I can't tell from here if they are measuring walking without the device. The goal is walking without device help.
Effects of wearable ankle robotics for stair and over-ground training on sub-acute stroke: a randomized controlled trial
Journal of NeuroEngineering and Rehabilitation volume 18, Article number: 19 (2021)
Abstract
Background
Wearable ankle robotics could potentially facilitate intensive repetitive task-specific gait training on stair environment for stroke rehabilitation. A lightweight (0.5 kg) and portable exoskeleton ankle robot was designed to facilitate over-ground and stair training either providing active assistance to move paretic ankle augmenting residual motor function (power-assisted ankle robot, PAAR), or passively support dropped foot by lock/release ankle joint for foot clearance in swing phase (swing-controlled ankle robot, SCAR). In this two-center randomized controlled trial, we hypothesized that conventional training integrated with robot-assisted gait training using either PAAR or SCAR in stair environment are more effective to enhance gait recovery and promote independency in early stroke, than conventional training alone.
Methods
Sub-acute stroke survivors (within 2 months after stroke onset) received conventional training integrated with 20-session robot-assisted training (at least twice weekly, 30-min per session) on over-ground and stair environments, wearing PAAR (n = 14) or SCAR (n = 16), as compared to control group receiving conventional training only (CT, n = 17). Clinical assessments were performed before and after the 20-session intervention, including functional ambulatory category as primary outcome measure, along with Berg balance scale and timed 10-m walk test.
Results
After the 20-session interventions, all three groups showed statistically significant and clinically meaningful within-group functional improvement in all outcome measures (p < 0.005). Between-group comparison showed SCAR had greater improvement in functional ambulatory category (mean difference + 0.6, medium effect size 0.610) with more than 56% independent walkers after training, as compared to only 29% for CT. Analysis of covariance results showed PAAR had greater improvement in walking speed than SCAR (mean difference + 0.15 m/s, large effect size 0.752), which was in line with the higher cadence and speed when wearing the robot during the 20-session robot-assisted training over-ground and on stairs.
Conclusions
Robot-assisted stair training would lead to greater functional improvement in gait independency and walking speed than conventional training in usual care. The active powered ankle assistance might facilitate users to walk more and faster with their paretic leg during stair and over-ground walking.
Trial registration: ClinicalTrials.gov NCT03184259. Registered on 12 June 2017.
Introduction
Stroke is a leading cause of long-term disability [1]. Person with stroke commonly suffer from foot drop problem, with high falling risk because the affected foot would drag on the ground and easily stumble on obstacles [2]. Effective gait recovery is essential to improve quality of life [3] and independency of stroke survivors [4]. Early rehabilitation in sub-acute phase is known to be more effective [4, 5], but after completion of conventional gait rehabilitation, approximately 50–60% of stroke survivors still experienced some degree of motor impairment, and about half of them were still at least partly dependent in walking [6].
Conventional gait rehabilitation often involved intensive, repetitive, and task-specific gait practices [7,8,9], mainly walking on level surfaces; while some studies showed intensive stepping training on stairs could improve walking speed and balance in sub-acute [10] and chronic stroke [11, 12]. Previous researches showed sub-acute stroke survivors participating in early gait training together with electromechanical-assisted robotics, such as Lokomat, Gait Trainer, and G-EO system, could improve recovery of gait independency to a certain extent [4, 9]. But these gait training systems confined the users in constant treadmill-like setting. An important goal of gait rehabilitation is to enable independent walking and confidence to enhance their quality of life as soon as possible without assistance from caregivers [4, 13], and the real-world walking environment would involve varying terrains, like obstacles, slopes, and stairs. Following a task-specific training approach [8], early stroke rehabilitation on stair negotiation could potentially enhance gait re-education for better outcome on gait independency at hospital discharge. However, intensive stair training was not a common clinical practice for sub-acute stroke because of safety concern on stair environment.
To facilitate stair negotiation of person with stroke, ankle–foot orthoses (AFO) were commonly prescribed to passively support the dropped foot during swing phase [14, 15]. A meta-analysis showed the immediate effect of applying AFO could significantly improve walking speed and balance [16], but long-term application of rigid AFO did not influence gait pattern of sub-acute stroke, with limited therapeutic effects [17]. Studies also showed conventional rigid AFO did not mimic normal ankle movement during walking and might impose undesirable restrictions on ankle range of motion [14, 18]. In particular, restricted ankle joint could raise safety issue when the user was negotiating stairs onto a lower level. The major challenge was how to position the dropped foot properly and consistently to avoid tripping onto the step edge when negotiating stairs. In these cases, wearable ankle robotics could be a viable solution to enable better ankle joint control during stair training.
Existing lower-limb rehabilitation robots were often limited by their device weight and portability for stair environment, so few of these devices could be evaluated and developed to the stage of commercialization and clinical application [19]. G-EO system was a commercialized end-effector robot that could simulate stair climbing in a treadmill-like environment by moving foot plates in cycle to reproduce step length and height of stairs, but the system was bulky and stationary. The randomized controlled trial (RCT) evaluated the stair version of G-EO system focused on balance training of chronic stroke subjects [20]. Portable-power ankle–foot orthosis developed in the University of Illinois used a pneumatic bidirectional rotatory actuator to provide untethered ankle assistance on level ground and stairs. The robot and control algorithm were evaluated on healthy subjects (n = 5) as a technical feasibility test [21]. Recent development of ReStore exo-suit (ReWalk Robotics, USA) featured a soft garment-like design driven by Bowden cable, could offer potential solution to reduce device weight and bulkiness of robot at ankle joint [22]. Similar ankle rehabilitation robotics have also shown their potential to be an alternative gait rehabilitation for stroke [19, 23,24,25,26], like Anklebot [8]. However, few studies investigated how impaired subjects would respond to these rehabilitation robots immediately during walking on stairs, and few studies reported the therapeutic effects of these devices in multi-center RCT setting [4, 19, 25, 26].
Our research team has already developed an exoskeleton ankle robot for gait training on people with chronic stroke and foot drop problem [27]. The robot could provide active assistive torque to facilitate paretic ankle dorsiflexion for stair clearance and assist plantarflexion for loading response (power-assisted mode); alternatively, the motor could also lock the ankle joint at neutral position for foot clearance during swing phase like a rigid AFO, and release the lock for free ankle movement in stance phase (swing-controlled mode). The lightweight (0.5 kg on the paretic ankle) and portable design of this robot-assisted AFO could make a potential rehabilitation tool for gait training of hemiplegic stroke on over-ground walking and stair ascending/descending.
Our previous study has already evaluated the ankle robot in a pilot RCT for chronic stroke, which showed significant improvement in gait independency and enhanced gait confidence at heel strike after wearing this robot for 20-session stair and over-ground gait training [28]. Nevertheless, early rehabilitation in sub-acute stroke is known to have greater impact on functional recovery than chronic stroke. The primary objective of the current study was to evaluate the effects on sub-acute stroke survivors with the wearable robot-assisted AFO. We hypothesized conventional training integrated with 20-session robot-assisted training (10-min stair training plus 20-min over-ground walking) in early stroke wearing the ankle robot either in power-assisted mode or the swing-controlled mode, would result in greater functional improvement in gait independency, balance, and speed, than conventional training only. We further hypothesized active powered assistance would have more benefit on functional improvement than passive ankle swing control during the robot-assisted training.
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