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Improved protection for the child pedestrian requires a precise knowledge of the biomechanics of specific injury mechanisms for this particular category of pedestrian. In the absence of tests on cadaver subjects, numerical models are a possible route of investigation for developing a predictive model for the severity of injuries. The purpose of this study was to develop an Abbreviated Injury Scale-head (AIS-head) prediction model from numerical simulations of real accident configurations between a vehicle and a child pedestrian. Fifteen real accident configurations were collected from three different databases and simulated in order to identify a realistic injury criterion. For each configuration, a complete multi-body simulation of the accident, followed by a finite element simulation of the head/hood contact, was performed. Sixteen numerical indicators of injury, related to both the kinematics and the stress distribution, were recorded at the end of each reconstruction. To assess the predictive capacity of our model, four new cases of real accidents were also simulated. Statistical analysis showed that a combination of different numerical indicators predicted the AIS-head of an accident accurately, with a mean error of 0.25. [ABSTRACT FROM AUTHOR]

Use of bicycles on a large scale, encouraged in the context to develop an eco-friendly environment, is facing today a range of barriers. One of these barriers identified by researchers and governments is observed to include ‘road safety’. Hence, it is necessary to set up a protection system for bicyclists especially for the cephalic segment. Currently only few studies are available concerning the head impact loading in case of real accidents. Therefore, the objective of this work is to improve the knowledge of bicyclist head trauma by following a methodology to reconstruct real-world accidents. A step is to identify the initial condition of head impact in case of real accidents. Head impact velocity and head impact area are extracted and implemented in the last generation of head injury prediction tool to simulate the head trauma by impacting directly the Strasbourg University Finite Element Head Model (SUFEHM) on the vehicle structures. The present study can be divided into three activities, i.e. obtain real bicyclist accidents' data issued from in-depth accident investigation databases, reconstruct cyclist body kinematics to obtain the initial conditions of the head just before the impact, and simulate head impact to evaluate the head loading during impact and the injury risk. A total of 24 bicyclists’ accident cases with head injuries have been selected from both French and German accident databases. For each accident case, body kinematics has been simulated using Madymo® software. Two human multi-body models were used: 8 accident cases have been reconstructed by IFSTTAR using its owned developed human model and 18 accident cases have been reconstructed by Unistra using the human pedestrian TNO model. The results show that head is impacted more often on top parietal zone, and the mean impact velocity is 6.8 ± 2.7 m/s with 5.5 ± 3.0 m/s and 3.4 ± 2.1 m/s for normal and tangential components, respectively. Among these real accidents, 19 cases were selected for finite element computations by coupling the human head model and a windscreen model whose properties were extracted from literature. All reconstructed head impact gave results in accordance with the damage actually incurred to the victims. [ABSTRACT FROM AUTHOR]

Finite element analysis (FEA) has been widely used to study foot biomechanics and pathological functions or effects of therapeutic solutions. However, development and analysis of such foot modeling is complex and time-consuming. The purpose of this study was therefore to propose a method coupling a FE foot model with a model order reduction (MOR) technique to provide real-time analysis of the dynamic foot function. A generic and parametric FE foot model was developed and dynamically validated during stance phase of gait. Based on a design of experiment of 30 FE simulations including four parameters related to foot function, the MOR method was employed to create a prediction model of the center of pressure (COP) path that was validated with four more random simulations. The four predicted COP paths were obtained with a 3% root-mean-square-error (RMSE) in less than 1 s. The time-dependent analysis demonstrated that the subtalar joint position and the midtarsal joint laxity are the most influential factors on the foot functions. These results provide additionally insight into the use of MOR technique to significantly improve speed and power of the FE analysis of the foot function and may support the development of real-time decision support tools based on this method., (Copyright © 2021 by ASME.)

Pedestrian injuries occur in both the primary vehicle contact and the subsequent ground contact. Currently, no ground contact countermeasures have been implemented and no pedestrian model has been validated for ground contact, though this is needed for developing future ground contact injury countermeasures. In this paper, we assess the predictive capacity of the MADYMO ellipsoid pedestrian model in reconstructing six recent pedestrian cadaver ground contact experiments. Whole-body kinematics as well as vehicle and ground contact related aHIC (approximate HIC) and BrIC scores were evaluated. Reasonable results were generally achieved for the timings of the principal collision events, and for the overall ground contact mechanisms. However, the resulting head injury predictions based on the ground contact HIC and BrIC scores showed limited capacity of the model to replicate individual experiments. Sensitivity studies showed substantial influences of the vehicle-pedestrian contact characteristic and certain initial pedestrian joint angles on the subsequent ground contact kinematics and injury predictions. Further work is needed to improve the predictive capacity of the MADYMO pedestrian model for ground contact injury predictions., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The development of artificial prosthetic lower limbs aims to improve patient's mobility while avoiding secondary problems resulting from the use of the prostheses themselves. The residual limb is a pressure-sensitive area where skin injuries and pain are more likely to develop. Requirements for adequate prosthetic limbs have now become urgent to improve amputee's quality of life. This study aims to understand how socket design parameters related to geometry can influence pressure distribution in the residual limb. A finite element model was developed to simulate the mechanical loading applied on the residual limb of a below-knee amputee while walking. A sensitivity analysis to socket initial geometry, scaling the socket downward in the horizontal plane, was performed. Recordings include stress levels on the skin and in the residual limb deep soft tissues. Peak stress was reduced by up to 51% with a limited reduction of the socket size. More important scale reduction of the residual limb would lead to possible negative effects, such as stress concentrations in sensitive areas. This result confirms the interest of the prosthetist to develop a well-fitting socket, possibly a little smaller than the residual limb itself, in order to avoid residual limb mobility in the socket that could cause friction and stress concentrations. Non-homogeneous geometrical reductions of the socket should be further investigated.

