Current finite element human thoracic models are typically evaluated against a limited set of loading conditions; this is believed to limit their capability to predict accurate responses. In this study, a 50th-percentile male finite element model (GHBMC v4.1) was assessed under various loading environments (antero-posterior rib bending, point loading of the denuded ribcage, omnidirectional pendulum impact and table top) through a correlation metric tool (CORA) based on linearly independent signals. The load cases were simulated with the GHBMC model and response corridors were developed from published experimental data. The model was found to be in close agreement with the experimental data both qualitatively and quantitatively (CORA ratings above 0.75) and the response of the thorax was overall deemed biofidelic. This study also provides relevant corridors and an objective rating framework that can be used for future evaluation of thoracic models.

Clavicle injuries were frequently observed in automotive side and frontal crashes. Finite element (FE) models have been developed to understand the injury mechanism, although no clavicle loading response corridors yet exist in the literature to ensure the model response biofidelity. Moreover, the typically developed structural level (e.g., force-deflection) response corridors were shown to be insufficient for verifying the injury prediction capacity of FE model, which usually is based on strain related injury criteria. Therefore, the purpose of this study is to develop both the structural (force vs deflection) and material level (strain vs force) clavicle response corridors for validating FE models for injury risk modeling. 20 Clavicles were loaded to failure under loading conditions representative of side and frontal crashes respectively, half of which in axial compression, and the other half in three point bending. Both structural and material response corridors were developed for each loading condition. FE model that can accurately predict structural response and strain level provides a more useful tool in injury risk modeling and prediction. The corridor development method in this study could also be extended to develop corridors for other components of the human body.

Current finite element (FE) models of the human thorax are limited by the lack of local-level validation, especially in the ribcage. This study exercised an existing FE ribcage model for a 50th percentile male under quasi-static point loading and dynamic sternal loading. Both force-displacement and kinematic responses of the ribcage were compared against experimental data. The sensitivity of the model response to changes in the material properties of the costovertebral (CV) joints and intercostal muscles was assessed. The simulations found that adjustments to the CV joints tended to change the amount of rib rotation in the sagittal plane, while changes to the elastic modulus and thickness of the intercostal muscles tended to alter both the stiffness and the direction and magnitude of rib motions. This study can lend insight into the role that the material properties of these two thoracic structures play in the dynamics of the ribcage during a frontal loading condition.

This study aimed to develop and validate a finite element (FE) model of a human clavicle which can predict the structural response and bone fractures under both axial compression and anterior-posterior three-point bending loads. Quasi-static non-injurious axial compression and three-point bending tests were first conducted on a male clavicle followed by a dynamic three-point bending test to fracture. Then, two types of FE models of the clavicle were developed using bone material properties which were set to vary with the computed tomography image density of the bone. A volumetric solid FE model comprised solely of hexahedral elements was first developed. A solid-shell FE model was then created which modelled the trabecular bone as hexahedral elements and the cortical bone as quadrilateral shell elements. Finally, simulations were carried out using these models to evaluate the influence of variations in cortical thickness, mesh density, bone material properties and modelling approach on the biomechanical responses of the clavicle, compared with experimental data. The FE results indicate that the inclusion of density-based bone material properties can provide a more accurate reproduction of the force-displacement response and bone fracture timing than a model with uniform bone material properties. Inclusion of a variable cortical thickness distribution also slightly improves the ability of the model to predict the experimental response. The methods developed in this study will be useful for creating subject-specific FE models to better understand the biomechanics and injury mechanism of the clavicle.

A finite element model of the 50 percentile male was developed based on geometrical surface generated from medical images. First, an interactive multi-block meshing approach was used to generate high quality quadrilateral and hexahedral meshes of the thorax anatomical structures. Second, a methodology based on the mesh blocks was developed to assign cortical thickness data taken from a micro-CT study to each of the nodes in the cortical shell elements of the ribs along the longitudinal direction and around the cross-sectional perimeter. The whole thorax model (rib cage, internal organs, muscles, skin) was exercised under a wide range of loadings that include inertial and non inertial loadings (blunt impacts, and table top). Although the response of the thorax model was reasonable compared to the experimental results at a “global” level—such as under hub or belt loading onto the entire body—, it has not been evaluated at a local level -such as the strain distribution in the rib cage. The structural response of the rib cage was therefore investigated to evaluate the effect of cortical thickness distribution and intercostal muscle mechanical properties on the thorax mechanical response. The need for node dependent cortical thickness to predict force and deflection at the time of fracture was demonstrated at the rib level by simulating anteroposterior dynamic bending of individual ribs. As for the intercostal muscles, there is no experimental data available to aid with the definition of their mechanical properties. Therefore the impacts to the lateral thorax recently performed by CEESAR for the THOMO project were used to carry out a sensitivity analysis to assess the effect of the cortical thickness distribution and intercostal muscles material properties on rib fracture prediction. The FE model of the thorax was run for three cortical thickness distributions (one distribution with thicknesses defined for each node, and two distributions of uniform thickness values) and three values for the intercostal muscles’ Young’s modulus. The variation of the strain field was compared for the various combinations of parameters and loading conditions to assess how the fracture prediction was altered. In particular, the rib strain profiles measured in the experiments as well as the locations of the rib fractures were compared to the FE results. This study represents a major effort in the development and validation of the thorax finite element model for the Global Human Body Modeling Consortium, and provides insight for the development of anatomically detailed computational models for injury prediction.

