Computer Aided Engineering in the Foot Orthosis Development Process

An orthosis, or orthotic device is used to straighten or correct the posture of part of the body. A foot orthosis (FO) is the subject of study for this dissertation. A FO is situated between the foot and the midsole of the shoe and replaces the insole. Foot orthoses (FOs) are intended to prevent or aid in the recovery of injury by acting to redistribute pressure experienced by the plantar surface of the foot as well as cause adjustments to the relative positions of the foot's bones during standing and gait. Traditional methods for developing a FO require extensive skilled manual labour and are highly dependent on subjective input. Modern FO development methods have sought to address these issues through the use of computer driven technological advancements. Foot scanners record geometry, computer aided design (CAD) software is used to develop the FO geometry, and automated manufacturing tools are used to either fabricate the FO or fabricate a mould about which the FO can be formed. A variety of modern solutions have successfully automated the process, however, it remains highly subjective. Skilled manual labour has merely been replaced with equally subjective skilled computer labour. In particular, adjustments to the foot are made with basic deformation functions to the static surface foot models generated by modern digitizers. To improve upon this, a model that describes the mechanics and properties of the various tissues of the foot is required. Such a model will also be useful for validating and optimizing FO designs prior to fabrication through simulation of weight-bearing conditions. Given the deformable characteristics of the tissues of the foot, the finite element (FE) modeling method is appropriate. The FE foot model has become a common medical and engineering tool in recent years. Its application, however, has primarily been limited to research as few clinical applications warrant the development cost. High cost stems from the MRI or CT scan and the skilled labour required to assemble the model for FE analysis. Consequently, the FE modeling approach has previously been out of reach for the application of FO development. The solution proposed and implemented was to map a detailed generic FE foot model to an inexpensive surface scan obtained from a modern digitizer. The mapping accurately predicted anatomical geometry and resulted in simulation models that can be used in the FO development process first to carry out postural adjustments prescribed by a practitioner and second in a validation step where a FO design can be tested prior to fabrication. In addition to simulation tools, novel complementary tools were developed for designing and fabricating FOs. The simulation, design, and fabrication tools were incorporated into a novel, seven step FO development process. The proposed process is beneficial to FO development as it reduces the required subjective input from practitioners and lab technicians and allows for the validation of potential FO designs prior to fabrication. Future work is required to improve computational efficiency of the FE foot models and to fully automate the process to make it commercially viable. In addition to FOs, the proposed approach also presents opportunities for improving other orthoses and prostheses for the human body.1 yea

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

NASA Tech Briefs, December 1991

Topics include: Electronic Components and Circuits. Electronic Systems, Physical Sciences, Materials, Computer Programs, Mechanics, Machinery, Fabrication Technology, Mathematics and Information Sciences

Hand X-ray absorptiometry for measurement of bone mineral density on a slot-scanning X-ray imaging system

Includes bibliographical references.Bone mineral density (BMD) is an indicator of bone strength. While femoral and spinal BMDs are traditionally used in the management of osteoporosis, BMD at peripheral sites such as the hand has been shown to be useful in evaluating fracture risk for axial sites. These peripheral locations have been suggested as alternatives to the traditional sites for BMD measurement. Dual-energy X-ray absorptiometry (DXA) is the gold standard for measuring BMD due to low radiation dose, high accuracy and proven ability to evaluate fracture risk. Computed digital absorptiometry (CDA) has also been shown to be very effective at measuring the bone mass in hand bones using an aluminium step wedge as a calibration reference. In this project, the aim was to develop algorithm s for accurate measurement of BMD in hand bones on a slot - scanning digital radiography system. The project assess e d the feasibility of measuring bone mineral mass in hand bones using CDA on the current system. Images for CDA - based measurement were acquired using the default settings on the system for a medium sized patient. A method for automatic processing of the hand images to detect the aluminium step wedge, included in the scan for calibration, was developed and the calibration accuracy of the step wedge was evaluated. The CDA method was used for computation of bone mass with units of equivalent aluminium thickness (mmA1). The precision of the method was determined by taking three measurements in each of 1 6 volunteering subjects and computing the root - mean - square coefficient of variation (CV) of the measurements. The utility of the method was assessed by taking measurements of excised bones and assessing the correlation between the measured bone mass and ash weight obtained by incinerating the bones. The project also assessed the feasibility of implementing a DXA technique using two detectors in a slot-scanning digital radiography system to acquire dual-energy X-ray images for measuring areal and volumetric BMD of the middle phalanx of the middle finger. The dual-energy images were captured in two consecutive scans. The first scan captured the low- energy image using the detector in its normal set-up. The second scan captured the high- energy image with the detector modified to include an additional scintillator to simulate the presence of a second detector that would capture the low-energy image in a two-detector system. Scan parameters for acquisition of the dual-energy images were chosen to optimise spectral separation, entrance dose and image quality. Simulations were carried out to evaluate the spectral separation of the low- and high-energy spectra

