Even though exoskeletons for people requiring a wheelchair are nothing new, they are still controversial. After all, at first glance they suggest a miracle recovery, since patients are meant to be able to walk again by using them.
The fact that this is not the actual intention of the robot suit however is often being neglected. In fact, exoskeletons facilitate a special form of therapy that returns at least a small portion of independence to the respective person. This doesn’t actually cure people, but makes them mobile enough to where they can move with walking supports or walking frames.
Medical scientists under Professor Thomas A. Schildhauer, Medical Director of the Department of Surgery at the Bergmannheil University Hospital in Bochum are researching therapy using the Hybrid Assistive Limb Exoskeleton, HAL in short. In the affiliated Center for Neurorobotic Movement Training (German: Zentrum für Neurorobotales Bewegungstraining, ZNB), paraplegics or stroke patients train under clinical practice conditions with the robot suit.
The HAL exoskeleton originally comes from Japan and was developed by Dr. Yoshiyuki Sankai. It works with EMG electrodes that are attached to the lower extremities, the knee and hip area. The suit detects nerve impulses via the surface of the skin, analyzes and amplifies them so that the patient is able to move with the help of integrated electric motors. “The bioelectric signals are registered via sensors and analyzed by the power unit, which then knows which muscle group just sent the signal,“ explains Oliver Cruciger, attending physician of the studies at Bergmannsheil. The patient deliberately directs and controls his or her movements and is supported by the robot suit at the same time. This is what makes the HAL system so unique: unusual body functions are replaced or rather supported. This way, paraplegics are able to perform movements like standing or walking under certain conditions. Pressure sensor plates recognize the patient’s supporting leg and automatically move the non-supporting leg. The exoskeleton effectively supports and amplifies the patient’s movements, so that a significant increase in mobility can be achieved.
However, residual function in the hip and knee area is essential for therapy purposes. “We are primarily able to effectively train patients with motor incomplete paraplegia sub C7 (below the last spinal cord segment). You can also treat complete paraplegia in terms of Conus-Cauda Syndrome if there is minimal residual motor function in the knee and hip area,“ reports Cruciger. Medical scientists talk about incomplete paraplegia if the spinal canal and the spinal cord were only partially severed due to an accident or tumor for example. Depending on the lesion size and the respective degree of transection, residual function in movement or rather sensitivity can be maintained.
During the course of three months, patients train five times per week for at least one-half hour with the device on a treadmill. This is followed by comprehensive functional tests and physiotherapeutic measures before and after the treadmill workout.
So far, the results of the study are clear: “We were able to show that muscular efforts on the treadmill are improved with the device, meaning speed, distance and length of time. And – this is actually far more important – the patient’s functional ambulant mobility is increased. In a large number of patients, we were able to achieve positive effects such as faster walking on level ground, a more stable, fluid gait pattern, and a reduction in the required assist systems. If the patient was previously completely dependent on the wheelchair, where applicable, he or she was able to cover short distances with the walking frame or move with crutches following the therapy.“ This is also the study’s long-term goal: training with the HAL exoskeleton sets the stage for maintaining previously achieved rehabilitation progress in day-to-day life and covering at least small distances in daily life.
Rehabilitation, but not complete recovery
Cruciger is convinced that exoskeletons will continue to be used in rehabilitation in the future. “It’s clear that any kind of exoskeleton significantly reduces the time and effort associated with rehabilitation. The therapy can be conveniently done on the treadmill with just a physiotherapist.“ However, Cruciger emphasizes that patients will still continue to be wheelchair-dependent. There are exoskeletons that are geared toward medical supply. “The significance of an established process in medical supply is not being achieved as long as setup times, that being putting on and taking off the device are very long, as long as battery life is relatively short and as long as the machine is still as bulky and in part monstrous.“ This is why the robot suits are a long way from being marketable. Therefore, the study’s scientific emphasis is on establishing a type of therapy method that increases the patient’s functional mobility. This also includes other positive effects. “We definitely have patients, who exhibit improved sensitivity in the lower extremities. This provides a significant advantage in terms of decubitus prophylaxis. We have patients, who have significantly less neuropathic pain, which is why their medication could be reduced, which in turn decreased drug side effects of course. Along with effective training, these are concomitant effects that are very fundamental to patients.“