What has finite element analysis taught us about diabetic foot disease and its management?:a systematic review

Over the past two decades finite element (FE) analysis has become a popular tool for researchers seeking to simulate the biomechanics of the healthy and diabetic foot. The primary aims of these simulations have been to improve our understanding of the foot's complicated mechanical loading in health and disease and to inform interventions designed to prevent plantar ulceration, a major complication of diabetes. This article provides a systematic review and summary of the findings from FE analysis-based computational simulations of the diabetic foot.A systematic literature search was carried out and 31 relevant articles were identified covering three primary themes: methodological aspects relevant to modelling the diabetic foot; investigations of the pathomechanics of the diabetic foot; and simulation-based design of interventions to reduce ulceration risk.Methodological studies illustrated appropriate use of FE analysis for simulation of foot mechanics, incorporating nonlinear tissue mechanics, contact and rigid body movements. FE studies of pathomechanics have provided estimates of internal soft tissue stresses, and suggest that such stresses may often be considerably larger than those measured at the plantar surface and are proportionally greater in the diabetic foot compared to controls. FE analysis allowed evaluation of insole performance and development of new insole designs, footwear and corrective surgery to effectively provide intervention strategies. The technique also presents the opportunity to simulate the effect of changes associated with the diabetic foot on non-mechanical factors such as blood supply to local tissues.While significant advancement in diabetic foot research has been made possible by the use of FE analysis, translational utility of this powerful tool for routine clinical care at the patient level requires adoption of cost-effective (both in terms of labour and computation) and reliable approaches with clear clinical validity for decision making

FINITE ELEMENT ANALYZE OF THE FIRST METATARSAL VERTICAL ARCH OF THE FOOT IN THE HIGH-HEELED GAIT

A two-dimensional numerical model of the foot, incorporating, for the first time in the literature, realistic geometric and material properties of both skeletal and soft tissue components of the foot, was developed for biomechanical analysis of its structural behavior during gait. Using a Finite Element solver, the stress distribution within the first metatarsal vertical: arch of the foot (FMVA) structure was obtained and regions of elevated stresses for three subphases of the stance (heel-strike, push-off, and toe-off) were located. Validation of the pressure state was achieved by comparing model predictions of contact pressure distribution with Novel Pedar. The presently developed measurement and numerical analysis tools open new approaches for clinical applications, from simulation of the development mechanisms of common foot disorders to pre-and post-interventional evaluation of their treatment

Finite element modelling of the foot for clinical application: A systematic review

Over the last two decades finite element modelling has been widely used to give new insight on foot and footwear biomechanics. However its actual contribution for the improvement of the therapeutic outcome of different pathological conditions of the foot, such as the diabetic foot, remains relatively limited. This is mainly because finite element modelling is only been used within the research domain. Clinically applicable finite element modelling can open the way for novel diagnostic techniques and novel methods for treatment planning/optimisation which would significantly enhance clinical practice. In this context this review aims to provide an overview of modelling techniques in the field of foot and footwear biomechanics and to investigate their applicability in a clinical setting. Even though no integrated modelling system exists that could be directly used in the clinic and considerable progress is still required, current literature includes a comprehensive toolbox for future work towards clinically applicable finite element modelling. The key challenges include collecting the information that is needed for geometry design, the assignment of material properties and loading on a patient-specific basis and in a cost-effective and non-invasive way. The ultimate challenge for the implementation of any computational system into clinical practice is to ensure that it can produce reliable results for any person that belongs in the population for which it was developed. Consequently this highlights the need for thorough and extensive validation of each individual step of the modelling process as well as for the overall validation of the final integrated system

The Effect of Soft Tissue and Bone Morphology on the Stresses in the Foot and Ankle

The foot and ankle interface with the ground, thus they absorb reaction forces and initiate load distribution through the body. The plantar fascia (PF) is a flexible structure that absorbs reaction forces and distributes loading across the foot. It is frequently a source of foot pain especially when people have plantar fasciitis and/or diabetes mellitus. Finite element (FE) models of the foot and ankle were created to examine the function however, the plantar fascia is frequently modeled as a 1D tension only spring, which does not represent variations caused by injury and/or disease. As models move toward being patient specific, understanding what components of a model can be generic versus what should be patient specific is critical when minimizing the time to create and simulate results. The purpose of this dissertation was to develop 3D finite element foot and ankle models including different thickness of 3D solid plantar fascia (i.e., 3mm, 4mm, and 5mm) and different ankle positions (i.e., neutral position, 10° dorsiflexion, and 10° plantarflexion). Additionally, the effect of different thicknesses of cartilage (i.e., 0.5mm, 1.0mm, and 1.7mm) and bone morphology (health and injured) was investigated in a model of the talocrural joint. As the thickness of plantar fascia increased, the strains of plantar fascia were increased, and the peak plantar pressure moved from hindfoot to forefoot. Also, the peak plantar pressures were highest when the foot was in 10° of plantarflexion and lowest in the neutral position. Finally, contact area decreased with decreasing cartilage thickness, with a greater decrease in contact area in healthy ankles. In 3 models, contact stress increased as cartilage thickness decreased. The fourth model had little decrease in contact area, thus the contact pressures may have been affected more by bone morphology. In conclusion, in models of the foot and ankle, the plantar fascia can be generic if it is less than 4 mm thick, a variety of foot positions should be considered, and specific bone morphologies should be included in the ankle if there is a known pathology

