Effects of Data Smoothing on the Reconstruction of Helical Axis Parameters in Human Joint Kinematics

[+] Author and Article Information
A. de Lange, R. Huiskes, J. M. G. Kauer

Biomechanics Section, Institute of Orthopaedics and Department of Anatomy and Embryology, University of Nijmegen, 6500 HB NIJMEGEN, The Netherlands

J Biomech Eng 112(2), 107-113 (May 01, 1990) (7 pages) doi:10.1115/1.2891160 History: Received April 14, 1988; Revised December 15, 1989; Online March 17, 2008


In biomechanical joint-motion analyses, the continuous motion to be studied is often approximated by a sequence of finite displacements, and the Finite Helical Axis (FHA) or “screw axis” for each displacement is estimated from position measurements on a number of anatomical or artificial landmarks. When FHA parameters are directly determined from raw (noisy) displacement data, both the position and the direction of the FHA are ill-determined, in particular when the sequential displacement steps are small. This implies, that under certain conditions, the continuous pathways of joint motions cannot be adequately described. The purpose of the present experimental study is to investigate the applicability of smoothing (or filtering) techniques, in those cases where FHA parameters are ill-determined. Two different quintic-spline smoothing methods were used to analyze the motion data obtained with Roentgenstereophotogrammetry in two experiments. One concerning carpal motions in a wrist-joint specimen, and one relative to a kinematic laboratory model, in which the axis positions are a priori known. The smoothed and nonsmoothed FHA parameter errors were compared. The influences of the number of samples and the size of the sampling interval (displacement step) were investigated, as were the effects of equidistant and nonequidistant sampling conditions and noise invariance.

Copyright © 1990 by The American Society of Mechanical Engineers
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