27,450 research outputs found

    Dynamic biomechanical modelling for foot ulcer prevention.

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    International audienceThis paper introduces a 3D Dynamic Finite Element biomechanical model of the human foot used for diabetic foot pressure ulcer prevention. The model estimates the internal strains and send an alert to the user in case of high strains values

    Comparison of lower body segment alignment of elite level hockey players to age-matched non-hockey players

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    Master's Project (M.A.) University of Alaska Fairbanks, 2015Lower body overuse and insidious onset injuries are thought to have an underlying biomechanical component which may be predisposing to injury. The purpose of this study was to compare lower body biomechanical characteristics for elite hockey players to matched controls. I hypothesize that elite hockey players have a greater degree of anterior pelvic tilt, greater varus knee angle, a higher foot arch and feet held in parallel more during gait than a matched non-skating population. Measures were taken of elite level, college aged, male hockey players and compared to cross country runners (ten subjects in each group) who served as controls for trunk angle, pelvic tilt angle, knee alignment, (varus/valgus angle), foot angle, arch index (arch height), hip, center of range of motion, hip external rotation, hip internal rotation, hip total range of motion (ROM), knee transverse plane ROM, and step width. The results obtained support the hypothesis for anterior pelvic tilt and foot angle during gait. Although knee angle was in the expected varus direction it was not significant and no differences were observed in the foot arch between the groups. All other measurements not directly related to the hypothesis were not significantly different with the exception of mean step width. The obtained results are important as recent literature describes a lower body posture of medial collapse into "dynamic valgus" as being predisposing to injury. Results show, on the spectrum from lower body varus to lower body valgus, hockey players are on the varus side of the spectrum in all attributes except arch height, which was similar in both populations. Since lower body alignment is thought to be coupled, this inconsistency appears contrary to the "medial collapse into dynamic valgus" model and may explain why foot orthotics and athletic shoes used as an injury intervention often fail

    Running Form Analysis Based on Impact Dynamics: A Minimally Complex Mechanical Model

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    Biomechanical models of different complexity are used to understand the dynamics of human running. Low degrees-of-freedom models are appropriate for the prediction of the effect of certain parameter changes. We present a minimally complex biomechanical model which characterizes the effects of foot strike pattern and shank angle on the ground-foot impact intensity, which influences the risk of injuries and energy efficiency.A three segment leg model (thigh, shank and foot) is proposed combined with the mass of the rest of the body parts concentrated in the hip. The ground-foot impact intensity and the absorbed kinetic energy are analyzed using multibody dynamics tools. The impact intensity was discovered in the parameter space of the angle of the thigh, the angle of the shank, the foot strike pattern and the running speed.The results regarding the effect of strike pattern are in coincidence with the literature: forefoot strike implies lower impact intensity and energy absorption than rearfoot strike. However, in contrast of the previous result of a two segment foot model from the related literature, the calculations indicated that the shank angle highly affects the impact intensity: the impact intensity can be reduced by foot touchdown under the hip. We showed that foot and shank cannot be analyzed in itself without considering the thigh and the total body weight, and we also confirmed that the horizontal velocity cannot be neglected when foot impact is analyzed

    3D musculo-skeletal finite element analysis of the foot kinematics under muscle activation with and without ankle arthrodesis

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    International audienceThe choice between arthrodesis and arthroplasty in the context of advanced ankle arthrosis remains a highly disputed topic in the field of foot and ankle surgery. Arthrodesis, however, represents the most popular option. Biomechanical modeling has been widely used to investigate static loading of cadaveric feet as well as consequences of arthrodesis on bony structures. Although foot kinematics has been studied using motion analysis, this approach lacks accuracy in capturing internal joints motion due to limitations inherent to external “marker sets” and the fact that it imposed the foot to be considered as a rigid solid. The consequences of arthrodesis on kinematics of the unloaded foot are not well understood although it is of crucial importance during the swing phase and at heel contact. Investigating ankle mobility during muscle contraction with and without arthrosis could explain how the motion is produced by extrinsic muscles activations affected by an arthrodesis. This study aims at defining if a biomechanical model with Finite Elements could help arthrodesis understanding

    A foot-ground contact model for human motion analysis

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    Over the last decades, there has been a growing interest in the area of contact-impact modeling and analysis in the context of multibody system dynamics. However, it remains a difficult task to accurately model the contact mechanics when the geometric and material properties are of complex natures, such as in the case of the human foot-ground interaction. Bearing that in mind, the foot is the main source of interaction with the surrounding environment for most people, since it is the only part of the human body that is in contact with the ground and, therefore, contact models that describe the human foot-ground interaction are of extreme importance for biomechanical analysis. Thus, to accurately replicate the human motion during the analysis of biomechanical multibody systems, the computational models must consider realistic representations of the foot and appropriate numerical descriptions of its interaction with the ground surface. In this sense, the main purpose of this work is to present a two-dimensional biomechanical multibody model to describe the foot-ground contact. The interaction between the foot and the ground is geometrically defined by circles positioned at specific locations on the foot plantar surface, and a plane, describing the ground. The contact is detected based on the relative interpenetration of the surfaces, and appropriate constitutive laws associated with the normal and tangential forces developed during the contact are applied. With the purpose of correctly determining the contact forces, an optimization process is implemented to obtain the most suitable values for the geometric and contact parameters of the proposed model. Finally, the results obtained from computational and experimental analysis are compared using a multibody model of the right side of human body, with the aim of validating the proposed approach.This work has been supported by Portuguese Foundation for Science and Technology, under the national support to R&D units grant, with the reference project UIDB/04436/2020 and UIDP/04436/2020, as well as through IDMEC, under LAETA, project UIDB/50022/2020. The second author expresses her gratitude to the Portuguese Foundation for Science and Technology through the PhD grant (2021.04840.BD)

