Dr. Rymer and Robotic Interventions in Rehabilitative Treatment for Spinal Cord Injuries

Circa 2011

In addition to being fertile soil for big-screen thrills, the field of robotics is playing an increasingly crucial role in modern medical rehabilitation. ABILITY’s Chet Cooper and Dr. Thomas Chappell recently spoke to W. Zev Rymer, MD, at the Rehabilitation Institute of Chicago. As the Institute’s lead researcher, Rymer works closely with Northwestern University faculty from the departments of engineering and neuroscience, along with professors of medicine, to spearhead technological innovations in rehabilitative medical treatment.

At any given time, the Rehabilitation Institute of Chicago houses 20 to 25 spinal cord injury patients and receives patients who have undergone acute care in emergency hospitals throughout the Midwest. The Institute is one of 14 “model centers” for the early treatment of spinal cord injury patients throughout the country. Dr. Rymer has worked at the Institute since 1989.

Chet Cooper: Is it something of a challenge for a center like this to juggle research and treatment?

W. Zev Rymer: It can be. The early days are especially difficult for people with acute spinal cord injuries, and it’s not necessarily an opportune time for research, except on things that improve the early outcomes. Those things tend to be done by neurosurgery, rather than by rehabilitation.

Often we won’t see a person with a spinal cord injury until maybe four to six weeks after his initial incident. Considering the course of events after spinal cord injuries, that’s still a very difficult time for the injured person and his family. A lot of our early interventions are specially focused on the patient’s adaptation to new life needs, getting him thinking about being at home and in the workplace. Many of our research projects tend to focus on later in the course of events, often not until nearly the end of treatment at the rehabilitation center, or even beyond. For example, if someone has had multiple fractures or a chest injury, that might delay doing research on mobility recovery.

A lot of what we do here is based on outpatient testing, and sometimes it doesn’t even begin until many, many months after care. I say all of this because there is some notion we may have a greater effect with our experimental treatments if we intervened earlier.

Cooper: Can you discuss some of the work going on with robotic interventions in the world of spinal cord injuries?

Rymer: We have a number of projects focusing on spinal cord injury care, in general, and specifically with respect to the application of robotics. George Hornby, who is a neuroscientist and a physical therapy professor, directs one of our labs that specializes in spinal cord injury research. He’s interested in methods of improving locomotion in patients who have had incomplete spinal cord injuries: patients fortunate enough not to have suffered total destruction of the spinal cord from which there can be no recovery of function.

George has been testing robotic trainers of different kinds. The main one we’ve been using is called the Lokomat, which has been in the United States since 2001 and is now quite well-known.

Cooper: How does the Lokomat work?

Rymer: It was designed and developed in Zurich, in what’s called a paraplegia hospital. The Rehabilitation Institute of Chicago was one of the first places to have one, and we were among its earlier adopters in North America.

The idea behind the robotic trainer is that it uses what’s called an “exoskeleton”: metal limbs attached to the legs of a person with a spinal cord injury. The person is suspended above a treadmill with counterweights that offset the need for weight bearing. This is an important feature, especially early on, when many people who suffer incomplete spinal cord injuries can’t bear their own weight. The Lokomat takes the person’s limbs through programmed walking movements over the treadmill.

Meanwhile, the Lokomat also collects data about what’s happening during this walking exercise so we can measure things like distance, duration, number of steps, and amount of weight borne by the patient. We can also poll the electrical activity of the different muscles and even measure metabolic factors, like oxygen consumption, during this process.

The Lokomat allows us to provide better feedback about different features of movement, especially as a person is recovering and developing the ability for voluntary control. What we’ve seen in people who are exposed to Lokomat training over a period of several weeks to months is progressive recovery of their walking ability.

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Cooper: So this is better than working with therapists?

Rymer: In some respects, yes. Manual therapy does have the advantage of allowing a therapist to adjust the level of assistance to optimize intensity of the effort the injured person generates. That kind of pushes the injured person to be continuously active and to approach the limits of his strength and endurance.

The downside of the manual method, however, is that it requires a large number of therapists. A 45 minute training session, for somebody who’s got weakness in both legs, requires two therapists on each side. And one therapist can last maybe 10 minutes. The effort required by the therapists to move the patient’s leg is exhausting, especially if the person’s limbs are spastic. Spasticity is increased stiffness that develops in muscles that have lost input from nerves, such as that which occurs in the legs after spinal cord injury.

In the end, finding the expense and logistics for four therapists to work on one patient during a 45 minute training session is impractical. Manual therapy is at least comparable to the robot, but the robot can do on its own what is required of four therapists. Thus the robot has compelling practical advantages. Moreover, there is a safety benefit to therapists because the manual method often causes back injuries, since it requires they lie next to the treadmill and move the patient’s limbs.

Cooper: So there are pluses and minuses to both approaches.

Rymer: The problems with the machine are now being addressed. One of those problems was that the machine didn’t “know” exactly what a person was trying to do within it. Even though it has force and motion sensors, the Lokomat was initially programmed in such a way that it would replicate the movement task independently of what the person was trying to do.