Background: The prolonged standing position is an important factor in the onset of foot musculoskeletal disorders among workers. Safety shoes, designed to protect against the physical constraints of the work environment, do not address this issue to date., Objectives: The goal of this study is to assess the possible benefits of custom-made foot orthoses among prolonged standing workers., Study Design: repeated measures without control group., Methods: Thirty-four standing workers who suffer from foot pain volunteered for the study. Custom-made foot orthoses, designed by a podiatrist, were 3D-printed and distributed to each volunteer. Static balance as well as static and dynamic plantar pressure measurements were carried out with sensors inserted in the safety shoes, before and after three weeks of wearing foot orthoses daily. A questionnaire on pain and comfort was also distributed before and after treatment., Results: Feelings of pain, discomfort and heavy legs were found to be significantly reduced after wearing 3D-printed orthoses (p<0.05). Additionally, in static and dynamic conditions, a significant decrease in mean peak pressure in the rearfoot area was observed along with a significant increase in mean peak pressure in the midfoot area (p<0.05). There was also a significant improvement of balance in the medial-lateral direction., Conclusion: Custom-made orthoses significantly increase the well-being of standing workers in our experimental testing conditions. The custom-made shape allows for a better balanced distribution of foot peak pressure thanks to its support and stimulation of the foot arches particularly through a shift of pressure from the heel to the midfoot., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Motorcycle accidents lead to a high rate of traffic mortality and morbidity. While helmet development and mandatory wearing have reduced head injuries, little progress has been made regarding trunk protection. Wearable airbag devices represent a promising solution to prevent trunk injuries. Nevertheless, research investigations need to be performed to assess and optimise the efficiency of such devices. This work consisted in the analysis of motorcyclist trunk impact conditions involved in various crash configurations to provide critical information in order to evaluate and improve the performances of airbag devices. First, an epidemiological and an accidentological analysis of data collection related to 252 real accidents, focusing on victims admitted into the shock rooms of two French trauma centres were performed. The data obtained was combined with numerical multibody parametric investigations, allowing the reproduction of 240 accident situations. An original and representative analysis of motorcyclists' impact conditions was provided, weighting the numerical study output data according to the real accident database. The impacted regions of the human body, the impact velocity and the accident chronology obtained in this work made it possible to define critical information for airbag efficiency assessment: the zones and levels of protection, the impacted surfaces as well as the airbag intervention time and the duration of maintained inflation of the airbag., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Spinal injury (SPI) often causes death and disability in snow-sport accidents. SPIs often result from spinal compression and flexion, but the injury risks due to over flexion have not been studied. Back protectors are used to prevent SPIs but the testing standards do not evaluate the flexion-extension resistance. To investigate SPI risks and to better define back-protector specifications, this study quantified the flexion-extension range of motions (ROMs) of the thoracic-lumbar spine during typical snowboarding backward falls. A human facet-multibody model, which was calibrated against spinal flexion-extension responses and validated against vehicle-pedestrian impact and snowboarding backward fall, was used to reproduce typical snowboarding backward falls considering various initial conditions (initial velocity, slope steepness, body posture, angle of approach, anthropometry, and snow stiffness). The SPI risks were quantified by normalizing the numerical spinal flexion-extension ROMs against the corresponding ROM thresholds from literature. A high risk of SPI was found in most of the 324 accident scenarios. The thoracic segment T6-T7 had the highest injury risk and incidence. The thoracic spine was found more vulnerable than the lumbar spine. Larger anthropometries and higher initial velocities tended to increase SPI risks while bigger angles of approach helped to reduce the risks. SPIs can result from excessive spinal flexion-extension during snowboarding backward falls. Additional evaluation of back protector's flexion-extension resistance should be included in current testing standards. An ideal back protector should consider the vulnerable spinal segments, the snowboarder's skill level and anthropometry., (© 2018 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background: Prosthetic rehabilitation improves the overall quality of life of patients, despite discomfort and medical complications. No quantitative assessment of prosthesis-patient interaction is used in routine protocols and prosthesis quality still results from the manufacturer's know-how., Objective: Our objective is to investigate whether pressure can be a relevant factor for assessing socket adequacy., Methods: A total of 8 transtibial amputee volunteers took part in this experimental study. The protocol included static standing and 2 minutes walking tests while the stump-to-socket interface pressures were measured. Questionnaires on comfort and pain were also conducted., Results: During static standing test, maximum pressures were recorded in the proximal region of the leg, with a peak value reaching 121.1 ± 31.6 kPa. During dynamic tests, maximum pressures of 254.1 ± 61.2 kPa were recorded during the loading phase of the step. A significant correlation was found between the pain score and static maximum recorded pressure (r= 0.81)., Conclusions: The protocol proposed and evaluated in this study is a repeatable, easy-to-set quantified analysis of the patient to socket interaction while standing and walking. This approach is likely to improve feedback for prosthesis manufacturers and consequently the overall design of prostheses.

