Review of hybrid exoskeletons to restore gait following spinal cord injury

Abstract

Abstract-Different approaches are available to compensate gait in persons with spinal cord injury, including passive orthoses, functional electrical stimulation (FES), and robotic exoskeletons. However, several drawbacks arise from each specific approach. Orthotic gait is energy-demanding for the user and functionally ineffective. FES uses the muscles as natural actuators to generate gait, providing not only functional but also psychological benefits to the users. However, disadvantages are also related to the early appearance of muscle fatigue and the control of joint trajectories. Robotic exoskeletons that provide joint moment compensation or substitution to the body during walking have been developed in recent years. Significant advances have been achieved, but the technology itself is not mature yet because of many limitations related to both physical and cognitive interaction as well as portability and energy-management issues. Meanwhile, the combination of FES technology and exoskeletons has emerged as a promising approach to both gait compensation and rehabilitation, bringing together technologies, methods, and rehabilitation principles that can overcome the drawbacks of each individual approach. This article presents an overview of hybrid lower-limb exoskeletons, related technologies, and advances in actuation and control systems. Also, we highlight the functional assessment of individuals with spinal cord injury.

Hybrid FES–robotic gait rehabilitation technologies: a review on mechanical design, actuation, and control strategies

“…The individual then initiated the following step for the contralateral leg by pressing the "go" button again. Although during testing, the finite automaton controller successfully moved through the different states and the subjects showed sufficient joint angles and foot-ground clearance, this hybrid system has been reported to result in high energy cost of gait (del-Alma et al 2012). …”

“…These combined technologies are conventionally termed Hybrid Robotic Rehabilitation Systems and are defined as systems that aim to achieve motor recovery or compensate motor function by combining electrically stimulated muscle action and torque provision to the joints (del-Ama et al 2014). A previous review has identified and discussed the key technological aspects concerning hybrid exoskeletons (del-Alma et al 2012). However, a review not only focusing on the application of this technology to powered exoskeletons but also to robotic footplates systems, mobile platforms and cycling systems is still not recorded in literature.…”

Neuroprosthetic technology for individuals with spinal cord injury

“…[21][22][23] For a review of hybrid FES systems, see Ref. 24 There is currently no implantable FES system (with or without an orthosis) available commercially in the United States, although some devices are currently undergoing clinical trial. Work is underway to optimize the coupling of the FES and orthoses and to create controllers that adapt to changing muscle properties and/or modify stimulation parameters as part of a closed-loop system.…”

Sensor-based hip control with hybrid neuroprosthesis for walking in paraplegia

“…However, improvements to the standard RGO resulted in minimal increase in walking speed primarily with increased cadence since the constraints imposed on the sagittal kinematics by the 1:1 reciprocal hip coupling limiting step length were not addressed [16]. A promising new approach involves combining functional neuromuscular stimulation (FNS) with controllable exoskeletons to provide a more efficient power for ambulation with potential for the physiological benefits of active muscle contraction [17]. Exoskeleton portion of hybrid neuroprosthesis consisting of hydraulic variable-constraint hip mechanism, stance-control knee mechanisms, and locked ankle-foot orthoses.…”