Development Of Finite Element Model And Study Of Injury Mechanisms For Pediatric Thorax

In the study of pediatric accident injuries, Thoracic injury in the pediatricpopulation is a marker of injury severity and signifies a high mortality rate. As the ribcage protects the primary elements of the respiratory and circulatory systems andseveral abdominal organs. As such that, the pediatric thorax needs to be saved whenthe child is a car-passenger. Due to the large difference between anatomical structuresand material properties of child thorax and those of adult, the thoracic injury criteriaand tolerances associated with pediatric population may vary greatly from those ofadult. The protection devices for adults are not useful for the children, even cause childinjury. Therefore, studying of child thoracic injury and protection has the importanttheoretical significance and practical value. Biomechanical experiments andcomputational simulations are the primary methods used to study human injurymechanisms and to determine tolerances to reduce the severity of injury.Therefore,based on massive literature review, this paper focused on the study ofdevelopment of pediatric thorax finite element model and pediatric thoraxbiomechanical experiment. Finally, the injury mechanisms, injury criteria andtolerances, and scaling response data for the pediatric thorax were studied by the finiteelemtn method.Due to lack of available data on pediatric material properties, quantitativeage-dependent anatomical data, and pediatric impact response data, no complexpediatric chest component model has been developed directly from pediatric data.Clinical CT (Electronic Computer X-ray Tomography Technique) and MRI (MagneticResonance Imaging) scans of children treated at hospital were collected to obtain thegeometric data. A linear geometric scaling procedure was adopted for the rawgeometric data to obtain the final average geometric model using Hypermesh (10.0,Altair, Tory, MI). Based on the Block-controlled meshing method, the ANSYS ICEM(ANSYS, Canonsburg, Pennsylvania, U.S.A) was used to mesh solid elements for thebony skeleton and organs. Lastly, the FE model with the detail anatomical structuresincluded skin, rib, costal cartilage, heart, vessel, diaphragm, abdominal organs and soon. The material property parameters for the model were scaled from adult data basedon the literature.Accurate pediatric thoracic force-deflection data are critical to develop pediatricdummy/model. Due to regulatory and ethical concerns, using the traditional cadaver experiments to obtain the pediatric response data was greatly limited. As such, theclinical data which was collected in the clinical environment during pediatric CPR wasused to static verify the model, parametric study the material properties and CPRboundary conditions. All of these studies favored to improve the biofiedelity of model,obtain the accurate parameters of tissues’ material properties, and guide the futurework to obtain the accurate thoracic response data from the clinical CPR. In addition,the information of the pediatric injury and loading in the clinical environment duringCPR was used with the FE model to conduct analysis of injury under the quasi-staticloading. The results of injury analysis could to improve the injury prediction capabilityof model under the quasi-static loading.The CPR experiment was performed at a relatively low speed. The dynamicvalidation was needed for better understanding of pediatric injury mechanisms andinjury tolerances during high-speed impact such as traffic accident and development ofinjury protection countermeasures. The experimental pediatric cadaver data in frontpendulum impacts and diagonal belt dynamic loading test were used to validate themodel. The results of simulation, such as thoracic force-deflection curve and injuriesof rib and thoracic internal organs were compared with the test data. the results ofdynamic validation indicate that this pediatric FE model has good biofidelity under thedynamic loading conditions. The thoracic injuries analysis demonstrates that the FEmodel could be useful for prediction and research of thoracic injuries, and the adultthoracic compression criteria and viscous criterion can be used to predict the pediatricthoracic injuries. However, the pediatric tolerances should be lower than adults’.Due to lack of available data on pediatric validation response data, the scalingdata was used to verify the child dummy and mostly child computer models. However,no experiment cadaver data has been verified the veracity of scaling data. In this paper,the impact simulations were conducted under the loading conditions obtained fromscaling data. The thoracic response results predicted by the FE model were comparedwith the scaling corridor data. The effect of Young’s modulus of rib cortical bone forthe scaling data was studied. The mass, diameter and initial velocity of impactor werealso considered in this study. The results of this study could improve the veracity of thescaling data.At last, the pediatric cadaver test was conducted to obtain the thoracic responsedata. A new experimental program for the pediatric thorax was designed and verifiedby the Q6child dummy. Based on the dummy test results data, a non-fresh pediatriccadaver was tested to obtain the thoracic force-deflection curve. This work laid the foundation for further study of the pediatric thoracic injury biomechanics.The problem of pediatric safety becomes more apparent. The above describedwork can help to improve the pediatric mathematic model and mechanical dummy andunderstand pediatric injury mechanisms which provided background knowledge fordevelopment of pediatric protective devices. As such, this work has important practicalmeaning to improve the pediatric safety.