3D Muscle detailed ankle-foot model for finite element analysis

A three dimensional muscle detailed human anklefoot model was created. Starting from computed tomographies all bones and muscles of the foot were reconstructed. The development process, the modelfeatures and the thresholding and smoothing problems are explained. The finite element model developed will be used to study the mechanical performance of each muscle and bone allowing to simulate any pathology, treatment or surgery of the foot

Influencia de la geometría de la falange proximal del primer dedo del pie en la formación de juanetes

CONTEXTO: Existen numerosas patologías en el pie que precisan de tratamiento médico quirúrgico. Algunas de estas dolencias son debidas a deformidades adquiridas del antepié. El hallux valgus es una da las deformidades más frecuente del pie. Se presenta con mayor periodicidad en mujeres, siendo 10 veces más frecuente en mujeres que en hombres. Las causas del hallux valgus no están claras. Se trata de una patología de origen multifactorial con una clara relación hereditaria, además sea constatado que el uso de calzado ayuda a la progresión de la deformidad. Los cirujanos han observado, al operar la patología del hallux valgus, que la falange proximal es diferente, en cuanto a forma, en hombres y mujeres. OBJETIVO: En este proyecto se estudia la influencia de la geometría de la falange proximal del primer dedo del pie en la formación de juanetes. En particular se analiza, la influencia del dimorfismo sexual que presenta este hueso en el hecho de que las mujeres padezcan con mayor frecuencia que los hombres esta deformidad. METODOLOGÍA: Se realiza una simulación computacional mediante un modelo de elementos finitos en 3 dimensiones del esqueleto de un pie humano para el estudio de las tensiones y deformaciones en el primer radio. A partir de la descripción cualitativa y cuantitativa de las falanges del primer dedo, proporcionada por los cirujanos mediante la disección de cadáveres, se generan falanges de distintos tamaños y geometrías, tanto de hombre como de mujer e insertan en el modelo de partida. RESULTADOS: Las falanges proximales soportan esfuerzos de compresión en la zona medial y esfuerzos de tracción en la zona lateral, estas tensiones son más patentes cuanto más grande es la falange. Además en la concavidad de la base de la falange las tensiones son mayores cuanto menor es la profundidad. CONCLUOSINES: Las tensiones generadas en la falange proximal intensificadas por la sobrecarga en la base, producen una tendencia a la separación del metatarsiano del primer radio con respecto a la posición anatómica original, lo que constituye el inicio de la deformidad del hallux valgus

Computational foot modeling for clinical assessment

Esta Tesis desarrolla un modelo de elementos finitos del pie humano completo y detallado en tres dimensiones para avanzar hacia una simulación computacional más precisa que proporcione información realista y relevante para la práctica clínica. Desde el punto de vista ingenieril, el pie humano es una compleja estructura de pequeños huesos, soportados por fuertes ligamentos y controlada por una red de músculos y tendones con una capacidad de respuesta mecánica excepcional. La barrera actual en la simulación computacional del pie es la inclusión de estas estructuras musculotendinosas en los modelos. Para avanzar en esta dirección, se crea un modelo de elementos finitos del pie completo y detallado con geometría real de la estructura interna diferenciando hueso cortical y esponjoso, tendón, músculo, cartílago y grasa. Se realizan ensayos experimentales de los tendones del pie y la suela plantar para determinar sus propiedades materiales y estructurales y caracterizar computacionalmente su comportamiento mecánico no lineal. Estos avances están orientados hacia la mejora de la representación geométrica y caracterización del tejido de los componentes internos del pie. El modelo desarrollado en esta Tesis puede usarse en el campo de la biomecánica en áreas de ortopedia, lesiones, tratamiento, cirugía y deporte. La investigación está estructurada por capítulos en los cuales se desarrollan pequeños avances hacia el objetivo principal de la Tesis al mismo tiempo que se aplica el potencial de estos avances a casos particulares. Estas contribuciones parciales en el área de los ensayos experimentales son: la determinación de un completo conjunto de datos de las propiedades mecánicas de los tendones del pie, la definición de un criterio para cuantificar las regiones de la curva de tensión-deformación del tendón y el análisis de la respuesta a compresión de la suela plantar en función de la posición. Y, en el área de la biomecánica clínica las contribuciones son: la investigación de un parámetro del esqueleto como factor etiológico del hallux valgus, el estudio de sensibilidad de la fuerza de los cinco mayores tendones estabilizadores, el análisis cuasi-estático de la fase de apoyo de la marcha y el estudio del mecanismo de absorción de la fuerza de impacto del pie durante la carrera descalzo a diferentes ángulos de impacto.In this Thesis, a complete detailed three-dimensional finite element model of the human foot is described to advance towards a more refined computational simulation which provides realistic and meaningful information for clinical practice. From an engineering perspective, the human foot is a complex structure of small bones supported by strong ligaments and controlled by a network of tendons and muscles that achieves a superb mechanical responsiveness. The current barrier in foot computational simulation is the inclusion of these musculotendinous structures in the models. To advance in this direction, a complete detailed three-dimensional foot finite element model with actual geometry of the inner structure is created differentiating cortical and trabecular bone, tendon, muscle, cartilage and fat tissues. Experimental tests of foot tendons and plantar soles are performed to determine their structural and material properties and to characterize computationally their non-linear mechanical behavior. Those advances are oriented to refine the geometry and the tissue characterization of the internal foot components. The model developed in this Thesis can be used in the field of biomechanics, in the areas of orthopedics, injury, treatment, surgery and sports biomechanics. The research is structured by chapters where small steps towards the main objective are developed and the potential of these advances are applied to particular cases. These partial contributions in the area of the experimental testing are: the determination of a complete dataset of the mechanical properties of the balance foot tendons, the definition of a criteria to quantify the regions of the tendon stress-strain curve and the analysis of the compressive response of plantar soft tissue as function of the location. And, in the area of clinical biomechanics the contributions are: the investigation of a skeletal parameter as etiology factor of the hallux valgus, the tendon force sensitivity study of the five major stabilizer tendons, the quasi-static analysis of the midstance phase of walking and the study of the impact absorption mechanism of the foot during barefoot running at different strike patterns

