title: Survival of the 8.5 mm osseointegrated abutment, and its utility in the obese patient.
abstract: BACKGROUND
  Most of the literature regarding osseointegrated implantation for hearing rehabilitation focuses on the 5.5 mm abutment. This study aimed to add to the data available on the survival of the 8.5 mm abutment, and to describe its utility in obese patients.
  
  
  OBJECTIVE
  To review the outcomes of patients who received a bone-anchored hearing aid implant, and create a model comparing the mechanical forces acting upon combinations of fixture and abutment lengths.
  
  
  METHODS
  Retrospective chart review and mathematical modelling.
  
  
  RESULTS
  In this retrospective cohort study comprising 25 patients, less abutment overgrowth was observed in the 8.5 mm abutment recipients versus recipients of the 5.5 mm abutment. When the principle of equilibrium of a rigid body was applied, the 8.5 mm abutment was at a calculated mechanical disadvantage compared with the 5.5 mm abutment.
  
  
  CONCLUSIONS
  The 8.5 mm abutment may be useful in patients with copious subcutaneous soft tissue as in the obese population. The 8.5 mm abutment has a calculated mechanical disadvantage, potentially putting the implant under greater mechanical stress; however, the clinical relevance of this is unclear.
authors.affiliation: Department of Otolaryngology - Head and Neck Surgery, Saint Louis University School of Medicine, St. Louis, Missouri 63110, USA.
authors.forename: M D
authors.initials: MD
authors.lastname: Darley
authors.forename: A A
authors.initials: AA
authors.lastname: Mikulec
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D015331:Cohort Studies; D005260:Female; D006310:Hearing Aids / Q000009:adverse effects; D034381:Hearing Loss / Q000534:rehabilitation*; D046088:Hearing Loss, Unilateral; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications*; D016348:Osseointegration; D019919:Prosthesis Implantation / Q000009:adverse effects* / Q000295:instrumentation; D012189:Retrospective Studies; D053441:Suture Anchors; D016896:Treatment Outcome; D055815:Young Adult