title: Radiographic criteria for placement of translaminar facet screws.
abstract: BACKGROUND
  Screw fixation of the facet joint has been reported to stabilize the lumbar spine and facilitate spinal fusion. Accurate placement of translaminar facet screws (TLFSs) requires identification of the posterior spinal elements, and the facet joints in particular, which may be facilitated by intra-operative fluoroscopy.
  
  
  OBJECTIVE
  The purpose of this study was to define the radiographic parameters that will allow for successful placement of TLFSs.
  
  
  METHODS
  Eighteen TLFSs were placed in three human cadaver spines using fluoroscopic guidance, with screws placed from L3-L4 to L5-S1 bilaterally. After screw placement, the spines were dissected and examined for accuracy of screw placement.
  
  
  METHODS
  In the first cadaver spine, TLFSs were placed with direct visualization of the posterior lumbar spine, during which a fluoroscopic image intensifier was used to define the appropriate radiographic parameters for safe placement of the screws. Bilateral TLFSs were then placed percutaneously using the radiographic parameters developed, after which the spines were dissected to examine the positions of the screws.
  
  
  RESULTS
  The radiographic views identified to achieve proper TLFS placement were a true lateral, anteroposterior (AP), a 45-degree oblique and an AP view with the X-ray bean at 30- to 45-degree cephalad angle ("spinal outlet" view). Using these views and the defined radiographic criteria, proper positioning of percutaneously placed TLFSs was achieved, with no spinal canal breaches found.
  
  
  CONCLUSIONS
  This study defines intra-operative radiographic criteria that will assist in placement of TLFSs. The use of this technique may allow for screw placement with less extensive exposure of the posterior spine.
authors.affiliation: Rush-Presbyterian St. Luke's Medical Center, 1725 West Harrison Street, Suite 1063, Chicago, IL 60612, USA. frank.phillips@rushortho.com
authors.forename: Frank M
authors.initials: FM
authors.lastname: Phillips
authors.forename: Erling
authors.initials: E
authors.lastname: Ho
authors.forename: Benjamin W
authors.initials: BW
authors.lastname: Cunningham
mesh_terms: D000328:Adult; D001863:Bone Screws; D002102:Cadaver; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D015641:Radiography, Interventional; D012680:Sensitivity and Specificity; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods