title: Frameless stereotactic image-guided C1-C2 transarticular screw fixation for atlantoaxial instability: review of 20 patients.
abstract: OBJECTIVE
  We retrospectively studied 20 adults who underwent C1-C2 transarticular screw (TAS) fixation utilizing frameless stereotaxy.
  
  
  METHODS
  The study group comprised 13 men and 7 women, with a mean age of 63 years (range 12-87 years). All patients demonstrated clinical and radiographic evidence of C1-C2 instability. The cause of the instability was trauma in 11 patients, rheumatoid arthritis in 6 patients, failed prior surgery in 2 patients, and congenital malformation in 1 patient. All patients underwent stabilization with C1-C2 TASs using image-guided frameless stereotaxy.
  
  
  RESULTS
  There were no new or worsening neurologic symptoms reported at 18-month follow-up. Motor weakness improved in seven of nine patients, myelopathy in seven of seven, and gait in three of six patients in whom these deficits were present preoperatively. Postoperative complications included one surgical site abscess, one cutaneous pressure ulcer, and one iliac crest donor site infection. Of 36 screws placed, 33 (92%) were well positioned. Normal C1-C2 alignment was achieved in 17 of 20 (85%) patients. In 4 of 20 cases, screw implant, which was thought to be anatomically difficult, if not impossible, on the basis of routine magnetic resonance or computed tomography imaging, was actually accomplished successfully using surgical navigation.
  
  
  CONCLUSIONS
  C1-C2 TAS placement is a safe and accurate surgical technique that may improve neurologic function. Use of intraoperative navigation can facilitate achieving difficult surgical trajectories that match the patient's anatomy, thus allowing TAS implant in patients who otherwise would not be candidates for this type of internal fixation.
authors.affiliation: Department of Neurological Surgery, University of California-San Francisco, San Francisco, CA 94143-0112, USA. acostaf@neurosurg.ucsf.edu
authors.forename: Frank L
authors.initials: FL
authors.lastname: Acosta
authors.forename: Alfredo
authors.initials: A
authors.lastname: Quinones-Hinojosa
authors.forename: Chirag A
authors.initials: CA
authors.lastname: Gadkary
authors.forename: Meic H
authors.initials: MH
authors.lastname: Schmidt
authors.forename: Cynthia T
authors.initials: CT
authors.lastname: Chin
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Ames
authors.forename: William S
authors.initials: WS
authors.lastname: Rosenberg
authors.forename: Philip
authors.initials: P
authors.lastname: Weinstein
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D001368:Axis, Cervical Vertebra / Q000000981:diagnostic imaging / Q000601:surgery; D001863:Bone Screws; D001270:Cervical Atlas / Q000000981:diagnostic imaging / Q000601:surgery; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D038361:Neuronavigation; D011859:Radiography; D012189:Retrospective Studies; D013123:Spinal Fusion; D016896:Treatment Outcome