title: Radiological study of the anatomy of the keystone area of the nasal septum using computed tomography to aid septal surgery.
abstract: OBJECTIVE
  An optimum septoplasty result may require complete detachment of the superior osseocartilaginous junction (OCJ), but this may lead to disruption of the keystone area with loss of nasal support and consequent supratip depression deformity. The aim of this study was to analyse normal keystone anatomy using CT scan images and to estimate the incidence of risk of supratip depression when completely detaching the OCJ.
  
  
  METHODS
  Retrospective study.
  
  
  METHODS
  Tertiary referral centre.
  
  
  METHODS
  Adult patients who underwent CT paranasal sinuses prior to transsphenoidal hypophysectomy in a tertiary referral centre between 2009 and 2013.
  
  
  METHODS
  Length of the keystone area. A length of <5 mm and certain anatomical configurations were considered at risk of a supratip depression with complete detachment of the OCJ.
  
  
  RESULTS
  CT scans of 91 patients were reviewed. The mean keystone length was 9.04 mm (range 0-23 mm). Twenty-nine (32%) cases were at risk of supratip depression. Relatively shorter nasal bones (nasal bone length: overall dorsal length <0.37) (n = 26) were associated with a shorter keystone area (P = 0.0051).
  
  
  CONCLUSIONS
  Thirty-two per cent of patients have keystone anatomy on radiology predisposing them to supratip depression with complete detachment of the OCJ. Relatively shorter nasal bones were significantly associated with a shorter, higher risk keystone area. In cases with a high septal deviation undergoing a septoplasty, a preoperative CT enables the surgeon to assess the keystone area and determine whether it is safe to completely detach the OCJ.
authors.affiliation: Department of Otorhinolaryngology, Royal Hallamshire Hospital, Sheffield Teaching Hospitals NHS Trust, Sheffield, UK.
authors.forename: S
authors.initials: S
authors.lastname: Carr
authors.affiliation: Department of Otorhinolaryngology, Royal Hallamshire Hospital, Sheffield Teaching Hospitals NHS Trust, Sheffield, UK.
authors.forename: V
authors.initials: V
authors.lastname: Twigg
authors.affiliation: Department of Otorhinolaryngology, Royal Hallamshire Hospital, Sheffield Teaching Hospitals NHS Trust, Sheffield, UK.
authors.forename: S
authors.initials: S
authors.lastname: Mirza
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059925:Anatomic Landmarks; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009300:Nasal Septum / Q000000981:diagnostic imaging* / Q000601:surgery*; D012189:Retrospective Studies; D012225:Rhinoplasty / Q000379:methods*; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome