Sideways fall-induced hip fracture is a major worldwide health problem among the elderly population. Biomechanical modeling is a practical way to study hip fracture risk. However, all existing biomechanical models for assessing hip fracture risk mainly consider the femur-related parameters. Their accuracy is limited as hip fracture is significantly affected by loading conditions as well. The objective of this study is to introduce a two-level subject-specific model to improve the assessment of hip fracture risk. The proposed biomechanical model consists of a whole-body dynamics model and a proximal femur finite element model, which are constructed from the subject’s whole-body and hip DXA (dual energy X-ray absorptiometry) scan. The whole-body dynamics model is used to determine the impact force onto the hip during a sideways fall. Obtained load/constraint conditions are applied to the finite element model in order to determine the stress/strain distribution in the proximal femur. Fracture risk index is then defined over the critical locations of the femur using the finite element solutions. It is found that hip fracture risk is significantly affected by the subject’s body configuration during the fall, body anthropometric parameters, trochanteric soft tissue thickness, load/constraint conditions, and bone mineral density, which are not effectively taken into account by currently available hip fracture discriminatory tools. Predicted hip fracture risk of 130 clinical cases, including 80 females and 50 males, by the proposed model reveals that biomechanical determinants of hip fracture differ widely from individual to individual. This study presents the first in-depth subject-specific model that provides a comprehensive, fast, accurate, and non-expensive method for assessing the hip fracture risk. The proposed model can be easily adopted in clinical centers to identify patients at high risk of hip fracture who may benefit from the in-time treatment to reduce the fracture risk. / May 2016

In high impact human activities, much of the impact shock wave is dissipated through internal body structures, preventing excessive accelerations from reaching vital organs. Mechanisms responsible for this attenuation, including lower limb joint compression and spinal compression have been neglected in existing whole-body simulation models. Accelerometer data on one male subject during drop landings and drop jumps from four heights revealed that peak resultant acceleration tended to decrease with increasing height in the body. Power spectra contained two major components, corresponding to the active voluntary movement (2 Hz 14 Hz) and the impact shock wave (16 Hz 26 Hz). Transfer functions demonstrated progressive attenuation from the MTP joint towards the C6 vertebra within the 16 Hz 26 Hz component. This observed attenuation within the spine and lower-limb joint structures was considered within a rigid body, nine-segment planar torque-driven computer simulation model of drop jumping. Joints at the ankle, knee, hip, shoulder, and mid-trunk were modelled as non-linear spring-dampers. Wobbling masses were included at the shank, thigh, and trunk, with subject-specific biarticular torque generators for ankle plantar flexion, and knee and hip flexion and extension. The overall root mean square difference in kinetic and kinematic time-histories between the model and experimental drop jump performance was 3.7%, including ground reaction force root mean square differences of 5.1%. All viscoelastic displacements were within realistic bounds determined experimentally or from the literature. For an equivalent rigid model representative of traditional frictionless pin joint simulation models but with realistic wobbling mass and foot-ground compliance, the overall kinetic and kinematic difference was 11.0%, including ground reaction force root mean square differences of 12.1%. Thus, the incorporation of viscoelastic elements at key joints enables accurate replication of experimentally recorded ground reaction forces within realistic whole-body kinematics and removes the previous need for excessively compliant wobbling masses and/or foot-ground interfaces. This is also necessary in cases where shock wave transmission within the simulation model must be non-instantaneous.

