title: The anatomic suitability of the C2 vertebra for intralaminar and pedicular fixation: a computed tomography study.
abstract: BACKGROUND
  Several methods have been used to stabilize the atlantoaxial joint, including the use of C2 pedicle and laminar screws. No report has used computed tomography (CT) angiograms to compare the risk to the vertebral artery or assess the suitability for each fixation technique.
  
  
  OBJECTIVE
  To compare the suitability of C2 pedicle versus laminar screws using CT angiograms.
  
  
  METHODS
  We retrospectively evaluated the anatomic dimensions of the C2 lamina and pedicle in 50 patients using CT angiograms.
  
  
  METHODS
  We retrospectively reviewed the last 50 patients admitted who underwent CT angiograms of the head and neck. Data recorded included the pedicle length and width and the laminar length and width. Vertebral artery anatomy was also assessed to determine if an aberrant location would preclude pedicle fixation.
  
  
  RESULTS
  Mean pedicle length and width were 15.5±3.5 and 4.7±1.7 mm, respectively, with 24% of patients having anatomy that would preclude 3.5-mm pedicle screw fixation. The mean lamina length and width were 25.2±3.6 and 5.5±1.4 mm, and more than 90% of patients could tolerate a 3.5-mm C2 laminar screw.
  
  
  CONCLUSIONS
  Preoperative CT angiography or noncontrast CT is an excellent method to delineate the anatomy at C2 to determine the suitability for pedicle or intralaminar fixation. In cases where vertebral artery anatomy precludes C2 pedicle fixation, more than 90% of patients may be a candidate for C2 intralaminar fixation.
authors.affiliation: Department of Orthopaedic Surgery, George Washington University, 2150 Pennsylvania Ave., Washington, DC 20037, USA.
authors.forename: Rishi
authors.initials: R
authors.lastname: Bhatnagar
authors.forename: Warren D
authors.initials: WD
authors.lastname: Yu
authors.forename: Patrick F
authors.initials: PF
authors.lastname: Bergin
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Matteini
authors.forename: Joseph R
authors.initials: JR
authors.lastname: O'Brien
mesh_terms: D000328:Adult; D001268:Atlanto-Axial Joint / Q000033:anatomy & histology* / Q000000981:diagnostic imaging* / Q000601:surgery*; D001863:Bone Screws; D005260:Female; D006801:Humans; D008297:Male; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods