Repeatability of gait of children with spastic cerebral palsy in different walking conditions

Three-dimensional gait analysis is the 'gold standard' for measurement and description of gait. Gait variability can arise from intrinsic and extrinsic factors and may vary between walking conditions. This study aimed to define the inter-trial and inter-session repeatability in gait analysis data of children with cerebral palsy (CP) who were walking in four conditions, namely barefoot or with ankle-foot orthosis (AFO), and overground or treadmill. Ten children with spastic CP (7 female; 9.9y +/- 3.5y; GMFCS-level I-III) were included in this study. Overall, we found good to excellent intra-class correlation (ICC)-values and favourable standard error of measurement (SEM)-values for the inter-session Gait Profile Score (ICC = 0.85-0.98, SEM = 0.45-0.91 degrees) and Gait Variable Scores (ICC = 0.85-0.99, SEM = 0.22-1.11 degrees) for the lower-limb joints. Taking the total joint-range-of-motion into account, the knee joint showed the most repeatable motion (%SEM = 0.5-1.8 %), while ankle motions showed the lowest repeatability (%SEM = 0.8 %-3.0 %). For the continuous waveform data, only the ankle joint showed repeatability differences between walking conditions, namely, smaller SEM-values for the AFO-condition (mean inter-trial = 0.14 degrees; mean inter-session = 1.121 degrees) in comparison to the barefoot-condition (mean inter-trial = 0.55 degrees; mean inter-session = 2.22 degrees). For all the kinetic parameters, the treadmill conditions showed smaller SEM-values in comparison to the overground condition. In conclusion three-dimensional gait analysis was found to be reliable in all four walking conditions for children with CP. The resulting measurement errors can be used as a reference during clinical interpretations of gait analyses.