title: Study of the feasible size of a bone conduction implant transducer in the temporal bone.
abstract: OBJECTIVE
  The aim was to assess the temporal bone volume to determine the suitable size and position of a bone conduction implant (BCI) transducer.
  
  
  BACKGROUND
  A BCI transducer needs to be sufficiently small to fit in the mastoid portion of the temporal bone for a majority of patients. The anatomical geometry limits both the dimension of an implanted transducer and its positions in the temporal bone to provide a safe and simple surgery.
  
  
  METHODS
  Computed tomography (CT) scans of temporal bones from 22 subjects were virtually reconstructed. With an algorithm in MATLAB, the maximum transducer diameter as function of the maximum transducer depth in the temporal bone, and the most suitable position were calculated in all subjects.
  
  
  RESULTS
  An implanted transducer diameter of 16 mm inserted at a depth of 4 mm statistically fitted 95% of the subjects. If changing the transducer diameter to 12 mm, a depth of 6 mm would fit in 95% of the subjects. The most suitable position was found to be around 20 mm behind the ear canal.
  
  
  CONCLUSIONS
  The present BCI transducer casing, used in ongoing clinical trials, was designed from the results in this study, demonstrating that the present BCI transducer casing (largest diameter [diagonal]: 15.5 mm, height: 6.4 mm) will statistically fit more than 95% of the subjects. Hence, the present BCI transducer is concluded to be sufficiently small to fit most normal-sized temporal bones and should be placed approximately 20 mm behind the ear canal.
authors.affiliation: *Department of Signals and Systems, Chalmers University of Technology, Gothenburg, Sweden; and †Ear, Nose, and Throat Department, Sahlgrenska University Hospital, Gothenburg, Sweden.
authors.forename: Sabine
authors.initials: S
authors.lastname: Reinfeldt
authors.forename: Per
authors.initials: P
authors.lastname: Östli
authors.forename: Bo
authors.initials: B
authors.lastname: Håkansson
authors.forename: Hamidreza
authors.initials: H
authors.lastname: Taghavi
authors.forename: Måns
authors.initials: M
authors.lastname: Eeg-Olofsson
authors.forename: Joacim
authors.initials: J
authors.lastname: Stalfors
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D001844:Bone Conduction / Q000502:physiology; D004424:Ear Canal / Q000000981:diagnostic imaging; D005240:Feasibility Studies; D005260:Female; D006310:Hearing Aids; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011857:Radiographic Image Interpretation, Computer-Assisted; D013701:Temporal Bone / Q000000981:diagnostic imaging* / Q000601:surgery*; D014057:Tomography, X-Ray Computed; D014159:Transducers