    Challenging the foundations of the clinical model of foot function : further evidence that the Root model assessments fail to appropriately classify foot function

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    Background The Root model of normal and abnormal foot function remains the basis for clinical foot orthotic practice globally. Our aim was to investigate the relationship between foot deformities and kinematic compensations that are the foundations of the model. Methods A convenience sample of 140 were screened and 100 symptom free participants aged 18-45 years were invited to participate. The static biomechanical assessment described by the Root model was used to identify five foot deformities. A 6 segment foot model was used to measure foot kinematics during gait. Statistical tests compared foot kinematics between feet with and without foot deformities and correlated the degree of deformity with any compensatory motions. Results None of the deformities proposed by the Root model were associated with distinct differences in foot kinematics during gait when compared to those without deformities or each other. Static and dynamic parameters were not correlated. Conclusions Taken as part of a wider body of evidence, the results of this study have profound implications for clinical foot health practice. We believe that the assessment protocol advocated by the Root model is no longer a suitable basis for professional practice. We recommend that clinicians stop using sub-talar neutral position during clinical assessments and stop assessing the non-weight bearing range of ankle dorsiflexion, first ray position and forefoot alignments and movement as a means of defining the associated foot deformities. The results question the relevance of the Root assessments in the prescription of foot orthoses

    Clinical foot measurements as a proxy for plantar pressure testing in people with diabetes

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    Background: High plantar pressures are associated with increased foot ulcer risk in people with diabetes. Identification of high plantar pressures in people with diabetes is clinically challenging due to time and cost constraints of plantar pressure testing. Factors affecting foot biomechanics, including reduced joint range of motion and foot deformity, are implicated in the development of high plantar pressures and may provide a method to clinically identify those at risk of pressure related complications. The aim of this study was to investigate the contribution of joint range of motion and foot deformity measures on plantar pressures in a community dwelling group with diabetes. Methods: Barefoot (Tekscan HR Mat™) and in-shoe (Novel Pedar-X®) plantar pressure variables, weight bearing ankle dorsiflexion, hallux range of motion, lesser toe deformities and hallux abductus (HAV) scale were assessed in 136 adults with diabetes (52.2% male; mean age 68.4 years). Multivariate multiple linear regression was used to assess the effect of the four biomechanical factors plus neuropathy and body mass index on plantar pressure variables. Non-parametric bootstrapping was employed to determine the difference in plantar pressure variables for participants with two or more foot biomechanical pathologies compared to those with less than two pathologies. Results: Almost one third (32%) of the cohort had two or more foot biomechanical pathologies. Participants with two or more foot biomechanical pathologies displayed significant increases in all barefoot plantar pressure regions (except forefoot), compared to those with less than two pathologies. No significant changes were found for the in-shoe plantar pressure variables. The regression model explains between 9.9% (95%CI: 8.4 to 11.4%) and 29.6% (95% CI: 28.2 to 31%), and between 2.5% (1.0 to 4.0%) and 43.8% (95% CI: 42.5–44.9%), of the variance in the barefoot and in-shoe plantar pressure variables respectively. Conclusions: Participants presenting with two or more factors affecting foot biomechanics displayed higher peak pressures and pressure time integrals in all foot regions compared to those with less than two factors. The tests used in this study could help clinicians detect elevated plantar pressures in people with diabetes and present an opportunity for early preventative interventions


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    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

    Effects of extraosseous talotarsal stabilization on the biomechanics of flexible flatfoot subtalar joints in children: a finite element study

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    Background: Objective of the study was to generate an experimental foundation for the clinical application of extraosseous talotarsal stabilization (EOTTS) in treatment of flexible flatfeet in children by investigating the biomechanical characteristics of flexible flatfoot and the effects of EOTTS on hindfoot biomechanics.Methods: Three-dimensional finite element models of the foot and ankle complex were generated from computer tomography images of a volunteer’s left foot in three states: normal, flexible flatfoot, and post-EOTTS. After validation by X-ray, simulated loads were applied to the three models in a neutral position with both feet standing.Results: In the flexible flatfoot model, the contact stress on the subtalar joint increased and contact areas decreased, resulting in abnormal stress distribution compared to the normal model. However, following treatment of the foot with EOTTS, these parameters returned to close to normal. Subtalar joint instability leads to a flexible flat foot. Based on this study, it is proposed that EOTTS can restore the normal function of the subtalar joint in and is an effective treatment for flexible flatfoot in children. We and many clinical data studies provide evidence for sinus tarsi implants in pediatric patients. It is showed that the formation of flexible flatfoot is induced by subtalar joint instability.Conclusions: Because of the EOTTS provides the best biomechanical solution to subtalar joint instability, the EOTTS became an effective form for subtalar joint instability treatment
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