum and mesentery.
This paper contains a review of methods for deriving risk curves from biomechanical data obtained from impact experiments on human surrogates. It covers many of the problems and pitfalls of obtaining realistic human risk curves from impact experiments. The strength and weakness of both parametric and non-parametric methods are evaluated. The limitations of standard analysis of censored impact test data are presented. Methods are given for determining risk curves from both doubly censored data and data obtained from impacts to body regions in which there are more than one mechanism of injury. A detailed set of examples is presented in which different experimental data are analyzed using the Consistent Threshold method and the logistic approach. Finally risk curves for published data are presented for the femur, head, thorax, and neck.
Cadaver data from experiments and data from field studies collected for the purposes of risk analysis are almost always censored. If the form of the underlying distribution is known, then the best method of analysis is to estimate the parameters using a maximum likelihood approach, but if it is not known, the best method is a nonparametric approach. The Consistent Threshold Estimate (CTE), introduced in this paper, is a method to estimate the underlying distribution that is both nonparametric and a maximum likelihood estimate. This paper uses CTE to estimate threshold head injury criterion (HIC) values for skull fracture or tissue damage, but it can be used for any application that has censored data. In addition to mathematically defining the CTE, a simple method to compute it for doubly censored data is given, and it is compared with other estimators by means of Monte Carlo tests. The CTE is then applied to experimental head-impact cadaver data.
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.
A test method was developed to identify those variables important for assessing the performance of ultrasonic surgical devices in ex vivo ligature sealing of porcine carotid and uterine arteries. Ruggedness testing using a small sample size in pilot experiments was conducted using a newly developed test method in an effort to assess the usefulness of this methodology and to identify test variables that might warrant further testing. The development of this test method included the use of a custom-designed prototypic tension device for load-controlled ex vivo vessel stretching during saline perfusion and subsequent seal and transection of porcine arteries with an advanced energy surgical device. The quality of the seal was evaluated as a burst pressure (mmHg). The experimental set-up allowed for either monitoring or controlling specific test conditions, including blood vessel tension during cutting and sealing, saline infusion rate, cutting time, pressure generated in the vessel during cutting, and burst pressure. Both muscular-type uterine and elastic-type carotid arteries were investigated, since energy based devices are most frequently used on muscular-type arteries but are developed and tested using elastic-type arteries. Although confounded with the age of the animal, in the ruggedness test pilot, it was observed that porcine carotid arteries yielded a comparatively lower burst strength seal as compared to porcine uterine arteries. The data generated during ruggedness testing suggests that the artery type and saline infusion rate during transection may be important variables in ex vivo vessel seal testing.
The purpose of this study was to determine patterns of abdominal injuries using the publicly available National Automotive Sampling System (NASS) database. Data from the NASS database for the years between 1993 and 1997 were extracted in order to gain an enhanced understanding of abdominal injury patterns resulting from vehicular collisions. The liver was most frequently injured due to contact with components in the front of the passenger compartment, such as the steering assembly and the instrument panel. Injuries to the spleen frequently resulted from contact with components on the left side of the passenger compartment. When considering only contact with components on the sides of the passenger compartment, the liver was injured more frequently due to contact with components on the right side of the passenger compartment while contact with components on the left side of the passenger compartment were more likely to result in injuries of the spleen. A more in-depth survey of the NASS database will be needed to determine if the asymmetrical features of human anatomy must be considered in the design of crash test dummies and mathematical models used in the evaluation of abdominal impact protection in automotive accidents.
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.
This paper quantifies pediatric thoracoabdominal response to belt loading to guide the scaling of existing adult response data and to assess the validity of a juvenile porcine abdominal model for application to the development of physical and computational models of the human child.
Table-top belt-loading experiments were performed on 6, 7, and 15 year-old pediatric post-mortem human subjects (PMHS). Response targets are reported for diagonal belt and distributed loading of the anterior thorax and for horizontal belt loading of the abdomen.
