DrillMon – the surgical drill with nerve monitoring

People with severe hearing loss often require a cochlear implant. But the procedure is a tricky one and any injury to the facial nerve can result in facial paralysis. The solution is a surgical drill with integrated stimulation probes, which facilitates the continuous monitoring of the nerves.


  • Lead school(s) School of Engineering and Computer Science
  • Institute Institute for Human Centered Engineering (HUCE)
  • Funding organisation Innosuisse (ehem. KIT)
  • Duration (planned) 01.10.2016 - 31.01.2019
  • Project management Prof. Dr. Volker M. Koch
  • Head of project Prof. Dr. Volker M. Koch
  • Project staff Prof. Dr. Volker M. Koch
    Prof. Dr. Jörn Justiz
    Adrian Sallaz
    Roman Amrein
  • Partner Bien-Air Surgery, Le Noirmont
    Inomed Medizintechnik, Emmendingen, Deutschland
    Institut für Human-Centered Engineering
  • Keywords Surgery, Drilling, Cochlear Implants, Nerve Detection

Initial situation

Around the globe, 300,000 people with severe hearing loss wear a cochlear implant; in Switzerland the figure currently stands at 2,600. But the implantation requires drilling to be performed close to sensitive structures. Today, the biggest challenge for the surgeon is the facial nerve responsible for the muscles of the face and forehead, for facial expressions and gestures, and for eyelid movement. It runs through the middle ear and is on the way to where the implant has to be inserted. If the nerve is injured, it can cause the facial muscles on the implant side to droop temporarily or permanently.

Surgical drills and stimulation probes to stimulate the nerve are often used alternately. This means that the distance between the drill and the nerve is not determined continuously and the process of changing tools is time-consuming and interrupts the surgeon’s work.


The goal of the project was to enable continuous nerve monitoring when drilling close to sensitive structures. For this, surgical drills and stimulation probes have to be combined in a single instrument.


The project initially began with a successful master’s thesis in the degree programme ‘Master of Science in Biomedical Engineering’.

It also produced a patent and laid the foundation for a CTI project. The industrial partners involved were Bien-Air Surgery SA in Le Noirmont, the company that develops the drilling systems mentioned above, and inomed Medizintechnik GmbH in Germany, which designs the stimulation probes and monitoring systems. Thus two partners, each with an expertise that perfectly complements the other’s, teamed up for a joint venture to develop, manufacture and bring to market a combined drilling and nerve-monitoring system.


To use the drill as a stimulation probe, the electrical stimulation signal had to be transmitted to the drill, which rotates at up to 80,000 revolutions per second. A collaboration between BFH and industrial partners led to an ingenious solution for this complex procedure.

The drilling system needed to look as similar as possible to existing systems and be easy and efficient to clean and sterilise. For the key innovation, the integration of facial nerve monitoring, the engineers collaborated with an industrial partner specialising in intraoperative neurophysiological neuromonitoring. Here the specifications had to be precisely defined with regard to stimulation parameters, user needs, electrical safety and medical and regulatory aspects.