Elaboration d'un modèle mécanique de l'articulation de la hanche sous sollicitations dynamiques – Application à l'étude de l'influence d'une orthèse podale sur une hanche arthrosique

The aim of this study is to elaborate a mechanical model of the healthy hip joint. The main objective is to use it as a reference model in order to analyse pathological hip joint mechanical behaviours and evaluate prescribed treatment by comparison of pre vs. post simulated behaviours. Therefore, a generic finite element model of the hip joint is developed. Experimental acquisitions of kinematical and kinetic data are implemented in a musculo-skeletal model to calculate muscular forces acting at the hip joint. Our approach consists in coupling an inverse dynamic method with static optimisation. From the evaluation of each individual hip muscle force, the contact reaction force is computed. The contact reaction force is then implemented in the finite element model in order to perform simulations for several instants of the stance phase of gait and stair climbing. Contact pressure distributions during the stance phase of gait are compared to those available in the literature, measured in vivo by mean of instrumented prosthesis or cadaveric experiments simulating gait cycles. A clinical application concerns the evaluation of the effect of foot orthoses on the mechanical behaviour of an osteoarthritic hip joint. The loading conditions at the hip joint, when the patient is walking or climbing a step successively with and without foot orthoses, is determined in each experimental conditions using the approach previously described.L'objectif de ce travail est d'élaborer un modèle mécanique de la hanche saine susceptible d'être utilisé comme référence pour pouvoir ensuite analyser le comportement de hanches pathologiques en évaluant l'effet des traitements préconisés par comparaison des différents comportements simulés. Dans ce contexte, un modèle éléments finis générique de l'articulation de la hanche est développé. Il est également nécessaire de déterminer l'état de chargement de l'articulation de la hanche pour notre simulation. L'analyse du mouvement permet le calcul des données cinématiques et dynamiques à partir des mesures expérimentales. A partir de ces données, un modèle musculo-squelettique associant une méthode de dynamique inverse et d'optimisation statique, permet de déterminer les efforts musculaires mis en jeu par les muscles croisant l'articulation de la hanche. L'évaluation des forces développées par les muscles de la hanche permet de calculer la réaction de contact articulaire exercée par le fémur sur le bassin. C'est cette réaction que nous implémentons dans le modèle éléments finis. Ainsi, les simulations du comportement de la hanche saine sont réalisées pour la phase d'appui de la marche et la phase d'appui de la montée d'escaliers. Nous traitons ensuite d'une application clinique visant à évaluer l'influence du port d'une orthèse podale sur le comportement mécanique d'une hanche arthrosique. La démarche suivie est la même que celle mise en place pour l'étude du comportement de la hanche saine. L'état de chargement de la hanche arthrosique est déterminé chez le patient pendant la marche et la montée d'escaliers évoluant successivement avec puis sans orthèses

Elaboration d'un modèle mécanique de l'articulation de la hanche sous sollicitations dynamiques – Application à l'étude de l'influence d'une orthèse podale sur une hanche arthrosique

