Combining neural stimulation and a powered exoskeletal knee to enhance walking after stroke

Introduction: In this study, we developed a unilateral, hybrid exoskeleton designed to augment post-stroke mobility through integration of noninvasive neural stimulation and a motorized knee orthosis. We evaluated proof of concept for this hybrid exoskeleton in a stroke survivor by assessing whether: (1) the motor and transmission possess sufficient backdrivability to facilitate effective muscle-generated movements, (2) the motor can independently drive movement, and (3) the combined application of stimulation and motor generate kinematic improvements superior to either modality used in isolation. Methods: The device was evaluated on an ambulatory stroke survivor under four overground walking conditions: (1) without the device, (2) stimulation only while wearing the exoskeleton, (3) motor assistance only, and (4) hybrid stimulated and motorized assistance. A motion capture system was used to obtain lower limb joint angles to assess the differences in each walking condition. Results: Changes towards neurotypical hip, knee and ankle angles were found between the gait with no device compared to the assistive conditions. Hip-knee cyclograms suggest hybrid assistance most resembled neurotypical gait. Conclusions: Individually, neural stimulation and motor assistance resulted in improved gait kinematics and hybrid assistance provided greater improvement than each form of individual assistance.