Influence of Ankle-Foot Orthoses and Ankle-Foot Joint Immobility on Gait Stability

Abstract

Background/Aims: In this study, we observed the effects of orthotics and ankle immobility on lateral stability to establish screening procedures for people with potential fall risk, assess the effect of foot and ankle abnormalities on gait stability, and determine the balance between functionality and stability in the design of orthotics. Methods: We examined 19 young, healthy participants while walking at a fixed gait velocity on a level surface. To calculate the medial-lateral margin of stability (ML MoS), the center of mass (CoM) moving velocity and base of support (BoS) were analyzed. We also examined factors that influenced a significant difference in the medial-lateral components v x of the CoM moving velocity to obtain the ground reaction force (GRF), joint angles, joint moments, and co-relation of joints. The significant differences in these indicators by gait events were used to verify the effects of different foot and ankle conditions and the wearing of different ankle-foot orthoses (AFO) on the lateral stability of gait events in different stance phases. Results: The ML MoS differed significantly at right heel strike (RHS). In addition, the ML MoS of each of the 19 participants in this study was significantly different immediately before the left heel strike (pre-LHS). However, due to the large heterogeneity of the disturbance generated by the abnormal motion of the ankle joint at pre-LHS, a consistent pattern of differences between groups was not obtained. Conclusions: Limited ankle inversion-eversion and adduction-abduction, combined with poorer foot rigidity, resulted in significantly lower lateral stability in the initial stance phase (at RHS). The angular difference between dorsiflexion and pronation, as well as the greater CoM lateral velocity, are the main reasons for the low lateral stability at this moment. These could be the targeted gait events and ankle movements for further research, treatment, and training.