title: Frameless stereotaxy and anterior cervical surgery.
abstract: OBJECTIVE
  The role of a frameless image guidance system for anterior cervical surgery was evaluated in 40 patients with cervical spondylosis. An assessment was made of the challenges posed in achieving accurate three-dimensional image registration in the absence of multiple fixed anatomical landmarks, and a solution to this problem is outlined using a novel registration tracking device.
  
  
  METHODS
  Patients underwent preoperative CT scanning of the surgical field of interest, and the image data was reconstructed on a StealthStation (Sofamor Danek, Memphis, Tennessee, USA). An image guidance tracking device was attached to a modified Caspar retractor. Point matching and surface mapping were used for registration.
  
  
  RESULTS
  It was not possible to achieve accurate registration in the first 7 patients. In the next 5 patients, the time taken to achieve registration was prolonged. For 28 patients, registration was achieved in an acceptable time with an accuracy of 0.74 +/- 0.4 mm. Anatomical resection margins were accurately identified and 36 anterior cervical screws were precisely placed.
  
  
  CONCLUSIONS
  Frameless stereotaxy can now be applied to procedures involving the anterior cervical spine. Potential benefits include accurate definition of the anatomy, demonstration of resection margins, and intraoperative guidance. The technique may prove particularly useful in cases of complex or disrupted anatomy.
authors.affiliation: Department of Neurosurgery, Frenchay Hospital, Bristol, United Kingdom. cbolger@neurosurgery.demon.co.uk
authors.forename: C
authors.initials: C
authors.lastname: Bolger
authors.forename: C
authors.initials: C
authors.lastname: Wigfield
authors.forename: T
authors.initials: T
authors.lastname: Melkent
authors.forename: K
authors.initials: K
authors.lastname: Smith
mesh_terms: D000328:Adult; D000368:Aged; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009983:Orthopedic Equipment; D009985:Orthopedics / Q000379:methods*; D014057:Tomography, X-Ray Computed