The pediatric PMHS exhibited abdominal response similar to the swine, including the degree of rate sensitivity. The thoraces of the PMHS were as stiff as, or slightly more stiff than, published adult corridors.
An assessment of age-related changes in thoracic stiffness suggests that the effective stiffness of the chest increases through the fourth decade of life and then decreases, resulting in stiffness values similar for children and elderly adults.
Liver trauma research suggests that rapidly increasing internal pressure plays a role in liver injury. Previous work has shown a correlation between pressure and liver injury in pressurized ex vivo human livers when subjected to blunt impacts. The purpose of this study was to extend the investigation of this relationship between pressure and liver injury by testing full-body post-mortem human surrogates (PMHS). Pressure-related variables were compared with one another and also to previously proposed biomechanical predictors of abdominal injury. Ten PMHS were tested. The abdominal vessels were pressurized to physiological levels using saline, and a pneumatic ram impacted the right side of the specimen ribcage at a nominal velocity of 7.0 m/s. Specimens were subjected to either lateral (n = 5) or oblique (n = 5) impacts, and the impact- induced pressures were measured by transducers inserted into the hepatic veins and inferior vena cava. The liver injuries observed were similar to those documented in the Crash Injury Research Engineering Network (CIREN) trauma database. Using binary logistic regression to develop injury risk functions, it was determined the peak rate of pressure change (Ṗmax) was a statistically significant predictor of AIS ≥ 3 liver injury for both the PMHS and ex vivo testing. This suggests that Ṗmax is a good predictor of liver injury regardless of the impact boundary conditions.
A better coupling of the occupant to the car seat in the early phase of a frontal or far side impacts using pretensioner systems may reduce the likelihood of the submarining effect or increases the likelihood of seat belt engaging the shoulder, respectively. However, the high belt forces may also increase the risk of upper body injuries to the vehicle occupant (especially in abdominal region). It was hypothesized that human body characteristics, such as body mass index (BMI) influence the biomechanical response and injury outcome to the abdominal regions during static pretensioning deployment tests.
Four postmortem human specimens (PMHS), in a BMI range from 15.6 to 31.2, were positioned in production seats in a normal passenger position and were restrained using a standard three-point belt system. The pretension forces in the belts were generated at two points (retractor and right anchorage) or at all three locations (retractor, left anchorage, and right anchorage). An optical motion capture system and acceleration cubes mounted to the lumbar spine were used to measure the abdomen deformation during testing.
The normalized deflections of the thorax recorded at the level of fourth rib were under 10% (noninjury level). Two different patterns were observed in the time histories of abdominal penetration rate in the four PMHSs associated with lower and higher BMI. Abdominal injuries (spleen lacerations) were observed only in the two PMHS with highest BMI.
Based on data from this study and similar data from the literature, belt velocity and FmaxCmax were shown to be the best injury predictors for injury risk analysis for Abbreviated Injury Scale 2+ and for Abbreviated Injury Scale 3+ injuries, respectively.
