Force-reduction of alginate-coated cochlear implant electrode in porcine specimens

Abstract

Introduction: Cochlear implant surgery focuses on atraumatic insertion to preserve residual hearing. Coating electrode arrays (EAs) with a lubricating alginate hydrogel reduces insertion forces. Previous dip coating approaches have suffered from inconsistent thickness and droplet formation on the array tip. To overcome these limitations, a membrane-based coating method was developed and investigated in a cochlea model and porcine cochlear specimens. Methods: EAs were coated using a semi-permeable membrane and a 3D printed crimp to restrict total coating thickness below 0.8 mm. Following insertions in an artificial cochlea model ex vivo insertion experiments were conducted on 10 porcine specimens using an automated linear insertion test bench with both uncoated and coated EAs. Insertion forces were continuously measured, and microscopic imaging, 2D CBCT, and μCT scans were used to evaluate coating thickness, insertion depth, and scala tympani geometry. Results: All electrodes were coated successfully below the 0.8mm target thickness. The initial mean coating of 0.47mm ± 0.15mm decreased to 0.38mm ± 0.15mm after four insertions. Insertions into the artificial cochlea model yielded significant force reductions of more than 60 %. In porcine cochlear specimens, the coating produced measurable but non-significant reductions in peak force (5.3mN±7.0mN) and insertion work (15.5 μJ ± 16.9 μJ). Conclusion: The proposed coating method achieves consistent and complete alginate coverage. While force reductions in porcine cochleae were limited by anatomical constraints, the overall trend supports the coating’s potential to mitigate insertion friction. Studies in human temporal bones are expected to provide a more definitive evaluation of its clinical potential.