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An estimated 27 million Americans suffer from osteoarthritis (OA). Symptomatic OA is often treated with total knee replacement, a procedure which is expected to increase in number by 673% from 2005 to 2030, and costs to perform total knee replacement surgeries exceeded $11 billion in 2005. Subject-specific modeling and finite element (FE) predictions are state-of-the-art computational methods for anatomically accurate predictions of joint tissue loads in surgical-planning and rehabilitation. Knee joint FE models have been used to predict in-vivo joint kinematics, loads, stresses and strains, and joint contact area and pressure. Abnormal cartilage contact pressure is considered a risk factor for incidence and progression of OA. For this study, three subject-specific tibiofemoral knee FE models containing accurate geometry were developed from magnetic resonance images (MRIs). Linear (LIN), Neo-Hookean (NH), and poroelastic (PE) cartilage material models were implemented in each FE model for each subject under three loading cases to compare cartilage contact pressure predictions at each load case. An additional objective was to compare FE predictions of cartilage contact pressure for LIN, NH, and PE material models with experimental measurements of cartilage contact pressure. Because past studies on FE predictions of cartilage contact pressure using different material models and material property values have found differences in cartilage contact pressure, it was hypothesized that different FE predictions of cartilage contact pressure using LIN, NH, and PE material models for three subjects at three different loading cases would find statistically significant differences in cartilage contact pressure between the material models. It was further hypothesized that FE predictions of cartilage contact pressure for the PE cartilage material model would be statistically similar to experimental data, while the LIN and NH cartilage material models would be significantly different for all three loading cases. This study found FE and experimental measurements of cartilage contact pressure only showed significant statistical differences for LIN, NH, and PE predictions in the medial compartment at 1000N applied at 30 degrees, and for the PE prediction in the medial compartment at 500N applied at 0 degrees. FE predictions of cartilage contact pressure using the PE cartilage material model were considered less similar to experimental data than the LIN and NH cartilage material models. This is the first study to use LIN, NH, and PE material models to examine knee cartilage contact pressure predictions using FE methods for multiple subjects and multiple load cases. The results demonstrated that future subject specific knee joint FE studies would be advised to select LIN and NH cartilage material models for the purpose of making FE predictions of cartilage contact pressure.

Two-thirds of repetitive strain injuries affect the wrist joint. Although force is believed to be one of the major factors, the forces involved in wrist movements have not been thoroughly characterized in vivo. Computer simulations with a musculoskeletal model of the wrist have been used to estimate wrist muscle forces, but only at maximum voluntary contraction and only involving a single degree of freedom (DOF). In this study we present a method for creating a subject-specific model that can be used to estimate muscle forces and joint torques in both degrees of freedom of the wrist over a range of torques applicable to activities of daily living. Ten young, healthy subjects applied three levels of isometric wrist torque (about 7, 15, and 25% of maximum torque) in combinations of wrist flexion-extension and radial-ulnar deviation while joint torque in both DOF and surface electromyograms (sEMG) in the five major wrist muscles were measured. To find subject-specific parameters, we followed a two-step process. First, a pre-existing, generic musculoskeletal model of the wrist was scaled to individual subjects' height. Second, we compared joint torques predicted from measured sEMG using forward simulations of muscular dynamics to measured torques and minimized this error to optimize for subject-specific model parameter values. The model parameters optimized were the maximum isometric force and tendon slack length of each muscle. Optimization constraints were added to ensure physiologically plausible combinations of parameter values. The optimization produced model parameters that 1) were in a reasonable physiological range for each test subject and 2) significantly improved the accuracy of the model’s torque estimation. Scaling the generic model reduced the root mean squared (RMS) error between predicted and measured joint torques by 2.8±4.6% (mean±SD), whereas optimizing the scaled model further reduced the RMS error by 51.4±18.9% for the torque level at which the model was optimized. Testing the optimized model at other torque levels still significantly reduced the error between predicted and measured torques compared to the scaled model (43.7±28.0% and 25.0±24.0% for lower and higher torque levels, respectively). The mean error between predicted and measured torque was 0.23±0.04, 0.30±0.04, and 1.17±0.26 Nm at the low-, mid-, and high-torque levels, respectively. The method generally reduced the error in flexion-extension (FE) more than radial-ulnar deviation (RUD), likely in part because sEMG and torque were larger in FE than in RUD. Optimizing for subject-specific model parameters significantly improved prediction over both the generic and scaled models, in both degrees of freedom of the wrist, and at all three torque levels. The presented method for creating subject-specific models can be used in future studies to quantify muscle forces and joint torques of natural wrist movements in vivo.

