title: Computed Tomography Estimation of Cochlear Duct Length Can Predict Full Insertion in Cochlear Implantation.
abstract: OBJECTIVE
  To compare the rates of full insertion of electrodes and hearing outcomes obtained with 28-mm and 31-mm cochlear implant electrode arrays. To assess whether cochlear duct length (CDL) estimated by preoperative computed tomography (CT) predicts whether an electrode is fully inserted.
  
  
  METHODS
  A cohort study compared electrodes inserted and hearing outcomes after implantation with 28-mm or 31-mm arrays. CDL estimated from preoperative CT was compared in patients in whom full insertion of the 28-mm array was achieved compared with patients in whom at least one basal electrode was outside the cochlea.
  
  
  METHODS
  Tertiary referral cochlear implantation center.
  
  
  METHODS
  One hundred forty-eight patients implanted with 28-mm cochlear implant arrays (175 devices) and 74 patients implanted with 31-mm arrays (88 devices).
  
  
  METHODS
  Cochlear implantation with 28-mm or 31-mm array.
  
  
  METHODS
  Active electrodes at first programming, and at subsequent follow-ups. Bamford-Kowal-Bench sentence and auditory speech sound evaluation test results at 2 to 3 months in adult patients. CDL predicted by preoperative CT.
  
  
  RESULTS
  There was no difference in full insertion between the 28-mm and 31-mm array cohorts (p = 0.22). Early hearing outcomes at 2 to 3 months showed no difference in mean auditory speech sound evaluation (p = 0.19) or Bamford-Kowal-Bench results (p = 0.853) between the 28-mm and 31-mm cohorts. CDL was shorter in the 22 patients with less than full insertion of the array with a mean length of 28.7 mm compared with 29.6 mm in the 42 patients in whom full insertion was achieved (p = 0.046).
  
  
  CONCLUSIONS
  CT estimation of CDL predicts full insertion after cochlear implantation. Insertion depth does not affect early hearing outcome.
authors.affiliation: *Department of Otolaryngology, Cambridge University Hospitals NHS Foundation Trust †Department of Radiology, Cambridge University Hospitals NHS Foundation Trust ‡Emmeline Centre for Hearing Implants, Cambridge University Hospitals NHS Foundation Trust §Emmeline Centre for Hearing Implants, Cambridge University Hospitals NHS Foundation Trust, and Audiology, Anglia Ruskin University ||Department of Otolaryngology and Emmeline Centre for Hearing Implants, Cambridge University Hospitals NHS Foundation Trust, Cambridge, U.K.
authors.forename: James D A
authors.initials: JD
authors.lastname: Johnston
authors.forename: Daniel
authors.initials: D
authors.lastname: Scoffings
authors.forename: Mark
authors.initials: M
authors.lastname: Chung
authors.forename: David
authors.initials: D
authors.lastname: Baguley
authors.forename: Neil P
authors.initials: NP
authors.lastname: Donnelly
authors.forename: Patrick R
authors.initials: PR
authors.lastname: Axon
authors.forename: Roger F
authors.initials: RF
authors.lastname: Gray
authors.forename: James R
authors.initials: JR
authors.lastname: Tysome
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003051:Cochlea / Q000601:surgery; D019929:Cochlear Implantation / Q000295:instrumentation* / Q000379:methods*; D003054:Cochlear Implants; D015331:Cohort Studies; D005260:Female; D006309:Hearing; D006320:Hearing Tests; D006801:Humans; D008297:Male; D008875:Middle Aged; D016896:Treatment Outcome