Reliability and clinical correlates of 3D-accelerometry based gait analysis outcomes according to age and fall-risk

Purpose: To investigate the reliability of a 3D-accelerometry based gait analysis, and its correlates with clinical status and fall-risk. Methods: Forty elderly subjects presenting with increased fall-risk (OFR), 41 elderly controls (OC) and 40 young controls (aged 80.6 +/- 5.4, 79.1 +/- 4.9 and 21.6 +/- 1.4 years respectively) underwent three gait evaluations (two assessors in random order) each containing two walks of 18 m with a DynaPort MiniMod accelerometer on the pelvis. Intra- and inter-observer reliability of gait speed, step-time asymmetry, mediolateral and craniocaudal step and stride regularity were determined by ICC and CV of standard error of measurement (CV(SEM)). Relationships with cognition (MMSE), dependency, grip strength, muscle endurance, and fall-risk (fall-history, timed-get-up-and-go and Tinetti-test) were analysed in elderly participants. Results: Reliability for single walk was low (ICC < 0.70, 11% < CV(SEM) < 23%), except for mediolateral step regularity (0.70 <= ICC < 0.80) and gait speed (ICC > 0.80, CV(SEM) < 7%), but high (ICC > 0.70, 4% < CV(SEM) < 20%) when based on the mean of two walks; except for step-time asymmetry (42% < CV(SEM) < 77%). Compared to OC. OFR showed significantly (p < 0.05) slower gait speed, and worse step and stride regularity. Gait speed, step-time asymmetry, step and stride regularity related significantly (p < 0.05) with several functional outcomes. Besides gait speed (1.158 m/s, 78% sensitivity and 78% specificity), none of the gait features showed sufficient discriminative capacity according to fall-risk. Conclusions: In all participants together, 3D-accelerometry based gait speed and regularity showed high reliability when based on two walks of 18 m. Relationships with functional characteristics support the validity of gait variability features in elderly persons. More fundamental and prospective research is necessary to clarify their clinical value. (C) 2010 Elsevier B.V. All rights reserved.