In contrast, a therapist can sense when somebody is trying to walk on his own, and can assist as needed. So what the new control algorithms for this robotic system do is provide more sensible control that provides help only when it’s needed. It’s a strategy that’s being referred to as “corroborative control.” I think that’s a much more promising strategy, overall.

Cooper: Are there any other hurdles for the Lokomat?

Rymer: The other constraints of the standard Lokomat are cost and technical complexity. The device costs, depending on how it’s set up, somewhere between $250,000 and $350,000. A lot of places are not able to spend that kind of money on therapeutic devices for rehabilitation. And indeed, in most hospitals that have the machine, it has not been funded as a capital equipment item. It’s usually funded as a donation or a gift from a philanthropic source of some kind. In addition, the service contract for maintenance of the device costs $12,000 to $15,000 a year. Most facilities can’t afford that.

Also, while the Lokomat is sophisticated, it turns out human ambulation, walking, is much more complex. The machine is able only to assist with movement of the legs forward and backward, but walking involves swinging the legs out, moving the pelvis side to side, and rotating the body. Nor does the Lokomat help with other vital components of ambulation, such as the ability to maintain posture and balance.

Nonetheless, I believe it’s still very helpful, and I think in early stages of spinal cord injury, in particular, it’s been especially valuable. I think the group in Zurich that designed it deserves a lot of credit.

Cooper: What other devices are being tested?

Rymer: We have a device called a KineAssist, designed by a Northwestern University start-up called KineaDesign. KineAssist wasn’t intended to pick up where the Lokomat leaves off, but operationally that’s what it does. It carries a person safely as he walks over ground, and it has a frame that supports a person in a harness, allowing him to move his legs freely. The advantage of the KineAssist is that it allows for motion of pelvis and body axis and trunk. This actually allows a person to walk up and down slopes, to climb steps, to sit or stand—lots of things that are important for daily living. So the KineAssist is the next step in the retraining of walking.

Cooper: What patients does it primarily benefit?

Rymer: It’s mainly been used in the early period following a stroke. It’s not yet a commercial device, but I think it should prove useful in spinal cord injury cases. It brings one special benefit: safety. When people with spinal cord injuries begin to walk, they’re very unstable and need therapists on both sides to support them. That, in turn, limits the freedom of the patient to test the limits of his performance. This machine adds complete safety so people cannot fall. If they slip, the KineAssist allows them, essentially, to roll forwards and remain suspended in the harness.

We have several other projects here, linked broadly to walking via robotic systems. One of the big hazards of spinal cord injury is loss of bone mass. Though it’s not possible to completely prevent that from happening, we’ve found we may be able to slow down or even stop it before there’s been too much loss of bone density. Because of this, bone fractures are a big problem for people dealing with spinal cord injuries.

By using progressive weight-bearing, as we do in the Lokomat, we may be able to assist in preservation of bone mass, if not outright restoration of bone mass that’s been lost. We have a study running here, funded by the Department of Defense, on restoration of bone mass after spinal cord injury. Our lead investigator, a dermatologist named Tom Schnitzer, has been using walking studies—coupled with different hormonal and drug treatments—to improve bone health after spinal cord injury.

Thomas Chappell: That’s pretty crucial, isn’t it? The problems of bone mass reduction, muscle atrophy, down-regulation of the vascular system—all life-changing issues. Is there a way to light additional fire under some of these developments, to get them out to people sooner?

Rymer: The best solution—in terms of preservation of bone mass, vasculature, muscle, and skin—is not likely to be robotic. It may amount to standing or sitting with a vibrating foot plate which stimulates iron preservation, coupled with biophosphonates and some of these anti-osteoporosis drugs. I don’t think there are enough robots to be widely available to everybody with a spinal cord injury who might need them. I wish I could say that it’s all going to happen more quickly, but the Lokomat is complicated and expensive. With only 300 of these things existing, worldwide, they’re only being applied to a tiny, tiny fraction of all of the people who might need them.

We keep hearing that mass production methods are lowering costs, but with respect to rehabilitation technology, in general, that hasn’t happened. We don’t have the scale of production, we don’t have the uniformity of need. So that principle might be true of medicine, in general, but in the rehab world, it just hasn’t worked.

Over the 15 years in which the Lokomat has been in place, its price has stayed steady or dropped, slightly. Everything’s still too expensive. I think as health care cost issues escalate, these sorts of expensive devices are going to be harder and harder to fund. The onus is on us to come up with things that are essentially as effective as the more expensive options. Maybe they won’t be as flexible in terms of providing many functions, but they should provide appropriate functions in a targeted manner. They can be designed and constructed more simply.

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Cooper: Are there any projects you’re particularly excited about that are still in the early stages?

We’re doing some pilot work on a system called Armeo, for restoration of upper-limb function in people with quadriplegia. It supports the weight of the upper extremity and allows people to use residual function to train themselves to do voluntary tasks while interacting with a series of computer games designed to improve typical daily activities. It’s a bit more interesting than a lot of therapy routines, and we’re hopeful that intensive practice will help both strengthen muscles and improve voluntary coordination in people with spinal cord injury.

