A finite element model of a six-year-old child for simulating pedestrian accidents

Effectiveness of Wearable Protection Equipment for Seated Pedestrians

This study used finite element models to investigate the efficacy of seated pedestrian protection equipment in vehicle impacts. The selected safety equipment, a lap belt, an airbag vest, and a bicycle helmet, were chosen to mitigate the underlying biomechanical causes of seated pedestrian injuries reported in the literature. The impact conditions were based on the three most dangerous impact scenarios from a previous seated pedestrian impact study. Serious injury (AIS 3+) risks were compared with and without protective equipment. A 50th percentile male occupant model and two generic vehicle models, the family car (FCR) and sports utility vehicle (SUV), were used to simulate vehicle collisions. Three impact conditions were run with every combination of protective equipment (n = 24). The helmet reduced head and brain injury risks from the vehicle-head and ground-head contacts. The airbag reduced the head injury risk in the FCR vehicle-head contact but increased the brain injury risks in the SUV impacts from increased whiplash. The lap belt increased head injury risks for both the FCR and the SUV impacts because it created a stronger FCR vehicle-head contact and SUV ground-head contact. When the belt and airbag were used together the head injury risks dramatically decreased because the pedestrian body impacted the ground arm or leg first and slowly rolled onto the ground which resulted in softer ground-head contacts and in two instances, no ground-head contact. Only the helmet proved effective in all impact conditions. Future testing must be completed before recommending the belt or airbag for seated pedestrians.

Finite element analysis of Kirschner wire fixation for lateral condyle fracture in children in the sagittal plane

OBJECTIVE

This study aims to find the optimal arrangement of the Kirschner wire (K-wire) in the sagittal plane for fixation of a pediatric lateral condylar humeral fracture (Milch type II) by using finite element analysis (FEA).

METHODS

A model of lateral condyle fracture in a 6-year-old boy was developed, and an XYZ coordinate system was established based on this model. The YZ plane was defined as the sagittal plane to investigate the impact of the angle formed by the first and second K-wires on stability. Two configurations were studied for each angle: parallel and divergent. Evaluation indicators included the maximum displacement of the fracture fragment and the maximum von Mises stress in the pins and bone.

RESULTS

The model with a -60° angle showed the best performance in both evaluation indicators. The parallel and divergent pin configurations had different performances in each group. The displacement results for negative angles were similar, and this result was better than those for positive angles.

CONCLUSION

We successfully created a model of pediatric lateral condyle humerus fracture (Milch type II) and performed K-wire fixation with varying sagittal plane configurations, combined with FEA. Our findings demonstrate that the angle of -60° between the two pins in the sagittal plane provided the highest level of stability, with divergent configurations proving superior to parallel pinning at this angle.

Effect of Tissue Erosion Modeling Techniques on Pedestrian Impact Kinematics

The pedestrian is one of the most vulnerable road users and has experienced increased numbers of injuries and deaths caused by car-to-pedestrian collisions over the last decade. To curb this trend, finite element models of pedestrians have been developed to investigate pedestrian protection in vehicle impact simulations. While useful, modeling practices vary across research groups, especially when applying knee/ankle ligament and bone failure. To help better standardize modeling practices this study explored the effect of knee ligament and bone element elimination on pedestrian impact outcomes. A male 50th percentile model was impacted by three European generic vehicles at 30, 40, and 50 km/h. The pedestrian model was set to three element elimination settings: the "Off-model" didn't allow any element erosion, the "Lig-model" allowed lower-extremity ligament erosion, and the "All-model" allowed lower-extremity ligament and bone erosion. Failure toggling had a significant effect on impact outcomes (0 < p ≤ 0.03). The head impact time response was typically the smallest for the "Off-model" while the wrap around distance response was always largest for the All-model. Moderate differences in maximum vehicle-pedestrian contact forces across elimination techniques were reported in this study (0.1 - 1.7 kN). Future work will examine additional failure modelling approaches, model anthropometries and vehicles to expand this investigation.

