title: Utility of helical computed tomography in differentiating unilateral and bilateral facet dislocations.
abstract: OBJECTIVE
  Diagnosis of cervical facet dislocation is difficult when relying on plain radiographs alone. This study evaluates the interobserver reliability of helical computed tomography (CT) in the assessment of cervical translational injuries, correlates the radiographic diagnosis with intraoperative observation, and examines the role of neurologic injury in the evaluation and diagnosis of these injuries.
  
  
  METHODS
  Clinical histories and radiographic studies of 10 patients with cervical facet dislocations were presented to 25 surgeons. Participants classified cases as unilateral or bilateral facet dislocations after reviewing selected axial CT slices and sagittal reconstructions. Surgeons' interpretations were compared with intraoperative diagnosis. Participants interpreted the same radiographic studies with 3 different clinical scenarios: neurologically intact, incomplete, and complete spinal cord injury. Vertebral body translation from midsagittal CT was evaluated to confirm whether all unilateral facet dislocations had <25% translation.
  
  
  RESULTS
  Interrater kappa coefficient showed moderate agreement between observers in classifying injuries as unilateral or bilateral (kappa: 0.54-0.58), regardless of neurologic status. Percent agreement among observers varied from 50% to 100% for each individual case. Agreement was statistically higher for bilateral facet dislocation (85%) than for unilateral dislocations (78%), with 1 unilateral fracture showing nearly 50% translation on a midsagittal image.
  
  
  CONCLUSIONS
  The addition of helical CT to reconstruction enables spine surgeons to more reliably distinguish bilateral from unilateral cervical facet dislocations. Despite frequent occurrence of these injuries and presumed agreement on injury description, agreement may be improved by a more precise definition of facet dislocations and subluxations and thorough review of all imaging studies.
authors.affiliation: Department of Neurosurgery, University of Utah, 175 N. Medical Drive East, Salt Lake City, UT 84106, USA. Andrew.dailey@hsc.utah.edu
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Dailey
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Shaffrey
authors.forename: Raja
authors.initials: R
authors.lastname: Rampersaud
authors.forename: Joonyung
authors.initials: J
authors.lastname: Lee
authors.forename: Darrel S
authors.initials: DS
authors.lastname: Brodke
authors.forename: Paul
authors.initials: P
authors.lastname: Arnold
authors.forename: Ahmad
authors.initials: A
authors.lastname: Nassr
authors.forename: James S
authors.initials: JS
authors.lastname: Harrop
authors.forename: Jonathan
authors.initials: J
authors.lastname: Grauer
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Bono
authors.forename: Marcel
authors.initials: M
authors.lastname: Dvorak
authors.forename: Alexander
authors.initials: A
authors.lastname: Vaccaro
mesh_terms: D002574:Cervical Vertebrae / Q000000981:diagnostic imaging* / Q000293:injuries* / Q000601:surgery; D007839:Functional Laterality; D006801:Humans; D004204:Joint Dislocations / Q000000981:diagnostic imaging* / Q000601:surgery; D014057:Tomography, X-Ray Computed