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Gepubliceerd in: Journal of Foot and Ankle Research 1/2014

Open Access 01-04-2014 | Meeting abstract

A neuromusculoskeletal model to simulate the isokinetic ankle dorsiflexion test of spasticity

Auteurs: Ruoli Wang, Örjan Ekeberg, Anders Fagergren, Johan Gäverth, Hans Forssberg

Gepubliceerd in: Journal of Foot and Ankle Research | bijlage 1/2014

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Introduction

Spasticity is a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes [1], commonly seen in many neurological disorders. Clinically, spasticity is measured by an examiner rotating a joint and simultaneously estimating the resistance according to an ordinal scale. However, the limited reliability of the measurement and the impossibility to discriminate between the underlying neural (stretch reflex) and non-neural (i.e. muscle mechanics) contributions have been the motivation to develop methods describing resistance joint torque quantitatively. The aim of this preliminary study is to develop a forward neuromusculoskeletal model consisting of the explicit musculotendon, muscle spindle, and motoneuron pool, which can simulate the passive isokinetic ankle dorsiflexion test of spasticity.

Material and methods

In the model, the plantarflexors were considered as a lumped representation of all the muscles. Dorsiflexors were not included in the model. The musculoskeletal geometry was based on the anthropometrical data from a healthy female (height: 1.62m, weight: 53kg). The hill-type musculotendon model was used to simulate the musculotendon dynamics of the lumped plantarflexors. Activation dynamics were modeled as a first order differential equation. The hybrid v0.6 model was used to model the firing characteristics of the muscle spindle [2]. The input-output relation of the α-motoneuron pool can be simplified as a sigmoid function. The contributions of the moment from the passive muscle properties and the stretch reflex to the total resistance torque were computed from 0° to 40° ankle dorsiflexion at two constant angular velocities (5°s-1 vs. 236°s-1).

Results and discussions

Compared to the fast ankle rotation, there was almost no stretch reflex-induced moment in the slow ankle rotation (Figure 1), which agrees to the definition of the spasticity. It indicates that the current neuromusculoskeletal model can describe the individual contributions to the total resistance moment. In the future, by comparing the experimental measurements and the predicted moment, the important spasticity related parameters e.g. α-motoneuron pool properties may be identified individually.
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://​creativecommons.​org/​licenses/​by/​4.​0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://​creativecommons.​org/​publicdomain/​zero/​1.​0/​) applies to the data made available in this article, unless otherwise stated.
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Literatuur
1.
go back to reference Lance J: The control of muscle tone, reflexes, and movement. Neurology. 1980, 30: 1301- Lance J: The control of muscle tone, reflexes, and movement. Neurology. 1980, 30: 1301-
2.
go back to reference Prochazka A, Gorassini M: Models of ensemble firing of muscle spindle afferents recorded during normal locomotion of cats. J Physiol. 1998, 27: 21-34. Prochazka A, Gorassini M: Models of ensemble firing of muscle spindle afferents recorded during normal locomotion of cats. J Physiol. 1998, 27: 21-34.
Metagegevens
Titel
A neuromusculoskeletal model to simulate the isokinetic ankle dorsiflexion test of spasticity
Auteurs
Ruoli Wang
Örjan Ekeberg
Anders Fagergren
Johan Gäverth
Hans Forssberg
Publicatiedatum
01-04-2014
Uitgeverij
BioMed Central
Gepubliceerd in
Journal of Foot and Ankle Research / Uitgave bijlage 1/2014
Elektronisch ISSN: 1757-1146
DOI
https://doi.org/10.1186/1757-1146-7-S1-A87

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