title: Computed tomography evaluation of superior-segment facet-joint violation after pedicle instrumentation of the lumbar spine with a midline surgical approach.
abstract: METHODS
  Retrospective study.
  
  
  OBJECTIVE
  To determine the frequency of pedicle screw violation of superior nonfused facet joints adjacent to the most cephalad pedicle screws after a midline approach for lumbar fusion.
  
  
  BACKGROUND
  Facet-joint violations have been evaluated in patients undergoing lumbar pedicle screw instrumentation and fusion with a Wiltse muscle-splitting approach, but not via the more common midline approach.
  
  
  METHODS
  Between 1995 and 2003, 204 patients underwent this procedure. Computed tomography scans (within 1 year postsurgery) were evaluated independently for superior facet-joint violation. chi tests were used to examine bivariate associations of superior level facet-joint violation, patient age, construct level, diagnosis, and revision status for significance (P < or = 0.05).
  
  
  RESULTS
  Superior-level facet-joint violation occurred in 24% of patients and 15% of screws, twice as often on the left side (P = 0.0396) than on the right, more frequently in single than in multiple-level procedures (P < 0.0001), and most frequently with the most cephalad screws at L5 (48%). We found no significant associations between violation rates and other designated parameters.
  
  
  CONCLUSIONS
  The left side, single-level fusion, and most cephalad pedicle screws at L5 are targets for interventions to reduce pedicle violations in this procedure.
authors.affiliation: Department of Orthopaedic Surgery, Johns Hopkins Bayview Medical Center, Baltimore, MD 21224-2780, USA. ehenze1@jhmi.edu
authors.forename: Ali
authors.initials: A
authors.lastname: Moshirfar
authors.forename: Louis G
authors.initials: LG
authors.lastname: Jenis
authors.forename: Leo R
authors.initials: LR
authors.lastname: Spector
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Burke
authors.forename: Elena
authors.initials: E
authors.lastname: Losina
authors.forename: Jeffrey N
authors.initials: JN
authors.lastname: Katz
authors.forename: Frank F
authors.initials: FF
authors.lastname: Rand
authors.forename: Scott G
authors.initials: SG
authors.lastname: Tromanhauser
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Banco
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001863:Bone Screws / Q000009:adverse effects*; D005260:Female; D005593:Fracture Fixation, Internal / Q000009:adverse effects; D006801:Humans; D016268:Internal Fixators / Q000009:adverse effects; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods; D021801:Zygapophyseal Joint / Q000473:pathology / Q000601:surgery*