Locational and Directional Dependencies of Smooth Muscle Properties in Pig Urinary Bladder

The urinary bladder is a distensible hollow muscular organ, which allows huge changes in size during absorption, storage and micturition. Pathological alterations of biomechanical properties can lead to bladder dysfunction and loss in quality of life. To understand and treat bladder diseases, the mechanisms of the healthy urinary bladder need to be determined. Thus, a series of studies focused on the detrusor muscle, a layer of urinary bladder made of smooth muscle fibers arranged in longitudinal and circumferential orientation. However, little is known about whether its active muscle properties differ depending on location and direction. This study aimed to investigate the porcine bladder for heterogeneous (six different locations) and anisotropic (longitudinal vs. circumferential) contractile properties including the force-length-(FLR) and force-velocity-relationship (FVR). Therefore, smooth muscle tissue strips with longitudinal and circumferential direction have been prepared from different bladder locations (apex dorsal, apex ventral, body dorsal, body ventral, trigone dorsal, trigone ventral). FLR and FVR have been determined by a series of isometric and isotonic contractions. Additionally, histological analyses were conducted to determine smooth muscle content and fiber orientation. Mechanical and histological examinations were carried out on 94 and 36 samples, respectively. The results showed that maximum active stress (pact) of the bladder strips was higher in the longitudinal compared to the circumferential direction. This is in line with our histological investigation showing a higher smooth muscle content in the bladder strips in the longitudinal direction. However, normalization of maximum strip force by the cross-sectional area (CSA) of smooth muscle fibers yielded similar smooth muscle maximum stresses (165.4 ± 29.6 kPa), independent of strip direction. Active muscle properties (FLR, FVR) showed no locational differences. The trigone exhibited higher passive stress (ppass) than the body. Moreover, the bladder exhibited greater ppass in the longitudinal than circumferential direction which might be attributed to its microstructure (more longitudinal arrangement of muscle fibers). This study provides a valuable dataset for the development of constitutive computational models of the healthy urinary bladder. These models are relevant from a medical standpoint, as they contribute to the basic understanding of the function of the bladder in health and disease

