title: Quantitative anatomic study of the transciliary supraorbital approach: benefits of additional orbital osteotomy?
abstract: BACKGROUND
  The transciliary supraorbital approach (TCSO) provides an anterior view for visualizing sellar, parasellar, and suprasellar structures. Whether an orbital osteotomy adds to this exposure has not been quantified.
  
  
  OBJECTIVE
  We quantitatively evaluated the TCSO and benefits of an additional orbital osteotomy for exposing common sites of anterior circulation aneurysms.
  
  
  METHODS
  Under image guidance, TCSO and orbital osteotomy were performed on 10 sides of 5 cadaver heads to quantify exposures of 4 surgical targets: (1) the junction of the anterior cerebral and anterior communicating arteries (ACoA); (2) the internal carotid artery (ICA) at the level of the posterior communicating artery (PCoA); (3) the bifurcation of the ICA; and (4) the middle cerebral artery (MCA) bifurcation. Horizontal and vertical angles of attack and surgical freedom for instrument manipulation were measured before and after the orbital rim and roof were removed.
  
  
  RESULTS
  An orbital osteotomy significantly increased surgical freedom to the ACoA (from 471.15 +/- 182.14 mm2 to 683.35 +/- 283.78 mm2, P = .021); PCoA (from 746.58 +/- 242.78 mm2 to 966.23 +/- 360.22 mm2, P = .007); ICA bifurcation (from 616.08 +/- 310.95 mm2 to 922.38 +/- 374.88 mm2, P = .002); and MCA bifurcation (from 1160.77 +/- 412.03 mm2 to 1597.71 +/- 733.18 mm2, P = .004). There were no significant differences in horizontal angles of attack. The vertical angles of attack were significantly greater after orbital osteotomy, principally with the ACoA and ICA bifurcation as targets.
  
  
  CONCLUSIONS
  TCSO combined with orbital osteotomy improves exposure. Removing the orbital rim and roof increases the area for instrument use and improves the vertical angle of attack to common sites in the anterior circulation involving aneurysms.
authors.affiliation: Division of Neurological Surgery, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.
authors.forename: Daniel D
authors.initials: DD
authors.lastname: Cavalcanti
authors.forename: Ulises
authors.initials: U
authors.lastname: García-González
authors.forename: Abhishek
authors.initials: A
authors.lastname: Agrawal
authors.forename: Neil R
authors.initials: NR
authors.lastname: Crawford
authors.forename: Paulo Leonardo M S
authors.initials: PL
authors.lastname: Tavares
authors.forename: Robert F
authors.initials: RF
authors.lastname: Spetzler
authors.forename: Mark C
authors.initials: MC
authors.lastname: Preul
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D020771:Anterior Cerebral Artery / Q000033:anatomy & histology / Q000473:pathology / Q000601:surgery; D002102:Cadaver; D002343:Carotid Artery, Internal / Q000033:anatomy & histology / Q000502:physiology / Q000601:surgery; D002941:Circle of Willis / Q000033:anatomy & histology / Q000473:pathology / Q000601:surgery; D035262:Cranial Fossa, Anterior / Q000033:anatomy & histology / Q000601:surgery; D035301:Cranial Fossa, Middle / Q000033:anatomy & histology / Q000601:surgery*; D003399:Craniotomy / Q000379:methods* / Q000592:standards; D004210:Dissection / Q000379:methods; D005260:Female; D005624:Frontal Bone / Q000033:anatomy & histology / Q000601:surgery*; D006801:Humans; D002532:Intracranial Aneurysm / Q000473:pathology / Q000601:surgery*; D008297:Male; D020768:Middle Cerebral Artery / Q000033:anatomy & histology / Q000473:pathology / Q000601:surgery; D019635:Neurosurgical Procedures / Q000379:methods / Q000592:standards; D009915:Orbit / Q000033:anatomy & histology / Q000601:surgery*; D010027:Osteotomy / Q000379:methods* / Q000592:standards