A computational study on the basis for a safe speed limit for bicycles on shared paths considering the severity of pedestrian head injuries in bicyclist-pedestrian collisions

Bicyclists and pedestrians are two large vulnerable groups of road users. Many cities have allowed cyclists to share space with pedestrians on footpaths and off-road paths to reduce conflict with motor vehicles. The risk of bicyclist-pedestrian accidents is also increasing accordingly. Therefore, there is a need to understand the factors that affect the risk of injury in such accidents, especially to pedestrians who are considered more vulnerable. This paper presents a detailed investigation of bicyclist-pedestrian collisions and possible injury outcomes. The study has considered five levels of collision speed ranging from 10 km/h to 30 km/h, three pedestrian profiles (adult, child, and elderly) differentiated by their weight and height, three bicycles with different masses, and five impact directions. The bicyclist-pedestrian collision simulations have been analyzed based on four metrics: throw distance, peak head velocity on impact with the ground, head injury criterion (HIC) value, and the probability of severe head injury. For each simulation, the throw distance and peak head velocity on impact with the ground are extracted. Following that, the HIC and the probability of severe head injury to pedestrians are computed. The results show a significant effect of collision speed (p < 0.05) on all four metrics. The analysis has been further extended to study the effect of height and weight profile, bicycle mass, and impact directions on bicyclist-pedestrian collisions. According to the results, the impact directions largely influence the outcome of bicycle-pedestrian collisions. In general, direct impacts on pedestrian body center have been found to yield higher HIC values and probability of severe head injury to pedestrians than off-center impacts. Also, video analysis of simulated collisions has suggested that the accident mechanism depends on weight and height profiles (correlated with different age groups) and impact directions. Finally, recommendations have been proposed based on the study, including a speed limit of not more than 12 km/h for bicyclists on narrow shared paths and footpaths where risks of collisions with pedestrians are high. The results and analysis presented could be helpful for developing legislation to minimize conflicts between bicyclists and pedestrians on shared paths and to reduce potential injury to pedestrians.

The most stable pinning configurations in transverse supracondylar humerus fracture fixation in children: A novel three-dimensional finite element analysis of a pediatric bone model

PURPOSE

This study aimed at finding out the effect of exit height, trajectory and number of pins on the stability of cross and divergent-lateral pins used in the fixation of extension-type, transverse supracondylar humerus fracture (SHF) in children, based on finite element analysis.

METHODS

Distal humerus model consisting of the ossific nucleus of the capitellum (ONC) and distal cartilage of a 6-year-old boy was developed via three-dimensional finite modeling. Various cross and divergent-lateral pinning models with either two or three pins were simulated on an extension-type, transverse SHF and tested in six loading directions.

RESULTS

Two-cross pins and 2-divergent-lateral pins were more stable against torsional and translation forces respectively, while 3-cross pins were the most stable against all forces. The cross pins exiting at the upper border of the distal metaphyseal-diaphyseal junction (MDJ) had the best stiffness among the 2-cross pins, while the lateral pins with a middle third ONC distal pin provided the best stiffness among the 2-lateral pins. A third olecranon fossa pin greatly enhanced stability of the 2-lateral pins.

CONCLUSION

For typical transverse fractures, 2-cross pins are found to be superior to 2-divergent lateral pins only against torsional forces. Pins exiting at the upper border of the MDJ provides the best mechanical stability with 2-cross pins. Two-divergent-lateral pins with a distal pin going through the middle third of the ONC provides the best mechanical stability against translation forces for these transverse fractures. Three-cross pins however offer the best mechanical stability against both translation and torsional forces. This study offers important clues in the preoperative evaluation and management of extension-type supracondylar fractures in children.

Preliminary study on the mechanisms of ankle injuries under falling and impact conditions based on the THUMS model

