title: Facet violation with the placement of percutaneous pedicle screws.
abstract: METHODS
  Independent review and classification of therapeutic procedures performed on cadavers by surgeons blinded to purpose of study.
  
  
  OBJECTIVE
  The objective of this study is to determine the rate of facet violation with the placement of percutaneous pedicle screws.
  
  
  BACKGROUND
  Improvements in percutaneous instrumentation and fluoroscopic imaging have led to a resurgence of percutaneous pedicle screw insertion in lumbar spine surgery in an attempt to minimize many of the complications associated with open techniques of pedicle screw placement. Rates of pedicle breech and neurologic injury resulting from percutaneous insertion are reportedly similar to those of open techniques. Postoperative pain because of impingement and instability is believed to result from violation of the facet capsule or facet joint. To the authors' knowledge, however, the rate of facet injury associated with the placement of percutaneous pedicle screws is unreported in the literature.
  
  
  METHODS
  Percutaneous pedicle screw placement was performed on 4 cadaveric specimens by 4 certified orthopedic surgeons who had clinical experience in the procedure and who were blinded to the study's purpose. The surgeons were instructed to place pedicle screws from L1-S1 using their preferred clinical techniques and a 5.5-mm screw system with which they were all familiar. All surgeons utilized 1 OEC C-arm for fluoroscopic imaging. After insertion, 2 independent spine surgeons each reviewed and classified the placement of all facet screws.
  
  
  RESULTS
  A total of 48 screws were inserted and classified. The placement of 28 screws (58%) resulted in violation of facet articulation, with 8 of these screws being intra-articular. Interobserver reliability of the classification system was 100%.
  
  
  CONCLUSIONS
  Percutaneous pedicle screw placement may result in a high rate of facet violation. Facet injury can be reliability classified and therefore, perhaps, easily prevented.
authors.affiliation: Department of Orthopaedic Surgery, University of Michigan, Ann Arbor, MI 48109, USA. rakeshpa@med.umich.edu
authors.forename: Rakesh D
authors.initials: RD
authors.lastname: Patel
authors.forename: Gregory P
authors.initials: GP
authors.lastname: Graziano
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Vanderhave
authors.forename: Alpesh A
authors.initials: AA
authors.lastname: Patel
authors.forename: Michael C
authors.initials: MC
authors.lastname: Gerling
mesh_terms: D001863:Bone Screws; D002102:Cadaver; D005471:Fluoroscopy; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery; D019637:Orthopedic Procedures / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results; D012447:Sacrum / Q000601:surgery; D021801:Zygapophyseal Joint / Q000601:surgery*