Atypical walking in the months and years after stroke constrain community reintegration and reduce mobility, health, and quality of life. The ReWalk ReStore™ is a soft robotic exosuit designed to assist the propulsion and ground clearance subtasks of post-stroke walking by actively assisting paretic ankle plantarflexion and dorsiflexion. Previous proof-of-concept evaluations of the technology demonstrated improved gait mechanics and energetics and faster and farther walking in users with post-stroke hemiparesis. We sought to determine the safety, reliability, and feasibility of using the ReStore™ during post-stroke rehabilitation.
A multi-site clinical trial (NCT03499210) was conducted in preparation for an application to the United States Food and Drug Administration (FDA). The study included 44 users with post-stroke hemiparesis who completed up to 5 days of training with the ReStore™ on the treadmill and over ground. In addition to primary and secondary endpoints of safety and device reliability across all training activities, an exploratory evaluation of the effect of multiple exposures to using the device on users’ maximum walking speeds with and without the device was conducted prior to and following the five training visits.
All 44 study participants completed safety and reliability evaluations. Thirty-six study participants completed all five training days. No device-related falls or serious adverse events were reported. A low rate of device malfunctions was reported by clinician-operators. Regardless of their reliance on ancillary assistive devices, after only 5 days of walking practice with the device, study participants increased both their device-assisted (Δ: 0.10 ± 0.03 m/s) and unassisted (Δ: 0.07 ± 0.03 m/s) maximum walking speeds (P’s < 0.05).
When used under the direction of a licensed physical therapist, the ReStore™ soft exosuit is safe and reliable for use during post-stroke gait rehabilitation to provide targeted assistance of both paretic ankle plantarflexion and dorsiflexion during treadmill and overground walking.
Bipedal locomotion is characterized by alternating periods of single and double limb support, with ground clearance by the swing limb and propulsion by the trailing stance limb serving as crucial walking subtasks [1, 2]. Healthy individuals are able to generate an ankle dorsiflexion moment during each limb’s swing phase to lift the foot and facilitate ground clearance. They are also able to generate an ankle plantarflexion moment during each limb’s late stance phase to produce the propulsive force required to advance the limb and body . In contrast, post-stroke hemiparesis results in impaired paretic dorsiflexion and plantarflexion that, in turn, hinders ground clearance and propulsion [4,5,6,7,8] and, ultimately, necessitates compensatory walking strategies [9, 10] that make walking more effortful and unstable [11,12,13,14].
The ReWalk ReStore™ is a soft robotic exosuit designed to augment the paretic ankle’s ability to produce both dorsiflexor and plantarflexor moments during walking. In early proof-of-concept studies conducted with a research version of the device [15, 16], exosuits were shown to facilitate immediate increases in swing phase paretic ankle dorsiflexion by an average 5 degrees , the propulsion force generated by the paretic limb by an average 10% , and the positive center of mass (COM) power generated by the paretic limb during late stance phase by an average 22% . Together, these improvements in paretic limb function resulted in reduced propulsion asymmetry by 20%  and the asymmetry in positive COM power generated during late stance phase by 39% . Also observed were immediate reductions in hip hiking and circumduction compensations of over 20% , reductions in the energy cost of walking by an average 10% [17, 18], faster overground walking speeds by a median 0.14 m/s, and farther walking distances during the 6-min walk test by a median 32m .
Building on this foundational biomechanical, physiological, and clinical research, the objective of this multi-site clinical trial was to evaluate safety, feasibility, and reliability of using exosuits during post-stroke rehabilitation in preparation for a commercial clinical application to the United States Food and Drug Administration (FDA). In contrast to previous laboratory-based research that studied the immediate effects of exosuit prototypes on clinical, biomechanical, and physiological outcomes, this translational research sought to determine the safety of clinicians and patients with post-stroke hemiparesis using the commercially-adapted ReStore™ in clinical settings, the feasibility of clinician operators applying the ReStore™ during both treadmill and over ground gait training activities, and the reliability of the technology across multiple training visits. In addition to outcomes of safety, feasibility, and device reliability, an exploratory evaluation of the impact that multiple training visits with the device have on users’ maximum walking speeds, both with and without the device, was also included.
The ReStore™ is indicated for use by individuals with post-stroke hemiparesis undergoing stroke rehabilitation under the supervision of a licensed physical therapist. To assess the safety, device reliability, and clinical feasibility of using the ReStore™ during post-stroke gait rehabilitation, a multi-site trial was conducted. The trial included five clinical sites and 44 users with post-stroke hemiparesis. The study was approved by the Institutional Review Boards of Boston University, Spaulding Rehabilitation Hospital, The Shirley Ryan AbilityLab, TIRR Memorial Hermann Hospital, Kessler Rehabilitation Hospital, and Moss Rehabilitation Hospital. Written informed consent was secured for all participants.
