title: C1 anatomy and dimensions relative to lateral mass screw placement.
abstract: METHODS
  An anatomic surface osteometric analysis of cadaveric cervical spines.
  
  
  OBJECTIVE
  To assess the feasibility of placing a 3.5-mm cortical screw in the lateral mass of C1 in a large number of specimens for the purpose of gaining internal fixation for various conditions.
  
  
  BACKGROUND
  Previous studies have addressed surface dimensions of the atlas vertebra and computerized tomography-measured dimensions of the lateral masses of the atlas. These studies used a limited number of specimens with potentially homogeneous origins.
  
  
  METHODS
  A total of 120 atlas (C1) vertebrae for a total of 240 lateral masses were examined and external measurements obtained to assess the feasibility of placing a 3.5-mm cortical screw in the lateral mass.
  
  
  RESULTS
  The minimum lateral mass dimensions found from 240 C1 lateral masses were 13.15 mm anterior-posterior, 4.22 mm medial-lateral, and 4.73 mm cephalocaudal. The height of the posterior arch at the groove for the vertebral artery (pedicle analog) was less than 4 mm in 46 of 240 (19.2%) arches.
  
  
  CONCLUSIONS
  It is feasible to safely and reproducibly place a 3.5-mm cortical screw in the lateral mass of C1 when the appropriate starting point and trajectory of the screw are chosen.
authors.affiliation: Intermountain Spine and Orthopaedics, Twin Falls, ID, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Christensen
authors.forename: Robert K
authors.initials: RK
authors.lastname: Eastlack
authors.forename: James J
authors.initials: JJ
authors.lastname: Lynch
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Yaszemski
authors.forename: Bradford L
authors.initials: BL
authors.lastname: Currier
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001368:Axis, Cervical Vertebra / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery; D001863:Bone Screws; D001270:Cervical Atlas / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000601:surgery*; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D013123:Spinal Fusion; D014057:Tomography, X-Ray Computed