Determining insertion depth of silica optical fiber-integrated cochlear implant electrode array using optical frequency domain reflectometry

Cochlear implantation surgery is currently the only effective treatment for restoring hearing in individuals with severe to profound sensorineural hearing loss. This procedure requires the precise insertion of a cochlear implant electrode array (EA) into cochlea, which has bending radii as small as 2 mm. Surgeons face two major challenges during this process: minimizing cochlear damage and achieving optimal EA positioning within the cochlear pathway. Although optical fiber sensors have been proposed to provide real-time feedback during insertion, the rigidity of traditional silica optical fibers makes them unsuitable for this application. This study examines the integration of three types of silica optical fibers— commercial 50-μm single-mode fiber, customized 70-μm eight-shaped fiber, and customized 80-μm six-hole fiber—into straight EAs to evaluate their impact on insertion force and stiffness. The results indicate that EAs with integrated fibers measuring 50 μm in diameter have comparable rigidity to those without fibers, up to an insertion depth of about 23 mm in the 25-mm long EAs. Additionally, an optical frequency domain reflectometry sensing system, utilizing 50-μm singlemode fiber, is employed to facilitate precise real-time positioning of the EA during insertion. Results show that the proposed innovative sensing solutions for cochlear implantation have great potential to enhance surgical precision, improve outcomes, and reduce complications in cochlear implant procedures.