Study inclusion and exclusion criteria
Study participant eligibility requirements consisted of: (i) one-sided ischemic or hemorrhagic stroke, (ii) > 2 weeks post-stroke, (iii) age > 18 years, (iv) height between 4′8″ and 6′7″, (v) weight < 264lbs, (vi) medical clearance, (vii) ability to ambulate at least 5 ft without an AFO and with no more than minimal contact assistance, (viii) ability to follow a 3-step command, (ix) ability to fit suit components, (x) no greater than 5 degrees of ankle plantar flexion contracture, and (xi) Modified Ashworth Scale for tone at 3 or less for ankle dorsiflexor and plantarflexor muscles. Exclusion criteria included: (i) severe aphasia limiting ability to express needs or discomfort verbally or non-verbally, (ii) serious co-morbidities that interfere with ability to participate, (iii) significant Peripheral Artery Disease, (iv) colostomy bag, (v) current pregnancy, (vi) uncontrolled hypertension, (vii) participation in any other clinical trial, (viii) open wounds or broken skin at device locations requiring medical management, (ix) urethane allergies, (x) and current DVT.
After screening and enrollment, study participants completed up to two walking evaluations and five device exposure visits. Each exposure visit consisted of up to 20 min of overground walking practice and 20 min of treadmill walking practice while receiving assistance from the device. The visit schedule consisted of a minimum of two visits per week, with the expectation of no more than 4 weeks between the pretraining and posttraining evaluations. Actual activities and durations were dependent on each study participant’s abilities as determined by the treating physical therapist as per their usual practices. The target level for plantarflexion assistance during all active walking with the ReStore™ was 25% of the user’s bodyweight [17, 19]. The target level for dorsiflexion assistance was the minimum needed for adequate ground clearance and heel strike, as determined visually by the physical therapist.
The exosuit consists of motors worn at the waist that generate mechanical forces that are transmitted by cables to attachment points located proximally on a functional textile worn around the calf and distally on a shoe insole (Fig. 1). The overall weight of the exosuit is approximately 5kgs, with the vast majority of the weight located proximally in the actuation pack worn at the waist. Each functional textile contains a detachable liner that can be washed. For users who require medio-lateral ankle support in addition to ankle plantarflexion and dorsiflexion assistance, an optional textile component that prevents ankle inversion without restricting dorsiflexion and plantarflexion can also be used. Inertial sensors that attach to a patient’s shoes measure gait events and automate the independent timing of the active ankle plantarflexion and dorsiflexion assistance provided by the ReStore™ as previously described . Load cell sensors located at the end of each cable are used to monitor the interaction between user and exosuit and ensure that the target level of assistance is achieved [16, 17]. A hand-held device with a graphical interface allows clinicians to monitor patients’ performance and select and progress, in real-time, the assistance parameters (Fig. 2).
Because an acquired neurologic injury (such as a stroke) affects both sensory and motor function, walking can be severely affected. Sensory changes, weakness, and spasticity affect movement strategies, which alter a person’s ability to successfully respond to losses of balance. A stroke affects how much and how often a person walks and also affects walking adaptability—the ability to adapt to different conditions during ambulation—as well as endurance. Gait training generally starts as soon as possible following a stroke, using manual techniques, task-specific training, strengthening, and, when available, body weight-assisted treadmill training and robotic devices.
An example of over-ground gait training.
Movement Strategies Altered by Stroke
A movement strategy or synergy is a flexible, repeatable pattern of movement that can be quickly and automatically accessed by the central nervous system. Movement strategies allow us to store and reuse patterns of movement that have been successful in the past. Strategies are efficient, automatic movement patterns that evolve over time. Each time a loss of balance threatens, the nervous system draws on these pre-programmed movement strategies to ensure the maintenance of balance.Movement strategies used by the nervous system to respond to perturbations are diminished following a stroke.
The ankle strategy is used in response to small perturbations is also called ankle sway. Source: Lauren Robertson.
The ankle strategy—also called ankle sway—is used in response to small perturbations or losses of balance. When a small loss of balance occurs—as when standing on a moving bus—the foot acts as a lever to maintain balance by making continuous automatic adjustments to the movement of the bus. When a small balance adjustment is needed, muscles close to the floor (anterior tibialis and gastrocnemius) activate first and flow upward in a distal to proximal pattern.
When a perturbation is too large to be successfully handled by the ankle strategy, the hip strategy is needed. When the hip strategyis used, movement is centered about the hip and ankle muscles (anterior tibialis and gastrocnemius) are almost silent. The muscles in the trunk activate first as activation flows downward to the legs in a proximal to distal pattern. So, if the bus stops suddenly and the body bends forward, the low back and hamstrings will contract in that order to return the body to upright.
If the perturbation is strong and your center of gravity moves well past your base of support, it is necessary to take a forward or backward step to regain balance. This is referred to as a stepping strategy. Studies have shown age-related changes in stepping in older adults. Compared to younger people, older adults initiate the stepping strategy in response to smaller losses of balance and tend to take several small steps rather than one larger step (Maki & McIlroy, 2006).
