title: An extrapedicular approach to the placement of screws in the thoracic spine: an anatomic and radiographic assessment.
abstract: METHODS
  A radiographic and anatomic study of an extrapedicular method of screw placement in cadaveric thoracic spines.
  
  
  OBJECTIVE
  To evaluate an alternative method of thoracic vertebral body screw fixation using an extrapedicular screw technique. To evaluate the anatomic safe zones and proper starting point for this alternative approach to the placement of screw fixation in the thoracic spine.
  
  
  BACKGROUND
  Despite the clinical successes reported with thoracic pedicle screw-rod constructs, controversy exists about the safety of this technique in pedicles that are anatomically too small for transpedicular fixation. An alternative method of extrapedicular screw fixation was evaluated in this present study.
  
  
  METHODS
  Two fresh, unfixed, adult cadavers were obtained randomly; 6.0-mm AO Synthes pedicle screws were placed using an extrapedicular approach bilaterally from T3 to T10. The screws were placed according to one defined method described later. Computerized tomographic (CT) images were obtained. The position of each screw was analyzed. The cadavers were then dissected with the screw pathway exposed and the relation of the screw to surrounding anatomy documented.
  
  
  RESULTS
  All screws did not penetrate the spinal canal. All screws were within the pedicle rib unit and did not penetrate the neural foramen or pleura.
  
  
  CONCLUSIONS
  This study, although only introductory, indicates the potential for extrapedicular vertebral body fixation in the thoracic spine. Biomechanical evaluations are presently being conducted to evaluate the use of extrapedicular thoracic screw fixation.
authors.affiliation: Yale School of Medicine, Department of Orthopaedic Surgery and Rehabilitation, New Haven, CT 06520-8071, USA.
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Husted
authors.forename: James J
authors.initials: JJ
authors.lastname: Yue
authors.forename: Todd A
authors.initials: TA
authors.lastname: Fairchild
authors.forename: Andrew H
authors.initials: AH
authors.lastname: Haims
mesh_terms: D000328:Adult; D001863:Bone Screws; D002102:Cadaver; D006801:Humans; D016268:Internal Fixators; D019637:Orthopedic Procedures / Q000295:instrumentation / Q000379:methods*; D013904:Thoracic Vertebrae / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000601:surgery*; D014057:Tomography, X-Ray Computed