In this paper, a ribcage FE model of the 50 percentile male composed of all quadrilateral and hexahedral elements were developed using an interactive multi-block hex meshing approach. The block-building and meshing techniques for reducing the model development effort and time were presented by the use of the anatomical symmetry and multiple block edition tools. Furthermore, regional variations in cortical bone thickness along the parameter and longitudinal directions of the rib structure were assigned to each of the ribs by mapping the actual cortical thickness distribution of the ribs measured in the published data. The ribcage FE model was then validated against experimental data under the hierarchical structure level from rib segment, rib ring and to full ribcage. Overall, the FE model predictions were reasonably within the range of the force-displacement corridors in experiments. This study represents a major effort in the development and validation of the thorax model for the Global Human Body Modeling Consortium. The combined hex meshing and cortical thickness mapping techniques presented here would be useful for the development of anatomically-detailed FE models to understand the biomechanics of human thorax and other human body structures.

The purpose of this paper was to investigate the sensitivity of the structural responses and bone fractures of the ribs to mesh density, cortical thickness, and material properties so as to provide guidelines for the development of finite element (FE) thorax models used in impact biomechanics. Subject-specific FE models of the second, fourth, sixth and tenth ribs were developed to reproduce dynamic failure experiments. Sensitivity studies were then conducted to quantify the effects of variations in mesh density, cortical thickness, and material parameters on the model-predicted reaction force–displacement relationship, cortical strains, and bone fracture locations for all four ribs. Overall, it was demonstrated that rib FE models consisting of 2000–3000 trabecular hexahedral elements (weighted element length 2–3 mm) and associated quadrilateral cortical shell elements with variable thickness more closely predicted the rib structural responses and bone fracture force–failure displacement relationships observed in the experiments (except the fracture locations), compared to models with constant cortical thickness. Further increases in mesh density increased computational cost but did not markedly improve model predictions. A ±30% change in the major material parameters of cortical bone lead to a −16.7 to 33.3% change in fracture displacement and −22.5 to +19.1% change in the fracture force. The results in this study suggest that human rib structural responses can be modeled in an accurate and computationally efficient way using (a) a coarse mesh of 2000–3000 solid elements, (b) cortical shells elements with variable thickness distribution and (c) a rate-dependent elastic–plastic material model.

The goal of this study was to investigate the response and failure properties of the human sternum under bending loading. Nine sternum specimens from post mortem human surrogates (n=7 male, n=2 female, age: 62.7 +/- 10.9 years) were extracted and potted in a three point bending test setup. Specimens were loaded to failure at their center points in bending at 1100 mm/s, with some specimens previously loaded in a non-failure quasi-static loading test. In two cases, the non-failure test was repeated to show that specimens were not damaged during non-failure testing. The sternum specimens were found generally to be unable to support shear forces in the anterior-posterior direction and as a result had relatively low failure moments (24.1 Nm +/- 20.1 Nm). While two of the specimens did fail in bending, the remaining specimens failed as a result of the high tensile forces introduced by the bending loads. These specimens first experienced compressive loads, and then, as the potted ends continued to rotate, tensile loads, which resulted in failure of the specimens (400-800 N).

A finite element (FE) model of a 10-years-old child pelvis was developed and validated against experimental data from lateral impacts of pediatric pelves. The pelvic bone geometry was reconstructed from a set of computed tomography images, and a hexahedral mesh was generated using a new octree-based hexahedral meshing technique. Lateral impacts to the greater trochanter and iliac wing of the seated pelvis were simulated. Sensitivity analysis was conducted to identify material parameters that substantially affected the model response. An optimization-based material identification method was developed to obtain the most favorable material property set by minimizing differences in biomechanical responses between experimental and simulation results. This study represents a pilot effort in the development and validation of age-dependent musculoskeletal FE models for children, which may ultimately serve to evaluate injury mechanisms and means of protection for the pediatric population.