Arm movements have a considerable role in balance control and are part of the strategies discussed above. The upper limbs start to react at the very beginning of a disruption of balance and continue to be active as the body attempts to regain control. By automatically reaching and grasping for support, the arms perform a protective function. In the case of a small perturbation, upper limb movements can prevent a fall by shifting the center of gravity away from the imbalance.
When upper extremity paresis or spasticity is present, post stroke subjects exhibit poor protective reactions during a perturbation of balance. They demonstrate a deficit in anticipatory and reactive postural adjustments. These impairments of the affected upper limbs limit a person’s ability to recover from perturbations during functional tasks such as walking (Arya et al., 2014).
Even in the absence of a neurologic disorder, age-related changes affect upper extremity reaction time when balance is disrupted. Older adults reach for support surfaces more readily than younger adults but the reach-reaction time is slower. Increased tendency to reach for support and a slowing of these reactions have been found to be predictive of falling in daily activities (Maki & McIlroy, 2006).
Comparing Reflexes, Automatic Reactions, and Volitional Movement
Think for a moment that you are cooking dinner and accidentally touch a scalding hot fry pan. You feel the heat and withdraw instantaneously. You aren’t thinking “I better take my hand off the hot pan before it burns me”—your reflexes take care of that for you. The withdrawal is almost instantaneous because your nervous system senses danger and reflexively withdraws.
This type of reaction is used in movement strategies; they are slower than reflexes but faster than volitional movement. They are fast enough to help us respond to losses of balance without having to think.
This type of movement requires thought and is relatively slow compared to reflexive and automatic movement. Using our brains to think about movement isn’t very practical when we need something done really fast—by the time your brain warns you to bend your waist, step forward, or grab onto something when the bus stops abruptly, it’s already too late to regain balance.
Stand up next to your chair. Make sure you are standing on a flat, firm surface. Now close your eyes. Notice that your body sways a little—you are using the ankle strategy to stay balanced. Notice also that after a short amount of time you sway less—that means your nervous system is adjusting. Often, following a stroke, a person looses the ability to use the ankle strategy. This can have a profound impact on balance.
Stand up again. Ask someone to give you a little nudge from behind. Try not to take a step. If it was a truly small nudge you will likely bend at the waist to try to regain your balance. This is an example of the hip strategy.
Now ask your partner to give you a slightly bigger nudge from behind. If the nudge is big enough you’ll have to take a step. This is the stepping strategy.
We use these strategies automatically, all day long, without effort. Someone who has had a stroke can’t access these strategies as quickly as you can. If faced with a nudge from a passerby, or a bus starting/stopping, or a walk on uneven ground, the inability to adjust quickly may result in a fall.
Importance of Walking Early and Often
Regaining the ability to walk following a stroke is of paramount importance to patients and caregivers alike; improving balance and walking leads to greater independence and improves general well-being.
In the first week following a stroke, only one-third of patients are able to walk without assistance. In the following weeks, walking ability generally improves. At 3 weeks, or at hospital discharge, more than half of stroke survivors can walk unaided. By 6 months, more than 80% are able to walk independently without physical assistance from another person (Balasubramanian et al., 2014).
Following a stroke, walking can take a lot of energy; impaired muscle function, weakness, and poor cardiovascular conditioning can double the amount of energy expended. The high energy cost of walking can affect a person’s ability to participate in daily activities and lead to a vicious cycle where physical activity is avoided. For example, in one study, stroke patients walked 50% of the daily amount of matched sedentary adults and used 75% of their VO2 peak for walking at a submaximal rate (Danielsson et al., 2011).
Walking may improve more rapidly when patients are involved in setting specific goals. The results of several motor learning studies in which the person’s attention was focused on the outcome of an action rather than the action itself produced more effective performance than focusing on the quality of the movement (Carr & Shepherd, 2011).
In the hospital, an early goal for walking might be to walk to the next appointment, or to walk at least part of the way, rather than being transported in a wheelchair. Each day the patient should be encouraged to select a distance to walk independently and safely. Initially, this may be only a few steps. The goal is to walk the chosen distance a certain number of times a day, increasing distance as soon as possible, and keeping a record of progress, which gives the patient a specific focus (Carr & Shepherd, 2011).
Walking Adaptability, Stepping, and Postural Control
Walking is greatly dependent upon our ability to adapt to varying environmental conditions and tasks. Walking from the bedroom to the bathroom with a walker requires a different level of attention and adaptability than walking across a busy street carrying a bag of groceries. Even walking and talking can be a challenge for post stroke patients.
Over time, up to 85% of individuals with a stroke regain independent walking ability, but at discharge from inpatient rehab only about 7% can manage steps and inclines or walk the speeds and distances required to walk competently in the community. Limited ability to adjust to changes in the task and environment means a person either avoids walking in complex situations (a safety strategy) or has a heightened risk of falls when required to walk under these challenging conditions (Balasubramanian et al., 2014).
