title: Assessment of intracochlear trauma caused by the insertion of a new straight research array.
abstract: OBJECTIVE
  To assess the degree of intracochlear trauma using the Cochlear™ Straight Research Array (SRA). This electrode has recently been released by Cochlear™ on the CI422 implant.
  
  
  BACKGROUND
  Electroacoustic stimulation (EAS) enables recipients to benefit from cochlear implantation while retaining their natural low-frequency hearing. A disadvantage of short EAS electrodes is that short electrodes provide limited low-frequency stimulation. Thus, loss of the residual hearing may require reimplantation with a longer electrode. In order to overcome this problem, the slim diameter SRA with increased length (20-25 mm) has been designed to provide a deeper, yet non-traumatic insertion.
  
  
  METHODS
  Two insertion studies into temporal bones were undertaken. The first involved dissection of the cochlea to gain a view into the scala vestibuli and insertion of the SRA and control electrodes with a microactuator for a surgeon-independent yet controlled insertion. High-speed photography was used to record data. The second study involved a high-resolution X-ray microcomputed tomography (microCT) study to assess electrode placement and tissue preservation in surgeon-implanted bones.
  
  
  RESULTS
  The SRA had a smooth insertion trajectory. The average angular insertion depth was 383° when inserted until resistance was encountered, and 355° if inserted to a predetermined mark for EAS use. In addition, microCT data showed that this caused no significant trauma or distortion of the basilar membrane up to 20 mms depth.
  
  
  CONCLUSIONS
  Temporal bone studies show that the SRA appears to cause no intracochlear trauma if used as an EAS electrode up to 20 mm depth of insertion.
authors.affiliation: Department of Otology, Royal Prince Alfred Hospital, Sydney, Australia.
authors.forename: Payal
authors.initials: P
authors.lastname: Mukherjee
authors.forename: Hilal
authors.initials: H
authors.lastname: Uzun-Coruhlu
authors.forename: Chris C
authors.initials: CC
authors.lastname: Wong
authors.forename: Ian S
authors.initials: IS
authors.lastname: Curthoys
authors.forename: Allan S
authors.initials: AS
authors.lastname: Jones
authors.forename: William P R
authors.initials: WP
authors.lastname: Gibson
mesh_terms: D003051:Cochlea / Q000293:injuries* / Q000473:pathology; D019929:Cochlear Implantation / Q000009:adverse effects*; D003054:Cochlear Implants / Q000009:adverse effects*; D004567:Electrodes, Implanted / Q000009:adverse effects*; D034381:Hearing Loss / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D006801:Humans; D007089:Image Enhancement; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D011474:Prosthesis Design; D017755:Prosthesis Fitting; D012086:Reoperation / Q000379:methods; D013018:Sound Spectrography; D013701:Temporal Bone / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D055114:X-Ray Microtomography