title: A New Electromagnetic Navigation System for Pedicle Screws Placement: A Human Cadaver Study at the Lumbar Spine.
abstract: BACKGROUND
  Technical developments for improving the safety and accuracy of pedicle screw placement play an increasingly important role in spine surgery. In addition to the standard techniques of free-hand placement and fluoroscopic navigation, the rate of complications is reduced by 3D fluoroscopy, cone-beam CT, intraoperative CT/MRI, and various other navigation techniques. Another important aspect that should be emphasized is the reduction of intraoperative radiation exposure for personnel and patient. The aim of this study was to investigate the accuracy of a new navigation system for the spine based on an electromagnetic field.
  
  
  METHODS
  Twenty pedicle screws were placed in the lumbar spine of human cadavers using EMF navigation. Navigation was based on data from a preoperative thin-slice CT scan. The cadavers were positioned on a special field generator and the system was matched using a patient tracker on the spinous process. Navigation was conducted using especially developed instruments that can be tracked in the electromagnetic field. Another thin-slice CT scan was made postoperatively to assess the result. The evaluation included the position of the screws in the direction of trajectory and any injury to the surrounding cortical bone. The results were classified in 5 groups: grade 1: ideal screw position in the center of the pedicle with no cortical bone injury; grade 2: acceptable screw position, cortical bone injury with cortical penetration ≤ 2 mm; grade 3: cortical bone injury with cortical penetration 2,1-4 mm, grad 4: cortical bone injury with cortical penetration 4,1-6 mm, grade 5: cortical bone injury with cortical penetration >6 mm.
  
  
  RESULTS
  The initial evaluation of the system showed good accuracy for the lumbar spine (65% grade 1, 20% grade 2, 15% grade 3, 0% grade 4, 0% grade 5). A comparison of the initial results with other navigation techniques in literature (CT navigation, 2D fluoroscopic navigation) shows that the accuracy of this system is comparable.
  
  
  CONCLUSIONS
  EMF navigation offers a high accuracy in Pedicle screw placement with additional advantages compared to other techniques. The short set-up time and easy handling of EMF navigation should be emphasized. Additional advantages are the absence of intraoperative radiation exposure for the operator and surgical team in the current set-up and the operator's free mobility without interfering with navigation. Further studies with navigation at higher levels of the spine, larger numbers of cases and studies with control group are planned.
authors.affiliation: Center for Spine Surgery and Pain Therapy, Center for Orthopaedics and Traumatology of the St. Elisabeth Group - Catholic Hospitals Rhein-Ruhr, St. Anna Hospital Herne/Marienhospital Herne University Hospital/Marien Hospital Witten, Herne, Germany.
authors.forename: Patrick
authors.initials: P
authors.lastname: Hahn
authors.affiliation: Center for Spine Surgery and Pain Therapy, Center for Orthopaedics and Traumatology of the St. Elisabeth Group - Catholic Hospitals Rhein-Ruhr, St. Anna Hospital Herne/Marienhospital Herne University Hospital/Marien Hospital Witten, Herne, Germany.
authors.forename: Semih
authors.initials: S
authors.lastname: Oezdemir
authors.affiliation: Center for Spine Surgery and Pain Therapy, Center for Orthopaedics and Traumatology of the St. Elisabeth Group - Catholic Hospitals Rhein-Ruhr, St. Anna Hospital Herne/Marienhospital Herne University Hospital/Marien Hospital Witten, Herne, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Komp
authors.affiliation: Center for Spine Surgery and Pain Therapy, Center for Orthopaedics and Traumatology of the St. Elisabeth Group - Catholic Hospitals Rhein-Ruhr, St. Anna Hospital Herne/Marienhospital Herne University Hospital/Marien Hospital Witten, Herne, Germany.
authors.forename: Athanasios
authors.initials: A
authors.lastname: Giannakopoulos
authors.affiliation: Center for Orthopaedics and Traumatology of the St. Elisabeth Group - Catholic Hospitals Rhein-Ruhr, St. Anna Hospital Herne/Marienhospital Herne University Hospital/Marien Hospital Witten, Herne, Germany.
authors.forename: Roderich
authors.initials: R
authors.lastname: Heikenfeld
authors.affiliation: Clinic for Orthopaedics and Orthopaedic Surgery, University Medicine of Greifswald, Greifswald, Germany.
authors.forename: Richard
authors.initials: R
authors.lastname: Kasch
authors.affiliation: Clinic for Orthopaedics and Orthopaedic Surgery, University Medicine of Greifswald, Greifswald, Germany.
authors.forename: Harry
authors.initials: H
authors.lastname: Merk
authors.affiliation: Center for Orthopaedics and Traumatology of the St. Elisabeth Group - Catholic Hospitals Rhein-Ruhr, St. Anna Hospital Herne/Marienhospital Herne University Hospital/Marien Hospital Witten, Herne, Germany.
authors.forename: Georgios
authors.initials: G
authors.lastname: Godolias
authors.affiliation: Center for Spine Surgery and Pain Therapy, Center for Orthopaedics and Traumatology of the St. Elisabeth Group - Catholic Hospitals Rhein-Ruhr, St. Anna Hospital Herne/Marienhospital Herne University Hospital/Marien Hospital Witten, Herne, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Ruetten
mesh_terms: D002102:Cadaver; D004574:Electromagnetic Fields; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D065289:Pedicle Screws