Thousands of people born deaf or who became deaf in childhood have benefitted from cochlear implants, enabling them to distinguish sounds for the first time.
However, current cochlear implant surgery is complex and invasive, involving drilling through the patient’s skull and placing an implant under the skin behind the ear. Now, a joint project between the Swiss ARTORG Center of Biomedical Engineering Research, the Institute of Surgical Technologies and Biomechanics of the University of Bern, and the University Hospital Inselspital of Bern aims to make the procedure less invasive using a surgical robot.
Surgery by robots
The procedure involves a surgical robot drilling a small tunnel hole behind the ear, into which the implant can be inserted. First a CT scan is taken of the patient’s head, and the drilling route precisely planned. During the surgery, the CT scan information is aligned with the patient on the table. The surgical robot can drill with a deviation of less than 0.2mm, which is vital as its route passes though a crucial 0.5mm range near the patient’s facial nerve.
Keeping the facial nerve safe
During standard cochlear implant surgery, there is a small risk of damage to the facial nerve, and also the nerve carrying taste sensations from the tongue to the brain. The current method of facial nerve monitoring during the operation involves placing needles in the face, rather than precisely mapping the progress of the drill.
Turning down the heat
Like all drilling, the robotic drill’s action raises the temperature of the bone it is drilling into. This in turn can affect and potentially damage the facial nerve, so the temperature must be closely monitored and kept within strict parameters.
The team at the University of Bern conducted a rigorous pre-study test using a combination of a thermal imaging camera and load cells to measure the force exerted by the drill:
“A purpose-built test rig was constructed in order to measure the temperature increase in the skull as a result of the drilling process. The entire process, for which cow bones were used, was monitored in detail by means of a FLIR thermal imaging camera and a load cell was used to measure drilling forces and torques.”
Safer and less invasive cochlear implant surgery
Through their tests, the team have gained major insights into creating an optimised drilling process, such that “Safer, more gentle and less invasive cochlear implant surgery will be possible in the future”, according to team leader Arne Feldmann.
The team have patented a new design of surgical drill bit that significantly reduces the drilling temperature, as well as an interval-based drilling procedure, that lowers the temperature further.
So, a new generation may be able to benefit from a safer, less invasive procedure thanks to a clever combination of thermal imaging and load cell measurements.
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