In a literature review on the use of robotic exoskeletons for gait rehabilitation of adults post stroke, researchers at the University of British Columbia determined exoskeletons can be used safely in gait training intervention and, in some cases, offer additional benefits for patients.
The review was conducted by Dennis R. Louie, PT, doctoral student in the Graduate Program in Rehabilitation Sciences, and Janice J. Eng, PhD, PT, professor in the Department of Physical Therapy, both of the University of British Columbia. Louie and Eng hope their findings could be used to guide research and propose recommendations.
“Powered robotic exoskeletons were originally intended [for] rehabilitation for individuals with spinal cord injury, but more recently had been marketed as an intervention for other neurological conditions, including stroke,” Louie told O&P News. “Furthermore, after stroke there is a window of opportunity for neurological and functional recovery given the neuroplasticity of the brain. While for spinal cord injured patients the exoskeleton is used as an assistive device for walking, for stroke patients the exoskeleton is a possible training tool to potentially augment standard physiotherapy.”
Louie and Eng noted that although conventional physical therapy gait rehabilitation leads to speed and endurance improvements for patients post stroke, it can be physically straining for therapists. While treadmill-based robotics have been shown to reduce the strain on therapists, research has shown these require less control from patients, leading to less active participation. Powered robotic exoskeletons could provide an alternative training option as these require the user to actively control swing initiation and foot placement while maintaining trunk and balance control and navigating a path over varying surfaces, according to the researchers.
Because the use of powered exoskeletons for post-stroke treatment is still new, the goal of the review was to determine the safety and efficacy of this option.
Overview of literature
Louie and Eng searched five databases — PubMed, OVID MEDLINE, CINAHL, Embase and Cochrane Central Register of Clinical Trials — for articles from the inception of the databases to October 2015. A total of 11 studies, all published within the past 5 years, met the inclusion criteria. Among the 11 articles, five studies were conducted in the United States, five in Japan and one in Sweden. Studies included patients ranging from sub-acute (less than 7 weeks) to chronic (greater than 6 months). Seven studies were pre-post clinical and four were controlled trials.
The studies used a variety of exoskeletons with different setups and control mechanisms. Five studies used a robotic exoskeleton unilaterally on the affected leg, another five used a bilateral setup for gait training and one study progressed patients from bilateral to unilateral configuration. The most-used exoskeleton was the Hybrid Assistive Limb (HAL), used in six studies. Others included the AlterG Bionic Leg, the H2 and the Stride Management Assist (SMA) system.
Training periods ranged from a single session to several weeks or months, with sessions running between 20 minutes and 90 minutes, and frequency ranging between two sessions and five sessions per week. Training protocol was different for each study but in general, training began with weight-bearing functional tasks, such as sit-to-stand, standing balance and weight shift, and progressed to walking practice. Two studies utilized a treadmill for walking practice. Several studies utilized an overhead harness to support body weight, ensure safety and improve walking mechanics.
Ten studies included a measure of gait speed, directly or via the 10-minute walk test. Other walking measures included walking endurance, measured by five studies; Timed Up and Go, measured by seven studies; and functional ambulation category, measured by two studies. Participants did not wear the exoskeleton for walking measures.
Results showed 10 of the studies reported varying degrees of improved walking ability after exoskeleton training.
“Clinical trials demonstrate that powered robotic exoskeletons can be used safely as a gait training intervention for both sub-acute and chronic [stroke] patients,” Louie said.
However, improvements were different between patients with chronic stroke vs. patients with sub-acute stroke.
“Preliminary findings suggest exoskeletal gait training is equivalent to traditional therapy for chronic stroke patients, as there were not significant differences found between control groups and exoskeletal intervention groups in several studies,” Louie said.
For sub-acute patients, exoskeleton training was shown to have additional benefits compared to conventional gait training.
“Several studies in sub-acute stroke show that exoskeletal gait training results in greater recovery of walking ability,” Louie said.
Better results for sub-acute patients may have occurred due to the timing and baseline levels of participants, Louie said. Sub-acute patients began their training at a greater level of dependency and therefore had greater room for improvement.
The researchers were surprised to find many well-known exoskeletons in North America, such as those from Ekso Bionics, ReWalk Robotics and Parker Hannifin, had not yet been used in stroke trials. Louie said this may have been related to the availability to the devices and FDA approvals at the time.
“As more devices are approved for clinical use with other populations, more research can be conducted in this area of gait training,” he said.
Although study results are preliminary, Louie said the studies show the potential for exoskeleton use to help rehabilitate stroke patients.
“The exoskeletons provide an opportunity for weight-bearing, walking practice and task-specific practice; clinicians may choose to utilize exoskeletons for these reasons as part of their intervention, exercising their clinical judgment,” Louie said.
In terms of possible benefits for patients, he said, “the use of exoskeletons may allow for earlier waking practice as the physical support from the device exceeds the capacity of a single or even two therapists to provide prolonged, repetitious gait training.”
Questions for future research
Louie and Eng noted in their paper that although exoskeletons are safe for use in stroke rehabilitation, there is not yet sufficient evidence to advocate for or against using these devices in clinical practice. They developed seven questions to guide future research. They hope research will compare the results of chronic vs. sub-acute stroke patients; will examine the impact of initial functional presentation on improvement in walking ability; will compare different exoskeletons; will compare bilateral vs. unilateral design; will determine the optimal dose of exoskeletal training to improve walking ability; will compare exoskeletal gait training to weight-supported treadmill-walking; and will determine whether exoskeletons can be used to safely ambulate two-person assisted patients immediately post stroke with minimal injury risk to therapists.
“Future research in this area should focus on incorporating aspects that have not yet been explored in current literature,” Louie said. – by Amanda Alexander
- Louie DR, et al. J Neuroeng Rehabil. 2016;doi:10.1186/s12984-016-0162-5.
Disclosures: Louie reports the project was supported by funding from a Grant-in-Aid from the Heart and Stroke Foundation of Canada and the Research Chairs Program. The researchers declare no competing interests.