title: Impact of floating mass transducer coupling and positioning in round window vibroplasty.
abstract: OBJECTIVE
  The round window application of the Vibrant Sound bridge, the so-called round window vibroplasty, is gaining increasing popularity for hearing rehabilitation of patients with mixed hearing loss or conductive hearing loss. In these patients, conventional hearing amplification and/or surgical restoration is either not possible or has failed because of chronic ear disease, extensive otosclerosis, or malformations. The exact mechanisms of direct cochlear stimulation via the round window membrane are not yet completely understood. It is unclear what kind and what degree of contact is required between the floating mass transducer (FMT) and the round window membrane (RWM) to elicit a functional hearing perception with the implant. We investigated the coupling efficiency between the FMT and the RWM and how the efficiency is altered by the FMT position, the degree of FMT-RWM contact, and the use of a soft tissue coupler.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Tertiary referral center in Western Australia.
  
  
  METHODS
  Patients undergoing round window vibroplasty for a mixed or conductive hearing loss otherwise not aidable.
  
  
  METHODS
  Patients underwent round window vibroplasty and received audiological and coupling analysis in the follow-up. These data were then correlated with FMT positioning and the extent of FMT-RWM interface as determined by postoperative high-resolution temporal bone computed tomography.
  
  
  METHODS
  Coupling and hearing levels in relation to FMT positioning and degree of FMT-RWM contact.
  
  
  RESULTS
  Of 10 patients, 8 were available for vibroplasty behavioral threshold testing. In 2 patients, testing could not be done because of wound breakdown requiring device explantation in 1 case, and in the other case, the bone conduction thresholds dropped 2 months after implantation, thus falling out of the performance range of the device. Postoperative FMT migration occurred in 50% of the patients (3/6) with recurrent chronic ear disease and status after multiple previous ear operations. All patients, including the 3 patients requiring surgical repositioning of the FMT, attained significantly improved speech in quiet and speech in noise when compared with the preoperatively best aided performance. All patients showed significantly improved average Abbreviated Profile of Hearing Benefit scores with the use of the FMT. Direct (partial or complete) contact with the RWM resulted in good coupling efficiency; soft tissue coupling resulted in a reduced coupling efficiency.
authors.affiliation: Otolaryngology, Head & Neck Surgery Unit, School of Surgery, University of Western Australia, Australia. Gunesh.Rajan@health.wa.gov.au
authors.forename: Gunesh P
authors.initials: GP
authors.lastname: Rajan
authors.forename: Peter
authors.initials: P
authors.lastname: Lampacher
authors.forename: Ranjeeta
authors.initials: R
authors.lastname: Ambett
authors.forename: Gregor
authors.initials: G
authors.lastname: Dittrich
authors.forename: Jafri
authors.initials: J
authors.lastname: Kuthubutheen
authors.forename: Bradley
authors.initials: B
authors.lastname: Wood
authors.forename: Anne
authors.initials: A
authors.lastname: McArthur
authors.forename: Roberta
authors.initials: R
authors.lastname: Marino
mesh_terms: D000328:Adult; D000368:Aged; D001298:Audiology; D001307:Auditory Perception / Q000502:physiology; D001309:Auditory Threshold / Q000502:physiology; D001844:Bone Conduction / Q000502:physiology; D003054:Cochlear Implants; D004429:Ear Ossicles / Q000473:pathology / Q000601:surgery; D005260:Female; D006309:Hearing / Q000502:physiology; D006311:Hearing Disorders / Q000601:surgery*; D006314:Hearing Loss, Conductive / Q000628:therapy; D046089:Hearing Loss, Mixed Conductive-Sensorineural / Q000628:therapy; D006801:Humans; D008297:Male; D008875:Middle Aged; D019919:Prosthesis Implantation / Q000379:methods*; D012086:Reoperation; D012405:Round Window, Ear / Q000601:surgery*; D013067:Speech Perception; D013701:Temporal Bone / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed; D014159:Transducers; D016896:Treatment Outcome