title: Stabilization of the atlantoaxial joint with C1-C3 lateral mass screw constructs: biomechanical comparison with standard technique.
abstract: BACKGROUND
  Anatomically and biomechanically, the atlantoaxial joint is unique compared with the remainder of the cervical spine.
  
  
  OBJECTIVE
  To assess the in vitro stability provided by 2 C2 screw sparing techniques in a destabilized model of the atlantoaxial joint and compare with the gold standard system.
  
  
  METHODS
  The 3-dimensional intervertebral motion of 7 human cadaveric cervical spine specimens was recorded stereophotogrammetrically while applying nonconstraining, nondestructive pure moments during flexion-extension, left and right axial rotation, and left and right lateral bending. Each specimen was tested in the intact state, followed by destabilization (odontoidectomy) and fixation as follows: (1) C1 and C3 lateral mass screws rods with sublaminar wiring of C2 (LC1-C3 + SW), (2) C1 and C3 lateral mass screws rods with a cross-link in the C1-2 interlaminar space (LC1-C3 + CL), (3) C1 and C3 lateral mass screw rods alone (negative control), and (4) C1 lateral mass and C2 pedicle screws rods augmented with C1-2 interspinous wire and graft (LC1-PC2, control group).
  
  
  RESULTS
  Compared with the intact spine, each instrumented state significantly stabilized range of motion and lax zone at C1-2 (P < .001, 1-way repeated-measures analysis of variance). LC1-C3 + SW was equivalent to LC1-PC2 during flexion and lateral bending and superior to LC1-C3 + CL during lateral bending, while LC1-C3 + CL was equivalent to LC1-PC2 only during flexion. In all other comparisons, LC1-PC2 was superior to both techniques.
  
  
  CONCLUSIONS
  From a biomechanical perspective, both C2 screw sparing techniques provided sufficient stability to be regarded as an alternative for C1-2 fixation. However, because normal motion across C2-3 is sacrificed, these constructs should be used in patients with unfavorable anatomy for standard fixations.
authors.affiliation: Spinal Biomechanics Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, Arizona, USA.
authors.forename: Leonardo B C
authors.initials: LB
authors.lastname: Brasiliense
authors.forename: Bruno C R
authors.initials: BC
authors.lastname: Lazaro
authors.forename: Phillip M
authors.initials: PM
authors.lastname: Reyes
authors.forename: Douglas
authors.initials: D
authors.lastname: Fox
authors.forename: Volker K H
authors.initials: VK
authors.lastname: Sonntag
authors.forename: Neil R
authors.initials: NR
authors.lastname: Crawford
mesh_terms: D000368:Aged; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D001368:Axis, Cervical Vertebra / Q000033:anatomy & histology / Q000601:surgery*; D001696:Biomechanical Phenomena / Q000502:physiology; D001863:Bone Screws / Q000592:standards*; D001270:Cervical Atlas / Q000033:anatomy & histology / Q000601:surgery*; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care / Q000379:methods; D011859:Radiography; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods*