Keywords

Robot-assisted rehabilitation
Acute stroke
Gait training
HAL
FIM
Measures

1. Introduction

Minimizing physical impairment and facilitating functional recovery following stroke is the most important target of managing patients with acute stroke. There is accumulating evidence of enhanced plasticity, such as alterations of gene expression, inhibitory/excitatory synaptic input balance, and structural changes including synaptogenesis, which occur immediately after stroke [[1], [2], [3], [4], [5]]. Task-specific motor training that is initiated soon after stroke facilitates the reorganization of connections in a sensitive manner, which reportedly induces dramatic recovery if residual motor cortical areas are spared [[6], [7], [8]]. Thus, motion-focused training during the early phase of post-stroke may prove to be a promising intervention to increase the resolution of impairment in a proportional manner in patients with stroke.
There are still several challenges associated with making an acute stroke rehabilitation protocol. A very early rehabilitation trial (AVERT) demonstrated that a higher dose and very early mobilization within 24 h of stroke onset in acute strokes did not improve functional outcome at 3 months in patients with very early mobilization, compared to those who received usual care [9]. According to a meta-analysis, newly developed electromechanical-assisted training using various devices for walking, in combination with physical therapy, within 3 months after stroke improved independent walking compared with gait training without a device [10]. However, a device selection and rehabilitation protocol to enhance recovery of function in patients with acute stroke has not yet been established.
A cyborg-type robot, Hybrid Assistive Limb (HAL), which is manufactured by Cyberdyne Inc., Tsukuba, Japan, is a promising robotic device using innovative technology cybernics, where man and machine are connected mechanically and electronically, is used in the system. A biped non-medical model of HAL, HAL-FL05, was chosen in the present clinical setting according to Japanese device regulation. Briefly, HAL can estimate and decode the wearer's motion intension of bilateral hips and knee joints in real time from bioelectrical signals, such as the wearer's motor unit potentials on the skin with joint angles and shoe force plate signals analyses. It can enhance the wearer's gait movement by means of appropriate actuator torque using four actuators on the bilateral hip and knee joints, as described in detail elsewhere [11]. In Japan, HAL was approved as a medical device for patients with eight rare neuromuscular diseases in 2015; however, it has not yet been approved for patients with acute stroke. Although there are reports on the safety or feasibility of the HAL system [12,13], and its beneficial effects on gait [14,15], its effectiveness on gait training following acute stroke has not yet been confirmed. Before a randomized controlled clinical trial to test the efficacy of HAL in patients with acute stroke can be conducted, appropriate outcome measures must first be established.
The aim of the present study was to evaluate several outcome measures following gait training, which was initiated within 1 week of acute stroke onset, to design a confirmatory clinical trial for gait training using HAL in the future.