title: Percutaneous pedicle screw placement in the thoracic spine: A cadaveric study.
abstract: METHODS
  A cadaveric study to determine the accuracy of percutaneous screw placement in the thoracic spine using standard fluoroscopic guidance.
  
  
  BACKGROUND
  While use of percutaneous pedicle screws in the lumbar spine has increased rapidly, its acceptance in the thoracic spine has been slower. As indications for pedicle screw fixation increase in the thoracic spine so will the need to perform accurate and safe placement of percutaneous screws with or without image navigation. To date, no study has determined the accuracy of percutaneous thoracic pedicle screw placement without use of stereotactic imaging guidance.
  
  
  METHODS
  Eighty-six thoracic pedicle screw placements were performed in four cadaveric thoracic spines from T1 to T12. At each level, Ferguson anterior-posterior fluoroscopy was used to localize the pedicle and define the entry point. Screw placement was attempted unless the borders of the pedicle could not be delineated solely using intraoperative fluoroscopic guidance. The cadavers were assessed using pre- and postprocedural computed tomography (CT) scans as well as dissected and visually inspected in order to determine the medial breach rate.
  
  
  RESULTS
  Ninety pedicles were attempted and 86 screws were placed. CT analysis of screw placement accuracy revealed that only one screw (1.2%) breached the medial aspect of the pedicle by more than 2 mm. A total of four screws (4.7%) were found to have breached medially by visual inspection (three Grade 1 and one Grade 2). One (1.2%) lateral breach was greater than 2 mm and no screw violated the neural foramen. The correlation coefficient of pedicle screw violations and pedicle diameter was found to be 0.96.
  
  
  CONCLUSIONS
  This cadaveric study shows that percutaneous pedicle screw placement can be performed in the thoracic spine without a significant increase in the pedicle breach rate as compared with standard open techniques. A small percentage (4.4%) of pedicles, especially high in the thoracic spine, may not be safely visualized.
authors.affiliation: Department of Surgery, Division of Neurosurgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: Carolyn A
authors.initials: CA
authors.lastname: Hardin
authors.affiliation: Department of Surgery, Division of Neurosurgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: Shahid M
authors.initials: SM
authors.lastname: Nimjee
authors.affiliation: Department of Surgery, Division of Neurosurgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: Isaac O
authors.initials: IO
authors.lastname: Karikari
authors.affiliation: Department of Surgery, Division of Neurosurgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Agrawal
authors.affiliation: Department of Neurological Surgery, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.
authors.forename: Richard G
authors.initials: RG
authors.lastname: Fessler
authors.affiliation: Department of Surgery, Division of Neurosurgery, Duke University Medical Center, Durham, NC, USA.
authors.forename: Robert E
authors.initials: RE
authors.lastname: Isaacs
keywords: Minimally invasive surgery; pedicle screw; thoracic spine