Today’s modern society is multicultural, school is therefore a meeting place for pupils withdifferent experiences, prior knowledge, and mother tongue. Second language students whohave not yet developed good skills in various subject languages, face several challenges inupper secondary school. To succeed in different school subjects these students need todevelop language that is specialized for each school subject. The purpose of this study is toexamine how social science teachers in the upper secondary school experience and work withsecond language students who have difficulties with content-based language. The appliedmethod in the study is qualitative interviews. The theoretical framework is based on differentconcepts of literacy to analyze the results. The results in this study show that the teachers useboth similar and different methods to develop second language students’ understanding ofconcepts, reading, and writing skills, subject language, and subject knowledge. However,several differences between teachers’ perceptions and approaches are also discerned. Theteachers in this study understand the importance of placing the language in focus within thesubject, however some of the teachers experience difficulties with integrating language andsubject into the teaching.

The aim of this paper is to compare the subject-specific concepts and their use in two chapters dealing with the subject force in two different physics textbooks for grades 4-6. To achieve the aim, the following questions have been formulated: What subject-specific concepts are used and how often? What representations are used to clarify the subject-specific concepts? To achieve the purpose and the issues raised in the paper, the chapter will be analysed with two different content analysis. The material will then be analysed based on Vygotsky's theory of the development of scientific concepts. The results show that both chapters have about as many subject-specific concepts in comparison to the rest of the words in the chapters. One of the chapters show greater variety of representations with different contexts than the second chapter. Both chapters have used everyday contexts when the subject-specific concepts were explained, but one of the chapters show that different contexts were used depending on the subject-specific concepts.

An imaging-based computational framework for simulation of airflow in subject specific breathing human lungs is established. The three-dimensional (3D) airways of up to 9 generations and lobes are segmented and reconstructed from computed tomography (CT) images. Beyond the CT-resolved 3D airways, a volume filling method is applied to generate the one-dimensional (1D) conducting airway tree that bridges the central airway with the lung parenchyma. Through 3D-1D airway coupling, a novel image-registration-based boundary condition (BC) is proposed to derive physiologically-consistent regional ventilation for the whole lung and provide flow-rate fractions needed for the 3D airway model via the 1D-tree connectivity and the mass conservation. The in-house parallel finite-element large-eddy simulation (LES) code enables to capture genuinely complex airflow characteristics in a computationally-efficient manner. The 3D-1D coupling framework is multiscale because it can not only predict detailed flows in the 3D central airways at a local level, but also yields subject-specific physiologically-consistent regional ventilation at the whole lung level. The framework has been applied to investigate pulmonary airflow and lung physiology. For example, the study of intra- and inter-subject variability provides insight into the effect of airway geometry on airflow structure. The relations between airflow structure, energy dissipation, and airway resistance under normal breathing condition have also been studied, showing similarity behaviors for inspiratory and expiratory flows. In the study of high-frequency oscillatory ventilation, we have compared counter-flow structures near flow reversal (namely phase change between inspiration and expiration) and quantified associated convective mixing in both idealized and CT-based airway models. Furthermore, the image-registration-derived displacement field is used to deform 3D-1D airway models for breathing lung simulation and estimate diameter changes of 1D airway segments during deformation. In conjunction with an arbitrary Lagrangian Eulerian method, airflow in a breathing lung has been simulated and compared with that of a rigid airway model. The results show that the proposed computational framework is promising in better understanding the human lung physiology and improving the treatment of diseased lung.