Ankle injuries are common in forensic practice, which are mainly caused by falling and traffic accidents. Determining the mechanisms and manners of ankle injuries is a critical and challenging problem for forensic experts. The identification of the injury mechanism is still experience-based and strongly subjective. There also lacks systematic research in current practice. In our study, based on the widely used Total Human Model of Safety 4.0 (THUMS 4.0), we utilized the finite element (FE) method to simulate ankle injuries caused by falls from different heights (5 m, 10 m and 20 m) with different landing postures (natural posture, inversion, eversion, plantar-flexion and dorsi-flexion) and injuries caused by impacts from different directions (anterior-posterior, lateral-medial and posterior-anterior) with different speeds (10 m/s, 15 m/s and 20 m/s) at different sites (ankle and lower, middle and upper sections of leg). We compared the injury morphology and analyzed the mechanisms of ankle injuries. The results showed that falling causes a specific compression fracture of the distal tibia, while fractures of the tibia and fibula diaphysis and ligament injuries caused by falling from a lower height or inversion, planter flexion or dorsiflexion at a large angle are not distinguishable from the similar injury patterns caused by impact on the middle and upper segments of the leg. No obvious compression fracture of the tibia distal was caused by the impacts, whereas ligament injuries and avulsion fractures of the medial or lateral condyle and fractures of the diaphysis of the tibia and fibula were observed. Systematic studies will be helpful in reconstructing the ankle injury processes and analyzing the mechanisms in forensic practice, providing a deeper understanding of ankle injury mechanisms for forensic experts.

Development and Application of Digital Human Models in the Field of Vehicle Collisions: A Review

In the human-vehicle-road system of collisions, the human is the most important factor, and digital human models (DHMs) are developed with the aim of preventing or at least reducing human injury. Because most of the relevant literature is focused mainly on collisions in traffic accidents (TAs), only some of the literature reviewed in this paper involves research results on other aspects of collisions. In this review, based on the background of DHMs and the application of DHMs regarding human injury biomechanics in collisions field, research results regarding the development of DHMs are described, the methods for verifying such models are introduced, and the application of the research results is discussed based on the aspect of human injury biomechanics. From the research literature, the development and validation of DHMs and their application in human injury biomechanics are summarized, and future research trends are proposed and discussed.

Validation of a finite element model with six-year-old child anatomical characteristics as specified in Euro NCAP Pedestrian Human Model Certification (TB024)

Accident statistics show that more than 80% of car-to-pedestrian collisions (CPC) occur when pedestrians cross the road. It is very important to establish a finite element model with natural walking posture to study the kinematics and injury mechanism of pedestrians. In this study, a finite element model of six-year-old child pedestrian is developed with detailed anatomical characteristics and posture parameters as specified in Euro NCAP Pedestrian Human Model Certification (TB024). The numerical human body model is validated in total twelve simulations in which the pedestrian is impacted against four generic vehicle models at speeds 30, 40, 50 km/h prescribed in TB024. The Head Impact Time (HIT), Contact Force and the Trajectories of HC, T12 and AC of all twelve simulations are compared with the reference corridors provided by Technical Bulletin 024. The results indicate that the numerical human body model of a six-year-old child can be used to demonstrate the suitability of the sensing system for the range of pedestrian sizes; the timing of system deployment, and the bonnet deflection due to body loading. Furthermore, the model could be a good tool for further research on pedestrian injury mechanism and the development of pedestrian protection devices.

Mechanical stability study of three techniques used in the fixation of transverse and oblique metaphyseal-diaphyseal junction fractures of the distal humerus in children: a finite element analysis

Background

Management of distal humerus metaphyseal-diaphyseal junction (MDJ) region fractures can be very challenging mainly because of the higher location and characteristics of the fracture lines. Loss of reduction is relatively higher in MDJ fractures treated with classical supracondylar humerus fractures (SHFs) fixation techniques.

Methods

Three different fracture patterns including transverse, medial oblique and lateral oblique fractures were computationally simulated in the coronal plane in the distal MDJ region of a pediatric humerus and fixated with Kirschner Wires (K-wires), elastic stable intramedullary nails (ESIN), and lateral external fixation system (EF). Stiffness values in flexion, extension, valgus, varus, internal, and external rotations for each fixation technique were calculated.

Results

In the transverse fracture model, 3C (1-medial, 2-lateral K-wires) had the best stiffness in flexion, varus, internal, and external rotations, while 3L (3-divergent lateral K-wires) was the most stable in extension and valgus. In the medial oblique fracture model, EF had the best stiffness in flexion, extension, valgus, and varus loadings, while the best stiffness in internal and external rotations was generated by 3MC (2-medial, 1-lateral K-wires). In the lateral oblique fracture model, 3C (1-medial, 2-lateral K-wires) had the best stiffness in flexion and internal and external rotations, while ESIN had the best stiffness in extension and valgus and varus loadings.

Conclusion

The best stability against translational forces in lateral oblique, medial oblique, and transverse MDJ fractures would be provided by ESIN, EF, and K-wires, respectively. K-wires are however superior to both ESIN and EF in stabilizing all three fracture types against torsional forces, with both 2-crossed and 3-crossed K-wires having comparable stability. Depending on the fracture pattern, a 3-crossed configuration with either 2-divergent lateral and 1-medial K-wires or 2-medial and 1-lateral K-wires may offer the best stability.

Investigating rolling as mechanism for humeral fractures in non-ambulant infants: a preliminary finite element study

AIM

To use personalised computed tomography (CT)-based finite element models to quantitatively investigate the likelihood of self-inflicted humeral fracture in non-ambulant infants secondary to rolling.

MATERIALS AND METHODS

Three whole-body post-mortem CT examinations of children at the age of rolling (two 4-month-old and one 6-month-old) were used. The mechanical moment needed by each infant to perform a rolling manoeuvre was calculated and applied to the finite element model in order to simulate spontaneous rolling from the prone to the supine position.

RESULTS

The maximum predicted strains were found to be substantially lower (with a difference of >80%) than the elastic limit of the bone.

CONCLUSION

Results of this study challenge the plausibility of self-inflicted humeral fracture caused by rolling in non-ambulant infants and indicate that it is unlikely for a humeral fracture to result from this mechanism without the assistance of an external force.

Evaluation of finite element human body models for use in a standardized protocol for pedestrian safety assessment

Objective: Finite element human body models (HBMs) must be certified for use within the EuroNCAP pedestrian safety assessment protocol. We demonstrate that the Global Human Body Model Consortium (GHBMC) simplified pedestrian series of HBMs meet all criteria set forth in Technical Bulletin (TB) 024 (v 1.1 Jan. 2019) for model certification. We further explore variation in head contact time (HIT) and location by HBM size and impact speed across 48 full body impact simulations.Methods: The EuroNCAP Pedestrian Protocol (v. 8.5, Oct. 2018) assesses the overall safety of adult and child pedestrians by outlining a variety of physical tests and finite element simulations using HBMs. These tests are designed to assess the efficacy of vehicle safety technology such as active bonnets. The 50th percentile male simplified pedestrian model (M50-PS, H:175 cm, W:74.5 kg), six-year-old (6YO-PS, H:117 cm, W:23.4 kg), 5th percentile female (F05-PS, H:150 cm, W:50.7 kg), and 95th percentile male (M95-PS, H:190 cm, W:102 kg) were simulated through the suite of cases totaling 48 simulations (12 each). The process gathers three kinematic trajectories and contact force data from designated anatomical locations. The impacting vehicles include a family car (FCR), multi-purpose vehicle (MPV), roadster (RDS), and sports utility vehicle (SUV), all provided by TU Graz, Vehicle Safety Institute as part of the Coherent Project, each simulated at 30 kph, 40 kph, and 50 kph. Each simulation underwent a 23-point pre-simulation check and post-simulation model response comparison. The posture of all HBMs met criteria consisting of 15 measures. All simulations were conducted in LS-Dyna R. 7.1.2.Results and Conclusions: All simulations normal terminated. For each of the simulations, sagittal plane coordinate histories of the center of the head, 12th thoracic vertebrae, and center of acetabulum were compared with standard corridors and did not exceed the tolerance of 50 mm deviation. Head contact time was also compared with the reference values and did not exceed the tolerance interval of +3.5% and -7%. Comparison of contact forces was required for monitoring purposes only. The head contact time of the models for each simulation was recorded and compared by model size, impact speed, and vehicle geometry. Head contact times varied by roughly 3-fold, were lowest for the child model, and showed the greatest sensitivity for the tallest stature model (M95-PS). As stated in the certification process, other body sizes within a model family qualify for certification if the 50th percentile male model passes, provided that model sizes meet the required posture.

