From the waist down, white plastic extremities – not unlike those of a robot – are attached to her thin legs with Velcro, whilst her feet are clad in clunky white shoes. Meanwhile, a low motor sound accompanies each step that the woman takes on the treadmill. The sound is made by HAL, a robot suit. Without it, she could not possibly walk – she is a paraplegic.
Since 2011, an expert team headed by Professor Thomas Schildhauer, Medical Director at the university hospital in Bergmannsheil, Germany, has been testing HAL (Hybrid Assisted Limb*) at the Centre for Neurorobotic Movement Training (ZNB) in Bochum, Germany, which was founded specifically for this purpose.
In order for the robot suit to work, it requires a wearer who wishes to make a voluntary movement. The process is as follows: via the spinal cord and the surrounding nerves, the brain sends a signal to a muscle, for example to one in the arm or the leg, and it responds accordingly.
However, the signals inside a paralysed patient’s muscle are very weak, which is why he or she is no longer able to walk. This is where HAL comes into play; the robot suit picks up those weak signals through sensors that are attached to the patient’s skin and it sets its motors in the pelvic and knee-joint regions in motion. Thus, HAL takes over locomotion on the patient’s behalf by connecting directly to their nervous system. Professor Schildhauer takes up the story:
“This is how we wish to activate and foster the residual function of the muscles and, ultimately, to help the patients attain better activity levels. But to what extent the HAL therapy will enable a paralysed patient to walk unaided, depends on the type of injury. After all, the robot does not repair the injured nerve structures in the spine; it merely ensures that the weakened signals reach the leg. Our aim is to optimise this loop and strengthen the residual functions that the patient possesses.”
Each training session begins with physiotherapy exercises designed to improve the patient’s agility. The therapist then wires up the patient and puts him into the robot suit. At first, the treadmill session takes only five to ten minutes; later, it can take up to an hour, its duration being determined by the stability of the patient’s cardiovascular system, the strength of his muscles and so on. The robot can be individually adjusted via computer to the respective patient, supporting his or her movements to a greater or a lesser extent.
Professor Schildhauer’s team uses the clinical trials at the ZNB to determine, among other things, how much training is required and how long the training effects will or will not last. They have implemented a three-month training cycle, with five training sessions per week. A control group in Japan undergoes only eight training sessions, which nonetheless result in functional improvement. When comparing the trials in Japan with those in Bochum, however, it is evident that much better results are achieved with the more intensive training programme over a period of three months.
Patients on the training programme attain activity levels which improve their ability to navigate around their surroundings. A patient who had been permanently confined to a wheelchair, for example, will be able to walk short distances with the aid of a walking frame after a three-month training period. Moreover, the patients appear to maintain their activity levels if they continue to train on a weekly or bi-weekly basis following the three-month HAL therapy phase. But because only 14 patients in all age groups have completed their training at the ZNB to date, the expert team will have to conduct further trials to verify their results.
Professor Schildhauer says they have arrived at conclusions that are surprising in many ways, but he warns that these are individual results and, in his words, does not want to stir up too much hope too soon. One thing is clear: following training sessions with the robot suit, muscle activity and consequently agility has improved in all patients.
Given these encouraging results, ZNB has succeeded in obtaining financial support from the State of North Rhine-Westphalia and the Japanese Ministry of Economy, Trade and Industry. These funds are now used to expand the centre, including the purchase of new robots as well as the foray into new research areas. To date, the centre has been studying robots aiding both lower extremities; future studies will focus on applications for one single leg or one single arm.
These specific robot suits are targeted at patients who, for example, have suffered a stroke or who suffer from conditions such as multiple sclerosis. In the first quarter 2014, the ZNB will conduct a trial with stroke patients in collaboration with the neurological clinic at Bergmannsheil, headed by Professor Martin Tegenthoff.
In Germany, Bergmannsheil is the only hospital where the robot suit is in use. In Japan, similar suits are being utilised in some 200 geriatric rehabilitation centres. Those suits, however, are much more basic and do not offer as many motor setting options.
In addition to Bochum and Tsukuba, Japan, the Karolinska Institute in Sweden is also conducting research into the robot suit, deploying it in stroke therapy. The three organisations have agreed which of them focuses on what kind of research and are thus able to solve specific questions in a more targeted manner.
The long-term objective is to launch HAL into the German market so that it can be used as a therapy instrument to help as many people as possible. In the near future, this treatment method for paraplegic patients is to become available in other centres across Germany - in Berlin and in Frankfurt/Main, for example.
Insurance companies will not incorporate the therapy into their clearing system until well-founded data are available, which will only be the case once further trials have been conducted. Occupational health insurance associations do already consider the robot suit a therapy instrument; negotiations with other insurance companies are currently ongoing. As Professor Schildhauer says: if the therapy method is demonstrably effective, insurance companies will have to include it in their treatment catalogue sooner or later.
*The HAL robot suit was developed by a research group led by Professor Yoshiyuki Sankai at the Tsukuba University, Japan, more than 20 years ago. In 2004, the company Cyberdyne Inc. emerged from the group, whose European headquarters were set up in the BioMedizinPark in Bochum in 2011.