Effect of Different Ankle-Foot Immobility on Lateral Gait Stability in the Stance Phase

Abstract

Background: This study aimed to investigate the effect of limited foot and ankle mobility on the lateral stability of gait through the observation of the mediolateral margin of stability and related kinematic parameters.

Methods: Thirty young, healthy participants walked at a fixed gait velocity on a level surface. Participants achieved different degrees of restricted mobility by wearing soft-soled shoes (S), an ankle-foot orthosis with unrestricted dorsiflexion-plantarflexion activity only (A), and an ankle-foot orthosis with unrestricted dorsiflexion-plantarflexion and adjustable horizontal rotation of the foot (OU/OR). Furthermore, the spatiotemporal parameters, mediolateral margin of stability, center of pressure, angle of the fore and hind foot relative to the tibia, and correlation coefficients of the factors were analyzed. Regression analysis was also performed.

Results: At right heel strike, group A had a significantly lower mediolateral margin of stability than group S and group OU. Meanwhile, forefoot adduction (0.2 < |r| <0.4) and plantarflexion (0.2 < |r| <0.4), as well as hindfoot internal rotation (0.2 < |r| <0.6) and inversion (0.2 < |r| <0.4), correlated negatively with lateral stability. Regression analysis revealed forefoot dorsiflexion and supination were the main independent variables for group A. At right heel off, groups OU and OR had a significantly lower mediolateral margin of stability than those in groups A and S. Forefoot adduction (0.2 < |r| <0.4) and dorsiflexion (0.4 < |r| <0.6) were correlated with lateral stability, as were hindfoot dorsiflexion (0.2 < |r| <0.4) and inversion (0.2 < |r| <0.4). Regression analysis revealed forefoot abduction and plantarflexion were the main independent variables for groups OU and OR.

Conclusions: The present study verified from gait data that forefoot dorsiflexion and supination at the initial contact of the stance phase were relevant factors for the differences in lateral gait stability, whereas abduction and plantar flexion of the forefoot at the terminal stance phase were the main influencing factors of lateral gait stability.

Figure 1

Soft‒soled shoes (a) and Agilium‒freestep orthosis (b). The soft-soled shoes have no restrictions on the foot and ankle joints, and the bottom surface is soft and has the same thickness as the orthosis. The bottom surface of the Agilium-freestep orthosis forefoot is soft.

Figure 2

Matsumoto custom orthosis (a) and bottom view of the Matsumoto orthosis (b). The bottom surface is hard, which limits the rotation of the forefoot and midfoot to a certain extent. The screw marked by the red circle is the horizontal rotation limiter.

Figure 3

The mediolateral margin of stability (ML MoS) during the stance phase. The ML MoS of each gait event during the stance phase. The results in the figure are the mean values of the ML MoS of each group at different gait events (∗p < 0.05), (∗∗p < 0.01). A:gray column with stripes; S: black column; OU: red column; OR: red column with lattice.

Figure 4

Center of pressure (COP) x at each gait event. The figure shows the mean values with SD of the COP x of each group in the different gait events (^∗p < 0.05, ^∗∗p < 0.01). A: gray interrupted lines with dots; S: solid black line with squares; OU: solid red line with triangles; OR: red dotted line with inverted triangles.

Figure 5

FFTBA and HFTBA during the gait cycle. (a)–(c) are the results of adduction (ADD) (+)/abduction (ABD) (-), dorsiflexion (DF) (+)/plantarflexion (PF) (-), supination (SP) (+)/pronation (PR) (-) of the FFTBA. (d)–(f) are the results of internal rotation (IR) (+)/external rotation (ER) (-), dorsiflexion (DF) (+)/plantarflexion (PF) (-), inversion (IV) (+)/eversion (EV) (-) [24] of HFTBA. A: black interrupted line, S: black realized, OU: red solid line, OR: red dotted line.

Figure 6

Scatter plots of the FFTBA and HFTBA with significant effects on ML MoS and corresponding ML MoS values at RHS. The solid black line is the reference line of the best-fit equation obtained from the stepwise multiple regression analysis.

Figure 7

Scatter plots of the joint motion angles with significant effects on ML MoS and corresponding ML MoS values at RHO. The solid black line is the reference line of the best-fit equation obtained from the stepwise multiple regression analysis.