Abstract
Disorders of the central nervous system sometimes cause severe sensory motor paralysis accompanied by gait impairment. Recently, there are several reports on the effectiveness of robot-assisted gait training for patients experiencing these issues. The purpose of this case report was to assess the neuromechanical effect of a wearable robot suit HAL (Hybrid Assistive Limb) during post-operative gait training in a patient with gait impairment due to compressive myelopathy caused by ossification of the posterior longitudinal ligament (OPLL). For this purpose, we compared lower limb muscular activities while the patient was walking with and without the robot through a course of treatment sessions by (i) gait phase-dependent muscle usage analysis, (ii) muscle synergy analysis, and (iii) muscle network analysis. The results show (i) enhanced activity of the extensor muscles for weight-bearing in the initial sessions by using HAL and reduced knee extensor and increased hip extensor activations for achieving larger steps and faster gait in the later sessions; (ii) involvement of a greater number of synergies during walking with HAL than without HAL; and (iii) modulated muscle network property during walking with HAL remaining until the next HAL session. The patient's gait was improved after completing HAL sessions, acquiring close to normal joint profile with greater range of joint movement, faster walking speed, and larger step length. We discuss that the muscular activity modulation during walking with HAL suggests altered control of the muscles by the central nervous system during post-operative walking. Activity-dependent sensorimotor augmentation by HAL is discussed in the context of recovery of gait control by the central nervous system. The relationship between the altered control and the achieved gait recovery requires further investigation.
Highlights
Disorders of the central nervous system sometimes cause severe sensory motor paralysis accompanied by gait impairment
The observed issues were redness on the skin due to attachment of the electrodes and minor scratches due to interference with belts and harnesses
In order to evaluate the effect of gait training using robot suit HAL, gait and lower limb muscle activity were recorded through HAL sessions and analyzed in a thoracic myelopathy patient who experienced a severe sensory motor paralysis and gait impairment before and after spine surgery
Summary
Disorders of the central nervous system sometimes cause severe sensory motor paralysis accompanied by gait impairment. Robot suit HAL (Hybrid Assistive Limb; Cyberdyne, Tsukuba, Japan) assists motion of the bilateral hip and knee joints during walking in accordance with voluntary motion intension of the user [9]. It actuates the electric motors embedded in the hips and knees of its exoskeleton in real time, amplifying bioelectric activation of the relevant muscles which are detected using surface electrodes attached on the hip and knee muscles. Surgical treatment for spinal cord decompression is recommended when symptomatic neurological deterioration is observed, including gait disturbance, bladder disorder, and a myelopathic hand [22,23,24]; otherwise, the risk of cervical spinal cord injury is suggested [25, 26]. Patients are prescribed with a rehabilitation program
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