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

COMBINING MUSCULOSKELETAL MODELING AND FEM IN DIABETIC FOOT PREVENTION

Recently the development of Patient-specific models (PSMs) tailored to patient-specific data, has gained more and more attention in clinical applications. PSMs could represent a solution to the growing awareness of personalized medicine which allow the realization of more effective rehabilitation treatments designed on the subject capabilities. PSMs have the potential of improving diagnosis and optimizing clinical treatments by predicting and comparing the outcomes of different approaches of intervention. Furthermore they can provide information that cannot be directly measured, such as muscle forces or internal stresses and strains of the bones. Given the considerable amount of diseases affecting motor ability, PSMs of the lower limbs have been broadly addressed in literature. Two techniques are mostly used in this area: musculoskeletal (MS) modeling and finite element (FE) analysis. (MS) models represent a valuable tool, as they can provide important information about the unique anatomical and functional characteristics of different subjects, through the computation of human internal variables, such as muscle activations and forces and joint contact forces. The flexibility and adaptability of FE analysis makes it a perfect solution to model biological geometries and materials and to simulate complicated boundary and loading conditions. Accurate and descriptive FE models would serve as an excellent tool for scientific and medical research. Furthermore they could be used in clinical settings if combined with medical imaging, in order to improve patient care. Several 3-dimensional (3D) foot FE models were recently developed to analyze the biomechanical behavior of the human foot and ankle complex that is commonly studied with experimental techniques like stereophotogrammetry, force and plantar pressure plates. In this context, many gait analysis protocols have been proposed to assess the 3D kinetics, kinematics and plantar pressure distribution. This evaluation has shown to be useful in characterizing the foot biomechanics in different pathologies like the diabetic foot. Diabetic foot is an invalidating complication of diabetes mellitus, a chronic disease frequently encountered in the aging population. It is characterize by the development of ulcers which can lead to amputation. Models for simulations of deformations and stresses in the diabetic plantar pad are required to predict high risk areas on the plantar surface and can be used to investigate the performance of different insoles design for optimal pressure relief. This work represents a first effort towards the definition of a more complete PSM which combining both a MS model and a FE model, can increase the understanding of the diabetic foot pathology. To achieve this objective, several limitations and issues have been addressed. As first, MS models of diabetic and control subjects were developed using OpenSim, to estimate muscle forces. The objective was to evaluate whether the diabetic population exhibit lower limb muscle strength deficits compared to the healthy one. Subjects routine gait analysis was performed and lower limb joints kinematics, kinetics, time and space parameters estimated by means of a modified version of the IORgait protocol. 3D lower limb joints kinematics and kinetics was also calculated with OpenSim. Both methodologies were able to highlight differences in joint kinematics and kinetics between the two populations. Furthermore MS models showed significant differences in healthy muscle forces with respect to the diabetic ones, in some of the muscles. This knowledge can help the planning of specific training in order to improve gait speed, balance, muscle strength and joint mobility. After the use of MS models proved to be applicable in the diabetic population, the next step was to combine them with foot FE models. This was done in two phases. At first the impact of applying the foot joints contact forces (JCFs) obtained from MS models as boundary condition on the foot FE models was verified. Subject specific geometries from MRI were used for the development of the foot FE models while the experimental plantar pressures acquired during gait were used in the validation process. A better agreement was found between experimentally measured and simulated plantar pressure obtained with JCFs than with the experimentally measured ground reaction forces as boundary conditions. Afterwards the use of muscles forces as boundary condition in the FE simulations was evaluated. Subject-specific integrated and synchronized kinematic-kinetic data acquired during gait analysis were used for the development of the MS models and for the computation of the muscle forces. Muscle insertions were then located in the MRI and correspondent connectors were created in the FE model. FE subject-specific simulations were subsequently run with Abaqus by conducting a quasi-static analysis on 4 gait cycle phases and adopting 2 conditions: one including the muscle forces and one without. Once again the validation of the FE simulations was done by means of a comparison between simulated and experimentally measured plantar pressures. Results showed a marked improvement in the estimation of the peak pressure for the model that included the muscles. Finally, an attempt towards the definition of a parametric foot finite element model was done. In fact, despite the recent developments, patient-specific models are not yet successfully applied in a clinical setting. One of the challenges is the time required for mesh creation, which is difficult to automate. The development of parametric models by means of the Principle Component Analysis (PCA) can represent an appealing solution. In this study PCA was applied to the feet of a small cohort of diabetic and healthy subjects in order to evaluate the possibility of developing parametric foot models and to use them to identify variations and similarities between the two populations. The limitations of the use of models have also been analyzed. Their adoption is indeed limited by the lack of verification and validation standards. Even using subjects’ MRI or CT data for the development of FEM together with experimentally acquired motion analysis data for the boundary and loading conditions, the subject specifity is still not reached for what regards all the material properties. Furthermore it should be considered that everything relies on algorithm and models that would never be perfectly representing the reality. Overall, the work presented in this thesis represents an extended evaluation of the possible uses of modeling techniques in the diabetic foot prevention, by considering all the limitations introduced as well as the potential benefits of their use in a clinical context. The research is organized in six chapters: Chapter 1 - provides a background on the modeling techniques, both FE modeling and MS modeling. Furthermore it also describes the gait analysis, its instrumentation and some of the protocols used in the evaluation of the biomechanics of the lower limbs; Chapter 2 - gives a detailed overview of the biomechanics of the foot. It particularly focuses on the diabetes and the diabetic foot; Chapter 3 - introduces the application of MSs for the diabetic foot prevention after a brief background on the techniques usually chosen for the evaluation of the motor impairments caused by the disease. Aim, material and methods, results and discussion are presented. The complete work flow is described, and the chapter ends with a discussion on new key findings and limitations. Chapter 4 – reports the work done to combine the use of musculoskeletal models with foot FEMs. At first the impact of applying the foot joints contact forces obtained from MS models as boundary condition on the foot FEMs is verified. Then the use of muscles forces (again obtained from MS models) as boundary condition in the FE simulations is evaluated. For both studies a brief background is presented together with the methods applied, the results obtained and a discussion of novelties and drawbacks. Chapter 5 – explores the possibility of defining a parametric foot FEM applying the Principle Component Analysis (PCA) on the feet of a small cohort of diabetic and healthy subjects. A background on the importance of patient specific models is presented followed by material and methods, results and discussion of what obtained with this study. Chapter 6 - summarizes the results and the novelty of the thesis, delineating the conclusions and the future research paths

