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Publications

Koehler, SR, Dhaher, YY, Hansen, AH (2014) Cross Validation of a Portable, Six Degree-of-Freedom Load Cell for Use in Lower-Limb Prosthetics Research, Journal of Biomechanics, 47(6), 1542-1547.


Abstract:
The iPecs™ load cell is a lightweight, six-degree-of-freedom force transducer designed to fit easily into an endoskeletal prosthesis via a universal mounting interface. Unlike earlier tethered systems, it is capable of wireless data transmission and on-board memory storage, which facilitate its use in both clinical and real-world settings. To date, however, the validity of the iPecs™ load cell has not been rigorously established, particularly for loading conditions that represent typical prosthesis use. The aim of this study was to assess the accuracy of an iPecs™ load cell during in situ human subject testing by cross-validating its force and moment measurements with those of a typical gait analysis laboratory. Specifically, the gait mechanics of a single person with transtibial amputation were simultaneously measured using an iPecs™ load cell, multiple floor-mounted force platforms, and a three-dimensional motion capture system. Overall, the forces and moments measured by the iPecs™ were highly correlated with those measured by the gait analysis laboratory (r>0.86) and RMSEs were less than 3.4% and 5.2% full scale output across all force and moment channels, respectively. Despite this favorable comparison, however, the results of a sensitivity analysis suggest that care should be taken to accurately identify the axes and instrumentation center of the load cell in situations where iPecs™ data will be interpreted in a coordinate system other than its own (e.g., inverse dynamics analysis).




Clinical Reliability of a Device for Measuring Forces and Moments in Amputee Gait

Title: Clinical Reliability of a Device for Measuring Forces and Moments in Amputee Gait
Author: LeGare, Stephanie
Abstract: Practitioners find it difficult to measure forces and moments on a prosthesis when an amputee walks. Traditional measures, such as using force platforms, are expensive and inaccessible. Practitioners also question the applicability of lab measurements to everyday activities. The iPecs is a portable device that measures forces and moments on a prosthesis. The device demonstrates reliable data over multiple gait speeds and over two testing days (r > 0.9). The iPecs captures characteristic gait data similar to a force platform; however, variations occur due to different coordinate reference planes and the stiffness of the prosthetic foot. Compared to a force platform, iPecs captures more data in less time and fewer overall steps. Portability of the iPecs allows use in daily activities, outdoors, or in clinic, making it an alternative to traditional methods of measuring kinetic data.
Description: MSPO Research Presentation, April 8, 2009 at the Centennial Research Building (CRB) Room 119J on the Georgia Tech campus.
Type: Masters Project
VideoURI: http://hdl.handle.net/1853/28681
Date: 08-Apr-2009
Contributor: Georgia Institute of Technology. School of Applied Physiology
Publisher: Georgia Institute of Technology
Format: MPEG-4 video

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Wireless load cell sensor provides accurate measurement of forces within prosthesis


News item about a paper presented at the 2014 American Academy of Orthotists and Prosthetists Annual Meeting and Scientific Symposium that compared force and moment measurements made by an iPecs with a force plate. Click on the title to link to the news item.