Research and Life

Power steering for the knee

Auxiliary systems are being developed at the Institute of Medical Device Technology based on the KISS principle

Whether knee joint orthoses or entire operating theaters, the way medical equipment is received by doctors and patients is not only measurable in performance parameters. They also have to be ergonomic, easy to use and as cost-effective as possible, which is why the University of Stuttgart’s Institute of Medical Device Technology bases its development activities on the “keep it simple and save” principle.

Medical devices must be ergonomic, easy to handle and as cheap as possible. (c) University of Stuttgart/Max Kovalenko
Medical devices must be ergonomic, easy to handle and as cheap as possible.

The room is penetrated by a high-pitched whizzing sound, two fi shing lines twist together, and the angled rails on Professor Peter Pott's desk rapidly straighten out. “There – now he’d be standing”, says the Head of the Institute of Medical Device Technology, referring to someone with knee problems. The apparatus is the prototype for an active knee orthosis, designed to help patients become more mobile in daily life and enable, the elderly in particular, to stay in their own four walls for longer. “Someone who can no longer get out of their chair, for example, due to arthritis”, Pott explains, clarifying the benefi ts of this kind of orthosis, “can also no longer go to the toilet by themselves and will become an invalid in need of care”. In this context, active means that, by contrast with the traditional models, the orthosis not only stabilizes and takes the strain off the ligament apparatus, but also applies a force or torque to actively support the affected joint. This is achieved using a cost-effective, dynamic light-weight propulsion device consisting of a motor and gears.

“You can think of it as being similar to power-assisted steering”, Pott explains, which – in simple terms – uses a small motor to boost the force exerted by the driver making it easier for him or her to steer. As simple as the principle may be, it raises numerous questions, as the acceptance of medical engineering products esstansentially depends on their usability under everyday conditions, and this can often involve rather mundane requirements, including such things as whether or not the orthosis fits under long trousers, whether it is quiet and lightweight and works in an energy- efficient manner. So, “keep it simple and save” is Pott’s central idea, which is based on the frequently quoted KISS principle, a paradigm for the reduction of complexity. “For us”, Pott explains, “that means coming up with simple systems, and not just in the sense of basic and cheap, but rather so technically sophisticated that they are no longer laborious”.

At times, this kind of thinking can be at odds with industry in which the Mannheim native worked for a year. “We're not interested in the ‘gold standard’, in ever increasing performance parameters, but rather in systems that help people”, including in countries that don’t invest so much money in the health system as they do in Germany.

“Keep it simple and save”: the active knee orthosis being developed at the Institute of Medical Device Technology helps patients to be more mobile in daily life. (c) University of Stuttgart/Max Kovalenko
“Keep it simple and save”: the active knee orthosis being developed at the Institute of Medical Device Technology helps patients to be more mobile in daily life.

Standard robots rather than special solutions

This way of thinking applies not only to the prototype orthosis, but also to the entire infrastructure currently being built by the institute, which was founded just one year ago. In the adjacent laboratory, for instance, stands a small commercially available industrial robot. Pott and his team want to find out if it would be possible to further develop the high-precision device to the point that it would be suitable for use in the specific conditions of robot-assisted surgery. This question encompasses the issues of sterilization, surgical instrument interfaces and the control system, whereby the latter is subject to extremely high stansentially dards in medical robots in the interests of preventing injury. The attempt to construct medical engineering systems using standard devices rather than special solutions could pay off. “The cost of surgical robots such as the DaVinci system, which is currently so popular, can soon spiral up to 1.5 million”, says Pott. “Prices for industrial robots such as this one, on the other hand, start at around 10,000 euro”. So the research could result in significantly cheaper and, therefore, more plentiful surgical robots.

Medical robot based on an industrial robot. (c) University of Stuttgart/Max Kovalenko
Medical robot based on an industrial robot.

Clean air in the operating theater

An experimental operating theater is currently being constructed in another laboratory, in which researchers and students can gain first-hand experience of what takes place in an operating theater from a technical perspective. Usability testing is also carried out there. At its heart is the interface between man and machine: how should instruments be arranged around a patient; where are the access points; where do the doctors stand? Following its metamorphosis to a medical device, the industrial robot next door might also be tested here to see how it interacts with the other operating theater element. Pott refers to this kind of investment in infrastructure as seed projects, facilities with which one can try things out and that are designed to become the nucleus for further projects.

A student is currently analyzing the airflows in the operating theater as part of her course work for her BSc in Medical Engineering. More specifically, this involves the so-called laminar airflow system, which ensures that the air in the operating theater is clean. In this system, turbulence-free air is directed from above and around the patient to that no germs are deflected downwards and eventually sucked up. The problem with this is that anesthetic signal lights, surgical devices and lamps disturb the airflow, because they present barriers and, in some cases, radiate heat, which causes turbulence. The infrastructure in the experimental operating theater also gives researchers and students the opportunity to analyze the influence of system components or peripherals on the airflow, in addition to hygiene-related factors and energy consumption.

Andrea Mayer-Grenu

Dieses Bild zeigt Mayer-Grenu

Andrea Mayer-Grenu

Scientific Consultant, Research Publications

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