title: New bone and fibrous tissue formation around ceramic cochlear implant receiver--stimulators and the measurement of their anchorage in the bony implant bed.
abstract: OBJECTIVE
  To determine (1) levels on fibrous tissue and bony growth around the ceramic receiver-stimulator of cochlear implants in situ and (2) if these ceramic receiver-stimulators can withstand a tractive force of 5 N without displacing.
  
  
  METHODS
  During revision surgery, we measured the extent of the fibrous tissue and bone growth around the receiver-stimulators in 13 subjects. After completely exposing the receiver-stimulator, we measured the tractive force it could withstand without displacing. The tractive force was gradually increased until either displacement or a force of approximately 5.5 N was reached.
  
  
  RESULTS
  In 6 out of 10 subjects the receiver-stimulator did not displace when up to 5 N of tractive force was applied. Three subjects could not be evaluated. Statistical analysis was not possible due to the small sample size; however, we found no correlation between the degree of bone growth around the receiver-stimulator and (1) the length of time the implants remained in situ before revision or (2) the tractive force a receiver-stimulator could withstand without displacing. Discussion As bone growth around the receiver-stimulator is often limited, even years after implantation, it might therefore only play a minor role in preventing displacement. In contrast, fibrous tissue encapsulation of the implant bed of the receiver-stimulator may be the key stabilizing factor. In any case, when completely exposed, the 6 out of 10 receiver-stimulators could still withstand a tractive force of 5 N (calculated force generated by magnetic resonance imaging (MRI) with 1.5 T) without displacing.
  
  
  CONCLUSIONS
  During MRI, it is strongly recommended to secure ceramic receiver-stimulators with an external pressure bandage in order to minimize risk and possible user discomfort.
authors: Robert
authors: R
authors: Mlynski
authors: Kristen
authors: K
authors: Rak
authors: Stefan
authors: S
authors: Kaulitz
authors: Fabian
authors: F
authors: Kraus
authors: Rudolf
authors: R
authors: Hagen
authors: Andreas
authors: A
authors: Radeloff
mesh_terms: D000293:Adolescent; D000328:Adult; D002516:Ceramics; D002648:Child; D002675:Child, Preschool; D019929:Cochlear Implantation / Q000009:adverse effects* / Q000295:instrumentation; D003054:Cochlear Implants / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D016348:Osseointegration; D010012:Osteogenesis; D013997:Time Factors
keywords: Bone growth; Cochlear implant fixation; Fibrous tissue growth; Magnetic resonance imaging