Purpose: Proper evaluation of ski helmet designs and safety standards should rely on head impact conditions involved in skiing and snowboarding head injuries. To study these impacts, main crash scenarios involving head injuries are numerically replicated., Methods: Multibody models of skiers and snowboarders were developed to investigate five common crash scenarios involved in traumatic brain injury: forward and sideways skiing falls, snowboarding backward falls, collisions between users and collisions with obstacles. For each scenario, the influence of crash conditions on head impact (location, speed, linear and rotational accelerations) and risk of injury are evaluated. Crash conditions were initial velocity, user height, position and approach angle, slope steepness, obstacles, and snow stiffness., Results: One thousand one hundred forty-nine crashes were simulated and three significant levels of impact conditions were discriminated over the investigated crash scenarios: 1) the smallest normal-to-slope impact velocities (6 km·h; 22 km·h) and peak linear accelerations (42g; 75g) were obtained during forward and sideways skiing falls; 2) snowboarding backward falls and collisions between users were associated with high normal-to-surface impact velocities (26 km·h; 32 km·h) and head accelerations (80g; 149g) above one published threshold for mild traumatic brain injury but below the pass/fail criteria of helmet standard tests; 3) collisions with obstacles were associated with high normal-to-surface impact velocities (19 km·h; 35 km·h) and the highest head accelerations (626g; 1885g)., Conclusions: Current impact conditions of helmet standard evaluations consistently replicate collisions with obstacles, but need to be revised to better reflect other significant crash scenarios leading to traumatic brain injury.

Objective: We compared the differences in the braking response to vehicle collision between an active human emergency braking (control condition) and cruise control (CC) or adaptive cruise control (ACC)., Methods: In 11 male subjects, age 22 to 67 years, we measured the active emergency braking response during manual driving using the accelerator pedal (control condition) or in condition mimicking CC or ACC. In both conditions, we measured the brake reaction time (BRT), delay to produce the peak braking force (PBD), total emergency braking response (BRT + PBD), and peak braking force (PBF). Electromyograms of leg and thigh muscles were recorded during braking. The tonic vibratory response (TVR), Hoffman reflex (HR), and M-waves were recorded in leg muscles to explore the change in sensorimotor control., Results: No difference in PBF, TVR amplitude, HR latency, and H max /M max ratio were found between the control and CC/ACC conditions. On the other hand, BRT and PBD were significantly lengthened in the CC/ACC condition (240 ± 13 ms and 704 ± 70 ms, respectively) compared to control (183 ± 7 ms and 568 ± 36 ms, respectively). BRT increased with the age of participants and the driving experience shortened PBD and increased PBF., Conclusions: In male subjects, driving in a CC/ACC condition significantly delays the active emergency braking response to vehicle collision. This could result from higher amplitude of leg motion in the CC/ACC condition and/or by the age-related changes in motor control. Car and truck drivers must take account of the significant increase in the braking distance in a CC/ACC condition.

We present an original method using a low cost accelerometer and a Kalman-filter based algorithm to monitor cardiopulmonary resuscitation chest compressions (CC) depth. A three-axis accelerometer connected to a computer was used during CC. A Kalman filter was used to retrieve speed and position from acceleration data. We first tested the algorithm for its accuracy and stability on surrogate data. The device was implemented for CC performed on a manikin. Different accelerometer locations were tested. We used a classical inertial navigation algorithm to reconstruct CPR depth and frequency. The device was found accurate enough to monitor CPR depth and its stability was checked for half an hour without any drift. Average error on displacement was ±0.5mm. We showed that depth measurement was dependent on the device location on the patient or the rescuer. The accuracy and stability of this small low-cost accelerometer coupled to a Kalman-filter based algorithm to reconstruct CC depth and frequency, was found well adapted and could be easily implemented., (Copyright © 2016 IPEM. Published by Elsevier Ltd. All rights reserved.)