ESTABLISHMENT AND APPLICATION OF LOWER LIMB FINITE ELEMENT MODEL BASED ON MUSCLE GROUPS

Living body or corpse could be replaced with the virtual human tissue model for biomechanical experimental study, which effectively avoids the non-reusability, great social controversy, huge costs and difficulty in extracting parameters, and finally, the accurate analysis results are obtained. Unlike the previous lower limb models, the finite element models of hip and thigh were established based on the concept of muscle group in this paper. The cortical bones of hip bone and femur were set as *MAT_PIECEWISE_LINEAR_ PLASTICITY. The material of cancellous bone was set as *MAT_ELASTIC_PLASTIC_ WITH_DAMAGE_FAILURE. The material of articular cartilage was set as *MAT_ISOTROPIC_ELASTIC. The materials of muscle and fat were set as *MAT_VISCOELASTIC. The accuracy of the finite element model was verified by dynamic three-point bending experiment of the thighs. Mechanical simulation was carried out to the stump-prosthetic socket and the comfort of socks by the established model. The simulation results were all between the upper and lower bounds of the experimental results in the dynamic three-point bending experiment of the thighs where the loads were separately applied to one-third of the distal end of thighs and the middle part of thighs. The simulation results of the stump-prosthetic socket example show that the optimal elastic modulus of silicone pad is 2.5[Formula: see text]MPa. Simulation results of socks comfort show that the distribution of stress and deformation of the anterior and posterior thighs is different when the human lower limbs are in stockings. The established simulation model meets the accuracy requirement and can replace the living body or corpse to carry out biomechanical experimental study. The finite element simulation results converge, and the time to complete a finite element calculation is less than or equal to 10[Formula: see text]min.

A finite element model of an anthropomorphic test device lower limb to assess risk of injuries during vertical accelerative loading

Improvised explosive devices (IEDs) were used extensively to target occupants of military vehicles during the conflicts in Iraq and Afghanistan (2003-2011). War fighters exposed to an IED attack were highly susceptible to lower limb injuries. To appropriately assess vehicle safety and make informed improvements to vehicle design, a novel Anthropomorphic Test Device (ATD), called the Warrior Injury Assessment Manikin (WIAMan), was designed for vertical loading. The main objective of this study was to develop and validate a Finite Element (FE) model of the WIAMan lower limb (WIAMan-LL). Appropriate materials and contacts were applied to realistically model the physical dummy. Validation of the model was conducted based on experiments performed on two different test rigs designed to simulate the vertical loading experienced during an under-vehicle explosion. Additionally, a preliminary evaluation of the WIAMan and Hybrid-III test devices was performed by comparing force responses to post-mortem human surrogate (PMHS) corridors. The knee axial force recorded by the WIAMan-LL when struck on the plantar surface of the foot (2 m/s) fell mostly within the PMHS corridor, but the corresponding data predicted by the Hybrid-III was almost 60% higher. Overall, good agreements were observed between the WIAMan-LL FE predictions and experiments at various pre-impact speeds ranging from 2 m/s up to 5.8 m/s. Results of the FE model were backed by mean objective rating scores of 0.67-0.76 which support its accuracy relative to the physical lower limb dummy. The observations and objective rating scores show the model is validated within the experimental loading conditions. These results indicate the model can be used in numerical studies related to possible dummy design improvements once additional PMHS data is available. The numerical lower limb is currently incorporated into a whole body model that will be used to evaluate the vehicle design for underbody blast protection.

A Review of Pediatric Lower Extremity Data for Pedestrian Numerical Modeling: Injury Epidemiology, Anatomy, Anthropometry, Structural, and Mechanical Properties

Pedestrian injuries are the fourth leading cause of unintentional injury-related death among children aged 1 to 19. The lower extremity represents the most frequently injured body region in car-to-pedestrian accidents. The goal of this study was to perform a systematic review of the data related to pedestrian lower extremity injuries, anatomy, anthropometry, structural, and mechanical properties, which can be used in the development of new pediatric computational models. The study began with a review of epidemiologic data related to pediatric pedestrian accidents. Anatomy of the child lower extremity and age-related anthropometry data were presented as well. Then, both the mechanical and structural properties of the lower extremity main components (e.g., bones, cartilages, knee ligaments, muscles, tendons, and growth plates) available in literature were summarized. The study concluded with a brief description of current child pedestrian models, which included a discussion about their limitations. We believe that data included in this review study can help in improving the biofidelity of current child models and support the development and validation of new child models used by safety researchers for protection of pediatric population.

