NiLiBoRo robot cuts around corners for safer head surgery

The current prototype (pictured) is five times the size of the final instrument, which is expected to be complete in two years time(Credit: Fraunhofer Institute)

Removing tumors from the inner ear can be a tricky business, with surgeons often having to remove a large amount of bone to safely complete procedures. Researchers at Germany's Fraunhofer Institute have created a new tool, likened to a robotic worm, that is designed to revolutionize the process, while lowering the physical impact of the surgery on the patient.

Modern technology is continuing to expand the number of tools surgeons have at their disposal. In fact, the Fraunhofer Institute itself has been responsible for some ingenious inventions of late, recently unveiling a robotic device designed to act as a third arm for doctors during procedures.

Its latest work is the NiLiBoRo – a German acronym which standards for Non-linear Drilling Robot. The prototype tool is designed to allow surgeons to perform tumor removals from the inner ear through a small tunnel, where current methods usually require the removal of the entire mastoid bone in order for the procedure to be completed safely.

While devices exist to allow doctors to accurately drill through bone, the NiLiBoRo is the first tool that's able to alter its orientation, quite literally turning corners inside the patient's head. For inner ear surgery, a hole bored by a straight line tool could be no wider than 2 mm (0.08 in) – any wider and there would be a risk of damaging nerve tissue. Unfortunately, that's too small a gap through which to perform the procedure.

The NiLiBoRo's ability to turn corners allows it to drill a hole 5 mm (0.2 in) wide, which is a spacious enough tunnel through which to perform surgery. The secret to the design of the little robot lies in a series of hydraulic lines that allow it to crawl forward in a motion similar to that of a real worm.

The device consists of "head" and "tail" sections, similar to a dual carriage articulated bus. The two sections are connected by an expandable, bellows mechanism, and there are numerous hydraulic lines running from the top of the tool where the drill bit is located, back out to the operating theater from where it's controlled.

Hydraulic fluid is pumped into the rear section of the device, causing it to expand and lock into place against the surrounding bone. The bellows section is then expanded, pushing the drill-carrying head of the tool further into the bone. Finally, the front section is filled with fluid to hold it in place against its surroundings, at which time the tail section deflates and is pulled forward by the head. The direction of the tool is controlled by filling different bladders in the head section with liquid.

"We can alter the robot's direction of travel by adjusting the bladders in the front section." said project scientist Lennart Karstensen. "For instance, if we wanted to move left then we fill the left bladder with less fluid than the right, which will cause the robot to veer to the left."

While the NiLiRoBo makes its way forward, its progress is monitored by the surgeon via an electromagnetic tracking system that intermittently captures still images of the robot using computer tomography. This tracking system, known as EMT, was designed by researchers at the Technical University of Darmstadt.

The NoLiRoBo is an ambitious, but potentially highly effective tool. There's a little way to go before it'll be ready for use, though, with the current prototype version being five times the size of the planned final version. The team plans to continue developing the device, perfecting the technologies involved as it moves towards a smaller device that is expected to be ready for testing in two years time.

The research was completed in collaboration with the University of Aachen and the Dusseldorf University Clinic. The NiLiBoRo robot is being shown at the Compamed exhibition in Dusseldorf, Germany this week.

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