The aim of this study is to elaborate a mechanical model of the healthy hip joint. The main objective is to use it as a reference model in order to analyse pathological hip joint mechanical behaviours and evaluate prescribed treatment by comparison of pre vs. post simulated behaviours. Therefore, a generic finite element model of the hip joint is developed. Experimental acquisitions of kinematical and kinetic data are implemented in a musculo-skeletal model to calculate muscular forces acting at the hip joint. Our approach consists in coupling an inverse dynamic method with static optimisation. From the evaluation of each individual hip muscle force, the contact reaction force is computed. The contact reaction force is then implemented in the finite element model in order to perform simulations for several instants of the stance phase of gait and stair climbing. Contact pressure distributions during the stance phase of gait are compared to those available in the literature, measured in vivo by mean of instrumented prosthesis or cadaveric experiments simulating gait cycles. A clinical application concerns the evaluation of the effect of foot orthoses on the mechanical behaviour of an osteoarthritic hip joint. The loading conditions at the hip joint, when the patient is walking or climbing a step successively with and without foot orthoses, is determined in each experimental conditions using the approach previously described.L'objectif de ce travail est d'élaborer un modèle mécanique de la hanche saine susceptible d'être utilisé comme référence pour pouvoir ensuite analyser le comportement de hanches pathologiques en évaluant l'effet des traitements préconisés par comparaison des différents comportements simulés. Dans ce contexte, un modèle éléments finis générique de l'articulation de la hanche est développé. Il est également nécessaire de déterminer l'état de chargement de l'articulation de la hanche pour notre simulation. L'analyse du mouvement permet le calcul des données cinématiques et dynamiques à partir des mesures expérimentales. A partir de ces données, un modèle musculo-squelettique associant une méthode de dynamique inverse et d'optimisation statique, permet de déterminer les efforts musculaires mis en jeu par les muscles croisant l'articulation de la hanche. L'évaluation des forces développées par les muscles de la hanche permet de calculer la réaction de contact articulaire exercée par le fémur sur le bassin. C'est cette réaction que nous implémentons dans le modèle éléments finis. Ainsi, les simulations du comportement de la hanche saine sont réalisées pour la phase d'appui de la marche et la phase d'appui de la montée d'escaliers. Nous traitons ensuite d'une application clinique visant à évaluer l'influence du port d'une orthèse podale sur le comportement mécanique d'une hanche arthrosique. La démarche suivie est la même que celle mise en place pour l'étude du comportement de la hanche saine. L'état de chargement de la hanche arthrosique est déterminé chez le patient pendant la marche et la montée d'escaliers évoluant successivement avec puis sans orthèses

Normal and osteoarthritic hip joint mechanical behaviour: a comparison study

The assessment of contact areas within the hip joint during activities of daily living is of critical importance to understand why degeneration mechanisms are sometimes initiated. A generic finite element model is developed and constrained with experimental personalized conditions to locate contact areas and determine pressure distribution, both during walking and stair climbing. Bony structures are positioned in relation to each other by using experimental kinematical data. Implemented loading conditions are computed from an inverse dynamic approach coupled with an optimization method. The mechanical behaviour of a healthy hip joint is first simulated. This model is then used as a reference for the evaluation of a pathological mechanical behaviour. Thus, experimental data are collected for a patient presenting a coxarthrosis. The comparison of the pathological and normal behaviours emphasizes that the contact area swept within the osteoarthritic hip joint is limited both during walking and stair climbin

Élaboration d'un modèle mécanique de l'articulation de la hanche sous sollicitations dynamiques (application à l'étude de l'influence d'une orthèse podale sur une hanche arthrosique)

L objectif de ce travail est d élaborer un modèle mécanique de la hanche saine susceptible d être utilisé comme référence pour pouvoir ensuite analyser le comportement de hanches pathologiques en évaluant l effet des traitements préconisés par comparaison des différents comportements simulés. Dans ce contexte, un modèle éléments finis générique de l articulation de la hanche est développé. Il est également nécessaire de déterminer l état de chargement de l articulation de la hanche pour notre simulation. L analyse du mouvement permet le calcul des données cinématiques et dynamiques à partir des mesures expérimentales. A partir de ces données, un modèle musculo-squelettique associant une méthode de dynamique inverse et d optimisation statique, permet de déterminer les efforts musculaires mis en jeu par les muscles croisant l articulation de la hanche. L évaluation des forces développées par les muscles de la hanche permet de calculer la réaction de contact articulaire exercée par le fémur sur le bassin. C est cette réaction que nous implémentons dans le modèle éléments finis. Ainsi, les simulations du comportement de la hanche saine sont réalisées pour la phase d appui de la marche et la phase d appui de la montée d escaliers. Nous traitons ensuite d une application clinique visant à évaluer l influence du port d une orthèse podale sur le comportement mécanique d une hanche arthrosique. La démarche suivie est la même que celle mise en place pour l étude du comportement de la hanche saine. L état de chargement de la hanche arthrosique est déterminé chez le patient pendant la marche et la montée d escaliers évoluant successivement avec puis sans orthèsesThe aim of this study is to elaborate a mechanical model of the healthy hip joint. The main objective is to use it as a reference model in order to analyse pathological hip joint mechanical behaviours and evaluate prescribed treatment by comparison of pre vs. post simulated behaviours. Therefore, a generic finite element model of the hip joint is developed. Experimental acquisitions of kinematical and kinetic data are implemented in a musculo-skeletal model to calculate muscular forces acting at the hip joint. Our approach consists in coupling an inverse dynamic method with static optimisation. From the evaluation of each individual hip muscle force, the contact reaction force is computed. The contact reaction force is then implemented in the finite element model in order to perform simulations for several instants of the stance phase of gait and stair climbing. Contact pressure distributions during the stance phase of gait are compared to those available in the literature, measured in vivo by mean of instrumented prosthesis or cadaveric experiments simulating gait cycles. A clinical application concerns the evaluation of the effect of foot orthoses on the mechanical behaviour of an osteoarthritic hip joint. The loading conditions at the hip joint, when the patient is walking or climbing a step successively with and without foot orthoses, is determined in each experimental conditions using the approach previously describedLYON1-BU.Sciences (692662101) / SudocSudocFranceF