The ability to measure six degrees of freedom (6 DOF) head kinematics in motor vehicle crash conditions is important for assessing head-neck loads as well as brain injuries. A method for obtaining accurate 6 DOF head kinematics in short duration impact conditions is proposed and validated in this study. The proposed methodology utilizes six accelerometers and three angular rate sensors (6aω configuration) such that an algebraic equation is used to determine angular acceleration with respect to the body-fixed coordinate system, and angular velocity is measured directly rather than numerically integrating the angular acceleration. Head impact tests to validate the method were conducted using the internal nine accelerometer head of the Hybrid III dummy and the proposed 6aω scheme in both low (2.3 m/s) and high (4.0 m/s) speed impact conditions. The 6aω method was compared with a nine accelerometer array sensor package (NAP) as well as a configuration of three accelerometers and three angular rate sensors (3aω), both of which have been commonly used to measure 6 DOF kinematics of the head for assessment of brain and neck injuries. The ability of each of the three methods (6aω, 3aω, and NAP) to accurately measure 6 DOF head kinematics was quantified by calculating the normalized root mean squared deviation (NRMSD), which provides an average percent error over time. Results from the head impact tests indicate that the proposed 6aω scheme is capable of producing angular accelerations and linear accelerations transformed to a remote location that are comparable to that determined from the NAP scheme in both low and high speed impact conditions. The 3aω scheme was found to be unable to provide accurate angular accelerations or linear accelerations transformed to a remote location in the high speed head impact condition due to the required numerical differentiation. Both the 6aω and 3aω schemes were capable of measuring accurate angular displacement while the NAP instrumentation was unable to produce accurate angular displacement due to double numerical integration. The proposed 6aω scheme appears to be capable of measuring accurate 6 DOF kinematics of the head in any severity of impact conditions.
While seat belts are the most effective safety technology in vehicles today, there are continual efforts in the industry to improve their ability to reduce the risk of injury. In this paper, seat belt pretensioners and current trends towards more powerful systems were reviewed and analyzed. These more powerful systems may be, among other things, systems that develop higher belt forces, systems that remove slack from belt webbing at higher retraction speeds, or both. The analysis started with validation of the Ford Human Body Finite Element Model for use in evaluation of abdominal belt loading by pretensioners. The model was then used to show that those studies, done with lap-only belts, can be used to establish injury metrics for tests done with lap-shoulder belts. Then, previously-performed PMHS studies were used to develop AIS 2+ and AIS 3+ injury risk curves for abdominal interaction with seat belts via logistic regression and reliability analysis with interval censoring. Finally, some considerations were developed for a possible laboratory test to evaluate higher-powered pretensioners.
According to accident analysis, submarining is responsible for most of the frontal car crash AIS 3+ abdominal injuries sustained by restrained occupants. Submarining is characterized by an initial position of the lap belt on the iliac spine. During the crash, the pelvis slips under the lap belt which loads the abdomen. The order of magnitude of the abdominal deflection rate was reported by Uriot to be approximately 4 m/s. In addition, the use of active restraint devices such as pretensioners in recent cars lead to the need for the investigation of Out-Of-Position injuries. OOP is defined by an initial position of the lap belt on the abdomen instead of the pelvis resulting in a direct loading of the abdomen during pretensioning and the crash. In that case, the penetration speed of the belt into the abdomen was reported by Trosseille to be approximately 8 to 12 m/s. The aim of this study was to characterize the response of the human abdomen in submarining and OOP. A total of 8 PMHS abdomens were loaded using a lap belt. In order to investigate the injury mechanisms, the abdominal deflection rate and the compression were imposed such that they were not correlated. The specimens were seated upright in a fixed back configuration. The lap belt was placed at the level of the mid-umbilicus, between the iliac crest and the 12th rib. The belt was pulled horizontally along the sides of the specimens causing a symmetrical loading of the abdomen. In addition to the local parameters such as the belt and back forces or the belt displacements, the 3D external deformation of the abdomen was recorded. The forces measured between the back of the cadaver and the seat showed that a mass effect should be taken into account in the abdominal behaviour in addition to viscosity. The back force was greater than the belt force in low speed (submarining like) tests while it was lower for high-speed (OOP like) tests. A lumped parameter model was developed to confirm the experimental results and to be able to compare the load penetration characteristics to the results reported in the literature. The injury outcomes are provided and compared to all the published data. The PMHS sustained MAIS2-3 abdominal injuries in the low speed tests and MAIS2-4 injuries in the high speed tests. Finally, the dynamic 3D deformation of the abdominal wall was reconstructed and is provided for further validation of finite element models of the human abdomen.
