title: A method for radiographic evaluation of pedicle screw violation of the vertebral endplate. Technique.
abstract: METHODS
  This study evaluated the utility of intraoperative radiographs for minimizing the risk of pedicle screw tip violation of the superior vertebral endplate.
  
  
  OBJECTIVE
  An intraoperative radiographic technique is demonstrated that ensures that a screw has not penetrated the intervertebral disk.
  
  
  BACKGROUND
  Although methods to avoid penetration of the medial pedicle cortex and the anterior body cortex have been described, no study has discussed screw penetration of the superior endplate and disc.
  
  
  METHODS
  Pedicle screws were inserted into 11 cadaveric lumbar spines, randomly, with the tip interior to the endplate, at the endplate, and through the endplate. Radiographs were evaluated to measure the penetration, if any, of the screws. Spine segments were dissected and evaluated anatomically. The anatomic and radiographic results were then compared.
  
  
  RESULTS
  The overall error rate for radiographs was 22/312 (7%). Oblique radiographs gave a much higher error rate.
  
  
  CONCLUSIONS
  A true lateral or anteroposterior radiographic view of the vertebra provides a high degree of certainty that the screw has not crossed the endplate when a "safe zone" of 3 mm remains superior to the screw tip. Intraoperative radiography can reduce concern about violation of the superior vertebral endplate.
authors.affiliation: Orthopaedic Surgery Service, Walter Reed Army Medical Center, Washington, DC., USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: Meter
authors.forename: D W
authors.initials: DW
authors.lastname: Polly
authors.forename: D W
authors.initials: DW
authors.lastname: Miller
authors.forename: N A
authors.initials: NA
authors.lastname: Popovic
authors.forename: S L
authors.initials: SL
authors.lastname: Ondra
mesh_terms: D000328:Adult; D001863:Bone Screws / Q000009:adverse effects*; D002102:Cadaver; D005069:Evaluation Studies as Topic; D006801:Humans; D007403:Intervertebral Disc / Q000601:surgery; D007432:Intraoperative Period; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery*; D008297:Male; D011859:Radiography / Q000379:methods*