But the surgeons must not drill at random, because the hole for the cochlear implant must lie exactly between the taste nerve and the facial nerve. At one point, these nerves are only three millimeters apart and must not be damaged under any circumstances. Until now, surgeons proceeded like this: Just before the constriction, they stopped drilling and irritated the facial nerve with an electric tip. If the twitching in the patient’s face is not too strong, drilling can continue carefully.
Drill and stimulator at the same time
The physicians at the ARTORG Center approached Empa with the question: Couldn’t we develop a drill that would also electrically stimulate the facial nerve, i.e. a drill that would indicate its position in the patient’s skull? Kerstin Thorwarth from Empa’s Surface Science and Coating Technologies lab went to work. Together with a colleague, she developed a drill with a conductive tip as part of a master’s thesis and an Innosuisse project. The conductive and insulating hard coatings of titanium nitride (TiN) and silicon nitride (Si3N4) were applied to the drill tip by magnetron sputtering. For this, the individual windings of the drill had to be covered with special masks.
Not yet certified for medical applications
The drill with the special surface developed at Empa finally exhibited the appropriate electrical properties and also passed drilling tests in bone material carried out in the laboratory. The partners in Bern were pleased. “The smart drill for cochlear surgery could also be used for spinal surgery, for example,” says project leader Stefan Weber.
Now the Empa researchers are working with the surgeons to find an industrial partner who can manufacture the smart drill in accordance with the legal requirements for medical devices. “This will require further significant development effort,” says Weber. And that still needs to be funded.