title: "Two-step" technique with OsiriX™ to evaluate feasibility of C2 pedicle for surgical fixation.
abstract: BACKGROUND
  Surgical treatment of craniovertebral junction pathology has evolved considerably in recent decades with the implementation of short atlanto-axial fixation techniques, notwhithstanding increasing neurovascular risks. Also, there is strong evidence that fixation of C2 anatomical pedicle has the best biomechanical profile of the entire cervical spine. However, it is often difficult and misleading, to evaluate anatomical bony and vascular anomalies using the three orthogonal planes (axial, coronal, and sagittal) of CT.
  
  
  OBJECTIVE
  The authors describe an innovative and simple technique to evaluate the feasibility of C2 pedicle for surgical screw fixation using preoperative planning with the free DICOM (Digital Imaging and Communications in Medicine) software OsiriX™.
  
  
  METHODS
  The authors report the applicatin of this novel technique in 5 cases (3 traumatic, 1 Os Odontoideum, and 1 complex congenital malformation) collected from our general case series of the Department in the last 5 years.
  
  
  RESULTS
  In this proof of concept study, the pre-operative analysis with the two-step tecnique was detrimental for choosing the surgical tecnique. Detailed post-operative analysis confirmed correct position of C2 screws without cortical breach. There were no complications or mortality reported.
  
  
  CONCLUSIONS
  This two-step technique is an easy and reliable way to determine the feasibility of C2 pedicle for surgical fixation. The detailed tridimensional radiological preoperative evaluation of craniovertebral junction anatomy is critical to the sucess and safety of this surgeries, and can avoid, to certain degree, expensive intra-operative tridimensional imaging facilities.
authors.affiliation: Department of Neurosurgery, Egas Moniz Hospital, Lisbon, Portugal.
authors.forename: Luis Miguel Sousa
authors.initials: LM
authors.lastname: Marques
authors.affiliation: Department of Neurosurgery, Egas Moniz Hospital, Lisbon, Portugal.
authors.forename: Gonçalo Neto
authors.initials: GN
authors.lastname: d'Almeida
authors.affiliation: Department of Neurosurgery, Egas Moniz Hospital, Lisbon, Portugal.
authors.forename: José
authors.initials: J
authors.lastname: Cabral
keywords: C2 pedicle; OsiriX™; multi-planar reformatting (MPR)