Despite its importance, assessment of walking adaptability has received relatively little attention. Frequently used assessments of walking ability after stroke involve walking short distances (such as the Timed Up and Go test) and examination of isolated limb movements (such as the Fugl-Meyer Assessment). Although valuable, these assessments do not take into account the skills needed to re-engage in safe and independent ambulation in the home and community. Comprehensive assessments and specific interventions are needed to improve walking adaptability (Balasubramanian et al., 2014).
In addition to the ability to adapt to different conditions and tasks, walking adaptability has two other requirements: (1) stepping, and (2) postural control (Shumway-Cook & Woollocott, 2012). Stepping involves the ability to generate and maintain a rhythmic, alternating gait pattern as well as the ability to start and stop. Postural control involves both the musculoskeletal and nervous systems.
To walk effectively, the central nervous system must:
Generate the basic stepping pattern of rhythmic reciprocal limb movements while supporting the body against gravity and propelling it forward.
Maintain control of posture (equilibrium) to keep the center of mass over a constantly moving base of support and maintain the body upright in space.
Adapt to environmental circumstance or changes in the behavioral goal (Balasubramanian et al., 2014).
Source: Balasubramanian et al., 2014.
These components are especially necessary for complex tasks. For example, walking adaptability is crucial on uneven ground or cluttered terrains and when the task requires walking and turning or negotiating a curved path. There are endless combinations of task goals and environmental circumstances that must be considered to comprehensively capture walking adaptability (Balasubramanian et al., 2014).
Walking adaptability is very important for community ambulation. Patla and Shumway-Cook have described “dimensions” that affect a person’s ability to adapt while walking. These are external demands that must be met for successful community mobility:
Distance (distance walked)
Temporal factors (time needed to cross a busy street or crosswalk, ability to maintain the same speed as those around them)
Ambient conditions (rain, heat, snow, etc.)
Physical load (packages carried, number of doors that need to be opened)
Traffic density (number of people within arm’s reach, unexpected collisions and near collisions with other people) (Shumway-Cook et al., 2002)
Improving Endurance for Walking
It is evident that many patients are discharged from inpatient rehabilitation severely deconditioned, meaning that their energy levels are too low for active participation in daily life. Physicians, therapists, and nursing staff responsible for rehabilitation practice should address this issue not only during inpatient rehabilitation but also after discharge by promoting and supporting community-based exercise opportunities. During inpatient rehabilitation, group sessions should be frequent and need to include specific aerobic training. Physical therapy must take advantage of the training aids available, including exercise equipment such as treadmills, and of new developments in computerized feedback systems, robotics, and electromechanical trainers.
Janet Carr and Roberta Sheperd
University of Sydney, Australia
Although many people affected by stroke have regained some ability to walk by the time they are discharged from rehab, many have low endurance, which limits their ability to perform household tasks or even to walk short distances. After a stroke, walking requires a much higher level of energy expenditure, and upon discharge many stroke patients are not necessarily functionalwalkers (Carr & Sheperd, 2011).
Functional walking is assessed using tests of speed, distance, and time. Minimal criteria for successful community walking include an independent walking velocity of 0.8 m/s or greater (about 2.6 feet/second), the ability to negotiate uneven terrain and curbs, and the physical endurance to walk 500 meters or more. In a review of 109 people discharged from physical therapy, only 7% achieved the minimum level. Cardiorespiratory fitness training can address both the efficiency with which people affected by stroke can walk and the distance they are able to achieve (Carr & Sheperd, 2011).
The loss of independent ambulation outdoors has been identified as one of the most debilitating consequences of stroke. Among stroke survivors 1 year after stroke, the most striking area of difficulty was low endurance measured by the distance walked in a 6-minute walk test. Those subjects able to complete this test were able to walk on average only 250 meters (820 feet) compared to the age-predicted distance of >600 meters (almost 2,000 feet), equivalent to 40% of their predicted ability and not far enough for a reasonable and active lifestyle. The detrimental effect of low exercise capacity and muscle endurance on functional mobility and on resistance to fatigue is likely to increase after discharge if follow-up physical activity and exercise programs are not available (Carr & Sheperd, 2011).
In 2002 the American Thoracic Society (ATS) published guidelines for the 6-minute walk test with the objective of standardizing the protocol to encourage its further application and to allow direct comparisons among different studies and populations. The American Thoracic Society guidelines include test indications and contraindications, safety measures, and a step-by-step protocol as well as assistance with clinical interpretation (Dunn et al., 2015).
Key components of the protocol include the test location, walkway length, measurements, and instructions. According to the American Thoracic Society protocol, the test should be performed on a flat, enclosed (indoor) walkway 30 m (just under 100 feet) in length. This protocol requires 180° turns at either end of the walkway and additional space for turning. The guidelines advise that shorter walkway lengths require more directional changes and can reduce the distances achieved. The influence of directional changes may be amplified in the stroke population, who characteristically have impaired balance, asymmetric gait patterns, and altered responses for turn preparation. Conversely, reducing the number of directional changes may increase the distance achieved (Dunn et al., 2015).
