title: Accuracy of freehand fluoroscopy-guided placement of C1 lateral mass and C2 isthmic screws in atlanto-axial instability.
abstract: BACKGROUND
  The C1 lateral mass and C2 isthmic stabilization, as introduced by Goel and Laheri and by Harms and Melcher, is a well-known fixation technique. We present the clinical and radiographic results with freehand fluoroscopy guided C1 lateral mass and C2 isthmic fixation in a consecutive series of 28 patients, evaluating the accuracy of screw placement.
  
  
  METHODS
  Twenty-eight consecutive patients suffering from post-traumatic and other C1-C2 instability were operated on between 2001 and 2010. Indications for surgery were: trauma (n = 21 cases), os odontoideum (n = 1), cranio-verterbal malformation (n = 1), and arthritis (n = 3) and idiopathic instability (n = 2). C1 lateral mass and C2 isthmic screws were placed according to the usual anatomical landmarks with lateral fluoroscopy guidance. All patients underwent a postoperative CT scan. The extent of cortical lateral or medial breach was determined and classified as follows: no breach (grade A), 0-2 mm (grade B), 2-4 mm (grade C), 4-6 mm (grade D), more than 6 mm (grade E). Grade A and B screws were considered well positioned.
  
  
  RESULTS
  A total of 56 C1 lateral mass and 55 C2 isthmic screws were placed. Accuracy of screw placement was as follows: 107 grade A (96.4%), four grade B (3.6%), and no grade C, D or E. Clinical and radiological follow-up showed improvement in symptoms (mainly pain) and stability of the implants at the end of the follow-up.
  
  
  CONCLUSIONS
  Freehand fluoroscopy-guided insertion of C1 lateral mass and C2 isthmic screws can be safely and effectively performed.
authors: Department of Neurosurgery, Geneva University Medical Center, Faculty of Medecine, University of Geneva, 6, Rue Perret-Gentil, 1211 Geneva, Switzerland. enrico.tessitore@hcuge.ch
authors: Enrico
authors: E
authors: Tessitore
authors: Andrea
authors: A
authors: Bartoli
authors: Karl
authors: K
authors: Schaller
authors: Michael
authors: M
authors: Payer