The purpose of this study was to investigate whether using a finite-element (FE) mesh composed entirely of hexahedral elements to model cortical and trabecular bone (all-hex model) would provide more accurate simulations than those with variable thickness shell elements for cortical bone and hexahedral elements for trabecular bone (hex-shell model) in the modeling human ribs. First, quasi-static non-injurious and dynamic injurious experiments were performed using the second, fourth, and tenth human thoracic ribs to record the structural behavior and fracture tolerance of individual ribs under anterior-posterior bending loads. Then, all-hex and hex-shell FE models for the three ribs were developed using an octree-based and multi-block hex meshing approach, respectively. Material properties of cortical bone were optimized using dynamic experimental data and the hex-shell model of the fourth rib and trabecular bone properties were taken from the literature. Overall, the reaction force-displacement relationship predicted by both all-hex and hex-shell models with nodes in the offset middle-cortical surfaces compared well with those measured experimentally for all the three ribs. With the exception of fracture locations, the predictions from all-hex and offset hex-shell models of the second and fourth ribs agreed better with experimental data than those from the tenth rib models in terms of reaction force at fracture (difference <15.4%), ultimate failure displacement and time (difference <7.3%), and cortical bone strains. The hex-shell models with shell nodes in outer cortical surfaces increased static reaction forces up to 16.6%, compared to offset hex-shell models. These results indicated that both all-hex and hex-shell modeling strategies were applicable for simulating rib responses and bone fractures for the loading conditions considered, but coarse hex-shell models with constant or variable shell thickness were more computationally efficient and therefore preferred.

Clavicle fractures are common injuries in three-point belt restrained occupants involved in frontal and lateral car collisions. Therefore, better understanding of clavicle loading which occurs during an impact and clavicle structural/material properties could help in the optimization of seatbelt restraint systems. Six clavicles from three post mortem human subjects were tested in a three point -bending test setup with pinned-pinned boundary conditions. The clavicle extremities were fixed into potting cups which were able to rotate freely about a single rotational axis (inferior-superior axis) and then, were loaded in the anterior-posterior direction by an impactor at the middle shaft level. Two tests were performed on each clavicle: a) A noninjurious quasi-static test (1mm/s impactor rate) up to approximately 400 N b) A dynamic test (1m/s impactor rate) to failure. Reaction forces and moments were measured at both clavicle supports. The results showed an averaged clavicle stiffness of 211+/-30 N/mm in the quasi-static tests. Concerning the dynamic tests to failure, the average maximum force was 1159+/-133 N, the average maximum deflection was 4.9+/-0.7 mm, the average clavicle stiffness was 237+/-64 N/mm, and the average maximum strain was 1+/-0.2%. The most common failure location was the middle third of the bone, which is consistent with literature data. A finite element model of a human clavicle was developed and used to simulate the tests. The optimization of the elastic parameters of clavicle finite element model during the simulations of quasi-static tests provided an 8.1 GPa Young modulus for cortical bone. In addition to providing validation data for computational human models and dummies, the results of this study may lend insight into the development of advanced belt restraint systems.

The pediatric pelvis is vulnerable to injuries in motor vehicle collisions, sport activities, and fall accidents. Pelvic fractures and injury mechanisms in children differ substantially from those found in adults [1]. While the injury mechanisms and tolerances of the adult pelvis have been fairly well characterized through cadaveric experiments and computational models, efforts related to the pediatric pelvis have been limited due to difficulties in acquiring and testing pediatric cadavers. The objective of this study was to develop a finite element (FE) model of a 10-year-old (10YO) human pelvis to provide more comprehensive understanding of injury mechanisms experienced by children.

Fireside corrosion in coal-fired power plants is a leading mechanism for boiler tube failures. Online monitoring of fireside corrosion can provide timely data to plant operators for mitigation implementation. This paper presents a novel sensor concept for measuring metal loss based on electrical capacitance. Laboratory-scale experiments demonstrated the feasibility of design, fabrication, and operation of the sensor. The fabrication of the prototype sensor involved sputtering deposition of a thin metal coating with varying thickness on a ceramic substrate. Corrosion metal loss resulted in a proportional decrease in electrical capacitance of the sensor. Laboratory experiments using a muffle furnace with an oxidation environment demonstrated that low carbon steel coatings on ceramic substrate survived cyclic temperatures over 500 degrees C. Measured corrosion rates of sputtered coating in air had an Arrhenius exponential dependence on temperature, with metal thickness loss ranging from 2.0 nm/h at 200 degrees C to 2.0 microm/h at 400 degrees C. Uncertainty analysis indicated that the overall measurement uncertainty was within 4%. The experimental system showed high signal-to-noise ratio, and the sensor could measure submicrometer metal thickness changes. The laboratory experiments demonstrated that the sensor concept and measurement system are capable of short term, online monitoring of metal loss, indicating the potential for the sensor to be used for fireside corrosion monitoring and other metal loss measurement.