Body Weight-Supported Treadmill Training
Body weight-supported treadmill training (BWSTT) is an increasingly being used to encourage early walking following a stroke. It is a rehabilitation technique in which patients walk on a treadmill with their body weight partly supported. Body weight-supported treadmill training augments walking by enabling repetitive practice of gait (Takeuchi & Izumi, 2013).
In patients who have experienced a stroke, partial unloading of the lower extremities by the body weight-support system results in straighter trunk and knee alignment during the loading phase of walking. It can also improve swing1 asymmetry, stride length, and walking speed, and allows a patient to practice nearly normal gait patterns and avoid developing compensatory walking habits, such as hip hiking and circumduction2 (Takeuchi & Izumi, 2013).
1Swing phase of gait: during walking, the swing phase begins as the toe lifts of the ground, continues as the knee bends and the leg moves forward, and ends when the heel come in contact with the ground.
2Circumduction: a gait abnormality in which the leg is swung around and forward in a semi-circle. The hip is often hiked up to create enough room for the leg to swing forward.
Locomotor Training Program (LTP). Source: Duncan et al., 2007.
Another example of a body-weight supported treadmill. Source: NIH, 2011.
Treadmill walking allows for independent and semi-supervised practice, for those with more ability, as well as improving aerobic capacity and increasing walking speed and endurance. The very early practice of assisted over-ground and harness-supported treadmill walking is probably critical to good post-discharge functional capacity in terms of both performance and energy levels (Carr & Shepherd, 2011).
The Locomotor Experience Applied Post Stroke (LEAPS) trial—the largest stroke rehabilitation study ever conducted in the United States—set out to compare the effectiveness of the body weight-supported treadmill training with walking practice. Participants started at two different stages—two months post stroke (early locomotor training) and six months post stroke (late locomotor training). The locomotor training was also compared to a home exercise program managed by a physical therapist, which was aimed at enhancing flexibility, range of motion, strength, and balance as a way to improve walking. The primary measure was improvement in walking at 1 year after the stroke (NINDS, 2011).
In the LEAPS trial, stroke patients who had physical therapy at home improved their ability to walk just as well as those who were treated in a training program that requires the use of a body weight-supported treadmill device followed by walking practice. The study, funded by the NIH, also found that patients continued to improve up to 1 year after stroke—defying conventional wisdom that recovery occurs early and tops out at 6 months. In fact, even patients who started rehabilitation as late as 6 months after stroke were able to improve their walking (NINDS, 2011).
“We were pleased to see that stroke patients who had a home physical therapy exercise program improved just as well as those who did the locomotor training,” said Pamela W. Duncan, principal investigator of LEAPS and professor at Duke University School of Medicine. “The home physical therapy program is more convenient and pragmatic. Usual care should incorporate more intensive exercise programs that are easily accessible to patients to improve walking, function, and quality of life.”
Robotic Gait Training Devices
Several lower-limb rehabilitation robots have been developed to restore mobility of the affected limbs. These systems can be grouped according to the rehabilitation principle they follow:
Treadmill gait trainers
Foot-plate-based gait trainers
Over-ground gait trainers
Stationary gait trainers
Ankle rehabilitation systems
Active foot orthoses (Díaz et al., 2011)
The Lokomat System
Source: Diaz et al., 2011.
Many robotic systems have been developed aiming to automate and improve body weight-assisted treadmill trainers as a means for reducing therapist labor. Usually these systems are based on exoskeleton type robots in combination with a treadmill. One such system—the Lokomat—consists of a robotic gait orthosis and an advanced body weight-support system, combined with a treadmill. It uses computer-controlled motors (drives) that are integrated in the gait orthosis at each hip and knee joint. The drives are precisely synchronized with the speed of the treadmill to ensure a precise match between the speed of the gait orthosis and the treadmill (Díaz et al., 2011).
The LocoHelp System
The LokoHelp gait trainer “Pedago.” Source: Diaz et al., 2011.
The LokoHelp is another device developed for improving gait after brain injury. The LokoHelp is placed in the middle of the treadmill surface, parallel to the walking direction and fixed to the front of the treadmill with a simple clamp. It also provides a body weight-support system. Clinical trials have shown that the system improves the gait ability of the patient in the same way as the manual locomotor training; however, the LokoHelp required less therapeutic assistance and thus therapist discomfort is reduced. This fact is a general conclusion for almost all robotic systems to date (Díaz et al., 2011).
Source: Diaz et al., 2011.
Over-ground gait trainers consist of robots that assist the patient in walking over ground. These trainers allow patients to move under their own control rather than moving them through predetermined movement patterns. The KineAssist is one robotic device used for gait and balance training. It consists of a custom-designed torso and pelvis harness attached to a mobile robotic base. The robot is controlled according to the forces detected from the subject by the load cells located in the pelvic harness (Díaz et al., 2011).
