Simulation Methods in the Foot Orthosis Development ProcessComputer-Aided Design and Applications

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Authors
Samuel J. Lochner, Jan P. Huissoon, Sanjeev S. Bedi
Year
2014
DOI
10.1080/16864360.2014.914375
Subject
Computer Graphics and Computer-Aided Design / Computational Mathematics / Computational Mechanics

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Computer-Aided Design and Applications

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Simulation Methods in the Foot Orthosis Development

Process

Samuel J. Lochnera, Jan P. Huissoona & Sanjeev S. Bedia a University of Waterloo

Published online: 10 Jun 2014.

To cite this article: Samuel J. Lochner, Jan P. Huissoon & Sanjeev S. Bedi (2014) Simulation Methods in the Foot Orthosis

Development Process, Computer-Aided Design and Applications, 11:6, 608-616, DOI: 10.1080/16864360.2014.914375

To link to this article: http://dx.doi.org/10.1080/16864360.2014.914375

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Simulation Methods in the Foot Orthosis Development Process

Samuel J. Lochner, Jan P. Huissoon, Sanjeev S. Bedi

University of Waterloo, sjlochne@engmail.uwaterloo.ca

ABSTRACT

Traditional methods for developing foot orthoses require extensive skilled manual labor. More modern methods have sought to address this with the introduction of computer enabled technologies such as digital scanning, computer aided design, and automated manufacturing. The current work further advances the process with the introduction of an additional computer enabled technology, simulation models, into two additional steps. First, a simulation model is used to achieve the postural adjustments to the foot normally done by a practitioner. This has the benefit of further automating the process, improving repeatability, and preventing the deformation of the plantar soft tissues that normally occurs with physical postural adjustment. Second, the simulation model is used in a routine to optimize plantar pressure distribution. When compared to a conventional method, the proposed approach yielded a 61% reduction in peak plantar pressure. Future work includes automating the optimization routines for a variety of metrics. Other applications for the current work include the development processes of orthoses and prostheses for other parts of the body.

Keywords: foot orthosis, finite element, simulation, optimization. 1. INTRODUCTION

A foot orthoses (FO) is intended to prevent injury or aid in recovery by acting to redistribute pressure experienced by the plantar surface of the foot and/or cause adjustments to relative bone positions during standing and gait. FO geometry originates from a duplicate of the plantar foot surface and then geometrical deviations are made to this base shape in order to control how the FO influences plantar pressure and foot posture. Methods for developing FOs can be categorized as either traditional or modern, where traditional methods rely on manual techniques and modern methods include new computer enabled technologies. 1.1. Traditional FO Development Methods

A variety of paradigms for controlling posture exist, the earliest being that proposed by Merton Root in the 1970’s [22]. While Root’s methods have been questioned or criticized [15,23], they still form the predominant theory known and practiced today. Though the current work could be adapted to a variety of different postural control paradigms, it will be adapted here to Root’s approach. Traditional methods following Root’s techniques and those later described in greater detail by J.W. Philps in, “The Functional FO” [20] can be summarized and broken down into the following five steps: 1. Patient assessing: The practitioner examines the patient while non weight bearing and during standing and gait. Any pathologies are noted and appropriate orthotic interventions recommended. The tibial stance, subtalar joint, and midtarsal joint angles are measured with the subtalar joint in the neutral position and the midtarsal joint locked to arrive at the ideal midstance rearfoot and forefoot angles. Various characteristics of the FO are decided at this point such as the FO’s type, materials, and any local regions requiring decreased pressure. The definitions for the angular measurements are as follows: • The tibial stance angle is measured in the frontal plane as the angle between a line bisecting the lower leg and vertical during standing. • The subtalar joint angle is measured in the frontal plane as the angle between the lower leg bisection line and a line bisecting the calcaneus.

Computer-Aided Design & Applications, 11(6), 2014, 608–616, http://dx.doi.org/10.1080/16864360.2014.914375 c© 2014 CAD Solutions, LLC, http://www.cadanda.com

D ow nl oa de d by [N ew

Y or k U niv ers ity ] a t 1 8:3 7 3 0 N ov em be r 2 01 4 609 • The midtarsal joint angle is measured in the frontal plane as the angle between a line connecting the metatarsal joints along the plantar surface of the foot and the calcaneus bisection line. • The rearfoot angle is the addition of the tibial stance angle and the subtalar joint angle.