Low multiscale entropy of ankle joint position during toe gait in children with cerebral palsy is related to contracture development

Background: Toe walking in children with cerebral palsy is typically less stable and less energy-efficient than plantigrade walking in typically developing children. We hypothesized that children with cerebral palsy may, nevertheless, show more stable toe walking due to the development of contractures compared to age-matched typically developing children. Methods: Multiscale entropy of the vertical position of the ankle joint was used to measure ankle joint stability during the stance phase of walking. Kinematic data were obtained from 37 children with spastic cerebral palsy and habitual toe walking, who walked on a treadmill at their preferred speed (1.3 ± 0.5 km/h for cerebral palsy children and 1.5 ± 0.4 km/h for typically developing children). Recordings from 21 age-matched typically developing children were used for comparison. Typically developing children walked both normally (plantigrade) and on toes. Findings: Multiscale entropy was significantly higher during toe walking than plantigrade walking in typically developing children (P < 0.001). For children under 6 years, multiscale entropy was higher in cerebral palsy children than in typically developing children. For children over 6 years, the opposite was observed. In children with cerebral palsy, multiscale entropy decreased with reduced passive range of motion in the ankle joint (P < 0.001). Interpretation: These findings suggest that contractures in children with cerebral palsy stabilize the ankle during toe walking. Younger children may show greater stability due to early contracture development, while advanced contractures in older children may reduce stability.