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Volume 42 Number 3, May/June 2005
Pages 315 — 326

Abstract - A shear and plantar pressure sensor based on fiber-optic bend loss

Wei-Chih Wang, PhD;1* William R. Ledoux, PhD;1-3 Bruce J. Sangeorzan, MD;2-3 Per G. Reinhall, PhD1

Departments of 1Mechanical Engineering and 2Orthopaedics and Sports Medicine, University of Washington, Seattle, WA; 3Department of Veterans Affairs (VA) Rehabilitation Research and Development, Center of Excellence for Limb Loss Prevention and Prosthetic Engineering, VA Puget Sound Health Care System, Seattle, WA
Abstract — Lower-limb complications associated with diabetes include the development of plantar ulcers that can lead to infection and subsequent amputation. While we know from force-plate analyses that medial/lateral and anterior/posterior shear components of ground-reaction forces exist, little is known about the actual distribution of these stresses during daily activities or about the role that shear stresses play in causing plantar ulceration. Furthermore, one critical reason why these data have not been obtained previously is the lack of a validated, widely used, commercially available shear sensor, partly because of the various technical issues associated with measuring shear. In this study, we present a novel means of transducing plantar pressure and shear stress with a fiber-optic sensor. The pressure/shear sensor consists of an array of optical fibers lying in perpendicular rows and columns separated by elastomeric pads. We constructed a map of normal and shear stresses based on observed macrobending through the intensity attenuation from the physical deformation of two adjacent perpendicular fibers. Initial results show that this sensor exhibits low noise and responds to applied normal and shear loads with good repeatability.
Key words: anterior/posterior shear, biomechanics, biosensing techniques, diabetes mellitus, foot ulcers, gait, lower-limb complications, plantar pressure, plantar ulcers, ulcer.

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