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

Objectives 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. Design Test-retest repeatability study. Setting Rehabilitation facility with a human motion analysis laboratory. Participants Ten ambulatory children with spastic CP (age=5-15years). In addition, two control datasets (N=56; N=18) of typically developing children were used as a reference. Interventions Not applicable. Main Outcome Measures Inter-trial and inter-session variability was measured using intra-class correlations (ICC’s) with accompanying confidence intervals, standard error of measurement (SEM), as well as the SEM expressed as percentage (%SEM) of the total joint-range-of-motion of typically developed children. Results Overall we found good to excellent ICC-values and favourable SEM-values for the inter-session Gait Profile Score (ICC=0.85-0.98, SEM=0.45°-0.91°) and Gait Variable Scores (ICC=0.85-0.99, SEM=0.22-1.11°) for the lower-limb joints. The %SEM was the highest for the ankle joint (%SEM=0.8%–3.0%). For the continuous waveform data, only in the ankle joint, differences were observed. Namely, smaller SEM-values for the AFO-condition (mean inter-trial=0.14°; mean inter-session=1.121°) in comparison to the barefoot-condition (mean inter-trial= 0.55°; mean inter-session=2.22°). For all the kinetic parameters, the treadmill conditions showed smaller SEM-values in comparison to the overground condition. Conclusions All conditions proved to be repeatable, showing good to excellent ICC-values. The ankle kinematics were more repeatable when the participants were walking with their AFOs in comparison to barefoot walking. Taking the total joint-range-of-motion into account, the knee joint showed the most repeatable motion, while ankle motions showed the lowest repeatability. For kinetics, treadmill conditions showed better repeatability than the overground conditions.