Impact of adjustable dorsiflexion range and stiffness in articulated ankle-foot orthosis on center of pressure progression in post-stroke gait.

Abstract

A multi-function articulated ankle-foot orthosis (AFO) allows independent adjustment of dorsiflexion and plantarflexion range of motion (ROM) and stiffness to optimize gait performance in individuals post-stroke. This study investigated the effects of varying two parameters of an articulated AFO (dorsiflexion ROM and stiffness) on center of pressure (CoP) trajectories, plantar forces, and spatiotemporal parameters during treadmill walking in 10 individuals post-stroke. After individualized tuning of the plantarflexion settings, dorsiflexion ROM was set at 0°, 5°, and 10° using the Triple Action joint under two dorsiflexion joint stiffness conditions: low (0.44 Nm/deg) and high (1.13 Nm/deg). Gait data were acquired using a Zebris FDM-T instrumented treadmill across six dorsiflexion joint configurations. A two-way repeated measures ANOVA was used to evaluate the main and interaction effects of ROM and stiffness on gait parameters (CoP, plantar forces, and spatiotemporal) in both paretic and non-paretic limbs, as well as on their symmetry indices. Significant main effects of dorsiflexion ROM were observed for the length of the single support line and its symmetry (p = 0.012; p = 0.023), as well as for maximum forefoot loading (p = 0.012) in the non-paretic limb. Dorsiflexion stiffness also significantly affected the length of the gait line (p = 0.037) and loading response time (p = 0.021) in the non-paretic limb. These findings suggest that adjustments to dorsiflexion ROM and stiffness in an articulated AFO induce measurable biomechanical adaptations in the contralateral non-paretic limb. The results highlight the importance of individualized AFO tuning and bilateral gait assessment in post-stroke rehabilitation to enhance gait symmetry and overall performance.