title: Accuracy of pedicle screw placement in lumbar fusions by plain radiographs and computed tomography.
abstract: METHODS
  Postoperative radiographs and computed tomography scans were used to evaluate 74 pedicle screws in 16 consecutive patients who underwent lumbar spine fusion with pedicle screw fixation.
  
  
  OBJECTIVE
  To evaluate pedicle screw placement using plain radiographs versus computed tomographic scans.
  
  
  BACKGROUND
  Plain radiographs are the primary means of assessing pedicle screw placement. Comparison of plain radiographs and computed tomography has not been done.
  
  
  METHODS
  Screws were graded as IN, OUT, or QUESTIONABLE; the direction of misplacement was noted. All evaluations were performed independently by three observers.
  
  
  RESULTS
  Fewer screws were clearly within the pedicle on computed tomography when compared with plain radiographs. Computed tomography showed 10 times as many screws violating the medial cortex as did radiographs. Interobserver differences were not statistically significant. Intraobserver differences approached statistical significance when the two tests were compared. No recognized neurologic complications resulted from pedicle screw placement.
  
  
  CONCLUSIONS
  Plain radiographs alone may not accurately reveal pedicle screw placement. Plain radiographs and thin section computed tomographic scans should be used to evaluate postoperative neurologic deficits in patients undergoing instrumented lumbar spine fusion with pedicle screws.
authors.affiliation: Orthopedic Service, Fitzsimons Army Medical Center, Aurora, Colorado, USA.
authors.forename: G L
authors.initials: GL
authors.lastname: Farber
authors.forename: H M
authors.initials: HM
authors.lastname: Place
authors.forename: R A
authors.initials: RA
authors.lastname: Mazur
authors.forename: D E
authors.initials: DE
authors.lastname: Jones
authors.forename: T R
authors.initials: TR
authors.lastname: Damiano
mesh_terms: D001863:Bone Screws; D003627:Data Interpretation, Statistical; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery; D011184:Postoperative Period; D011446:Prospective Studies; D013123:Spinal Fusion / Q000009:adverse effects / Q000295:instrumentation* / Q000592:standards; D014057:Tomography, X-Ray Computed; D014965:X-Rays