The variability of force platform, kinematic and kinetic data in normal and cerebral palsy gait
Gait analysis can produce useful results once the natural and systematic variability of gait measurements is established . It was therefore the purpose of this study to investigate the variability of temporal-spatial, kinematic and kinetic parameters of gait, in adults and children with normal gait as well as in children with cerebral palsy (CP) gait, using three-dimensional motion analysis. Investigations of the variability and symmetry of ground reaction force (GRF) data, in healthy and CP children, using time and frequency domain analysis, concluded that GRF data in CP children was more variable compared to normal. The vertical force was the least and the mediolateral force the most variable parameter. Time domain analysis is limited since it involves only selected points of the force-time curves, whereas frequency domain analysis contains information about the entire waveforms. Motion analysis require reflective markers attached on the subject's skin. Marker misplacement is considered a major source of variability in gait analysis . A marker placement protocol was established and validated by eight different marker applicators. Within and between-applicators reproducibility was high. Consistency in applying an established protocol is important, although the marker positions may not be entirely accurate. The effect of marker misplacement on the kinematics and kinetics of gait was quantified by using modelling software. The gait parameters in the transverse plane were the most sensitive to market misplacement, which should be taken into account during examination of gait analysis reports. Temporal-spatial, kinematic and kinetic patterns of gait, in adults and children (healthy and CP), were determined. All parameters of normal gait showed considerable repeatability, with kinetics being more repeatable than kinematics. CP gait showed repeatability in the sagittal and frontal plane, however the transfer plane kinematic parameters were highly variable.