The biomechanical response of the lower abdomen was investigated by simulated belt-restraint loading to the lower abdomen in a supine, rigidly supported, anesthetized swine. Impacts were delivered through a belt interface to the external ventrodorsad dimension of the lower abdomen at L4. A combination of a velocity and compression varying from 1.6-6.6 m/s and 6-67%, respectively, constituted one impact. Logist analysis indicated that maximum Compression (Cmax), maximum Viscous response (VCmax), and particularly peak Force-maximum Compression (FmaxCmax), were effective correlates to injury severity at AIS greater than or equal to 3 and 4. Statistical fit to AIS greater than or equal to 4 injury probability was strongest with a multi-parametric Logist analysis of Cmax and VCmax which indicated that abdominal injury may be related to both a velocity and compression mechanism. Force-deformation curves, characterized by a gradual, almost linear rise followed by rapid unloading, provided information on the stiffness of the lower abdomen in response to belt loading. Force-deflection curves based on total load indicated a reasonable correlation (R2 = 0.61) between estimated lower abdominal stiffness and velocity.
Lateral impacts of automobiles frequently result in abdominal injury to the occupants. While there have been important advances in the clinical management of this lateral impact trauma, the abdominal tolerance to injury from lateral impacts remains uncertain. The present report describes a series of 117 experiments in which the effect of changing the impact velocity and the forced abdominal compression upon the abdominal injuries sustained was monitored. The impact velocity was varied from 3 to 15 m/s, and the abdominal compression was varied from 10 to 50%. Serious injuries (AIS greater than or equal to 3) occurred in the following proportions of the total number of serious injuries: renal (54%), hepatic (44%), and splenic (1%). Impact side was a significant factor in hepatic and splenic tolerance, but not in renal tolerance. An abdominal injury criterion (AIC) is proposed which is a function of the impact velocity times the forced abdominal compression, but more work is necessary before it can be applied to human beings.
Insights into the science and the dynamics associated with the stimulus-injury relationship of the human system are often gained by focusing on the results obtained from human surrogate testing. These results are commonly mapped into an injury risk paradigm for the purpose of characterizing the stimulus injury response: the injury risk curve. However, the quality and quantity of the data along with the experimental design are critical factors when considering the value of the estimated risk curve. Presented in this article is an analysis of injury risk curves in terms of their usability and appropriateness with respect to the sample size, stimulus distribution over the critical range, censoring, shape of the underlying risk function, and the inclusion of "actual" (uncensored) along with censored data. The results from this analysis indicate that for "large" biomechanical injury data sets there is no advantage to using actual data; censored data will yield the same injury risk curve as actual data. However, for "small" biomechanical injury data sets the inclusion of actual data will significantly improve the quality of the resulting risk curve. In addition, the results show that the amount of injury data needed to generate a risk curve with a given confidence bound is not only dependent on the relative contribution of the censored data and actual data but also on the shape of the risk function along with the stimulus distribution over the critical range. Confidence intervals are presented for the thoracic injury risk and the head injury risk to show the influence of data distribution on the goodness of the risk function estimation.
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This study was conducted to address injury risk due to high-speed loading of the abdomen by a seatbelt during the pretension phase. Indeed, a better coupling of occupants to the structure of the vehicle in frontal impact can be achieved by a strong pretension of the lap belt. However, out of position considerations have to be taken into account in the development of pretension systems. In particular, when the lap belt is on the abdomen instead of the pelvis at the time of pretension, the penetration of the belt into the abdomen should not lead to injuries. Given the sensitivity of pyrotechnic pre-tensioners to the resistance that they encounter, it is important to have an understanding of the behaviors of both human and dummy abdomens in order to evaluate injury risk. These data are indispensable for the evaluation, with dummy tests, of the effects of pre-tensioners on occupants and for the estimation of the levels of injury risk. New experiments were necessary to obtain data on abdomenbehavior in the pretension range of velocity. Six fixed-back cadavers were tested in two configurations: the belt was placed just above the iliac crest and tensed either symmetrically or not from 11 m/s to 23 m/s. Belt forces and kinematics were measured. Autopsies were performed. Tests were duplicated on the THOR dummy.