The ReWalk Robotic Suit
Source: Diaz et al., 2011.
ReWalk is a wearable, motorized quasi-robotic suit that can be used for therapeutic activities. ReWalk uses a light, wearable brace support suit that integrates motors at the joints, rechargeable batteries, an array of sensors, and a computer-based control system. Upper-body movements of the user are detected and used to initiate and maintain walking processes (Díaz et al., 2011).
The capacity of robots to deliver high-intensity and repeatable training make them potentially valuable tools to provide high-quality treatment at a lower cost and effort. These systems can also be used at home to allow patients to perform therapies independently, not replacing the therapist but supporting the therapy program. However, despite the attractiveness of robotic devices, clinical studies still show little evidence for the superior effectiveness of robotic therapy compared to current therapy practices, although robotics have been shown to reduce therapist effort, time, and costs (Díaz et al., 2011).
The ReWalk is a robotic Exoskeleton that can be worn for personal use at home and out in the community.
The robotic device provides hip and knee motion to enable individuals with spinal cord injury to stand upright, walk, turn, climb and descend stairs. The system can be customised to provide optimal fit to ensure safety, function and joint function.
ReWalk allows people to walk independently as the robotic device mimics the natural gait pattern of the legs.
What are the benefits?
The benefits of using the ReWalk include:
Ability to walk upright rather than sit in a wheelchair
Improve mobility and quality of life measures such as:
Improvements in bowel and bladder function
Maintenance of bone mass
Reduction of some medications for certain ailments
Emotional and psychosocial benefits
How can you trial and purchase a ReWalk for home use?
At our Midlands ‘Centre of Excellence Clinic’ in Northampton.
Firstly, we will book you into our clinic for an initial assessment where you will be able to trial the device*.
Providing you are suitable for the device, you will be given the option to purchase your own ReWalk and at the same time we will discuss the rehab package on offer that will help you achieve maximum use of your ReWalk.
If you live outside the Midlands and need accommodation, we can also help find you an accessible place to stay.
*Prior to the assessment we will need to establish your suitability for the device as ReWalk is intended for use by individuals with lower limb disabilities whose hands and shoulders can support crutches or a walker. Your height will need to be between 160cm – 190cm (5’3″ to 6’2″). Weight requirement is up to 100kg (220lbs). Other factors such as bone density and range of motion will be considered and evaluated.
MyndMove attached to patient’s arms at University of Toronto Milos PopovicEnter a caption
Watching someone who has suffered a stroke try to perform everyday actions such as walking down the sidewalk or even bringing a cup to their lips can serve as a sobering reminder of how fragile full and robust health is, and also serves as an inspiration for those dedicated to improving the lives of those patients.
Steven Plymale, recently named CEO of Toronto-based MyndTec, said his reaction to watching videos of patients using the company’s MyndMove functional electrical stimulation (FES) rehabilitation system was one of the reasons he joined MyndTec.
“They are very compelling,” Plymale said of the demonstration videos, “and, to be honest with you, were one of the visceral reasons why I took this job. It really is technology we have to get out there.”
MyndMove’s potential market just increased exponentially with recent 510(k) marketing clearance from the U.S. Food and Drug Administration. Plymale said MyndTec has already sent several units of the MyndMove system—which uses an eight-channel electrode array programmable with more than 30 protocols to specifically target muscles in the arm—to a partner institution in the U.S. for a pilot.
“Meanwhile, we have had lots of facilities reach out once they heard of the FDA clearance actively trying to get us to work with them both in terms of further research and also in the commercial setting,” Plymale said.
The MyndMove technology, which received Health Canada approval for clinical use in 2014, is based on repeated stimulation of targeted muscles by the FES system (activated by a therapist who has asked a patient to try a specific movement, such as lifting a cup to the mouth or grasping a pen). The stimulation causes muscles to contract and the movement sends a signal from the muscle to the brain.
Based on the concept of neuroplasticity, this coordinated effort trains a new neural pathway that enables improvement and recovery of voluntary movement. The technology was born nearly a decade ago in the research lab of Milos Popovic at the University of Toronto; it is just one example of cutting-edge technology aiding stroke patients, plus some with spinal cord and traumatic brain injuries, to regain more normal function in everyday movements.
From Battlefield To Rehab
While MyndMove aims to improve arm and hand function, another emerging, early-stage technology, is attempting to help stroke patients regain a more natural walking gait. The technology, a soft “exosuit” from Marlborough, Mass.-based ReWalk Robotics, will be entering pre-clinical trials early in 2018.
The exosuit is the product of a collaborative agreement between ReWalk and Harvard University’s Wyss Institute for Biologically Inspired Engineering, and a salient example of how publicly-funded research for one idea can be re-purposed in other areas. The exosuit research began in 2012 as a Defense Advanced Research Projects Agency (DARPA) project intended for the battlefield.
