title: Minimally invasive posterior atlantoaxial fusion: a cadaveric and clinical feasibility study.
abstract: OBJECTIVE
  Minimally invasive surgical (MIS) techniques have several potential advantages for the patient over open techniques, including decreased loss of blood, postoperative pain, and recovery time. We aimed to demonstrate atlantoaxial fusion by using the MIS techniques, shown previously in only two reports. A smaller operating corridor with MIS may increase difficulty of instrumentation placement and risk of instrumentation-related complications.
  
  
  METHODS
  Five cadaveric specimens were studied presurgically with computed tomography (CT) to determine bony anatomy, vertebral artery course, and the trajectory for C1/C2 screw placement. Four specimens had adequate C2 pedicle sizes to accommodate screw placement. Specimens were used to perform C1-2 instrumentation through minimal access tubular retractors. After procedures, specimens were re-examined with CT to assess accuracy of MIS C1-2 screw placement.
  
  
  RESULTS
  Through minimal access expandable tubular retractors, C1-lateral mass and C2 pedicle screws were placed in all four specimens. Postinstrumentation CT analysis demonstrated no violation of the foramen transversarium in all cases. There was one grade 1 medial breach from C1 lateral mass screw placement. Two patients with type-2 odontoid fractures were treated with MIS C1-2 fusion with follow-up 4-24 months. Average operating time was 3.5 hours, and average surgical blood loss was 125 mL. Both cases were examined with CT scan postsurgically, and there were no bony breaches with screw placement. Both patients remained neurologically intact postoperatively, with significant improvement revealed in pain scores. Follow-up imaging at two years demonstrated union of odontoid fracture.
  
  
  CONCLUSIONS
  Minimally invasive atlantoaxial fixation is feasible and safe. Preoperative CT is paramount for preoperative evaluation of the vertebral artery anatomy in relation to C1/2 vertebra.
authors.affiliation: Department of Neurological Surgery, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Taghva
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Attenello
authors.forename: Gabriel
authors.initials: G
authors.lastname: Zada
authors.forename: Alexander A
authors.initials: AA
authors.lastname: Khalessi
authors.forename: Patrick C
authors.initials: PC
authors.lastname: Hsieh
mesh_terms: D000058:Accidental Falls; D000368:Aged; D000369:Aged, 80 and over; D001268:Atlanto-Axial Joint / Q000002:abnormalities* / Q000000981:diagnostic imaging / Q000293:injuries / Q000473:pathology / Q000601:surgery*; D002102:Cadaver; D000013:Congenital Abnormalities / Q000473:pathology* / Q000601:surgery*; D005071:Evoked Potentials / Q000502:physiology; D019054:Evoked Potentials, Motor / Q000502:physiology; D005240:Feasibility Studies; D005260:Female; D005593:Fracture Fixation, Internal / Q000379:methods*; D006801:Humans; D007091:Image Processing, Computer-Assisted; D019060:Minimally Invasive Surgical Procedures / Q000009:adverse effects / Q000379:methods*; D019635:