The ReWalk ReStore™ soft robotic exosuit: a multi-site clinical trial of the safety, reliability, and feasibility of exosuit-augmented post-stroke gait rehabilitation

Abstract

Background: Atypical walking in the months and years after stroke constrain community reintegration and reduce mobility, health, and quality of life. The ReWalk ReStore™ is a soft robotic exosuit designed to assist the propulsion and ground clearance subtasks of post-stroke walking by actively assisting paretic ankle plantarflexion and dorsiflexion. Previous proof-of-concept evaluations of the technology demonstrated improved gait mechanics and energetics and faster and farther walking in users with post-stroke hemiparesis. We sought to determine the safety, reliability, and feasibility of using the ReStore™ during post-stroke rehabilitation.

Methods: A multi-site clinical trial (NCT03499210) was conducted in preparation for an application to the United States Food and Drug Administration (FDA). The study included 44 users with post-stroke hemiparesis who completed up to 5 days of training with the ReStore™ on the treadmill and over ground. In addition to primary and secondary endpoints of safety and device reliability across all training activities, an exploratory evaluation of the effect of multiple exposures to using the device on users' maximum walking speeds with and without the device was conducted prior to and following the five training visits.

Results: All 44 study participants completed safety and reliability evaluations. Thirty-six study participants completed all five training days. No device-related falls or serious adverse events were reported. A low rate of device malfunctions was reported by clinician-operators. Regardless of their reliance on ancillary assistive devices, after only 5 days of walking practice with the device, study participants increased both their device-assisted (Δ: 0.10 ± 0.03 m/s) and unassisted (Δ: 0.07 ± 0.03 m/s) maximum walking speeds (P's < 0.05).

Conclusions: When used under the direction of a licensed physical therapist, the ReStore™ soft exosuit is safe and reliable for use during post-stroke gait rehabilitation to provide targeted assistance of both paretic ankle plantarflexion and dorsiflexion during treadmill and overground walking.

Trial registration: NCT03499210. Prospectively registered on March 28, 2018.

Keywords: Exoskeleton; Exosuit; Physical therapy; Rehabilitation; Stroke; Walking.

Fig. 1

The ReWalk ReStore™ consists of an actuator assembly, calf wrap assembly, and shoe insole. A power supply is integrated into the actuator assembly. Bowden cables span these components to transmit assistive forces generated by the actuator to the ankle. More specifically, two Bowden cables are used in the ReStore™, each having attachment points proximal (on the Calf Wrap Assembly) and distal (on the Insole) to the ankle. One of the cables is located anterior to the ankle and the other is located posterior to the ankle. When the anterior cable is retracted, an ankle dorsiflexion torque is produced. When the posterior cable is retracted, an ankle plantarflexion torque is produced

Fig. 2

Left - The ReWalk ReStore™ graphical user interface allows three modes of use: Assist, where ankle plantarflexion and dorsiflexion are actively assisted; Slack, where the device is made transparent to the user; Brace, where the ankle dorsiflexion cable is tensioned throughout the entire gait cycle to mimic an ankle foot orthosis during swing phase without hindering ankle dorsiflexion during the stance phase. In addition, the user’s stance time symmetry is shown and updated on a step-by-step basis. Right - The amplitude of ankle plantarflexion and dorsiflexion assistance can be modified in real-time using a visual slide ruler with a 0 to 100% scale. 100% plantarflexion assistance corresponds to a force equal to 25% of the wearer’s bodyweight. 100% dorsiflexion assistance corresponds to the maximum allowed cable travel distance (50 mm). For the study, the target level for plantarflexion assistance was 100% (i.e., 25% of the wearer’s bodyweight) and the target level for dorsiflexion assistance was the minimum needed for adequate ground clearance and heel strike, as determined visually by the physical therapist. See previous work [19] for visual depiction of the forces applied by the exosuit

Fig. 3

Individual subject and group-level changes in (a) exosuit-assisted and (b) unassisted maximum walking speeds after 5 days of walking practice with the ReStore™ relative to different walking speed change thresholds reported in the literature: 0.05 m/s (small meaningful change), 0.10 m/s (large meaningful change), and 0.16 m/s [20]. T1 – visit 1; T2 – visit 7 Error bars are Standard Error

Fig. 4

The magnitude of improvements in (a) exosuit-assisted and (b) unassisted maximum walking speed did not significantly differ between the participant subset that required the use of an AFO or cane for the walking evaluations (n = 16) versus the subset that did not require use of an assistive device (n = 20) Error bars are Standard Error