On the benefit of ultra-slow insertion speed: reduced insertion forces in cochlear implantation surgery

Introduction:

Preservation of residual hearing in cochlear implantation surgery requires atraumatic insertion which is associated with low insertion forces. Therefore, reduction of insertion forces is a dominant aim in development of improved electrode arrays (EA) as well as surgical technique. We wanted to investigate whether performing EA insertion in a very slow, manually no longer feasible, manner can solely reduce insertion forces.

Methods:

Three commercially available, straight electrode arrays (slim straight electrode, Cochlear Ltd., Sydney, Australia) were automatically inserted in a custom-made artificial cochlear model (made of Teflon, filled with soap solution) using three different insertion speeds: 2.0 mm/s, 0.4 mm/s and 0.03 mm/s. Insertion forces were measured using a load cell with 0.5 N nominal force. Each electrode was inserted nine times with different order of speed values.

Results:

The average maximal insertion force (arising at the point of maximal insertion depth) was 18.7 mN ± 5.1 mN for an insertion speed of 2.0 mm/s, 18.7 mN ± 2.4 mN in case of 0.4 mm/s and goes down significantly to 12.7 mN ± 2.1 mN when the insertion was performed with ultra-slow speed of 0.03 mm/s.

Conclusions:

Our results indicate that insertion forces can be significantly reduced if only the insertion is conducted very slowly. This finding discloses a high potential to improve residual hearing preservation as it goes without change in the design of the electrode array. However, further studies are necessary to confirm that effect also in cochlea specimens as well as with electrode arrays of different manufacturers.

Publication History

Publication Date:
18 April 2018 (online)