2017 GineersNow, Science Robotics and Live Science
Researchers from the University of Bern, Switzerland have created a robot that drills holes in a patient’s skull to aid doctors in Cochlear Implant surgery. The procedure involved in this microsurgery is performed by a lot of doctors to a lot of patients per year, but that doesn’t remove the fact that it’s a very, very delicate surgery. One wrong move and they could cause permanent damage to the patient. And of course, where precision and care is the critical part of a job, it’s always handy to let a robot, programmed to have much, much less margin of error than humans, to do the job. This is where the skull drilling robot comes in. The robot performs the most crucial and delicate part of the surgery: drilling the skull at the exact location and the right depth to access the correct part of the cochlea they need. The creation of the robot is not only useful for this type of surgery, but also provides a platform for other microsurgeries to prove that robots can be used in surgery planning systems, stereo vision, live detection of tissue types etc.
For the first time, the robot successfully performed this tricky, delicate operation. A 51-year-old woman who was completely deaf in both ears due to a rare autoimmune disease received a cochlear implant in her right ear. "The patient is progressing well with speech and language training, and is expressing high satisfaction on the benefits of having a cochlear implant," said study lead author Stefan Weber, director of the ARTORG Center for Biomedical Engineering Research at the University of Bern in Switzerland. "Six months after the surgery, she is even able to partially communicate via telephone, which is a big step for her personal freedom.”
The most delicate, trickiest part involves placing the 0.01-inch-to-0.04-inch-wide (0.3 to 1 millimeter) electrode array in an opening that is typically 1.2 inches (30 mm) in diameter, according to the researchers. "When discussing much-needed surgical innovations for use in ear, nose and throat procedures, our surgeon colleagues would repeatedly mention that gaining access to the inner ear in a minimally invasive manner was a major hurdle that had not been resolved," Weber said. "This spurred us on to research and design a way to enable ear, nose and throat surgeons to perform keyhole surgery to access the inner ear.” Most of the procedure is still completed manually by humans. However, the robot is responsible for one of the operation's riskiest steps: drilling a microscopic hole in the skull bone surrounding the ear without causing heat-related injury to nearby nerves. "The drill needs to pass between nerves at a distance of less than 1 millimeter," Weber said.
The researchers developed a robotic drill with the highest degree of accuracy reported yet for such a medical device, straying as little as about 0.015 inches (0.4 mm) in 99.7 percent of all drilling attempts, the scientists said. A camera also helped track the robot with 25-micron accuracy; in comparison, the average human hair is about 100 microns wide. Moreover, the research team designed stainless-steel drill bits with grooves and cutting edges that are optimised for cutting into bone and transporting away bone chips, thus helping to minimise the amount of heat generated during drilling. A rim on the outside of the drill also reduces friction between the bit and the surrounding tissue while it rotates. During the procedure, there were several pauses during drilling to limit the accumulation of heat, and during each pause, bone chips were washed off the drill bits to keep them from adding to friction during drilling, the researchers said. In addition, before surgery, the researchers used computed tomography (CT) scans of the patient's skull before, during and after the surgery to verify that the robot would steer clear of delicate areas. During surgery, the scientists also used electrodes attached to facial muscles to look for any damage to facial nerves.
"We are very excited about the results and that we were able to demonstrate such a complex technology in the operating room," Weber said. "It adds to the mounting evidence in many other areas that robots can potentially do things in surgery in a way a human surgeon would not be able to carry out without technology.” The researchers are working with a surgical robotics manufacturer and an implant manufacturer to begin commercial development of their technology. "This will allow the development of the surgical robotics platform into a medical technology product that hospitals can buy for their surgical departments," Weber said. However, Weber cautioned that this new approach is only "the very first stage of changing how hearing surgery is done by ear, nose and throat surgeons. We think there is plenty of potential, but it will take lots more work before more hard-of-hearing people can have their hearing restored with new technology."