“We started to call it the exosuit because there is no rigid component,” Kathleen O’Donnell, the program lead for Wyss Institute’s medical exosuit program, said. “It does not restrict movement like an exoskeleton might. The first suits were developed to help able-bodied soldiers carry heavy loads and walk long distances. The purpose was to reduce the metabolic burden on them. They often carry 100 or more pounds of equipment on long marches and the goal was to make them less fatigued when they got to their destination.
“About a year or so into that program, we started looking at where we could find more medical applications of this same technology. We talked to clinicians in the Boston area, and it seemed like stroke was a really good application area that could benefit from this type of technology. The reason for that is that a stroke patient who could benefit from this has some residual walking capacity – it’s not somebody who requires total support in order to walk, but they need a little help in learning how to walk better.”
The exosuit is powered by a motor unit worn on a waist belt, which activates sheathed Bowden cables anchored in two spots: one in a calf-worn fabric sleeve and one in the insole of the shoe the unit is activating to achieve a more natural gait.
ReWalk already markets a rigid exoskeleton for people who have suffered a spinal cord injury who are unable to walk unassisted, and O’Donnell said the exosuit collaboration is meant for a different market—”with the exosuit we’re taking somebody with some underlying ability to walk and we are injecting small levels of assistance at critical times in their gait cycle to improve their walking ability and coordination rather than taking over for them.”
ReWalk CEO Larry Jasinski said the upcoming trial is not expected to enroll a large number of patients – comparable trials have consisted of 40 patients or so – and also said the trial is in the middle of IRB approval at four top research institutions nationwide.
Jasinski said the Wyss Institute researchers had shown the device worked, but didn’t have a product that would meet commercial requirements.
“It could not have gotten past the FDA, would not have been durable enough for a rehab lab and use by 100 patients, and it wasn’t really designed for home use,” he said. “And that’s why this relationship is so ideal. They are doing a high level of fundamental research that, generally, small companies can not afford to do. They are making it work for that individual situation. We are going to be able to take it through the FDA, through the reimbursement processes, and manufacture it at a price point with the quality control and functional level that can meet a mass audience. That is why it’s a good marriage.”
Clinical scores for evaluating walking skills with lower limb exoskeletons are often based on a single variable, such as distance walked or speed, even in cases where a host of features are measured. We investigated how to combine multiple features such that the resulting score has high discriminatory power, in particular with few patients. A new score is introduced that allows quantifying the walking ability of patients with spinal cord injury when using a powered exoskeleton.
Four spinal cord injury patients were trained to walk over ground with the ReWalk™ exoskeleton. Body accelerations during use of the device were recorded by a wearable accelerometer and 4 features to evaluate walking skills were computed. The new score is the Gaussian naïve Bayes surprise, which evaluates patients relative to the features’ distribution measured in 7 expert users of the ReWalk™. We compared our score based on all the features with a standard outcome measure, which is based on number of steps only.
All 4 patients improved over the course of training, as their scores trended towards the expert users’ scores. The combined score (Gaussian naïve surprise) was considerably more discriminative than the one using only walked distance (steps). At the end of training, 3 out of 4 patients were significantly different from the experts, according to the combined score (p < .001, Wilcoxon Signed-Rank Test). In contrast, all but one patient were scored as experts when number of steps was the only feature.
Integrating multiple features could provide a more robust metric to measure patients’ skills while they learn to walk with a robotic exoskeleton. Testing this approach with other features and more subjects remains as future work.
Clinical scores of walking ability are crucial in many areas of physical rehabilitation to assess the efficacy of a therapeutic intervention or an assistive device, as well as to discriminate the ability between different patients [1, 2]. One domain of interest is evaluating functional ambulation in individuals who suffered a spinal cord injury (SCI). Even though many outcome measures target the SCI population [3, 4], currently there exist no specific measures targeting the ability of a patient to use a lower limb robotic exoskeleton to walk overground and achieve functional ambulation.
Lower limb exoskeletons are bilateral powered orthoses designed to provide assistance for sit-to-stand and for walking and, in some cases, to assist lower extremity function in individuals with incomplete or complete SCI [5–8]. Currently, several exoskeletons are transitioning from purely research and rehabilitation devices to personal mobility systems that individuals with SCI could use to walk inside their home and in their communities [9, 10]. A paradigmatic case is the ReWalk™, which has been approved by the Food and Drug Administration to be sold to individuals with SCI as a take-home personal mobility device.
Quantitative clinical assessment of exoskeletons is fundamental to evaluate their safety and effectiveness when used by individuals with disabilities. Specifically, individuals with complete SCI, who aim at taking an exoskeleton home as a personal mobility device, require an intensive training protocol to become independent users. Such training is typically delivered in a clinical setting and therefore clinicians need a robust metric to evaluate if a patient has reached a level of ability and expertise to independently use the device at home and in the community. Obtaining a robust index of the patients’ walking skills with an exoskeleton could also be used to inform health insurance companies about the actual improvements in functional mobility for potential reimbursement. This point is crucial as the cost of these devices is extremely high and therefore any support funding has to be justified.