Development and Validation of an Age-Specific Lower Extremity Finite Element Model for Simulating Pedestrian Accidents

The objective of the present study is to develop an age-specific lower extremity finite element model for pedestrian accident simulation. Finite element (FE) models have been used as a versatile tool to simulate and understand the pedestrian injury mechanisms and assess injury risk during crashes. However, current computational models only represent certain ages in the population, the age spectrum of the pedestrian victims is very large, and the geometry of anatomical structures and material property of the lower extremities changes with age for adults, which could affect the injury tolerance, especially in at-risk populations such as the elderly. The effects of age on the material mechanical property of bone and soft tissues of the lower extremities as well as the geometry of the long bone were studied. Then an existing 50th percentile male pedestrian lower extremity model was rebuilt to depict lower extremity morphology for 30- to 70-year-old (YO) individuals. A series of PMHS tests were simulated to validate the biofidelity and stability of the created age-specific models and evaluate the lower extremity response. The development of age-specific lower extremity models will lead to an improved understanding of the pedestrian lower extremity injury mechanisms and injury risk prediction for the whole population in vehicle-pedestrian collision accidents.

Child road traffic injury mortality in Victoria, Australia (0-14 years), the need for targeted action

INTRODUCTION

Extensive efforts to reduce unintentional injury were enacted in the last three decades of the 20th century. Examination of road traffic injury mortality indicates the extent of fatal, unintentional child injuries (0-14 years) future interventions must address.

AIMS

(1) describe in-depth child road traffic injury (RTI) deaths 2001-2012 in Victoria, Australia (2) identify the potential preventability of the RTI causes by currently available countermeasures and scope for enhanced implementation and novel solutions.

METHOD

Fatal Victorian child injury data were extracted from the National Coronial Information System (NCIS) for the 12 year period January 2001-December 2012. All on-road data was analysed. Data for passenger and pedestrian deaths was examined in depth. Associated factors were determined using univariate and pairwise analysis of factors. Published WHO key prevention strategies, and the recent literature were reviewed, focusing on the identified fatalities among children 0-14 years.

RESULTS

For 172 RTI deaths, head injury was the leading medical cause of death (68%). Significantly, the most vulnerable age group for both passengers and pedestrians was 0-4 years. Rural children were over-represented with children aged 0-4 years at greatest risk. Common factors for occupants were loss of control and veering to the incorrect side. For pedestrians the major factors related to rural residence and supervision.

DISCUSSION AND CONCLUSIONS

This study confirms that RTIs are complex and follow chains of events. Numerous promising interventions were identified. Wider implementation of these advanced engineering, education and enforcement strategies may further improve mortality rates in Victoria. Feasible solutions for aspects of the child pedestrian problem remain elusive. This study describes the RTI problem in greater depth than previous studies and reveals that some existing measures are not fully implemented. The need for targeted action in: 0-4 year olds; head injury; and rural regions of Victoria is highlighted. The need for a safe systems approach is paramount.

A Finite Element Model of a Midsize Male for Simulating Pedestrian Accidents

Pedestrians represent one of the most vulnerable road users and comprise nearly 22% the road crash-related fatalities in the world. Therefore, protection of pedestrians in car-to-pedestrian collisions (CPC) has recently generated increased attention with regulations involving three subsystem tests. The development of a finite element (FE) pedestrian model could provide a complementary component that characterizes the whole-body response of vehicle–pedestrian interactions and assesses the pedestrian injuries. The main goal of this study was to develop and to validate a simplified full body FE model corresponding to a 50th male pedestrian in standing posture (M50-PS). The FE model mesh and defined material properties are based on a 50th percentile male occupant model. The lower limb-pelvis and lumbar spine regions of the human model were validated against the postmortem human surrogate (PMHS) test data recorded in four-point lateral knee bending tests, pelvic\abdomen\shoulder\thoracic impact tests, and lumbar spine bending tests. Then, a pedestrian-to-vehicle impact simulation was performed using the whole pedestrian model, and the results were compared to corresponding PMHS tests. Overall, the simulation results showed that lower leg response is mostly within the boundaries of PMHS corridors. In addition, the model shows the capability to predict the most common lower extremity injuries observed in pedestrian accidents. Generally, the validated pedestrian model may be used by safety researchers in the design of front ends of new vehicles in order to increase pedestrian protection.