Computational foot modeling for clinical assessment

Exportado OPUSMade available in DSpace on 2019-08-14T18:06:17Z (GMT). No. of bitstreams: 1 tese_do_enrique_formato_a4.pdf: 15296449 bytes, checksum: d985e3fff6be144af661400a9f776b17 (MD5) Previous issue date: 27Esta Tese desenvolve um modelo de elementos finitos do pé humano completo e detalhado em três dimensões para avançar na direção de uma simulação computacional mais precisa que proporcione informação realista e relevante para a prática clínica. Desde o ponto de vista da engenharia, o pé humano é uma estrutura complexa de pequenos ossos, suportados por fortes ligamentos e controlada por uma rede de músculos e tendões. A barreira atual na simulação computacional do pé é a inclusão destas estruturas musculotendinosas nos modelos. Para avançar nesta direção, se cria um modelo de elementos finitos do pé completo e detalhado com geometria real da estrutura interna diferençando osso cortical e esponjoso, tendão, músculo, cartilagem e gordura. Se realizam ensaios experimentais dos tendões do pé e o solado plantar para determinar suas propriedades materiais e estruturais e caracterizar computacionalmente seu comportamento mecânico não lineal. Estes avanços estão orientados para a melhora da representação geométrica e caracterização do tecido dos componentes internos do pé. O modelo desenvolvido nesta Tese pode ser usado no campo da biomecânica, em áreas da ortopedia, lesões, tratamento, cirurgia e esporte. A pesquisa está estruturada por capítulos nos quais se desenvolvem pequenos avanços em direção ao objetivo principal da Tese enquanto se aplica o potencial destes avanços a casos particulares. Estas contribuições parciais na área dos ensaios experimentais são: a determinação de um conjunto completo de dados das propriedades mecânicas dos tendões do pé, a definição de um critério para quantificar as regiões da curva tensão-deformação do tendão e a análise da resposta à compressão do solado plantar em função da posição. E, na área da biomecânica clínica, as contribuições são: a investigação de um parâmetro do esqueleto como fator etiológico do hallux valgus, o estudo da sensibilidade da força dos cinco maiores tendões estabilizadores, o analise quase-estático da fase de apoio da marcha e o estudo do mecanismo de absorção da força de impacto do pé durante a corrida descalço a diferentes ângulos de impactoIn this Thesis, a complete detailed three-dimensional finite element model of the human foot is described to advance towards a more refined computational simulation which provides realistic and meaningful information for clinical practice. From an engineering persperctive, the human foot is a complex structure of small bones supported by strong ligaments and controlled by a network of tendons and muscles that achieves a superb mechanical responsiveness. The current barrier in foot computational simulation is the inclusion of these musculotendinous structures in the models. To advance in this direction, a complete detailed three-dimensional foot finite element model with actual geometry of the inner structure is created differentiating cortical and trabecular bone, tendon, muscle, cartilage and fat tissues. Experimental tests of foot tendons and plantar soles are performed to determine their structural and material properties and to characterize computationally their non-linear mechanical behavior. Those advances are oriented to refine the geometry and the tissue characterization of the internal foot components. The model developed in this Thesis can be used in the field of biomechanics, in the areas of orthopedics, injury, treatment, surgery and sports biomechanics. The research is structured by chapters where small steps towards the main objective are developed and the potential of these advances are applied to particular cases. These partial contributions in the area of the experimental testing are: the determination of a complete dataset of the mechanical properties of the balance foot tendons, the definition of a criteria to quantify the regions of the tendon stress-strain curve and the analysis of the compressive response of plantar soft tissue as function of the location. And, in the area of clinical biomechanics the contributions are: the investigation of a skeletal parameter as etiology factor of the hallux valgus, the tendon force sensitivity study of the five major stabilizer tendons, the quasi-static analysis of the midstance phase of walking and the study of the impact absorption mechanism of the foot during barefoot running at different strike pattern

On multiscale tension-compression asymmetry in skeletal muscle

Skeletal muscle tissue shows a clear asymmetry with regard to the passive stresses under tensile and compressive deformation, referred to as tension-compression asymmetry (TCA). The present study is the first one reporting on TCA at different length scales, associated with muscle tissue and muscle fibres, respectively. This allows for the first time the comparison of TCA between the tissue and one of its individual components, and thus to identify the length scale at which this phenomenon originates. Not only the passive stress-stretch characteristics were recorded, but also the volume changes during the axial tension and compression experiments. The study reveals clear differences in the characteristics of TCA between fibres and tissue. At tissue level TCA increases non-linearly with increasing deformation and the ratio of tensile to compressive stresses at the same magnitude of strain reaches a value of approximately 130 at 13.5% deformation. At fibre level instead it initially drops to a value of 6 and then rises again to a TCA of 14. At a deformation of 13.5%, the tensile stress is about 6 times higher. Thus, TCA is about 22 times more expressed at tissue than fibre scale. Moreover, the analysis of volume changes revealed little compressibility at tissue scale whereas at fibre level, especially under compressive stress, the volume decreases significantly. The data collected in this study suggests that the extracellular matrix has a distinct role in amplifying the TCA, and leads to more incompressible tissue behaviour. Statement of significance: This article analyses and compares for the first time the tension-compression asymmetry (TCA) displayed by skeletal muscle at tissue and fibre scale. In addition, the volume changes of tissue and fibre specimens with application of passive tensile and compressive loads are studied. The study identifies a key role of the extracellular matrix in establishing the mechanical response of skeletal muscle tissue: It contributes significantly to the passive stress, it is responsible for the major part of tissue-scale TCA and, most probably, prevents/balances the volume changes of muscle fibres during deformation. These new results thus shed light on the origin of TCA and provide new information to be used in microstructure-based approaches to model and simulate skeletal muscle tissue.ISSN:1742-7061ISSN:1878-756

Predicting muscle tissue response from calibrated component models and histology-based finite element models

Skeletal muscle is an anisotropic soft biological tissue composed of muscle fibres embedded in a structurally complex, hierarchically organised extracellular matrix. In a recent work (Kuravi et al., 2021) we have developed 3D finite element models from series of histological sections. Moreover, based on decellularisation of fresh tissue samples, a novel set of experimental data on the direction dependent mechanical properties of collagenous ECM was established (Kohn et al., 2021). Together with existing information on the material properties of single muscle fibres, the combination of these techniques allows computing predictions of the composite tissue response. To this end, an inverse finite element procedure is proposed in the present work to calibrate a constitutive model of the extracellular matrix, and supplementary biaxial tensile tests on fresh and decellularised tissues are performed for model validation. The results of this rigorously predictive and thus unforgiving strategy suggest that the prediction of the tissue response from the individual characteristics of muscle cells and decellularised tissue is only possible within clear limits. While orders of magnitude are well matched, and the qualitative behaviour in a wide range of load cases is largely captured, the existing deviations point at potentially missing components of the model and highlight the incomplete experimental information in bottom-up multiscale approaches to model skeletal muscle tissue.ISSN:1751-6161ISSN:1878-018