Subtalar Joint Biomechanics

Subtalar joint movement is transmitted proximally to the lower extremity and distally to the forefoot during gait. Thus, the entire lower kinetic chain is influenced by abnormal subtalar joint biomechanics. If the subtalar joint is forced to compensate for structural deformities of the foot and leg, various lower extremity injuries are likely to develop. The purpose of this study is to examine the normal and abnormal biomechanics of the subtalar joint. In the process, the clinician will be able to identify various subtalar joint abnormalities and relate these to their respective lower kinetic chain pathologies. By correctly assessing the cause of the lower extremity injury, the examiner will be able to initiate the appropriate form of treatment

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

Subtalar Joint Definition in Biomechanical Models

The effect of including a subtalar joint in a dynamic musculoskeletal model has not been fully explored or validated. The subtalar joint is often modeled as a one DOF hinge with the tri-planar axis defined as a combination of inclination and deviation angles measured from the ground and midline of the foot, respectively. The overall purposes of this dissertation were to explore how the inclusion of the subtalar joint and the definition of origin location and axis orientation affect the kinematics, joint kinetics, and muscle activations of the knee, ankle, and subtalar joint during dynamic tasks of walking and running through sensitivity analyses and validation using OpenSim (SimTK, Stanford, CA). The findings of this dissertation conclude that if the subtalar joint is to be included in a model, the location of the axis origin needs to be considered and accurately defined, especially if the inclination/deviation angles of the rotational axis will be modified to represent a more subject-specific definition. The models in this study were validated for walking using available in vivo joint contact data from the Grand Knee Challenge. Further inferences were made on the validity of the models for running based on similarities seen in the EMG and muscle activation patterns. The conclusions from this work are drawn from analysis of walking and running, which are primarily sagittal plane motions. Future studies analyzing more complex motion such as cutting or walking on uneven terrain, where there is more transverse and coronal plane motion, may further highlight the importance of the subtalar joint in musculoskeletal modeling as it plays a more active role during foot adaption

Impacts of Diabetic Neuropathy on the Human Neuromuscular System

Diabetes mellitus (DM) imparts vascular and metabolic stressors that cause damage and dysfunction to the human nervous system. The disorder associated with this dysfunction is termed diabetic polyneuropathy (DPN). Although DPN has been associated with muscle weakness and atrophy, the extent of its impacts on the neuromuscular system is not well understood. The five studies presented in my thesis investigated how DPN affects the neuromuscular system in humans, from the motor neuron to skeletal muscle contractile properties, using a combination of electromyography (EMG), dynamometry and magnetic resonance imaging (MRI) techniques. The purpose of Studies 1 and 2 was to determine whether the neurogenic loss of motor units underlies the muscle weakness and atrophy associated with DPN, and to investigate how these changes may differ in an upper and lower limb muscle. I determined DPN patients feature reduced motor unit estimates (MUNEs) compared to controls, and progression of motor unit loss in DPN may follow a length-dependent pattern. The purpose of Study 3 was to assess the stability of neuromuscular transmission in patients with DPN compared with healthy controls, using a novel set of electrodiagnostic parameters obtained via quantitative EMG. I determined DPN patients have less stable neuromuscular transmission, and the feature intermittent conduction failure at a relatively low contraction intensity. The purpose of Study 4 was to investigate skeletal muscle contractile properties and morphology in DPN patients associated with the severity of muscle denervation. I determined DPN patients possess slowed muscle, with greater proportional amounts of non-contractile muscle tissue compared to controls. The purpose of Study 5 was to explore the fatigability of DPN patients during a sustained, maximal voluntary contraction (MVC). I determined DPN patients have less endurance than controls, and their increased fatigability may be associated with neuromuscular transmission failure. Overall these foundational explorations greatly expand our knowledge of how DPN can impact the neuromuscular system in humans. Furthermore, the studies contained within my thesis may help direct further useful studies and strategies to understand, and direct clinical support in those with DPN

Anatomy and development of tendons in vertebrate limbs

The gross and microscopical anatomy of developing tendons in chick limbs is described. Expression patterns of genes encoding EphA4, a tyrosine kinase receptor involved in direct cell-cell signalling, Six-1, a transcription factor, and Follistatin, a TGF-β antagonist, are documented in developing chick tendons. EphA4 expression is compared with tenascin and collagen I expression. Follistatin applied ectopically to chick limbs inhibits tendon development suggesting a role for TGF-β signalling. Manipulations on chick limbs are carried out to examine co-ordination of tendon and cartilage development. Manipulations that invoke ectopic cartilage lead to ectopic tendons expressing both Follistatin and EphA4 while manipulations that invoke cartilage truncation lead to loss of tendons and expression. Ectodermal signalling is known to control dorso-ventral limb pattern including tendons. EphA4 is expressed in both dorsal and ventral tendons but the former are flattened while the latter round. In limbs of transgenic mice in which Wnt-7a, a dorsalising signal produced by dorsal ectoderm, had been functionally inactivated, the EphA4 expression pattern is ventralised early in dorsal tendon development. In chickens in which Lmx-1, a transcription factor expressed in dorsal mesenchyme in response to Wnt-7a signalling, is ectopically expressed ventrally, no early changes in EphA4 expression pattern in ventral tendons could be detected. However, later, established tendons in ventral regions come to resemble dorsal tendon and double nails form. Spatial and temporal expression patterns of Wnt-7a and Lmx-1 were examined and compared with EphA4 expression in tendons. These analyses suggest that dorso-ventral patterning and specification of tendons involves complex series of parallel interactions between tendon-forming cells and both ectoderm and mesenchyme. A polydactylous human foot with double nails is dissected and the toes identified by the tendons. The anatomy is interpreted from a developmental viewpoint

