Supplemental Stimulation Improves Swing Phase Kinematics During Exoskeleton Assisted Gait of SCI Subjects With Severe Muscle Spasticity

Abstract

Spasticity is a common comorbidity associated with spinal cord injury (SCI). Robotic exoskeletons have recently emerged to facilitate legged mobility in people with motor complete SCI. Involuntary muscle activity attributed to spasticity, however, can prevent such individuals from using an exoskeleton. Specifically, although most exoskeleton technologies can accommodate low to moderate spasticity, the presence of moderate to severe spasticity can significantly impair gait kinematics when using an exoskeleton. In an effort to potentially enable individuals with moderate to severe spasticity to use exoskeletons more effectively, this study investigates the use of common peroneal stimulation in conjunction with exoskeleton gait assistance. The electrical stimulation is timed with the exoskeleton swing phase, and is intended to acutely suppress extensor spasticity through recruitment of the flexion withdrawal reflex (i.e., while the stimulation is activated) to enable improved exoskeletal walking. In order to examine the potential efficacy of this approach, two SCI subjects with severe extensor spasticity (i.e., modified Ashworth ratings of three to four) walked in an exoskeleton with and without supplemental stimulation while knee and hip motion was measured during swing phase. Stimulation was alternated on and off every ten steps to eliminate transient therapeutic effects, enabling the acute effects of stimulation to be isolated. These experiments indicated that common peroneal stimulation on average increased peak hip flexion during the swing phase of walking by 21.1° (236%) and peak knee flexion by 14.4° (56%). Additionally, use of the stimulation decreased the swing phase RMS motor current by 228 mA (15%) at the hip motors and 734 mA (38%) at the knee motors, indicating improved kinematics were achieved with reduced effort from the exoskeleton. Walking with the exoskeleton did not have a significant effect on modified Ashworth scores, indicating the common peroneal stimulation has only acute effects on suppressing extensor tone and aiding flexion. This preliminary data indicates that such supplemental stimulation may be used to improve the quality of movement provided by exoskeletons for persons with severe extensor spasticity in the lower limb.

Effects of Robot-Assisted Gait Training in Individuals with Spinal Cord Injury: A Meta-analysis

“…From the 18 studies, 7 trials were done in the United States [36][37][38][39][40][41][42], 2 in Spain [43,44], 2 in Switzerland [45,46], 2 in Canada [47,48], 2 in Italy [49,50], 2 in Japan [51,52], and one in Germany [53].…”

“…Although age was not reported in all included studies, the participants' age of RCTs and non-RCTs ranged from 34 [46] to 59 [45] and 19 [51] to 62 [52] years, respectively. One RCT [36] and one non-RCT [39] did not report the proportion of gender. For other included RCTs, the proportion between males and females was 101 : 79.…”

“…All non-RCTs recruited representative SCI subjects and no control 3 BioMed Research International group. All studies had secure record on training protocol but one study [39] did not. All studies assessed outcomes independently.…”

Pavlovian Control of Intraspinal Microstimulation to Produce Over-Ground Walking

“…Walking is accomplished using open loop alternation between stimulation of the quadriceps muscles and the peroneal nerve, with each step initiated using push-buttons on a walker. Powered exoskeletons initiate open-loop walking by the user leaning forward (Chang et al 2015;Ekelem and Goldfarb 2018). The users are expected to adapt their walking to accommodate the control strategy in the device.…”

Development, Dynamic Modeling, and Multi-Modal Control of a Therapeutic Exoskeleton for Upper Limb Rehabilitation Training

“…Crea et al developed a semi-autonomous whole-arm exoskeleton for the stroke patients performing activities of daily living (ADL) utilizing hybrid electroencephalography and electrooculography feedback signals [ 16 ]. Many other representative exoskeleton-based therapeutic robot have also been designed, such as CAREX-7 [ 17 ], RUPERT [ 18 ], ULEL [ 19 ], ArmeoPower [ 20 ], Indego [ 21 ], and ETS-MARSE [ 22 ].…”