An integrative model of the self-sustained oscillating contractions of cardiac myocytes.

Computational cell models appear as necessary tools for handling the complexity of intracellular cell dynamics, especially calcium dynamics. However, while oscillating intracellular calcium oscillations are well documented and modelled, a simple enough virtual cell taking into account the mechano-chemical coupling between calcium oscillations and cell mechanical properties is still lacking. Considering the spontaneous periodic contraction of isolated cardiac myocytes, we propose here a virtual cardiac cell model in which the cellular contraction is modelled using an hyperelastic description of the cell mechanical behaviour. According to the experimental data, the oscillating cytosolic calcium concentrations trigger the spatio-temporal variation of the anisotropic intracellular stresses. The finite element simulations of the virtual cell deformations are compared to the self-sustained contractions of isolated rat cardiomyocytes recorded by time-lapse video-microscopy

Assessment of the influence of foot orthoses in the hip loading conditions during walking: a single case study

Despite their large clinical application, the understanding of the effects of foot orthoses on the lower limb kinematics and kinetics is limited. In this context, we propose an advanced musculoskeletal model to assess the influence of foot orthoses in the loading conditions within an osteoarthritic hip joint during gait. Experimental data are collected for a single pathological subject presenting a coxarthrosis (with and without orthoses), and a healthy subject during walking. An inverse dynamic approach coupled with an optimisation method evaluates the forces developed by 14 muscles and the hip contact reaction force. Contact reaction and muscular force magnitudes are closed whether the patient is walking with or without foot orthoses. Nevertheless, contact reaction amplitudes and orientations show differences in relation to those calculated for the healthy subject. The results obtained allow us to formulate some assumptions concerning the causes of coxarthrosis evolution and treatment

Evolution of a Coastal Beach/Barrier/Marsh System in Response to Sea Level Rise, Storm Events and Human Impacts: A Case Study of Trunvel Marsh, Western Brittany

International audienceThe evolution of coastal sites such as beach/barrier/marsh systems is known to be strongly forced by sea level rise and controlled by storms, sediment input and human impacts. The relative weight of each may vary in time. However, it is difficult to determine the relative importance of these forcing controls and, therefore, how coastal systems evolve through time. In order to study this evolution we have selected the case study of Trunvel marsh, western Brittany, France, which is directly exposed to the most violent storms and has been extensively depleted of sediment during and since WW2. The relative balance of anthropogenic and meteorological controls and relative sea level rise is compared. Sediment cores have been obtained from within the marsh, cross sections of the barrier have been studied and air photos and old maps have been analysed. From 4000 BP to recent times the system has behaved in a simple way: the beach and the barrier accumulated sand and gravel, seeming to migrate inland with relative sea level rise and the marsh was alternatively eroded by the local river or fed by aeolian drifted sands. Very occasional storms may have breached the barrier and temporarily invaded (flooded) the marsh. Conversely, large events of river discharge may have breached the barrier, although there appears to be some natural resilience and the barrier rebuilds itself after each storm and the marsh is, once again isolated from the sea. At the beginning of the Roman period land use change appears to have modified the river discharge, following which the marsh seems to have been in its natural condition again until WW2, although some dykes were built and channels excavated. During WW2 the gravel was almost totally removed and used for concrete to build fortifications along the coast. After WW2, the system was totally controlled by management practices, the aim of which was to recreate a “natural” environment so that today this is a “human made natural landscape” and is now classified as a nature reserve. The barrier is no longer able to withstand storms and the river discharge does not always reach the sea. Therefore human management of water level in the marsh is today the main morpho-dynamic control for the whole system