The anatomy of apparatus of motion (bones, joints, muscles). Nerves and vessels of extremities

The educational-methodical manual contains materials for practical training and final control of Human anatomy for Module 1. Drawn up in accordance with the working programs on pharmacology chair, approved SSC SE "Dnepropetrovsk Medical Academy Health Ministry of Ukraine" on the basis of a model program in human anatomy for medical students of III - IV levels of accreditation in the specialties 7.110101 - Medicine, 7.110104 – pediatrics. In the Instructor's Manual, which contains 259 pages, contains a list of topics of practical lessons and topics of the first module to be submitted to an independent study. The manual section reveals the anatomy of the musculoskeletal system, and innervations and blood supply to the extremities. Each theme is built practical lesson plan and outline its imple-mentation. The manual includes block diagrams. At the end of each topic contains the base tests for self-control. Meets all the requirements that relate to the teaching activities of this type is relevant and appropriate to the learning process as one of alternative textbooks in today's diversity of views and approaches to the process of studying anatomy. A team of members of the Department of Human Anatomy State Establish-ment «Dnepropetrovsk Medical Academy of Health Ministry of Ukraine», developed manua

Relationship Between Arch Height and Midfoot Joint Pressures During Gait

A foot arch is a multi-segmented curved structure which acts as a spring during locomotion. It is well known that ligaments are important components contributing to this spring-like property of the arch. In addition, intrinsic and extrinsic foot muscles contribute to arch support. According to the windlass foot model, arch height and midfoot joint orientation change during gait. However, it is not known whether altered joint configurations result in increased joint stress during gait. If so, it is possible for there to be a vicious cycle in which joint stress increases as the arch height diminishes, which may then lead to further increases in joint stresses and eventual bone destruction. The purpose of this study was to examine joint pressure differences of the midfoot in normal and diabetic feet during walking simulation using a robotic system. This study focused on the relative importance of muscles, ligaments and bony structures. Sixteen cadaver foot specimens were used in this study. Joint pressures were measured dynamically during full stance at four medial locations (the first cuneometatarsal, medial cuneonavicular, middle cuneonavicular, and first intercuneiform). Human gait at 25 typical walking speed and 66.7 body weight was simulated with the Universal Musculoskeletal Simulator. It was shown that diabetic cadaver feet had, on average, a 46 higher peak in pressures, than control cadaver feet across all four tested joints. There were inverse correlations between the arch height and the peak joint pressure during the simulated arch collapse. It was proven that the acquired flat foot, caused by the tibialis posterior dysfunction, caused medial peak joint pressure increase by 12 across all tested joints. These results could be used in furthering our understanding of the etiology of diabetic foot diseases. Also, these findings could suggest better treatment for diabetic patients, who are at risk for Charcot foot abnormalitie

Relationship Between Arch Height and Midfoot Joint Pressures During Gait

A foot arch is a multi-segmented curved structure which acts as a spring during locomotion. It is well known that ligaments are important components contributing to this spring-like property of the arch. In addition, intrinsic and extrinsic foot muscles contribute to arch support. According to the windlass foot model, arch height and midfoot joint orientation change during gait. However, it is not known whether altered joint configurations result in increased joint stress during gait. If so, it is possible for there to be a vicious cycle in which joint stress increases as the arch height diminishes, which may then lead to further increases in joint stresses and eventual bone destruction. The purpose of this study was to examine joint pressure differences of the midfoot in normal and diabetic feet during walking simulation using a robotic system. This study focused on the relative importance of muscles, ligaments and bony structures. Sixteen cadaver foot specimens were used in this study. Joint pressures were measured dynamically during full stance at four medial locations (the first cuneometatarsal, medial cuneonavicular, middle cuneonavicular, and first intercuneiform). Human gait at 25 typical walking speed and 66.7 body weight was simulated with the Universal Musculoskeletal Simulator. It was shown that diabetic cadaver feet had, on average, a 46 higher peak in pressures, than control cadaver feet across all four tested joints. There were inverse correlations between the arch height and the peak joint pressure during the simulated arch collapse. It was proven that the acquired flat foot, caused by the tibialis posterior dysfunction, caused medial peak joint pressure increase by 12 across all tested joints. These results could be used in furthering our understanding of the etiology of diabetic foot diseases. Also, these findings could suggest better treatment for diabetic patients, who are at risk for Charcot foot abnormalitie

Effects of a powered ankle prosthesis on shock absorption and residual limb/socket interface pressure

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 83-86).Lower-extremity amputees face potentially serious post-operative complications, including increased risk of further amputations, excessive stress on both limbs, and discomfort at the stump/socket interface. State of the art; passive prostheses have improved many negative consequences associated with lower-limb loss, but we believe the limit of uninformed elastic prostheses has been reached. Further strides require a more biomimetic approach. Through integration of "smart" technology (sensors and actuators), a new phase of bionic lower-limb prostheses is upon us, which enables prosthetic devices to more closely mimic biological behavior by generating human-like responses and power outputs. The closer we come to natural biology, gait abnormalities in amputees will decline. This project compares the first bionic ankle prosthesis to commonly used passive prostheses to determine how more biomimetic adaptability and work generation in the prosthetic joint affects discomfort and joint stress. We have put forth several metrics to describe discomfort (elements of shock absorption, pressure distribution, etc.) and will conduct level-ground walking tests with three unilateral amputee subjects using both passive and power devices. We hope to make a case for the pursuit of more biomimetic designs for rehabilitative devices, by showing a positive effect on "comfort" and a restoration of normal gait dynamics when using a bionic ankle prosthesis.by David Allen Hill.S.M