Factors Influencing Accuracy of Screw Displacement Axis Detection With a D.C.-Based Electromagnetic Tracking System

[+] Author and Article Information
M. Bottlang

Department of Biomedical Engineering, The University of Iowa, Iowa City, IA 52240

J. L. Marsh

Department of Orthopaedic Surgery, The University of Iowa, Iowa City, IA 52240

T. D. Brown

Department of Biomedical Engineering and Department of Orthopaedic Surgery, The University of Iowa, Iowa City, IA 52240

J Biomech Eng 120(3), 431-435 (Jun 01, 1998) (5 pages) doi:10.1115/1.2798011 History: Received December 27, 1996; Revised January 02, 1998; Online October 30, 2007


Recent technical improvements and cost reductions in electromagnetic motion tracking systems invite their application to motion axis determination in the surgical setting. After evaluation of the accuracy of a state-of-the-art D. C. electromagnetic tracking system, which generates complete three-dimensional kinematic outputs from just a single receiver, we calculated screw displacement axes (SDA’s) from its source data. The accuracy of SDA determination from such source data was evaluated for various rotational increment sizes around a revolute joint. A novel smoothing procedure, customized for this type of source data, was developed, enabling SDA detection from incremental rotations of less than 1 deg, at an accuracy appropriate for intra-operative measurement of human joint motion. Examples of SDA determination are given for motion tracking of a ball joint and of the elbow articulation.

Copyright © 1998 by The American Society of Mechanical Engineers
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