Three-dimensional finite element stress analysis of the polypropylene, ankle-foot orthosis: static analysis

Chu, Tai-Ming; Reddy, Narender P.; Padovan, J.

doi:10.1016/1350-4533(95)97317-i

Cited by 76 publications

(37 citation statements)

References 7 publications

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“…For instance, stress distribution was successfully predicted during ambulation using FEM. 21,22 The relation between trim line location and AFO stiffness was also simulated in a non-linear finite element model. 23 A recent theoretical study using a simple model showed the ability to predict the displacement of the cuff band due to misalignment of AFO.…”

Section: Introductionmentioning

confidence: 99%

Effects of joint alignment and type on mechanical properties of thermoplastic articulated ankle-foot orthosis

Gao

Carlton

Kapp

2011

Prosthetics &Amp; Orthotics International

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Background: Articulated or hinged ankle-foot orthosis (AFO) allow more range of motion. However, quantitative investigation on articulated AFO is still sparse. Objective: The objective of the study was to quantitatively investigate effects of alignment and joint types on mechanical properties of the thermoplastic articulated AFO. Study design: Tamarack dorsiflexion assist flexure joints with three durometers (75, 85 and 95) and free motion joint were tested. The AFO joint was aligned with the center of the motor shaft (surrogate ankle joint), 10 mm superior, inferior, anterior and posterior with respect to the motor shaft center. Methods: The AFO was passively moved from 20 plantar flexion to 15 dorsiflexion at a speed of 10 /s using a motorized device. Mechanical properties including index of hysteresis, passive resistance torque and quasi-static stiffness (at neutral, 5, 10 and 15 in plantar flexion) were quantified. Results: Significant effects of joint types and joint alignment on the mechanical properties of an articulated thermoplastic AFO were revealed. Specifically, center alignment showed minimum resistance and stiffness while anterior and posterior alignment showed significantly higher resistance and stiffness. The dorsiflexion assist torques at neutral position ranged from 0.69 AE 0.09 to 1.88 AE 0.10 Nm. Conclusions: Anterior and posterior alignment should be avoided as much as possible. Clinical relevanceThe current study suggested that anterior and posterior alignment be avoided as much as possible in clinical practice due to potential skin irritation and increase in stress around the ankle joint.

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Section: Introductionmentioning

confidence: 99%

Effects of joint alignment and type on mechanical properties of thermoplastic articulated ankle-foot orthosis

Gao

Carlton

Kapp

2011

Prosthetics &Amp; Orthotics International

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“…FE models have been widely used to quantify the biomechanical role of the plantar fascia in load bearing, and vertical displacement of the foot was found to increase with fasciotomy [10,11]. 3-D geometrical detailed FE models have also been developed [14][15][16][17][18][19], although those studies did not quantify the biomechanical role of the plantar fascia to the tarsal and metatarsal bone simultaneously, and did not examine the one-foot standing posture, which is important to support the body weight in walking. Based on both anatomy and computer software, we established a detailed FE model of a normal adult left foot that included the bone segments, articulations, foot intrinsic ligaments, and plantar soft tissue.…”

Section: Discussionmentioning

confidence: 99%

Deformation and stress distribution of the human foot after plantar ligaments release: A cadaveric study and finite element analysis

Liang

Yang

et al. 2011

Sci. China Life Sci.

