To remove tumors in the inner ear, is a tricky thing: The doctors usually have to remove all of the temporal bone. In future reaches a 5 mm wide tunnel through the bone, the mini-robot "Niliboro" milled from Fraunhofer. To sensitive areas such as blood vessels and nerves, he makes a broad sweep. Use the inflatable cushion of the robot is fixed during surgery. First, the researchers are developing the optimal pocket geometry with several prototypes.

Diagnosis of the inner ear tumor - there is no way around an operation. The inner ear, however, is not easily accessible: it is covered by a cranial skull bone called mastoid, also called petrous bone. In addition, many blood vessels and nerves go through the surrounding tissue. The doctors mill so much of the mastoid bone that they have tracked down each of these sensitive structures. That's the only way they can make sure they do not harm them. Mostly this means that the doctors have to remove the entire bone. The resulting hole is filled with fatty tissue from the abdomen after surgery.

Operating through small tunnel

In the future, this operation should be done more gently: Then a small hole of 5 mm diameter is enough to cut the tumor out of the inner ear. This is made possible by the Niliboro (non-linear drilling robot), a researcher of the Mannheim project group for automation in medicine and biotechnology at the Fraunhofer Institute for Manufacturing Engineering and Automation IPA, together with its colleagues at the Technical University of Darmstadt, the University of Aachen and of the University Hospital Dusseldorf.

Although there are already drills that can mill a tunnel into a bone - but they make their way only dead straight into the bone. "For the first time, Niliboro can drill around corners," says Lennart Karstensen, project group scientist. This property is what makes minimally invasive surgery of inner ear tumors possible. For if the tunnel had just run, he would come here and there the nerves dangerously close. In order not to injure them, the diameter of the tunnel should not be more than one to 2 mm. However, you can not operate through such a small hole. Niliboro, on the other hand, is able to bend around delicate areas, so the tunnel can be 5 mm wide. Broad enough to do the surgery.

Hydraulic lines make robot worm crawl forward

But how does the worm manage to mill through bones and around corners through the mastoid bone? "The worm consists of a head and a tail," explains Karstensen. »These two parts are flexibly connected via a bellow.« The structure is reminiscent of an extra-long bus, in which the front and rear parts are coupled by a hose-like construction that resembles an accordion.

On its way through the bone, the robot is connected via 8 to 12 hydraulic lines with the outside world, ie the control devices and pumps in the operating room. These lines let him crawl in the right direction: First, they pump hydraulic fluid into three cushions located at the back. The pillows fill the space between the worm and the bones and thus fix the back mini-robot part in place. Now the liquid flows into the bellows: The "accordion" unfolds and pushes the head forward. The worm literally stretches and moves its front part further into the bone.

The drill, which is attached to the head, mills the way freely. Now the rear part is tightened, similar to a living worm: To do so, the cushions are inflated at the front part and hold it while the hydraulic fluid escapes from the back cushions. The pipes now also suck the liquid out of the bellows. He pulls himself together and hauls the back part behind him. Bit by bit, Niliboro works his way forward. »The direction in which the robot should move can be adjusted via the cushions on the front part. If, for example, he turns left, we fill the left cushion less taut than the others, and the robot tilts to the left side, "says Karstensen.

First prototype developed

In the laboratory and later in the operating room, the path that Niliboro is making is being closely monitored: via an electromagnetic tracking system, or EMT for short, developed by colleagues at the Technische Universität Darmstadt. In addition, a computer tomograph sporadically takes pictures and checks the position.

The researchers have already built a first prototype. At the moment he is five times bigger than the planned final version. For the time being, it consists only of the front part and bellows, so the heart of it. Bit by bit, the scientists want to optimize and expand the prototype. Is the complete technology, Niliboro should shrink to its final size. In two years, the researchers hope, the doctors could test the mini-robot for the first time.