Variability of Child Rib Bone Hounsfield Units using in vivo Computed Tomography

The variability assessment of the rib bone mechanical properties during the growth process is still missing. These properties could not be obtained in vivo on children. Relationships have been obtained between Hounsfield Units from computed tomography (CT) and mechanical properties (e.g. for the cortical bone on adults). As a first step for investigation of the mechanical properties of child ribs, the aim of this study was to determine the Hounsfield Units variation of child ribs from CT‐scan data, by rib level, along the rib and within the rib sections. Twenty‐seven right ribs of levels 4, 6 and 9 were processed from 11 thoracic CT scans of children without bone lesions aged between 1 and 10 years. A first set of 10 equidistributed cross‐sections normal to the rib midline were extracted. Sixteen equally distributed elements defined 4 areas into the cortical band: internal, external, caudal and cranial. Within the rib sections, Hounsfield Units were found significantly higher in internal and external areas than in caudal and cranial. In a further step using calibrated CT scans, it would be possible to derive the mechanical properties of in vivo child ribs using bone density correlation with Hounsfield Units

Comportement biomécanique des usagers des transports lors de chargements rapides ex vivo et in vivo

Ce mémoire constitue une synthèse des travaux de recherche que j'ai menés à l'Institut National de Recherche sur les Transports et leur Sécurité (Inrets) puis à l'Institut Français des Sciences et Technologies des Transports de l'Aménagement et des Réseaux (Ifsttar) au sein du Laboratoire de Biomécanique et Mécanique des Chocs (LBMC) depuis janvier 1991. Ils portent essentiellement sur la biomécanique des chocs appliquée à la sécurité passive pour améliorer la protection des usagers des transports routiers. J'ai appliqué mes compétences pour l'évaluation des mannequins de choc. J'ai contribué à apporter des connaissances en biomécanique grâce à des expérimentations sur des corps entiers légués à la science (ex vivo) et sur des pièces anatomiques (côtes, cartilage costal...). Ces expérimentations m'ont permis l'acquisition de résultats en tolérance humaine au choc. J'ai complété ces expérimentations sur corps légués à la science par des observations sur des sujets volontaires in vivo à des niveaux de sollicitations infra lésionnelles, après approbation par les comités d'éthique et de protection des personnes. Ce document synthétise mes travaux qui visent à apporter de nouvelles connaissances en biomécanique des chocs. Ils sont nécessaires pour l'élaboration des normes françaises et internationales, des Directives Européennes, des règlements internationaux, et contribue in fine à l'amélioration de la sécurité routière. Ils contribueront aussi à faire le lien entre le comportement biomécanique ex vivo et in vivo des usagers des transports lors de chargements rapides

Human response to a frontal sled deceleration

IRCOBI Conference on the Biomechanics of Impact, MUNICH, ALLEMAGNE, 18-/09/2002 - 20/09/2002Sled tests were conducted with cadavers to obtain data on the behaviour of the human body under frontal deceleration. Two series of three tests were conducted corresponding to two levels of severity and types of restraint systems. The restraint systems used for the tests included a 4kN force-limited shoulder belt and a static lap belt. A driver airbag was mounted for the series at highest severity. The results show that the restraint systems and the test conditions modify the behaviour of the cadaver. The restrained conditions are not reflected in the same way for different segment of the body. The influence of the airbag is well observed for the chest spine behaviour, and not for the first thoracic vertebra. This study suggests that the chest acceleration (T8) could be a better predicting parameter than the Tl resultant in a combined parameters injury criterion

Virtual predictive testing of biomechanical effects of impacts on the human leg

PAM'94 Fourth international conference on virtual predictive testingof industrial prototypes, PARIS, FRANCE, 05-/10/1994 - 05/10/1994In car/pedestrian accident mathematical simulations, it is desirable to extend existing rigid body human model towards deformable finite element models. Thereby a wider range of front car structure/pedestrian interactions can be covered. Even though some injuries to pedestrian are due to contact with the ground, research concerning the severity of injuries due to the car contact, related to the bumper and the bonnet height and stiffness, and to the speed of the vehicle, are being carried out. In a previous study a finite element model of the pedestrian knee-joint in lateral impact was expanded. This paper presents a modelling of a human leg in lateral impact for use in an explicit finite element code. The articulation between each condyle of the femur and the corresponding tuberosity of the tibia is mainly described. The bones entering into the formation of the knee-joint are the condyles of the femur above, the head of the tibia below. The bones are connected together by ligaments, some of which are placed on the exterior (e. g. ; lateral and medial collateral...) of the joint, while others occupy its interior (e. g. ; anterior and posterior crucial...). This model will be impacted to estimate the severity of leg lesions and to predict the risk of leg injuries in car/pedestrian accidents. The effect of the impactor stiffness, velocity and height will be evaluated. Experimental results from static tests and impact tests, to characterise the mechanical behaviour of each part, like the ligaments or the bones, and the whole kinematics of the knee, serve as a basis for the validation of the model

