title: Sheep as a large animal model for middle and inner ear implantable hearing devices:  a feasibility study in cadavers.
abstract: OBJECTIVE
  Currently, no large animal model exists for surgical-experimental exploratory analysis of implantable hearing devices. In a histomorphometric study, we sought to investigate whether sheep or pig cochleae are suitable for this purpose and whether device implantation is feasible.
  
  
  METHODS
  Skulls of pig and sheep cadavers were examined using high-resolution 128-slice computed tomography (CT) to study anatomic relationships. A cochlear implant and an active middle ear implant could be successfully implanted into the sheep's inner and middle ear, respectively. Correct device placement was verified by CT and histology. The cochlear anatomy of the sheep was further studied by micro-CT and histology.
  
  
  RESULTS
  Our investigations indicate that the sheep is a suitable animal model for implantation of implantable hearing devices. The implantation of the devices was successfully performed by access through a mastoidectomy. The histologic, morphologic, and micro-CT study of the sheep cochlea showed that it is highly similar to the human cochlea. The temporal bone of the pig was not suitable for these microsurgical procedures because the middle and inner ear were not accessible owing to distinct soft and fatty tissue coverage of the mastoid.
  
  
  CONCLUSIONS
  The sheep is an appropriate large animal model for experimental studies with implantable hearing devices, whereas the pig is not.
authors.affiliation: Department of Otolaryngology, University Hospital, Medical University Innsbruck, Innsbruck, Austria.
authors.forename: Johannes
authors.initials: J
authors.lastname: Schnabl
authors.forename: Rudolf
authors.initials: R
authors.lastname: Glueckert
authors.forename: Gudrun
authors.initials: G
authors.lastname: Feuchtner
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Recheis
authors.forename: Thomas
authors.initials: T
authors.lastname: Potrusil
authors.forename: Volker
authors.initials: V
authors.lastname: Kuhn
authors.forename: Astrid
authors.initials: A
authors.lastname: Wolf-Magele
authors.forename: Herbert
authors.initials: H
authors.lastname: Riechelmann
authors.forename: Georg M
authors.initials: GM
authors.lastname: Sprinzl
mesh_terms: D000818:Animals; D002102:Cadaver; D003051:Cochlea / Q000033:anatomy & histology / Q000000981:diagnostic imaging; D019929:Cochlear Implantation; D003054:Cochlear Implants; D007758:Ear, Inner / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D004432:Ear, Middle / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D004724:Endoscopy; D005240:Feasibility Studies; D007091:Image Processing, Computer-Assisted; D007188:Incus / Q000033:anatomy & histology / Q000601:surgery; D008416:Mastoid / Q000601:surgery; D012405:Round Window, Ear / Q000033:anatomy & histology / Q000601:surgery; D012533:Scala Tympani / Q000033:anatomy & histology / Q000601:surgery; D012756:Sheep / Q000502:physiology*; D012886:Skull / Q000033:anatomy & histology; D013045:Species Specificity; D013552:Swine; D013701:Temporal Bone / Q000033:anatomy & histology; D014057:Tomography, X-Ray Computed