Results:
Load penetration characteristics and injury outcomes are provided and compared to other published data. A spring-damper equivalent model of the abdomen is provided in order to give a means by which to evaluate dummies. The stiffness is 12.9 kN/m and the damping is 765 Ns/m. Static stiffness for the THOR dummy is too high, while the viscous component is four times too low when compared to the tested cadavers.
This study characterizes the response of the human cadaver abdomen to high-speed seatbelt loading using pyrotechnic pretensioners. A test apparatus was developed to deliver symmetric loading to the abdomen using a seatbelt equipped with two low-mass load cells. Eight subjects were tested under worst-case scenario, out-of-position (OOP) conditions. A seatbelt was placed at the level of mid-umbilicus and drawn back along the sides of the specimens, which were seated upright using a fixed-back configuration. Penetration was measured by a laser, which tracked the anterior aspect of the abdomen, and by high-speed video. Additionally, aortic pressure was monitored. Three different pretensioner designs were used, referred to as system A, system B and system C. The B and C systems employed single pretensioners. The A system consisted of two B system pretensioners. The vascular systems of the subjects were perfused. Peak anterior abdominal loads due to the seatbelt ranged from 2.8 kN to 10.1 kN. Peak abdominal penetration ranged from 49 mm to 138 mm. Peak penetration speed ranged from 4.0 m/s to 13.3 m/s. Three cadavers sustained liver injury: one AIS 2, and two AIS 3. Cadaver abdominal response corridors for the A and B system pretensioners are proposed. The results are compared to the data reported by Hardy et al. (2001) and Trosseille et al. (2002).
The objective of this work was to develop a reusable, rate-sensitive dummy abdomen with abdominal injury assessment capability. The primary goal for the abdomen developed was to have good biofidelity in a variety of loading situations that might be encountered in an automotive collision. This paper presents a review of previous designs for crash dummy abdomens, a description of the development of the new abdomen, results of testing with the new abdomen and instrumentation, and suggestions for future work. The biomechanical response targets for the new abdomen were determined from tests of the mid abdomen done in a companion biomechanical study. The response of the abdominal insert is an aggregate response of the dummy's entire abdominal area and does not address differences in upper versus lower abdominal response, solid versus hollow organs, or organ position or mobility. While the abdomen developed has demonstrated good biofidelity in rigid bar, seat belt and airbag loading situations, some work remains to be done before it can be used in crash testing.
Liver trauma research suggests that rapidly increasing internal pressure plays a role in causing blunt liver injury. Knowledge of the relationship between pressure and the likelihood of liver injury could be used to enhance the design of crash test dummies. The objectives of this study were (1) to characterize the relationship between impact-induced pressures and blunt liver injury in an experimental model to impacts of ex vivo organs; and (2) to compare human liver vascular pressure and tissue pressure in the parenchyma with other biomechanical variables as predictors of liver injury risk. Test specimens were 14 ex vivo human livers. Specimens were perfused with normal saline solution at physiological pressures, and a drop tower applied blunt impact at varying energies. Impact-induced pressures were measured by transducers inserted into the hepatic veins and the parenchyma (caudate lobe) of ex vivo specimens. Experimentally induced liver injuries were consistent with those documented in the Crash Injury Research and Engineering Network (CIREN) database. Binary logistic regression analysis demonstrated that injury predictors associated with tissue pressure measured in the parenchyma were the best indicators of serious liver injury risk. The best injury predictor overall was the product of the peak rate of tissue pressure increase and the peak tissue pressure, P T max * P T max (pseudo-R2 = .82, p = .001). A burst injury mechanism directly related to hydrostatic pressure is postulated for the ex vivo liver loaded dynamically in a drop test experiment.
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