title: Anatomical feasibility for safe occipital condyle screw fixation.
abstract: The occipital condyle (OC) screw can be a viable alternative option for the occipito-cervical fixation. However, the risk of vertebral artery (VA) injury during the direct OC screw fixation has not been adequately assessed. The purpose of this study was to establish the course of the VA (V3) relative to the nearby osseous structures to estimate the feasibility of OC screw fixation and describe its anatomical relationship depending on patient's age and sex.
  
  
  
  A total of 387 three-dimensional computed tomographic angiograms (3D-CTA) were used and compared between two age groups. The vertebral artery diameter and two kinds of bony space were measured. The occipito-C1 arch space (O-C1S) and VA-occipital bone distance (VOD, six entry points) were measured on both sides. The feasibility of direct OC screw fixation can be represented by the VOD value; the minimum feasible value was determined to be 4 mm. Angular measurements (O-C1A and O-C2A) were also taken to assess their relationship to the bony space.
  
  
  
  The mean value of the O-C1S ranged from 9.0 to 9.9 mm. The mean value of the VOD ranged from 3.2 to 3.5 mm, and the proportion of individuals for which direct OC screw fixation was considered feasible ranged from 32 to 42 % in both age groups and there was no significant difference between two age groups. The VOD value was not affected by laterality or by gender (P > 0.05). The mean kyphosis of the O-C1A (-5° ± 5.2°, range -22° to 8°) was significantly smaller in the young age group compared to the older age group (-7.6° ± 5.3°, range -26° to 2°). The mean lordosis of the O-C2A (12.4° ± 6.4°, range 3°-33°) was significantly higher in the young age group compared to the older age group (10.4° ± 6.4°, range 0°-36°).
  
  
  
  The direct OC screw fixation was not possible in a considerable number of cases due to the limited space and the position of the VA regardless of age group. Only about one quarter (21-24 %) of all patients was affordable to place the direct OC screw bilaterally. There was more space available to place the direct OC screw when the angle of the upper cervical spine is more kyphotic.
authors.affiliation: Department of Neurosurgery, Incheon St. Mary's Hospital, The Catholic University of Korea, Incheon, Korea.
authors.forename: Ho Jin
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Department of Neurosurgery, Incheon St. Mary's Hospital, The Catholic University of Korea, Incheon, Korea.
authors.forename: Doo Yong
authors.initials: DY
authors.lastname: Choi
authors.affiliation: Department of Neurosurgery, Incheon St. Mary's Hospital, The Catholic University of Korea, Incheon, Korea.
authors.forename: Myoung Hoon
authors.initials: MH
authors.lastname: Shin
authors.affiliation: Department of Neurosurgery, Incheon St. Mary's Hospital, The Catholic University of Korea, Incheon, Korea.
authors.forename: Jong Tae
authors.initials: JT
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, St. Vincent Hospital, The Catholic University of Korea, 93-6 Ji-Dong, Paldal-gu, Suwon, 442-723, Korea.
authors.forename: Il Sup
authors.initials: IS
authors.lastname: Kim
authors.affiliation: Department of Neurosurgery, St. Vincent Hospital, The Catholic University of Korea, 93-6 Ji-Dong, Paldal-gu, Suwon, 442-723, Korea. jatagi15@gmail.com.
authors.forename: Jae Taek
authors.initials: JT
authors.lastname: Hong
mesh_terms: D000293:Adolescent; D000328:Adult; D001863:Bone Screws; D000072226:Computed Tomography Angiography; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009777:Occipital Bone / Q000000981:diagnostic imaging / Q000601:surgery; D019637:Orthopedic Procedures / Q000379:methods / Q000592:standards; D014711:Vertebral Artery / Q000000981:diagnostic imaging*; D055815:Young Adult
keywords: Computed tomographic angiography; Occipital condyle screw; Occipital fixation; Vertebral artery
references.citation: Spine (Phila Pa 1976). 2010 Apr 20;35(9):931-8
references.pmid: 20375778
references.citation: J Neurosurg Spine. 2008 Mar;8(3):230-6
references.pmid: 18312074
references.citation: J Neurosurg Spine. 2010 Oct;13(4):451-60
references.pmid: 20887142
references.citation: Neurosurgery. 2009 Dec;65(6):E1216-7; discussion E1217
references.pmid: 19934947
references.citation: J Spinal Disord Tech. 2008 Dec;21(8):540-6
references.pmid: 19057245
references.citation: Eur Spine J. 2014 Oct;23 (10 ):2182-8
references.pmid: 25070792
references.citation: Spine (Phila Pa 1976). 2014 Feb 1;39(3):E147-52
references.pmid: 24173015
references.citation: J Neurosurg Spine. 2008 Oct;9(4):347-53
references.pmid: 18939920
references.citation: J Neurosurg Spine. 2010 May;12 (5):509-16
references.pmid: 20433299
references.citation: Neurol Med Chir (Tokyo). 2011;51(10 ):701-6
references.pmid: 22027245
references.citation: J Neurosurg Pediatr. 2014 Jan;13(1):45-53
references.pmid: 24206344
references.citation: J Neurosurg. 2003 Jul;99(1 Suppl):80-3
references.pmid: 12859065
references.citation: Eur Spine J. 2014 Feb;23(2):328-36
references.pmid: 23982903
references.citation: Spine (Phila Pa 1976). 2013 Aug 15;38(18):E1149-55
references.pmid: 23698573
references.citation: J Spinal Disord Tech. 2014 Jun;27(4):232-6
references.pmid: 24866907
references.citation: Eur Spine J. 2014 May;23 (5):1109-14
references.pmid: 24509775