The iPecsTM 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 iPecsTM 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 iPecsTM 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 iPecsTM load cell, multiple floor-mounted force platforms, and a three-dimensional motion capture system. Overall, the forces and moments measured by the iPecsTM 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 iPecsTM data will be interpreted in a coordinate system other than its own (e.g., inverse dynamics analysis).
Bibliographical noteFunding Information:
The authors would like to acknowledge the use of the Jesse Brown VA Medical Center Motion Analysis Research Laboratory in Chicago, IL. We would also like to thank Jared Howell, CPO, and Rebecca Stine, MS, for their assistance during data collection, Steven Gard, PhD, for his help in the preparation of this manuscript, and Mike Leydet, Alan Hutchenreuther, Chris Johnson, Aaron Taszreak, Vinay Bharadwaj, and Mike Link at College Park Industries, Inc. for their technical support throughout this study. This publication was funded by the National Institute on Disability and Rehabilitation Research (NIDRR) of the US Department of Education under Grant No. H133E080009 . The opinions expressed in this publication are those of the authors and do not necessarily reflect those of the Department of Education.
- Force transducer
- Gait analysis
- Load cell