Computational modelling of ankle-foot orthosis to evaluate spatially asymmetric structural stiffness: Importance of geometric nonlinearity

Sumihira, Wataru; Otani, Tomohiro; Kobayashi, Yo et al.

Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 2022, 236(9), 1357-1364

Number of Access:266（2025-06-07 19:00 Counts）

Identifier to cite or link to this item: https://hdl.handle.net/11094/88623

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Title
Computational modelling of ankle-foot orthosis to evaluate spatially asymmetric structural stiffness: Importance of geometric nonlinearity
Creator
CreatorName
Sumihira, Wataru
NRID
1000040778990 1000040778990
ORCID
0000-0002-6431-2703 0000-0002-6431-2703
researchmap permalink
bigvalley bigvalley
Scopus Author ID
55625962900 55625962900
CreatorName
Otani, Tomohiro
NRID
1000050424817 1000050424817
ORCID
0000-0003-4358-6294 0000-0003-4358-6294
researchmap permalink
yokobayashi yokobayashi
Scopus Author ID
55516137200 55516137200
CreatorName
Kobayashi, Yo
NRID
1000040163571 1000040163571
CreatorName
Tanaka, Masao
Subject
AFO
buckling
corotational triangle element
dorsiflexion
large deflection
Description
Wataru Sumihira, Tomohiro Otani, Yo Kobayashi, Masao Tanaka, Computational modelling of ankle-foot orthosis to evaluate spatially asymmetric structural stiffness: Importance of geometric nonlinearity, Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine. pp. 9544119221114199. Copyright © 2022 SAGE Publications. DOI: 10.1177/09544119221114199.
Abstract
An ankle-foot orthosis (AFO) constructed as a single piece of isotropic elastic material is a commonly used assistive device that provides stability to the ankle joint of patients with spastic diplegic cerebral palsy. The AFO has asymmetric stiffness that restricts plantarflexion during the swing phase while it is flexible to allow dorsiflexion during the stance phase with a large deflection, including buckling originating from geometric nonlinearity. However, its mechanical implications have not been sufficiently investigated. This study aims to develop a computational model of an AFO considering geometric nonlinearity and examine AFO stiffness asymmetry during plantarflexion and dorsiflexion using physical experiments. Three-dimensional AFO mechanics with geometric nonlinearities were expressed using corotational triangle-element formulations that obeyed Kirchhoff–Love plate theory. Computational load tests for plantarflexion and dorsiflexion, using idealised AFOs with two different ankle-region designs (covering or not covering the apexes of the malleoli), showed that plantarflexion moment–ankle angle relationships were linear and dorsiflexion moment–ankle angle relationships were nonlinear; increases in dorsiflexion led to negative apparent stiffness of the AFO. Both ankle-region designs resisted both plantarflexion and dorsiflexion, and out-of-plane elastic energy was locally concentrated on the lateral side, resulting in large deflections during dorsiflexion. These findings give insight into appropriate AFO design from a mechanical viewpoint by characterising three-dimensional structural asymmetry and geometric nonlinearity.
Publisher
SAGE Publications
Source Title
Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine
Volume (Issue)
236(9)
Page
1357-1364
Date of Issued
2022-07-23
Language
English
Handle URL
https://hdl.handle.net/11094/88623
PISSN
09544119
eISSN
20413033
NCID
AA10698285
Relation.isVersionOf
DOI (Publisher Version)
https://doi.org/10.1177/09544119221114199
Relation.isIdenticalTo
PMID
35875899
Access Rights
open access
oaire:version
Accepted Manuscript
Category
学術雑誌論文 Journal Article