Hybrid therapy of walking with Kinesis overground robot for persons with incomplete spinal cord injury: A feasibility study

• We investigate the feasibility of providing the hybrid therapy of walking with Kinesis hybrid exoskeleton.
• We compare and investigate the role of the stimulation and the compliant robot control.
• Three case studies are presented. The cooperative controller of Kinesis adapted to patients and voluntary actions.
• No noticeable differences were observed between compliant and trajectory control.

Rehabilitation of walking ability is one of the most important objectives after a spinal cord injury. Robotic and neuroprosthetic technologies hold a considerable potential for driving walking rehabilitation therapies. However, new developments are needed in order to improve the walking rehabilitation interventions based in these technologies.We recently presented a cooperative control strategy of Kinesis, a lower limb exoskeleton for providing hybrid therapy of walking (Del-Ama, 2014). Its design aimed to actively manage muscle fatigue caused by surface electrical stimulation, and to implement the assist-as-needed control paradigm in which both stimulation and robotic controller cooperate with the residual functionality of the user. In this article we present three case studies for investigating the feasibility of the hybrid therapy of walking delivered with Kinesis in patients with incomplete spinal cord injury. Besides, the adaptability features of Kinesis stimulation–robot cooperative control are assessed, characterizing the behavior of the cooperative controller while providing hybrid therapy of walking.Patients with incomplete spinal cord injury participated in the experiments. The protocol consisted of walking with Kinesis during 6 min. Three configurations of the cooperative controller were tested for each patient in separate sessions in order to investigate its adaptability features. The immediate impact of the hybrid therapy of walking was assessed through several variables that represent the physiological impact, user–exoskeleton physical interaction, stimulation intensity and user subjective perception of the hybrid therapy of walking.Results show that the cooperative controller of Kinesis adapted to patient functional deficits and voluntary actions during walking, modulating stimulation and robotic assistance, which was the aim of the controller design. Nevertheless, no noticeable differences were observed in the comparison between compliant and trajectory exoskeleton control. Further work is envisioned regarding several aspects of hybrid walking control: stimulation control based on muscle activation estimate, improved semi-automatic control of walking, and improved muscle fatigue monitoring. The hybrid walking therapy was tolerated by the patients without adverse effects, along with a tolerable physical demand. This shows a potential for walking rehabilitation in motor incomplete SCI patients, guaranteeing further research on this topic.