The purpose of this study was to compare the algebraic performance gains of high school students who enroll in an integrated mathematics course pathway (i.e., Integrated Mathematics I-II-III) to the algebraic performance gains of high school students who enroll in a subject-specific course pathway (i.e., Algebra I-Geometry-Algebra II). Several studies have been performed in which researchers examined relationships between mathematics outcomes and the course-taking patterns of high school students enrolled in subject-specific course pathways. However, there is little extant research in which researchers have investigated effects of content organization on students' learning and achievement. Therefore, this study addresses calls for more studies that examine the high school mathematics performance of students who learn from subject-specific and integrated course pathways. Data from a large scale observational study known as the High School Longitudinal Study of 2009 was used to compare relationships between the course pathways and students' performance on an assessment of algebraic skills. A pretest-posttest study design was used to statistically compare gain scores of high school students who learn from subject-specific course pathways to the gain scores of a comparable group of high school students who learn from integrated course pathways. Propensity score matching was used to reduce the threat of selection bias due to nonrandom assignment. The results revealed no statistical differences exist in the algebraic performance gains between high school students who learn mathematics from integrated course pathways and high school students who learn from subject-specific course pathways. Suggestions for future research are discussed.

L'analyse du comportement du système musculo-squelettique est indispensable à la compréhension de pathologies ou de l'efficacité du geste sportif. Les modèles, représentants un sujet moyen, permettent l'identification de tendance. Cependant, leurs résultats sont limités à la plage de population qu'ils représentent. Il est donc nécessaire d'adapter leurs géométries et propriétés mécaniques afin de simuler le plus fidèlement possible le comportement biomécanique. L'IRM est l'outil de référence pour la construction de modèle personnalisé tridimentionnel. Cependant, son coût, sa disponibilité et les méthodes de reconstructions limitent son utilisation. Récemment, les développements de la stéréoradiographie, avec le système EOS®, et des techniques ultrasonores, avec l'élastographie ShearWave, ouvrent de nouvelles voies pour la personnalisation des modèles. Le but de ce travail était de proposer une nouvelle méthode pour la construction d'un modèle musculo-squelettique personnalisé, en position érigée, du membre inférieur combinant stéréoradiographie et ultrasons. Tout d'abord, des repères osseux robustes sur images IRM ont été définis pour construire un modèle de référence en position debout. Ensuite, la personnalisation de la géométrie osseuse et de l'enveloppe externe est obtenue par stéréoradiographie. Ces premières informations personnalisées sont utilisées pour estimer la géométrie des muscles. Ce modèle pré-personnalisé est déformé pour correspondre à la géométrie réelle des muscles obtenue par échographie. Cette méthode possède plusieurs avantages. Elle passe outre l'assemblage de coupes échographiques et de supprime la segmentation manuelle complète des coupes. Enfin, un protocole de mesure des propriétés mécaniques par élastographie ShearWave a été présenté. Les propriétés élastiques des muscles du membre inférieur peuvent alors être définies. / The analysis of the behavior of the musculoskeletal system is essential to understand diseases or effectiveness of the sporting gesture. Models, which represent a 50-percentile subject, allow tendencies identification. However, results are limited to the range of people they represent. Their geometry and mechanical properties must be personalized to simulate as closely as possible the biomechanical behavior. MRI is the reference device for the construction of three-dimensional personalized models. However, the cost, the availability and methods of reconstruction limit its use. Recent developments in stereoradiography, with the EOS® system, and in ultrasonic field, with ShearWave elastography, open up new horizons. The aim of this work was to propose a new method for building a personalized musculoskeletal model of lower limb combining stereoradiography and ultrasound, in standing position. First, robust bony frame on MR images were defined to build a reference model. Then, the personalized bones and external envelope geometries were obtained by stereoradiography. This first personalized information was used to estimate muscles geometry. This pre-personalized model was deformed to match the real muscle geometry obtained by ultrasound. This method has several advantages. It overrides the assembly of ultrasound cuts and removes the complete manual segmentation. Finally, a protocol for measuring the mechanical properties ShearWave elastography was introduced. Thus, the muscles elastic properties of the lower limb can then be defined in the model.