title: Serrated needle design facilitates precise round window membrane perforation.
abstract: The round window membrane (RWM) has become the preferred route, over cochleostomy, for the introduction of cochlear implant electrodes as it minimizes inner ear trauma. However, in the absence of a tool designed for creating precise perforation, current practices lead to tearing of the RWM and significant intracochlear pressure fluctuations. On the basis of RWM mechanical properties, we have designed a multi-serrated needle to create consistent holes without membrane tearing or damaging inner ear structures. Four and eight-serrated needles were designed and produced with wire electrical discharge machining (EDM). The needle's ability to create RWM perforations was tested in deidentified, commercially acquired temporal bones with the assistance of a micromanipulator. Subsequently, specimens were imaged under light and scanning electron microscopy (SEM). The needles created consistent, appropriately sized holes in the membrane with minimal tearing. While a four-serrated crown needle made rectangular/trapezoid perforations, the octagonal crown formed smooth oval holes within the membrane. Though designed for single use, the needle tolerated repeated use without significant damage. The serrated needles formed precise perforations in the RWM while minimizing damage during cochlear implantation. The octagonal needle design created the preferred oval perforation better than the quad needle. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1633-1637, 2016.
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Columbia University College of Physicians and Surgeons, New York, New York.
authors.forename: James P
authors.initials: JP
authors.lastname: Stevens
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Columbia University College of Physicians and Surgeons, New York, New York.|Department of Mechanical Engineering, Columbia University, New York, New York.
authors.forename: Hirobumi
authors.initials: H
authors.lastname: Watanabe
authors.affiliation: Department of Mechanical Engineering, Columbia University, New York, New York.
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Kysar
authors.affiliation: Department of Otolaryngology-Head and Neck Surgery, Columbia University College of Physicians and Surgeons, New York, New York.
authors.forename: Anil K
authors.initials: AK
authors.lastname: Lalwani
mesh_terms: D004867:Equipment Design; D006801:Humans; D008566:Membranes; D009339:Needles; D012405:Round Window, Ear / Q000473:pathology*
keywords: cochlear implant electrode insertion; cochlear implantation; crown needle; electron discharge machining; round window membrane