Periacetabular bone metastases cause severe pain and functional disability in cancer patients. Percutaneous acetabuloplasty (PCA) is a minimally invasive, image-guided procedure whereby cement is injected into lesion sites. Pain relief and functional restoration have been observed clinically; however, neither the biomechanical consequences of the lesions nor the effectiveness of the PCA technique are well understood. The objective of this study was to investigate how periacetabular lesion size, cortex involvement, and cement modulus affect pelvic bone stresses and strains under single-legged stance loading. Experiments were performed on a male cadaver pelvis under conditions of intact, periacetabular defect, and cement-filling with surface strains recorded at three strain gage locations. The experimental data were then employed to validate three-dimensional finite element models of the same pelvis, developed using computed tomography data. The models demonstrated that increases in cortical stresses were highest along the posterior column of the acetabulum, adjacent to the defect. Cortical stresses were more profoundly affected in the presence of transcortical defects, as compared to those involving only trabecular bone. Cement filling with a modulus of 2.2GPa was shown to restore cortical stresses to near intact values, while a decrease in cement modulus due to inclusion of BaSO4 reduced the restorative effect. Peak acetabular contact pressures increased less than 15% for all simulated defect conditions; however, the contact stresses were reduced to levels below intact in the presence of either cement filling. These results suggest that periacetabular defects may increase the vulnerability of the pelvis to fracture depending on size and cortical involvement and that PCA filling may lower the risk of periacetabular fractures.

Clearer understanding of the biomechanics of the pubic symphysis in lateral pelvic impact tests may serve to elucidate the mechanisms of injury in automotive side impacts. While numerous experimental and computational studies have been conducted on the human pelvis, stresses and deformations of the symphysis were never measured, and the role of the boundary conditions supporting the pelvis was not emphasized. The objective of the present study was to develop a biofidelic FE model to investigate the deformations and stresses experienced by the pubic ligaments and interpubic disc under side impact conditions simulating both drop tower experiments and automotive side impacts.

Automotive side impacts are a leading cause of injuries to the pubic symphysis, yet the mechanisms of those injuries have not been clearly established. Previous mechanical testing of isolated symphyses revealed increased joint laxity following drop tower lateral impacts to isolated pelvic bone structures, which suggested that the joints were damaged by excessive stresses and/or deformations during the impact tests. In the present study, a finite element (FE) model of a female pelvis including a previously validated symphysis sub-model was developed from computed tomography data. The full pelvis model was validated against measured force–time impact responses from drop tower experiments and then used to study the biomechanical response of the symphysis during the experimental impacts. The FE models predicted that the joint underwent a combination of lateral compression, posterior bending, anterior/posterior and superior/inferior shear that exceeded normal physiological levels prior to the onset of bony fractures. Large strains occurred concurrently within the pubic ligaments. Removal of the contralateral constraints to better approximate the boundary conditions of a seated motor vehicle occupant reduced cortical stresses and deformations of the pubic symphysis; however, ligament strains, compressive and shear stresses in the interpubic disc, as well as posterior bending of the joint structure remained as potential sources of joint damage during automotive side impacts.

Intact Post-Trans 15.8cc Post-Trans 9cc Post-Trab 13cc Sup-Trans 7cc Sup-Trab 7cc P ea k v on M ise s s tre ss (M Pa ) Intact Drill-hole defect Cement (0.87 GPa) Cement (2.2 GPa) FINITE ELEMENT MODELING OF PERIACETABULAR LESIONS AND ACETABULOPLASTY Zuoping Li, Neha B. Butala, Herrick J. Siegel, Jack E. Lemons, Alan W. Eberhardt Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, AL 2 Division of Orthopaedic Surgery, University of Alabama at Birmingham, Birmingham, AL School of Dentistry, University of Alabama at Birmingham, Birmingham, AL Zuoping Li, Hoehn 361, 1075 13 St. S., Birmingham AL 35294, Tel:205-975-4963, Fax:205-996-6946, lizp67@uab.edu

A new abeotaxane was isolated from the seeds of Taxus mairei. Its structure was determined to be 2 alpha, 5 alpha, 13 alpha-trihydroxy-7 beta, 10 beta-diacetoxy-2(3 -> 20) abeotaxa-4(20), 11-dien-9one on the basis of 1D and 2D spectral analysis.