title: Is It "In" or "Out"? The Optimal Fluoroscopic Views for Intraoperative Determination of Proper Lateral Mass Screw Placement.
abstract: METHODS
  Cadaveric.
  
  
  OBJECTIVE
  Determine optimal fluoroscopic views for detecting cervical lateral mass screw (LMS) violations.
  
  
  BACKGROUND
  Single plane intraoperative x-rays are commonly used but frequently inadequate due to its complex trajectory. Fluoroscopy can be taken in multiple planes, but the ideal fluoroscopic view to assess malposition is not known: depending on the view, any given screw may look "in" or "out."
  
  
  METHODS
  C3-6 LMS were inserted in three cadavers. To evaluate neuroforaminal violation, LMS were inserted into the foramen with the tip penetrating the anterior cortex by 0, 2, and 4 mm. To assess facet joint violation, LMS were inserted toward the subjacent facet joint with the tip penetrating the anterior cortex by 0 and 2 mm. Fluoroscopic views were taken 0°, 10°, 20°, 30°, and 40° to the lateral plane. Views were independently evaluated by three blinded spine surgeons.
  
  
  RESULTS
  Twenty-degree oblique view correctly identified a 2 mm penetration into the neuroforamen in 79%, and a 4 mm penetration in 86%, for a sensitivity of 83% and specificity of 90%. Thirty-degree view had lower sensitivity (76%) but slightly higher specificity (93%). Twenty-degree and 30° views were significantly more sensitive than the other views. Zero-degree view correctly identified a 2 mm penetration into the facet joint in 93%, for a sensitivity of 93% and specificity of 92%. Ten-degree view had lower sensitivity (72%) but higher specificity (100%). The 0° view was significantly more sensitive than the other views.
  
  
  CONCLUSIONS
  Twenty-degree and 30° oblique views significantly provided the most sensitive assessment of LMS potentially violating the neuroforamen, whereas the 0° neutral lateral view significantly provided the most sensitive assessment of facet violations. The specificities were also high (in the 90% range) for these views. We recommend the use of these views intraoperatively when assessing proper placement of LMS fluoroscopically.
  
  
  METHODS
  N/A.
authors.affiliation: Department of Orthopaedic Surgery, Konyang University Hospital, Daejeon, Korea.
authors.forename: Sang Bum
authors.initials: SB
authors.lastname: Kim
authors.affiliation: Department of Orthopaedic Surgery, Emory Spine Center, Atlanta, GA.
authors.forename: John M
authors.initials: JM
authors.lastname: Rhee
authors.affiliation: Department of Orthopaedic Surgery, Konyang University Hospital, Daejeon, Korea.
authors.forename: Byung Hak
authors.initials: BH
authors.lastname: Oh
authors.affiliation: Department of Orthopaedic Surgery, Konyang University Hospital, Daejeon, Korea.
authors.forename: You Gun
authors.initials: YG
authors.lastname: Won
authors.affiliation: Department of Orthopaedic Surgery, Konyang University Hospital, Daejeon, Korea.
authors.forename: Yousun
authors.initials: Y
authors.lastname: Jung
authors.affiliation: Department of Orthopaedic Surgery, Daejeon Veterans Hospital, Daejeon, Korea.
authors.forename: Kun Young
authors.initials: KY
authors.lastname: Park
authors.affiliation: Department of Orthopaedic Surgery, Emory Spine Center, Atlanta, GA.
authors.forename: William C
authors.initials: WC
authors.lastname: Hutton
authors.affiliation: Department of Mathematics, University of West Georgia, Carrollton, GA.
authors.forename: Chulmin
authors.initials: C
authors.lastname: Kim
mesh_terms: D001863:Bone Screws / Q000009:adverse effects; D002102:Cadaver; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery*; D005471:Fluoroscopy; D005593:Fracture Fixation, Internal / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D007432:Intraoperative Period; D013123:Spinal Fusion / Q000009:adverse effects / Q000295:instrumentation / Q000379:methods*