Objective: Some cardiopulmonary resuscitation (CPR) monitoring devices were released in recent years. Some of them are motion sensors. There are no guidelines were to position future or present sensors during CPR. We evaluate the possible influence of the location of motion sensors by a high-speed camera during a CPR on a manikin., Material and Methods: We performed a motion analysis by a high-speed camera during chest compression (CC) on a manikin to quantify chest inhomogeneous displacements and rescuer motion., Results: Midline chest was found to have an inhomogeneous depth during CC (19 mm for the upper sternum, 27 mm for the middle of the sternum, and 47 mm for the xiphoid). Rescuer anatomy has a complex motion., Conclusion: The direct application of the sensor under the hand performing CC seems to be the more accurate solution if the device allows it., (Copyright © 2015 Elsevier Inc. All rights reserved.)

In forensic research, biomechanical analyses of falls are widely reported. However, no study on falls consecutive to uncontrolled hanging release, when a hanging body is cut down, has ever been published. In such cases, the presence of cranial trauma can raise interpretation issues, and there may be doubt as to whether the fall was an accident or a crime disguised as suicide. The problem remains as to whether or not a fall after a free hanging release can lead to a skull fracture. To address this question, numerical simulations, post-mortem human subject tests and parametric studies were performed. We first recreated the kinematics and velocity of this atypical fall with post-mortem human subject tests and multibody simulations. We then tested the influence of biological variability on fracture production using a finite element model of the head. Our results show that fall severity depends largely on the direction of the fall. The risk of fracture is highest in the occipital region and with a backward fall. Our study also highlights the frequent occurrence of lower limb trauma in a free hanging release. Most importantly, we show that a fracture is produced in only 3.4% of falls that occur in a 10-90 cm height range. The overall findings of this study provide tools for pathologists and magistrates to decide on the most likely scenario and to justify further forensic investigations if required., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

In a forensic investigation, there is considerable difficulty in distinguishing between different mechanisms that could explain the head injury sustained. The key question is often whether the injury was the consequence of a fall, a blow, or a fall caused by a blow. Better understanding of the parameters influencing the mechanism of skull fracture could be of use when attempting to distinguish between different causes of injury. Numerous parameters concerning fall conditions and biological variability are reported in the literature to influence the mechanism of skull fracture. At the current time, there are no studies that investigate both the effect of a fall and biological parameters. The aim of this paper is to study the influence of these parameters on the mechanism of skull fracture using a numerical approach. We focused on accidental falls from a standing height. A multibody model was used to estimate head impact velocities and a finite element model was used to investigate the effect of the fall conditions and of biological variability on skull fracture. The results show that the mechanism of skull fractures is influenced by a combination of at least four parameters: impact velocity, impact surface, cortical thickness and cortical density.

This paper summarizes the results obtained within the framework of the French PROMOTO Project (PROtection of the MOTOrcyclist). The aim of this project was to analyze the impact between a motorcycle and a light vehicle from an epidemiological, accidentological and biomechanical point of view. The results have made it possible to outline the most frequent accident configurations such as the "turn on the left" and the most common injuries sustained by motorized two-wheelers (head and trunk). The biomechanic analysis has enabled a better understanding of the kinematics involved in an impact between a motorized two-wheeler and a light vehicle in various accident configurations (chronology and speed impact). While it is well known that motorcyclists frequently receive life threatening injuries to the head, spine and torso, this paper has been able to observe specific injury mechanisms such as pelvis impacts against the vehicle fuel tank and hyper-extension of the neck due to head impact on passenger cars., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Over the past decade, road safety research and impact biomechanics have strongly stimulated the development of anatomical human numerical models using the finite element (FE) approach. The good accuracy of these models, in terms of geometric definition and mechanical response, should now find new areas of application. We focus here on the use of such a model to investigate its potential when studying respiratory mechanics. The human body FE model used in this study was derived from the RADIOSS HUMOS model. Modifications first concerned the integration and interfacing of a user-controlled respiratory muscular system including intercostal muscles, scalene muscles, the sternocleidomastoid muscle, and the diaphragm and abdominal wall muscles. Volumetric and pressure measurement procedures for the lungs and both the thoracic and abdominal chambers were also implemented. Validation of the respiratory module was assessed by comparing a simulated maximum inspiration maneuver to volunteer studies in the literature. Validation parameters included lung volume changes, rib rotations, diaphragm shape and vertical deflexion, and intra-abdominal pressure variation. The HUMOS model, initially dedicated to road safety research, could be turned into a promising, realistic 3D model of respiration with only minor modifications.