The primary clinical outcome measures currently used to assess functional ambulation with exoskeletons are the 6-Minute-Walk-Test (6MWT) and the Ten-Meter-Walk-Test (10mWT) [11, 12]. These two tests measure, respectively, the distance walked in six minutes and the time to walk over a distance of 10 m, while walking at a constant speed. Despite being validated in spinal cord injury populations , it is questionable whether these measures are sufficient to fully evaluate a patient skill and the device efficiency. Indeed, other studies have measured additional features to characterize walking skills with robotic exoskeletons.
Specifically, amongst the features quantified there are: the kinematics of the hip, knee and ankle joints in patients trained to use the ReWalk™ , as recorded via a motion capture system; the exertion level based on the heart rate normalized to the walking speed (i.e. physiological cost index)  and the oxygen uptake [16, 17]. Other metrics used include the variation in vertical and lateral amplitude of the head motion , ground reaction forces analysis  and the ability to maintain eye contact to assess cognitive effort . Even when multiple features were measured, each study reports the values of each feature individually to characterize functional ambulation with exoskeletons. Therefore it is unclear how each feature contributes to the overall expertise of a subject. Furthermore, some of the captured features require complex and expensive lab equipment, commonly seen only in large hospitals and university settings.
In the current study, we propose to combine multiple features of walking performance by estimating their probability distribution over a set of expert users who have been previously trained extensively to use the exoskeleton. New participants are then scored based on how well their features fit the experts’ probability distribution. Building on this principle, we define a new score to quantify walking ability with exoskeletons: the Gaussian Naïve Bayes surprise. The term surprise is derived from information theory and represents the amount of unexpected information provided by an event . We apply our score to quantify the walking skills of four individuals with complete SCI, as they are trained to use the ReWalk™ exoskeleton. Four features are computed from the trunk accelerations, which are recorded using a commercial wearable accelerometer while subjects perform a 6MWT with the exoskeleton. We estimate the parameters of the features probability distribution from seven expert subjects (1 SCI and 6 able-bodied) that received extensive prior training with the device, and compute the Gaussian naïve Bayes surprise of the four SCI participants with respect to the experts. The score based on all four features is compared with one based only on number of steps (an equivalent of distance walked), in terms of the separation between experts and patients that is yielded by the two indices.
The ReWalk™ exoskeleton
The ReWalk™ (ReWalk Robotics Inc., Marlborough, MA, USA) is a motorized lower limb exoskeleton suit designed to provide legged mobility to paraplegic patients who suffered a spinal cord injury from level T4 to L5. The device has two actuated degrees of freedom – one at the hip and one at the knee on each side – and has a passive spring-assisted dorsiflexion joint at the ankle. Figure 1a shows a schematic of the device.
Fig. 1 ReWalk™ exoskeleton and measured trunk angles. a Schematic of the ReWalk™ exoskeleton suit. The tri-axial wearable accelerometer attached on the right flank of the robot recorded the body accelerations while the subject walked with the device. Features to score walking quality were computed from the accelerations (see text). b The trunk angles in the frontal (x-y) and lateral (y-z) plane during walking (φ, frontal, blue line; α, lateral, green line). c The power spectral density plots of the trunk angles: the x-value of each maximum corresponds to the frequency of the oscillations in the plane. The step frequency corresponds to the maximum in the x-y plane
The Indego exoskeleton, which was approved by the FDA today
The Indego robotic exoskeleton has received approval from the FDA. The device, which is 26 pounds and designed to be easy to put on and take off from a wheelchair, was tested in an extensive clinical trial, assessing its safety on a variety of indoor and outdoor surfaces.
“It is particularly gratifying because it is the first thing that has come out of my lab that has become a product that people can purchase, which hopefully will make a significant improvement in their quality of life,” Vanderbilt engineering professor Michael Goldfarb said in a statement.
Indego is strapped tightly around the torso, with rigid supports attaching to the hip, knee, and foot. Battery-powered, computer-controlled electric motors drive the joints, and the wearer navigates the device similar to a Segway, according to the engineers. Lean forward and the exoskeleton walks forward, lean back for a while and it will sit down.
Indego, which has been available in Europe since November, is the second exoskeleton to gain FDA approval in the U.S. The first, ReWalk was approved in 2014. Indego’s selling point is its weight–almost 20 pounds lighter than ReWalk–and its functional electrical stimulation, which sends little electrical pulses to the paralyzed muscles. Those pulses could help lessen muscle atrophy and improve circulation. Now, Parker Hannifin, the manufacturer, needs to show that the device can reduce the secondary medical conditions often caused by lower-body paralysis, in order to convince insurance companies to cover the $80,000 device. According to the Wall Street Journal, the company plans a commercial launch for Indego in the U.S. “in the coming months.”