Modelling considerations in finite element analyses of ankle foot orthoses

Abstract

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.

Computational and experimental evaluation of the mechanical properties of ankle foot orthoses

“…In the most recent article, 38 the authors aimed to assess the effect of changing parameters, such as geometry, loading, and boundary conditions. The AFO was divided into several areas and different thickness values were provided for each area for simulating the characteristics of a vacuum-formed AFO.…”

“…In general, most of the simulations focused on the evaluation of the AFOs in the sagittal plane, usually providing a full constraint of the AFO sole and a load at the calf region or vice versa, a full constraint at the calf region and a load applied at the metatarsal head region. When talking about computational models, a mesh sensitivity analysis should also be included, 38,40,44 for assessing that the results are independent of the mesh size and density. Moreover, they need to be validated in order to prove they can address reliable information: this is accomplished by most of the studies listed in Table 3; however, some of them require further refinements/evaluations for providing an optimal validation.…”

“…Other constraints were also imposed on the heel region to simulate the shoe and foot. Plantarflexion and dorsiflexion were imposed with 15° of rotation and the results compared to the experimental outcomes reported by Sumiya et al 4,28 In the most recent article, 38 the authors aimed to assess the effect of changing parameters, such as geometry, loading, and boundary conditions. The AFO was divided into several areas and different thickness values were provided for each area for simulating the characteristics of a vacuumformed AFO.…”

A New Design Method for Generating Surrogate Kinematic Truss Orthoses to Support Pathological Gait Patterns in Human Model Simulations

“…Unlike active AFO, passive ones do not require any additional energy input to the orthotic system. In the meantime, much research has been conducted in this area and sequential processes have been formulated and optimized (Chu et al, 1995;Pallari et al, 2010;Syngellakis and Arnold, 2012;Dickinson et al, 2017;Dhokia et al, 2017). A 3D-printed AFO optimized for a child with an energy-storing mechanism was designed by Banga et al (2020).…”

Novel Plantar Surface Design of a Hinged Ankle Foot Orthosis (HAFO) Manufactured by 3D Printing

“…Ankle-Foot Orthosis (AFO) is a complementary resource in the rehabilitation of individuals with neuromotor disorders used to prevent muscle shortening and bone deformities and to promote biomechanical alignment and improve gait functionality [1,2]; Hinged AFO (HAFO) can be used in different gait patterns such as equine or drop foot [3,4] because it stabilizes the ankle, limiting the plantar flexion movement, without restricting dorsal flexion [5].…”