A Continuous Loading Apparatus for Measuring Three-dimensional Stiffness of Ankle-Foot Orthoses

[+] Author and Article Information
Paolo Cappa, Fabrizio Patanè

Department of Mechanics and Aeronautics,  University of Rome “La Sapienza,” Via Eudossiana 18, Rome, Italy and Paediatric Neuro-rehabilitation Division,  Children’s Hospital “Bambino Gesù,” Via Torre di Palidoro, Passoscuro Rome, Italy

Giuseppe Di Rosa

Paediatric Neuro-rehabilitation Division,  Children’s Hospital “Bambino Gesù,” Via Torre di Palidoro, Passoscuro, Rome, Italy

J Biomech Eng 127(6), 1025-1029 (Jul 11, 2005) (5 pages) doi:10.1115/1.2049313 History: Received March 09, 2005; Revised July 11, 2005

This paper describes a novel device to evaluate the mechanical properties of ankle foot orthoses (AFOs). The apparatus permits the application to AFOs of continuous three-dimensional (3D) movements between specified and settable endpoints. Using an x-y robot with a rotary stage and a six-component load cell, characteristic displacement versus reaction force curves can be generated and consequently the ankle moments can be determined as a function of dorsi/plantar flexion, inv/eversion and int/external rotation. Representative curves for two polypropylene lateral leaf AFOs, different in shape but produced for the same leg by a skilled orthotist, are presented to illustrate the capabilities of the novel testing system. The metrological investigation showed that the apparatus creates a highly repeatable data set (uncertainty 1% FSO).

Copyright © 2005 by American Society of Mechanical Engineers
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Grahic Jump Location
Figure 2

Loading apparatus equipped with the IAFO. The EAFO is also depicted.

Grahic Jump Location
Figure 1

Kinematic scheme of the testing apparatus: (a) foot displacements decomposed in the three cardan’s rotations α, β, and γ; (b) reference frames 0, 3, 4, and S (fixed frame) in a generic foot position

Grahic Jump Location
Figure 3

Variation of total moment Mt, expressed in N m as a function of α and β, expressed in degrees. The diagrams are relative to: (a) γ=−15°,(β)γ=0°, (c) γ=15°, for the EAFO; (d) γ=−15°, (e) γ=0°, (f) γ=15°, for the IAFO. The directions and the values θ of maximum and minimum stiffness are also indicated.



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