title: Minimally invasive percutaneous transpedicular screw fixation: increased accuracy and reduced radiation exposure by means of a novel electromagnetic navigation system.
abstract: BACKGROUND
  Minimally invasive percutaneous pedicle screw instrumentation methods may increase the need for intraoperative fluoroscopy, resulting in excessive radiation exposure for the patient, surgeon, and support staff. Electromagnetic field (EMF)-based navigation may aid more accurate placement of percutaneous pedicle screws while reducing fluoroscopic exposure. We compared the accuracy, time of insertion, and radiation exposure of EMF with traditional fluoroscopic percutaneous pedicle screw placement.
  
  
  METHODS
  Minimally invasive pedicle screw placement in T8 to S1 pedicles of eight fresh-frozen human cadaveric torsos was guided with EMF or standard fluoroscopy. Set-up, insertion, and fluoroscopic times and radiation exposure and accuracy (measured with post-procedural computed tomography) were analyzed in each group.
  
  
  RESULTS
  Sixty-two pedicle screws were placed under fluoroscopic guidance and 60 under EMF guidance. Ideal trajectories were achieved more frequently with EMF over all segments (62.7% vs. 40%; p = 0.01). Greatest EMF accuracy was achieved in the lumbar spine, with significant improvements in both ideal trajectory and reduction of pedicle breaches over fluoroscopically guided placement (64.9% vs. 40%, p = 0.03, and 16.2% vs. 42.5%, p = 0.01, respectively). Fluoroscopy time was reduced 77% with the use of EMF (22 s vs. 5 s per level; p < 0.0001) over all spinal segments. Radiation exposure at the hand and body was reduced 60% (p = 0.058) and 32% (p = 0.073), respectively. Time for insertion did not vary between the two techniques.
  
  
  CONCLUSIONS
  Minimally invasive pedicle screw placement with the aid of EMF image guidance reduces fluoroscopy time and increases placement accuracy when compared with traditional fluoroscopic guidance while adding no additional time to the procedure.
authors.affiliation: GE Healthcare, Boston, MA, USA. drvonjako@comcast.net
authors.forename: Ron
authors.initials: R
authors.lastname: von Jako
authors.forename: Michael A
authors.initials: MA
authors.lastname: Finn
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Yonemura
authors.forename: Ali
authors.initials: A
authors.lastname: Araghi
authors.forename: Larry T
authors.initials: LT
authors.lastname: Khoo
authors.forename: John A
authors.initials: JA
authors.lastname: Carrino
authors.forename: Mick
authors.initials: M
authors.lastname: Perez-Cruet
mesh_terms: D001863:Bone Screws; D004574:Electromagnetic Fields; D004867:Equipment Design; D005471:Fluoroscopy / Q000009:adverse effects / Q000295:instrumentation*; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D019060:Minimally Invasive Surgical Procedures / Q000295:instrumentation*; D038361:Neuronavigation / Q000295:instrumentation*; D010043:Outcome and Process Assessment, Health Care; D011829:Radiation Dosage; D013123:Spinal Fusion / Q000295:instrumentation*; D013904:Thoracic Vertebrae / Q000601:surgery*; D013996:Time and Motion Studies