1st Joint ESMAC-GCMAS Meeting - Análise de Marcha

O-32
QUANTIFICATION OF KINEMATIC MEASUREMENT
VARIABILITY IN GAIT ANALYSIS
McGinley, Jennifer, Dr 1 , Baker, Richard, Dr 1,2,3,4 , Wolfe, Rory, Dr
1 Gait CCRE, Murdoch Childrens Research Institute, Melbourne, Australia
2 Royal Children’s Hospital, Melbourne, Australia. 3 The University of Melbourne, Melbourne,
Australia, 4 La Trobe University, Melbourne, Australia,
5 Monash University, Melbourne, Australia
Summary/conclusions
A method is proposed to identify the components of variability of gait analysis kinematic
measures. This quantifies the repeatability of data from individual assessors and will permit
identification of systematic differences between multiple assessors. Results demonstrate that
individual assessors differ in error magnitude across gait parameters. Such specific information
may direct clinical training and quality assurance programs.
Introduction
Repeated three-dimensional gait analysis (3DGA) of a single subject is known to exhibit
inconsistency. This can be attributed to the inherent variability of walking and errors associated
with the measurement process. Inconsistent marker placement has been identified as a key
factor contributing to data variability across repeat sessions [1]. This variability is increased
when different assessors perform the measures. Despite many reports of the reliability of
3DGA, there are limited methods available to clinical laboratories to quantify the sources of
variability within kinematic data. Further, few studies (most usefully Schwartz et al.[2]) have
quantifed this error in a manner that is readily accessible to gait laboratory clinical practice,
identifying variation attributable to the differences between trials within a single session (intertrial),
between sessions measured by a single assessor (inter-session), and between data
measured by different assessors (inter-assessor). The purpose of this study was to use the
statistical analysis approach of variance components estimation to evaluate the variability of
kinematic gait measures of a single unimpaired adult by six assessors from three Gait
Laboratories.
Statement of clinical significance
Three-dimensional kinematic gait measurements are routinely used within clinical gait analysis
to evaluate the effect of interventions on individuals. Detailed understanding of the error
associated with these measures may assist clinical decision-making and provide direction to
staff training and quality assurance activities within gait laboratories.
Methods
A single adult subject (22 years, height 165cm, weight 76kg) attended three Gait Laboratories
for 3DGA. At each laboratory, marker placement was independently conducted by two staff
members. Assessor experience ranged from novice (< 30 3DGA’s) to expert (>500 3DGA’s).
Each assessor repeated the analysis on two occasions within the same day. For each gait
session, six left and six right gait trials were captured, in a manner consistent with typical
laboratory procedures. Necessary anthropometric measures obtained at the first test session
were used in the subsequent session. A conventional biomechanical model (Plug-in-gait) was
used to calculate lower extremity joint kinematics. Components of variability due to session
and trial were estimated separately for each combination of staff member, kinematic variable
and percentage of the gait cycle. A multi-level mixed-effects linear regression model was fitted
with a fixed effect for side (right or left) and a random effect for session [3]. Variability due to
session was estimated by the standard deviation of the session random effect and variability
due to trial estimated by the standard deviation of the model’s residual error term. Maximum
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