Computational and Mathematical Methods in Medicine
Volume 2012 (2012), Article ID 368050, 6 pages
http://dx.doi.org/10.1155/2012/368050
Research Article

Effect of Relative Marker Movement on the Calculation of the Foot Torsion Axis Using a Combined Cardan Angle and Helical Axis Approach

Eveline S. Graf,1 Ian C. Wright,2 and Darren J. Stefanyshyn1

1Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, 2500 University Drive NW, Calgary, AB, Canada T2N 1N4
2Adidas Innovation Team, Adidas, 5055 N Greeley Avenue, Portland, OR 97217, USA

Received 19 December 2011; Revised 21 February 2012; Accepted 27 February 2012

Academic Editor: Thierry Busso

Copyright © 2012 Eveline S. Graf et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The two main movements occurring between the forefoot and rearfoot segment of a human foot are flexion at the metatarsophalangeal joints and torsion in the midfoot. The location of the torsion axis within the foot is currently unknown. The purpose of this study was to develop a method based on Cardan angles and the finite helical axis approach to calculate the torsion axis without the effect of flexion. As the finite helical axis method is susceptible to error due to noise with small helical rotations, a minimal amount of rotation was defined in order to accurately determine the torsion axis location. Using simulation, the location of the axis based on data containing noise was compared to the axis location of data without noise with a one-sample t-test and Fisher's combined probability score. When using only data with helical rotation of seven degrees or more, the location of the torsion axis based on the data with noise was within 0.2 mm of the reference location. Therefore, the proposed method allowed an accurate calculation of the foot torsion axis location.