REPEATED-MEASURES OF ADULT NORMAL WALKING USING A VIDEO TRACKING SYSTEM

The reproducibility of quantitative gait analysis measurements is an i mportant consideration when analyzing data of both normal subjects and patients. Waveform similarity statistics were used to assess the repr oducibility of lower extremity kinematic and kinetic data collected on 5 normal adult subjects. For each subject, gait evaluations were done on 3 separate test days with 3 trials collected each day. Pelvis angl es were fairly repeatable, however, with notably poor reproducibility in sagittal plane tilt. Re-application errors of the sacral wand coupl ed with a small range of motion are believed to be the principle contr ibutors to variability in this pelvis angle. The sagittal plane angles for the hip, knee, and ankle demonstrated excellent repeatability wit hin test days and between test days. Frontal and transverse plane angl es were fairly repeatable within test days but between-day repeatabili ty was considerably lower. The 'downstream' errors accompanying Euler angle calculations coupled with the smaller ranges of motion in the no n-sagittal plane angles are suggested to contribute to the ambient var iability already in these data and, thus, affect the within-day repeat ability. Errors in re-application of midthigh and midcalf wands furthe r contribute to the variability of these data between test days. Net r esultant joint forces and moments were repeatable overall with slightl y lower between-day statistical values. The exception to this observat ion was the adduction moment of the ankle which was notably variable b etween test days. Several explanations for this variability are presen ted. Results of this study have led to modifications in some marker pl acement procedures and reinforced the need for others already being us ed. (C) 1997 Elsevier Science B.V.