Paralyzed military veterans received a welcome boost in late 2015 when the U.S. Department of Veterans Affairs (VA) agreed to pay the costs of an innovative exoskeleton system that gives those with paraplegia the ability to walk. Developed by ReWalk Robotics, an Israeli firm with U.S. offices in Massachusetts, the battery-powered ReWalk system had previously passed another milestone in 2014 when it became the first exoskeleton product to be approved by the U.S. Food and Drug Administration for people with spinal cord injury.

For ReWalk Robotics, these developments were more than just marketing accomplishments. Amit Goffer, the PhD electrical engineer who invented the system and founded the company, was himself paralyzed in 1997 as a result of an accident. Although Goffer retired in 2015, the company continues to build on his original designs. ReWalk Robotics CEO Larry Jasinski describes the life-changing potential of exoskeleton systems in this interview with Engineering360 Contributing Editor Larry Maloney.

Maloney: What are the key components of the ReWalk system?

ReWalk Robotics CEO Larry Jasinski.Jasinksi: Rather than spend a lot of time developing custom components, Dr. Goffer’s design approach was to take proven, off-the-shelf components --batteries, DC brushless motors, sensors, gear assemblies -- and integrate them into an aluminum-steel-alloy structural frame. To achieve mobility, the design includes motor and gear assemblies situated at the knees and hips, as well as springs in the foot plates that lift the ankle joints. The most important innovations are in the areas of electrical efficiency and control software.

Maloney: How does the system function?

Jasinski: Typically, the user does a transfer from a wheelchair to an adjacent chair that holds the ReWalk system. After attaching cushioned straps at the hip, thigh and ankle areas, the user activates the exoskeleton from a small RF controller worn on the wrist. You simply push a button to control such actions as sit to stand, walk, climb stairs, and sit. In all these modes, the embedded software lets the person control movement using subtle changes in the upper body. The system is designed to operate on all kinds of surfaces, from carpets to sidewalks to grass (see user video for more). All these capabilities combine to give people the kind of independence that Dr. Goffer envisioned when he began his design work following his accident.

The 44-lb device features “tilt sensor” technology that allows users to control movement with subtle changes in a person’s center of gravity.The current system weighs about 44 lbs (20 kilograms) and is designed to support people weighing up to 220 lbs and as tall as six feet three. The device sits on its own weight, parallel to the user’s body. We did a lot of finite element analysis work to ensure that the system could handle these weight and height requirements and be durable enough for five years of use. As we further refine ReWalk, its weight will likely drop, as we incorporate lighter-weight components and explore alternate structural materials, such as composites.

Maloney: What were the key technical challenges in designing the system?

Jasinski: So that users can operate the system for up to four hours without recharging, the system needed to maximize electrical efficiency. The key to achieving that goal was incorporating software that would allow ReWalk to produce walking patterns that very closely resemble how you and I walk. That involved an enormous amount of time in laboratories, such as Sheba Medical Center in Israel and Moss Rehabilitation Research Center in Philadelphia, where our engineers gathered data from sensors measuring normal gait patterns, such as heel striking force. There were also safety considerations. If the system were to result in motions that were exaggerated or unnatural, it could damage ankles, hips, or knees. That’s a key consideration, since many users are young adults who expect to use an exoskeleton system for decades.

The system uses two lithium ion batteries, a primary and a secondary, both located in a housing built into the back of the unit. The wrist-mounted controller warns the user if the primary battery is running low, and the smaller secondary battery serves as a reserve. One final element in meeting energy efficiency goals is our patented tilt sensor technology, which is designed to react to very slight shifts in a person’s center of gravity. For example, a forward tilt of the upper body is sensed by the system to initiate the first step in a walking pattern. Repeated body shifts generate a sequence of steps that mimics a functional natural gait of the legs at speeds as high as 1.6 mph (2.6 km/h).

Maloney: What patient population did the FDA approve as the initial ReWalk recipients?

Jasinski: The FDA cleared ReWalk for spinal cord injury, both partial and complete, from the lower back to the top of the back (T7 to L1). People with this type of injury typically can maneuver their bodies from the mid-chest up and use their arms and hands to maneuver crutches. The FDA clearance also comes with certain medical requirements. For example, a recipient needs to have done enough exercise or rehab work to maintain sufficient bone density.

Maloney: What are the chief health benefits for ReWalk users?

Jasinski: We have published data from patients at the Bronx VA Hospital (Veteran Administration hospital in New York) who used ReWalk at least three days a week for an average of an hour and a half each day. That experience showed a dramatic change in patient metabolism. The benefits of walking are even greater for paralyzed individuals than for able-bodied people. Benefits included: gain of lean tissue in the legs, reduction in pain and spasm medications, improved bowel and bladder function, improved mental health, reduced fatigue and better sleep. The #1 cause of death in this population group is urinary tract infection, and that condition is far less prevalent in ReWalk users.

Maloney: Will your company be seeking FDA approval for use of ReWalk by other patient populations?

Jasinski: We fully believe that the system will benefit other populations beyond spinal cord injury. Our company is already planning clinical studies with ReWalk that will involve patients with stroke, multiple sclerosis, as well as some elderly individuals who need assistance. Individuals in these groups typically have greater mobility than those with spinal cord injury, so we will modify ReWalk to meet their particular needs. Our five and ten-year vision for the company is that exoskeletons will benefit many different populations. Some companies in this field of robotics are looking at other applications, including military and industrial, but we’ll continue to focus on medical.

Maloney: At $77,000, the cost of ReWalk represents a major outlay. Will the VA’s decision to provide ReWalk to veterans help gain more coverage from private insurers?

Jasinski: The VA decision applies not only to active-duty military, but also to vets who suffer spinal cord injuries after their military service is completed, such as someone injured in an auto accident. As for private insurance coverage for ReWalk, we have been working extensively with insurers on a case by case basis. We’ve had success, for example, in workman’s compensation cases where insurance coverage helps pay for use of ReWalk so that an individual can get back to work.

The VA’s decision, which was based on the agency’s own clinical studies at the Bronx VA Hospital, can certainly be viewed as a validation of the system on a national basis. There are 42,000 veterans in the U.S. with a spinal cord injury, which represents about one sixth of the 273,000 Americans with such injuries. We plan to do additional clinical studies to demonstrate the economic benefit of ReWalk. We believe that a person’s reduced medical costs from using ReWalk will outweigh the cost of the system itself. That’s what insurers want to see. An increase in the total population using the system could also lower system costs.

Maloney: What does the future hold for new exoskeleton designs from ReWalk Robotics?

Jasinski: As mentioned, we will be making refinements to the current system for those with spinal cord injuries, as well as designing modified versions for other patient populations. In addition, we are working on a version for patients will quadriplegia who cannot hold crutches.

Overall, there is an enormous unmet market for medical exoskeletons worldwide, perhaps tens of millions of potential users if you look a decade down the road. Last year, WinterGreen Research published a report predicting that the exoskeleton robotic rehabilitation market would grow from $16.5 million in 2014 to $2.1 billion by 2021. To achieve that growth, the industry still as a lot of work to do in areas ranging from design to training to regulatory approval, but we are definitely on our way.

For More Information

ReWalk Robotics: http://rewalk.com/

User video on ReWalk: https://www.youtube.com/watch?v=aBD6Chf0Hoc

Testimonial videos from ReWalk users: http://rewalk.com/testimonials/