Cooper: It works as a form of biofeedback?

Rymer: Indirectly. Biofeedback usually means that there’s a biological signal being given that somebody’s being asked to increase. In contrast, this is a game that says, “Can I move? Can I do a task? Can I move kitchen utensils around? Can I play other kinds of games?” These are games, not unlike kids’ games, but they’re targeting functions that are relevant and useful for somebody who has impairment of upper-limb and hand function.

We have a lab here dedicated to restoration of hand function, specifically. Stroke survivors can’t extend the wrist or open the hand, so there are a lot of devices being developed to help them do those things. Most of the work we’ve done has been in the stroke arena. We have a big stroke robotics center that’s uniquely focused on stroke. Stroke survivors are a more homogeneous population with which to work, but all the things we’ve learned from stroke robotics are also likely to be relevant to management of people with spinal cord injuries.

There are other robotic devices we’ve started to work on testing, designed for complete spinal cord injury. One of them is a device called ReWalk, developed by a company called Argo. We have not yet used the system here, although we hope to. This device was designed in Israel, by a paratrooper who had sustained a spinal cord injury. Originally he was just using it for himself. It’s a very lightweight, powered exoskeleton that can be carried. It works quite nicely for people who don’t have a lot of spasticity and who have incomplete spinal cord injuries. You have to use crutches for upper extremity control and balance, but the machine—as you tilt forward, to begin walking—allows the motors to bend the hip and knee, one side at a time, to produce relatively natural motion.

I saw the machine in action in New York, about six months ago. A trained user, an Israeli soldier who sustained an injury in an accident, walked the streets of Manhattan with us for about an hour. He was able to go up and down stairs and do all kinds of things. He’s exceptional. He’s relatively lightweight, very strong and agile, well-trained, has good upper extremity and trunk control. I don’t know if one could necessarily expect that level of performance from other users, but I thought the machine was excellent.

Chappell: How did he balance?

Rymer: He used crutches for balance, but the device’s motors are powered by a battery pack that sits on his back. About 15 pounds or so.

Cooper: There’s a pretty good YouTube video for the product.

Rymer: Yeah. It’s been on ABC and Good Morning, America. I’ve been trying to get the developers to work with me to test it in people with incomplete spinal cord injury. I’m hopeful that we can do that. There are potential liability issues: someone’s going to fall in the ReWalk device, at some point. I think it’s going to be a tough road to make this a commercial product. But it’s good engineering: top-notch, well-designed, lightweight, very effective. I’ve been talking to the inventor of this for nearly 10 years, and for a while I wasn’t convinced it was ready for primetime. Now I think it is. It’s an elegant product. I think the whole idea of using these portable exoskeletons to help people walk is going to become the center of attention in the field of rehabilitation in the next 10 years.

The final piece of the robot story is an interesting one, but I don’t know if it’s going to apply to the world of spinal cord injury. Honda Motorcar Company has designed the DiGORO robot systems. I don’t know if you’ve seen them on the Internet?

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Cooper: Yes, I think so.

Rymer: They actually were designed for use by frail people: a way for people to enhance their stamina and to walk greater distances. The Honda machine was originally designed for the Japanese elderly, but Honda started a study with us to see if we can use it in a different population, including spinal cord injury patients. It’s kind of like the ReWalk, but it’s smaller and lighter and less powerful. The Honda device would be used to extend walking ability for somebody with very mild impairment, whereas ReWalk is designed for those with severe injuries.

We’ve tested the Honda device with some spinal cord-injured people, and their walking did improve a little bit. There seems to be a range of robotic systems evolving. Some of them might find a market and long-term roles in therapy and management. Others, I’m not sure. For example, the Lokomat is expensive and complex, and it works quite well, but I think it will remain primarily in large hospitals and academic centers.

For a long time, rehabilitation science wasn’t really a productive field, but it’s highly productive now. As we get into stem cells and other therapies that will potentially make radical changes in recovery from spinal cord injury, I think there will be more and more room for translational work*—which is exactly the kind of work that we do.


*Note from Dr. Chappell: “Translational work” refers to a relatively new concept in medical science. For most of the history of modern medicine, scientific researchers (PhDs) and their work were mostly separated from MDs and the treatment of patients. Historically, there was even some animosity between the two camps, mostly because doctors tend to get paid better than scientists. My graduate school professor, a PhD, knew I intended to go to medical school. He used to tease me by saying, “Before we PhDs came along all you MDs could do was wave monkey skulls at your patients!” Yet, somehow, we have managed to advance medicine based on scientific endeavor. In many ways, however, the process is arduous. In recent years, scientists, and doctors interested in research, have more closely collaborated, even to the extent that it is no longer uncommon for people to hold both an MD and a PhD. Research involving close collaboration between laboratory or “basic science” research and actual treatment of patients is called “translational” research to connote proficient translation of information from scientific research into better treatment of disease.

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