Proceedings of the Second International Workshop on Mathematical Foundations of Computational Anatomy (MFCA'08) - Geometrical and Statistical Methods for Modelling Biological Shape Variability

International audienceThe goal of computational anatomy is to analyze and to statistically model the anatomy of organs in different subjects. Computational anatomic methods are generally based on the extraction of anatomical features or manifolds which are then statistically analyzed, often through a non-linear registration. There are nowadays a growing number of methods that can faithfully deal with the underlying biomechanical behavior of intra-subject deformations. However, it is more difficult to relate the anatomies of different subjects. In the absence of any justified physical model, diffeomorphisms provide a general mathematical framework that enforce topological consistency. Working with such infinite dimensional space raises some deep computational and mathematical problems, in particular for doing statistics. Likewise, modeling the variability of surfaces leads to rely on shape spaces that are much more complex than for curves. To cope with these, different methodological and computational frameworks have been proposed (e.g. smooth left-invariant metrics, focus on well-behaved subspaces of diffeomorphisms, modeling surfaces using courants, etc.) The goal of the Mathematical Foundations of Computational Anatomy (MFCA) workshop is to foster the interactions between the mathematical community around shapes and the MICCAI community around computational anatomy applications. It targets more particularly researchers investigating the combination of statistical and geometrical aspects in the modeling of the variability of biological shapes. The workshop aims at being a forum for the exchange of the theoretical ideas and a source of inspiration for new methodological developments in computational anatomy. A special emphasis is put on theoretical developments, applications and results being welcomed as illustrations. Following the very successful first edition of this workshop in 2006 (see http://www.inria.fr/sophia/asclepios/events/MFCA06/), the second edition was held in New-York on September 6, in conjunction with MICCAI 2008. Contributions were solicited in Riemannian and group theoretical methods, Geometric measurements of the anatomy, Advanced statistics on deformations and shapes, Metrics for computational anatomy, Statistics of surfaces. 34 submissions were received, among which 9 were accepted to MICCAI and had to be withdrawn from the workshop. Each of the remaining 25 paper was reviewed by three members of the program committee. To guaranty a high level program, 16 papers only were selected

Soft Biomimetic Finger with Tactile Sensing and Sensory Feedback Capabilities

The compliant nature of soft fingers allows for safe and dexterous manipulation of objects by humans in an unstructured environment. A soft prosthetic finger design with tactile sensing capabilities for texture discrimination and subsequent sensory stimulation has the potential to create a more natural experience for an amputee. In this work, a pneumatically actuated soft biomimetic finger is integrated with a textile neuromorphic tactile sensor array for a texture discrimination task. The tactile sensor outputs were converted into neuromorphic spike trains, which emulate the firing pattern of biological mechanoreceptors. Spike-based features from each taxel compressed the information and were then used as inputs for the support vector machine (SVM) classifier to differentiate the textures. Our soft biomimetic finger with neuromorphic encoding was able to achieve an average overall classification accuracy of 99.57% over sixteen independent parameters when tested on thirteen standardized textured surfaces. The sixteen parameters were the combination of four angles of flexion of the soft finger and four speeds of palpation. To aid in the perception of more natural objects and their manipulation, subjects were provided with transcutaneous electrical nerve stimulation (TENS) to convey a subset of four textures with varied textural information. Three able-bodied subjects successfully distinguished two or three textures with the applied stimuli. This work paves the way for a more human-like prosthesis through a soft biomimetic finger with texture discrimination capabilities using neuromorphic techniques that provides sensory feedback; furthermore, texture feedback has the potential to enhance the user experience when interacting with their surroundings. Additionally, this work showed that an inexpensive, soft biomimetic finger combined with a flexible tactile sensor array can potentially help users perceive their environment better