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The majority of foot deformities are related to arch collapse or instability, especially the longitudinal arch. Although the relationship between the plantar fascia and arch height has been previously investigated, the stress distribution remains unclear. The aim of this study was to explore the role of the plantar ligaments in foot arch biomechanics. We constructed a geometrical detailed three-dimensional (3-D) finite element (FE) model of the human foot and ankle from computer tomography images. The model comprised the majority of joints in the foot as well as bone segments, major ligaments, and plantar soft tissue. Release of the plantar fascia and other ligaments was simulated to evaluate the corresponding biomechanical effects on load distribution of the bony and ligamentous structures. These intrinsic ligaments of the foot arch were sectioned to simulate different pathologic situations of injury to the plantar ligaments, and to explore bone segment displacement and stress distribution. The validity of the 3-D FE model was verified by comparing results with experimentally measured data via the displacement and von Mise stress of each bone segment. Plantar fascia release decreased arch height, but did not cause total collapse of the foot arch. The longitudinal foot arch was lost when all the four major plantar ligaments were sectioned simultaneously. Plantar fascia release was compromised by increased strain applied to the plantar ligaments and intensified stress in the midfoot and metatarsal bones. Load redistribution among the centralized metatarsal bones and focal stress relief at the calcaneal insertion were predicted. The 3-D FE model indicated that plantar fascia release may provide relief of focal stress and associated heel pain. However, these operative procedures may pose a risk to arch stability and clinically may produce dorsolateral midfoot pain. The initial strategy for treating plantar fasciitis should be non-operative. The plantar fascia, or plantar aponeurosis, is the investing fascial layer of the plantar aspect of the foot, and forms part of the retinacular system, consisting of a network of connective and adipose tissues that supports and protects underlying vital structures of the body. The anatomy of the plantar fascia has been well described by Sarrafian [1] and others [2][3][4][5]. Partial or total plantar fascia release may relieve metatarsal and calcaneal stresses and painful heel syndromes of plantar fasciitis. However, reduction of plantar fascia stiffness may have a significant impact on arch stability, resulting in a more deformable longitudinal arch. Cadaveric studies have been performed to examine biomechanical consequences of release of the plantar ligaments. Huang [6] reported that the average vertical displacements

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“…Subsequent three-dimensional shell analyses assumed symmetry with respect to the midsagittal plane [7]. An AFO was also analysed as a three dimensional asymmetric solid [8] but this type of FE analysis is certainly less efficient than that using shell elements due to the greater number of generated degrees of freedom. In coupled lower limb -AFO models [6,8,9], the possibility of slip, friction and separation was not taken into account; the loading and constraints were not defined in a realistic manner.…”

Section: Introductionmentioning

confidence: 99%

“…An AFO was also analysed as a three dimensional asymmetric solid [8] but this type of FE analysis is certainly less efficient than that using shell elements due to the greater number of generated degrees of freedom. In coupled lower limb -AFO models [6,8,9], the possibility of slip, friction and separation was not taken into account; the loading and constraints were not defined in a realistic manner. It was also noted in previous FE work [5,6,8] that loading was generally applied at the heel or toe regions as point forces, which yield artificial stress concentrations.…”

Section: Introductionmentioning

confidence: 99%

“…In coupled lower limb -AFO models [6,8,9], the possibility of slip, friction and separation was not taken into account; the loading and constraints were not defined in a realistic manner. It was also noted in previous FE work [5,6,8] that loading was generally applied at the heel or toe regions as point forces, which yield artificial stress concentrations.…”

Section: Introductionmentioning

confidence: 99%

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Modelling considerations in finite element analyses of ankle foot orthoses

Syngellakis

Arnold²

2012

WIT Transactions on Ecology and the Environment

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An asymmetric Ankle Foot Orthosis (AFO) H model was generated from leg surface data and a number of design parameters through a versatile graphics routine. The effect of modelling parameters, geometry, loading and constraints on the AFO mechanical behaviour was assessed through finite element analyses. Moderate thickness non-uniformity was predicted to have a small effect on AFO stiffness although the extent of this effect may also depend on the trimline position. Variation of the heel constraints was found to have a significant effect on both the maximum stress and the moment required to produce a given rotation about the ankle axis. The magnitude and distribution of stresses in critical regions, as well as the ankle moment, were all found to depend on the distribution of imposed deformation. The results of the parametric studies point towards some possible strategies for design optimisation.

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Three-dimensional finite element stress analysis of the polypropylene, ankle-foot orthosis: static analysis

Cited by 76 publications

References 7 publications

Effects of joint alignment and type on mechanical properties of thermoplastic articulated ankle-foot orthosis

Effects of joint alignment and type on mechanical properties of thermoplastic articulated ankle-foot orthosis

Deformation and stress distribution of the human foot after plantar ligaments release: A cadaveric study and finite element analysis

Modelling considerations in finite element analyses of ankle foot orthoses

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