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This paper describes how a force response equation was created to model muscles, tendons, and ligaments of the hip joint to improve a biomechanical model of an infant hip to study Developmental Dysplasia of the Hip (DDH). DDH is the most common abnormality in newborn infants and is defined as any amount of instability in the hip including complete dislocation. Researchers at our institution are attempting to increase the success rate of treatment methods by creating computer models of the biomechanics of infant hip instability and dislocation. The computer model used a scaled adult pelvis, femur, tibia, fibula and foot to match the size of an infant for the bone geometry. The current infant muscle model is an undifferentiated model based on the area of a single infant muscle, for all muscles modeled. This muscle model was able to provide some insight into the nature of the biomechanics. To improve the infant muscle model, a set of equations differentiated by muscle area was developed. The new set of equations uses a ratio of infant over adult muscle area of a single muscle to create a ratio that can be used to scale all adult muscle areas to infant areas. This model will be more physiologically accurate because it will be differentiated based on muscle area.

Developmental dysplasia of the hip (DDH) is a condition that involves the dislocation of the head of the femur in the acetabulum of the pelvic bone. Although it may not interfere with a child's range of motion during infancy, DDH can cause various effects over time such as joint pain, abnormal gait, and even paralysis. It is crucial to catch this phenomenon early on so that permanent disability is not introduced to the patient. In this study, an excitation device was used to send a broadband frequency signal through a hip joint simulated by a 3D printed bone apparatus consisting of a left femur and left pelvic bone. Accelerometers were used to sense the transmission of this signal through the bones tested. Variability was induced through different experiments in order to determine where the optimal frequency for detection of DDH would be. After variability was quantified for all of the nonconsecutive and consecutive trials, the excitation device was tested on a raw chicken quarter through the knee joint since this was very similar to the hip joint. Coherence, phase, and transfer function graphs were used to demonstrate the degree of variability, optimal frequencies for detection, and degree of signal transmission through the joints tested. The results from the 3D printed bone model showed that the height of accelerometer suspension, loosened coupling of sensors, and vertical alignment of the bone model apparatus affected the transfer function and phase graphs of the experiments while coherence stayed relatively the same. On the other hand, the results from the raw chicken model displayed similarities between graphs for little to no joint dislocation but the complete dislocation of the bone yielded significantly different graphs.

The aim was to highlight the context of developmental dysplasia therapy with postural hip locomotor development for children aged 4 weeks to 12 months. General examination was carried out in 9 children with disabilities in hip joints, degrees IIa- III. without contractures of adductors. We investigated spontaneous activity, and spontaneous reactivity. We compared the clinical picture of hip joints with the ultrasound image. Investigation of spontaneous activity was done by aspection. The test of spontaneous reactivity was taken using video and photos. Experimental results of our study showed the incidence of pathology in the spontaneous activity of 88.89 % children. Spontaneous reactivity was pathology in all cases, with various tests are discussed in the work. Ultrasound findings correlated with clinical manifestation in 66,67 %, but we cannot say that the proportion of patients will generally be higher than 60 %. Hypotheses were tested using the relative frequency parameter. The results are further discussed and compared with the assumptions by other authors. Powered by TCPDF (www.tcpdf.org)

Les viroles en acier microallié 18MND5, destinées aux générateurs de vapeur, présentent une composition hétérogène à plusieurs échelles. Un écart au procédé de fabrication ou une teneur en hydrogène excessive, peuvent conduire à la formation des Décohésions Dues à l’Hydrogène. Ces DDH résultent de la désorption de l’hydrogène interne lors du refroidissement jusqu’à température ambiante. La pression interne n’étant pas mesurables expérimentalement, une modélisation du phénomène est requise. Afin de préciser les mécanismes sous-jacents, il est proposé un scénario de formation de ces défauts s’appuyant conjointement sur une expertise et la modélisation des processus de diffusion-désorption-propagation. Les observations ont révélé une corrélation entre les DDH, les zones ségrégées et les amas de MnS (sites préférentiels d’initiation). Un modèle de diffusion dans un milieu hétérogène a été proposé afin d’évaluer la pression interne associée. La pression maximale excède ainsi 8600 bar en considérant une loi d’Abel-Noble optimisée du gaz réel. Le couplage de ce modèle avec la mécanique de la rupture a permis de quantifier l’évolution des paramètres relatifs à la propagation (pression interne, taille finale, vitesse, …). Un scénario de formation des DDH industriel a ainsi pu être formulé sur la base d’une étude paramétrique. Bien que les simulations préliminaires corroborent le retour d’expérience, le modèle raffiné et la prise en compte du gonflement de la DDH semblent sous-estimer la cinétique. Le caractère multi-fissuré des amas de MnS (homogénéisation des propriétés mécaniques) associé à un critère de rupture à l’échelle locale permettrait d’ajuster ce modèle. / Heat generators are manufactured from ingots of 18MND5 (A508cl3) low alloy steel and present composition heterogeneities at different scales. Under specific conditions (non-respect of guidelines or high initial content of H), Hydrogen Induced Cracks (HIC) may result from diffusion-desorption of internal hydrogen during cooling down to room temperature. Since neither hydrogen redistribution nor its internal pressure within cavities could be measured by experimental techniques, quantitative investigation is based on the modelling of related physical phenomena. A scenario of HIC formation, based on industrial feedback and modelling, has been proposed. A correlation between these defects, segregated areas and clusters of MnS (preferred initiation sites) has been revealed by expertise of HIC. A model of diffusion in heterogeneous alloys has then been proposed to assess the maximal pressure of H2 in such HIC. Simulation has shown that internal pressures above 860MPa are reached by considering an optimized Abel-Noble real gas behavior. The previous model has then been coupled to a failure mechanics procedure to characterize and quantify the crack growth parameters. Based on a parametric study, a scenario of HIC formation during the cooling has been proposed regarding process. Although results from preliminary simulations matched with feedback, the refined model based on the pressure induced elastic deformation of HIC has been developed but provided an underestimated kinetic of crack growth. Consequently, the multi-cracked nature of MnS clusters (homogenization of mechanical properties) and the updated local failure criterion appear to be a viable path to adjust predictions.