Spatio-temporal alignment of pedobarographic image sequences

O documento em anexo encontra-se na versão post-print (versão corrigida pelo editor).This paper presents a methodology to align plantar pressure image sequences simultaneously in time and space. The spatial position and orientation of a foot in a sequence are changed to match the foot represented in a second sequence. Simultaneously with the spatial alignment, the temporal scale of the first sequence is transformed with the aim of synchronizing the two input footsteps. Consequently, the spatial correspondence of the foot regions along the sequences as well as the temporal synchronizing is automatically attained, making the study easier and more straightforward. In terms of spatial alignment, the methodology can use one of four possible geometric transformation models: rigid, similarity, affine or projective. In the temporal alignment, a polynomial transformation up to the 4th degree can be adopted in order to model linear and curved time behaviors. Suitable geometric and temporal transformations are found by minimizing the mean squared error (MSE) between the input sequences. The methodology was tested on a set of real image sequences acquired from a common pedobarographic device. When used in experimental cases generated by applying geometric and temporal control transformations, the methodology revealed high accuracy. Additionally, the intra-subject alignment tests from real plantar pressure image sequences showed that the curved temporal models produced better MSE results (p<0.001) than the linear temporal model. This paper represents an important step forward in the alignment of pedobarographic image data, since previous methods can only be applied on static images

Can plantar pressure predict foot motion?

In zijn voortbewegen onderscheidt de mens zich van andere zoogdieren door het gebruik van slechts twee benen. De meest voorkomende vormen van voortbewegen van de mens zijn wandelen, lopen, en sprinten. Het menselijk voortbewegingssyteem is onderhevig aan blessures en afwijkingen die het patroon verstoren van zijn natuurlijke vorm naar een onnatuurlijk, pijnlijk of ine±cient patroon. Hierdoor belemmeren ze de mens in zijn voortbewegen en functioneren. Een verstoring van het voortbewegingssysteem heeft een grote invloed op het indi- vidu, in het bijzonder het beperken van zijn mobiliteit, als mede op de maatschappij, in de vorm van ziektekosten en vermindering van arbeidsproductiviteit. Het moge duidelijk zijn dat er een uitgebreide medische en wetenschappelijke gemeenschap ac- tief is op het gebied van de ganganalyse. Eerst genoemde is het aanspreekpunt voor individuen met letsels of afwijkingen en poogt met een behandelingsplan de verstorin- gen van het systeem op te lossen. Laatst genoemde gemeenschap poogt een beter zicht te krijgen op de gang van de mens door het uitvoeren van onderzoek en exper- imenten. De opgedane kennis wordt op zijn beurt terug gekoppeld naar de medische gemeenschap. Bij het menselijk voortbewegen is de voet de verbinding tussen de omgeving en de zich voortbewegende mens. De voet bestaat uit tenminste 26 botjes en uit een veelvoud aan ligamenten, pezen en spieren. Samen vormen ze ¶e¶en functionele struc- tuur die een aantal functies vervult tijdens de voortbeweging. Bij ¶e¶en voetafwikkeling onderscheiden we vier fases: hielcontact, voorvoet vorming, stand, en propulsie. Tij- dens de eerste fase maakt de voet het eerste contact met de grond en absorbeert het zachte weefsel rond de hiel een deel van de schokgolf die door het contact ontstaat. Deze absorptie is vereist omdat hoger gelegen organen, zoals bijvoorbeeld de hersenen, slecht bestand zijn tegen schokgolven. Tijdens de voetafwikkeling is de kinematica van de voet gericht op een e±cient gebruik van de beweging van de rest van het lichaam. De voet gedraagt zich als een stabiele basis tijdens het middelste gedeelte van voet- grond contact, stand. In de propulsie fase verandert de taak van de voet van een stabiliserend systeem naar een voortstuwingssyteem. Het onderzoek naar het mechanisch gedrag van de voet is een belangrijk onderdeel van de ganganalyse, dat echter pas de laatste decennia de voet als een drie-dimensional segment is gaan beschouwen. Daarv¶o¶or bestond de meetapparatuur die kwantitatieve metingen mogelijk maakte niet. In het onderzoek dat geleid heeft tot dit proefschrift is gebruik gemaakt van een meetopstelling waarin drie typen metingen zijn uitgevoerd: plantaire drukverdelingen, krachten en drie-dimensionale bewegingen van de voet. De doelstelling van het onderzoek is het ontwerpen van een mechanische voetmodel dat de voetbeweging simuleert. Input van het model is data van plantaire drukmetingen uitgevoerd met een drukplaat. Het ontwerp richt zich vooral op de structuren van de voet die het meest bijdragen aan de beweging tijdens voet-grond contact, zoals het hielcomplex, de metatarsale hoofden, en de grote teen. Het onderzoek is gebaseerd op een breed opgezet experiment waaraan 126 in- dividuen hun medewerking hebben verleend. In dit experiment uitgevoerd in het biomechanisch laboratorium van de Vrije Universiteit Brussel is gebruik gemaakt van een bewegingsanalysesysteem, een krachten platform en een drukplaat. Deze meetap- paraten zijn op elkaar afgestemd zowel in tijd als ruimte. Voor zover bekent, is er in het verleden slechts ¶e¶en experiment uitgevoerd en gerapporteerd waarin deze meetap- paraten op elkaar werden afgestemd. Validatie van tijd- en ruimteafstemming komen in ons onderzoek ruim aan bod. Er werd aangetoond dat de afstemming binnen de meetnauwkeurigheid valt van het minst nauwkeurige apparaat. Het bewegingsanalysesysteem heeft 3D-posities bepaald van markers die bevestigd werden op de voet. In totaal is gebruik gemaakt van 12 markers per voet: 4 op de hiel, 3 op de grote teen, en 5 op de metatarsalen. Door deze marker set-up ontstaat een vier segmenten voetmodel. Het krachten platform en de drukplaat leggen grootte en plaats van de drukverdeling tijdens voetafrol vast. Onze populatie van 126 individuen bestond uit 78 mannen en 48 vrouwen met een leeftijdsvariatie van 10jaar tot 72jaar en een gewichtsvariatie van 32kg tot 116.5kg. De leeftijdsgroep tussen 15 en 25 jaar domineerde de populatie. Een belangrijk re- sultaat van het onderzoek is de database waarin de resultaten van de metingen op een gestructureerde wijze zijn weergegeven. Deze database wordt samen met het proefschrift beschikbaar gesteld. Achtereenvolgens is deze database geanalyseerd met betrekking tot de hielbeweging tijdens hielcontact, de bewegingen van de metatarsale hoofden, en de bewegingen in het eerste metatarsofalangaal gewricht. De hiel voert aan het begin van contact tussen voet en grond een rolbeweging uit die stopt ergens tijdens volledig voet contact. Het hielcomplex werd gemodelleerd als een star lichaam met een convexe vorm. De gemeten plantaire drukverdeling onder de hiel beschrijft in het model het contact tussen het rollende stare lichaam en de grond. De rollende beweging van het starre lichaam wordt eenduidig vastgelegd door de hoeksnelheid van het starre lichaam en het contactpad. Voor validatie werd als star lichaam een bol gebruikt. Een bol met een vaste straal van 7cm leidde tot acceptabele resultaten, waarbij het model 75% van de gemeten hielbewegingen verklaart tijdens de initiÄele contact fase. Voor de metatarsale hoofden blijkt beweging in zijwaartse en voor-achterwaartse richting te bestaan. Deze bewegingen zijn klein met betrekking tot de totale voetbe- wegingen. De gebruikte drukplaat kan deze bewegingen van de metatarsale hoofden niet waarnemen omdat de grote van de bewegingen binnen de sensor grootte liggen. In het model is dus aangenomen dat de grootte van de beweging van de metatarsale hoofden verwaarloosbaar is tijdens het grootste deel van contact. Met behulp van de plantaire drukverdeling kan een kromme bepaald worden, de metatarsale boog, waarop de hoofden zich blijvend bevinden. Validatie van de bepaling van de metatarsale boog op basis van drukverdelingen vond plaats met behulp van dezelfde boog maar bepaald op grond van het bewegingsanalysesysteem. Het voorvoetmodel maakt dus gebruik van het concept metatarsale boog. De bewegingsbepalende component van dit model is een gekromde cilinder waarbij de contactkromme met de grond gelijk is aan de metatarsale boog. Rollen rond deze cilinder beschrijft de propulsie fase van voet- contact. Deze beweging kan echter niet rechtstreeks uit de drukverdeling onder de metatarsale hoofden worden afgeleid. Het proefschrift beschrijft enige suggesties hoe deze rolbeweging indirect uit deze drukverdeling zou kunnen worden afgeleid. Een suggestie is deze beweging te bepalen van uit de beweging van het eerste metatarsofalangaal gewricht. In het onderzoek is de relatie tussen 92 druk gerela- teerde variabelen en 30 variabelen van de beweging van het eerste metatarsofalangaal gewricht nagegaan. Met correlaties en regressievergelijkingen is aangetoond dat de °exie/extensie beweging in het gewricht druk gerelateerd is. Het onderzoek dat we met dit proefschrift afsluiten concentreert zich op de vraag of met plantaire drukverdeling het bewegingsverloop van de voet kan worden voorspeld. We menen een bevestigend antwoord te hebben gevonden op de vraag die als titel van dit proefschrift fungeert

Biomechanical analysis of the diabetic foot: an integrated approach using movement analysis and finite element simulation

Objective:High plantar pressures have been associated with foot ulceration in patients with diabetes. Treatment usually includes an in-shoe intervention designed to reduce plantar pressure under the heel by using insoles. Finite element (FE) analysis provides an efficient computational framework to investigate the performance of different insoles for optimal pressure reduction [Goeske et al. 2005]. The aim of this study is to design a patient specific, 2-dimensional (2D) FE model of diabetic hindfoot and to apply on it patient-specific forces.Method: A 2D FE model of the hindfoot was developed from reconstruction of magnetic resonance images (Simpleware ScanIP-ScanFE, v.5.0 and Rhinoceros v.4.0). FE software ABAQUS was used to perform the numerical stress analyses. A diabetic subject (age, 72 years, BMI, 25.1 kg/m2) and a healthy subject (age 28 years, BMI 20.2 kg/m2) were acquired. The foot biomechanics analysis was carried out as in [Sawacha et al. 2012]. Vertical ground reaction forces (Bertec), taken from the various phases of the gait, were applied to the FE model. Validation of the pressure state was achieved by comparing model predictions of contact pressure distribution with experimental plantar pressure measures Result: A nonlinear 2D FE hindfoot model was developed and meshed with quadratic elements. The measured and model predicted peak plantar pressures of the diabetic subject was respectively 682.32 KPa and 602.82 KPa. The values for the healthy subject were 483.63 KPa for the measured peak plantar pressure and 428.63 KPa for the simulated one. The model predicted structural response of the heel pad was in agreement with experimental results unless 10% of error. Conclusion: The proposed model will be useful to simulate the different insole material and their contribution in decreasing the plantar pressure

Foot Behavior during Walking based on Foot Kinetics and Kinematics

Ph.DDOCTOR OF PHILOSOPH