Drone impact on human beings : Experimental investigation with sUAS

International audienceBeyond some application related to military and civilian operations [1], the major part of the financial market is related to the use of unmanned aircraft systems (UASs) by casual customers without specific training. This requires to solve a technological and legislative challenge to ensure the safety of the population regarding the use of an aeronautical system potentially near buildings and apt to fall over people on ground. For almost 10 years and even more recently, regulatory institutions at the global scale have performed a significant work to classify UAS regarding their lethal potential in a case of an impact with people on the ground [2, 3, 4, 5]. Nevertheless, the establishment of a consensus remains a challenging task given the lack of specific and exploitable experimental data on the problematic. Hence, the purpose of the study is twofold. It first aims at providing qualitative findings on the legal and scientific framework regarding the assessment of lethal injury thresholds related to UAS impacts on human-beings. Based on this framework, the study then relies on an experimental investigation. A dedicated protocol is developed in order to minimize the sources of discrepancy previously identified and in order to conduct representative impact test cases using commercially-availables UAS. The range of drones masses considered in this study is about 900 grams with respect to the open category defined by EASA

An overview of MADYMO uses at INRETS

4th meeting International MADYMO users meeting, EINDHOVEN, PAYS-BAS, 06-/09/1993 - 07/09/1993This paper describes the modelling approach using MADYMO 2D at INRETS (The French National Institute for Transport and Safety Research). A mathematical dynamic model of the pedestrian leg in lateral impact was developed (M.MATYJEWSKI) to test car fronts in order to estimate the severity of the knee joint lesions and to predict the risk of leg injuries in car/pedestrian accidents. Results of this model were compared with those obtained with an instrumented mechanical leg used in the bumper impact test. A train passenger behaviour during a crash at low speed was developed (J.BLOCH and F.MINNE) to improve the function of the fusible area at each carriage extremities. Results of this model were compared with those obtained during a real scale crash test. The kinematic of a 3 -year old child in a childseat on a passenger car seat is analysed (R.BIARD and J.L.CHANIAC) during a frontal impact. Experimental results from sled tests serve as a basis for the validation of the model

Post mortem human subject and dummy response in frontal deceleration

28ème congrès de la société de biomécanique, POITIERS, FRANCE, 11-/09/2003 - 12/09/2003In the European Union, the assessment of die protection offered by a vehicle to a restrained occupant in case of frontal collision, is based on biomechanical data measured on the Hybrid III crash test dummy as described by the European Frontal Directive (Directive 96/79/EC). Ibis dummy was developed in the 70's and is based on biomechanical knowledge from that time. The Thor dummy (Test device for Human Occupant Restraint) developed by NHTSA (USA Administration) is based on more recent biomechanical knowledge. Many parts of the dummy have been designed and modified to produce a more humanlike response to frontal impact loading. The general objective of the FID European research program (improved Frontal Impact protection through a world frontal impact Dummy) is a European contribution to the evaluation of a worldwide dummy in the frontal impact. The paper presents new biomechanical data, based PMHS (Post Mortem Human Subject) tests, under different frontal impact conditions. The same tests with exactly the same instrumentation mounted at the same location were performed with Hybrid III and with the Thor-alpha to assess die biofidelity of these dummies with respect to these biomechanical data

In vivo assessment of the mechanical properties of the child cortical bone using quantitative computed tomography

The mechanical properties of the rib cortical bone are extremely rare on children due to difficulties to obtain specimens to perform conventional tests. Some recent studies used cadaveric bones or bone tissues collected during surgery but are limited by the number of samples that could be collected. A non-invasive technique could be extremely valuable to overcome this limitation. It has been shown that a relationship exists between the mechanical properties (apparent Young’s modulus and ultimate strength) and the bone mineral density (assessed using Quantitative Computed Tomography, QCT), for the femur and recently by our group for the adult ribs ex vivo. Thus the aim of this study was to assess the mechanical properties of the child rib cortical bone using both QCT images in vivo and the previous relationship between bone mineral density and mechanical properties of the rib cortical bone. Twenty-eight children were included in this study. Seven age-groups have been considered (1, 1.5, 3, 6, 10, 15, 18 years old). The QCT images were prescribed for various thoracic pathologies at the pediatric hospital in Lyon. A calibration phantom was added to the clinical protocol without any modifications for the patient. The protocol was approved by the ethical committee. A 3D reconstruction of each thorax was performed using the QCT images. A custom software was then used to obtain cross-sections to the rib midline. The mean bone mineral density was then computed by averaging the Hounsfield Units in a specific cross-section and by converting the mean value (Hounsfield Units) in bone mineral density using the calibration phantom. This bone mineral density was assessed for the 6th rib of each subject. Our relationship between the bone mineral density and the mechanical properties of the rib cortical bone was used to derive the mechanical properties of the child ribs in vivo. The results give values for the apparent Young’s modulus and the ultimate strength. The mechanical properties increase along growth. As an example the apparent Young’s modulus in the lateral region ranges from 7 GPa +/-3 at 1 year old up to 13 GPa +/- 2 at 18 years old. These data are in agreement with the few previous values obtained from child tissues. This methodology opens the way to in vivo measurement of the mechanical properties of the child cortical bone based on calibrated QCT images

Compliance Thoracique : Quelles Valeurs ?

12ième Journée de Recherche en Kinésithérapie, ECHIROLLES, FRANCE, 25-/05/2007 - 25/05/200

Quantification de la compliance thoracique chez le nourrisson : étude préliminaire

12ème journée de recherche en kinésithérapie, ECHIROLLES, FRANCE, 25-/05/2007 - 25/05/200