Reducing Circumduction and Hip Hiking During Hemiparetic Walking Through Targeted Assistance of the Paretic Limb Using a Soft Robotic Exosuit

Abstract

Objective: The aim of the study was to evaluate the effects on common poststroke gait compensations of a soft wearable robot (exosuit) designed to assist the paretic limb during hemiparetic walking.

Design: A single-session study of eight individuals in the chronic phase of stroke recovery was conducted. Two testing conditions were compared: walking with the exosuit powered versus walking with the exosuit unpowered. Each condition was 8 minutes in duration.

Results: Compared with walking with the exosuit unpowered, walking with the exosuit powered resulted in reductions in hip hiking (27 [6%], P = 0.004) and circumduction (20 [5%], P = 0.004). A relationship between changes in knee flexion and changes in hip hiking was observed (Pearson r = -0.913, P < 0.001). Similarly, multivariate regression revealed that changes in knee flexion (β = -0.912, P = 0.007), but not ankle dorsiflexion (β = -0.194, P = 0.341), independently predicted changes in hip hiking (R = 0.87, F(2, 4) = 13.48, P = 0.017).

Conclusions: Exosuit assistance of the paretic limb during walking produces immediate changes in the kinematic strategy used to advance the paretic limb. Future work is necessary to determine how exosuit-induced reductions in paretic hip hiking and circumduction during gait training could be leveraged to facilitate more normal walking behavior during unassisted walking.

Figures

Figure 1:

An overview of the components of a unilateral soft wearable robot (exosuit). Functional textile anchors (waist belt, leg strap, calf wrap, and lateral support module) interact with an in-shoe insole to generate assistive ankle plantarflexion and dorsiflexion forces when the contractile elements of the exosuit (i.e., Bowden cables located adjacent to the ankle) are retracted by an off board actuation unit. The textile anchors integrate to make 2 modules that are active during different phases of the gait cycle. The waist belt and leg straps make up the plantarflexion module (blue), whereas the calf wrap forms the dorsiflexion module (red). Gyroscopes and load cells are used to detect gait events and measure the force being transmitted by the Bowden cables. These parameters serve as inputs in the exosuit’s control algorithm.

Figure 2:

Circumduction and hip hiking for a representative participant are shown during two walking conditions: the exosuit unpowered and powered. (A) The medial/lateral (x-axis) and posterior/anterior (y-axis) motion of the center of gravity (CoG) of the paretic and non-paretic foot during their respective gait cycles. Stance and swing phase are denoted. Circumduction is defined as the maximum lateral difference of the CoG during stance and swing phase. (B) Hip hiking was measured during the paretic limb’s swing phase (x-axis) as the difference between the vertical position of the paretic anterior superior illiac spine (ASIS) during walking and its position during quiet standing (y-axis). A y-axis value of “0” indicates that the ASIS position during walking was the same as the position during quiet standing. The maximum vertical position of the ASIS during the swing phase was used in the analyses.

Figure 3:

Average±SE are presented for paretic limb hip hiking (A and B) and circumduction (C and D) during exosuit unpowered and powered walking conditions. Paired t-tests were conducted at the group and individual levels. For panels A (N=7) and C (N=8), a significant difference between the exosuit powered and unpowered conditions is indicated by an asterisk (*). For panels B (N=7) and D (N=8), an asterisk located under the participant’s number indicates a significant between-condition difference for that individual.

Figure 4:

(A) Relationship between changes in peak paretic knee flexion angle and changes in hip hiking during swing phase. (B) Relationship between changes in peak paretic ankle dorsiflexion angle and changes in hip hiking during swing phase.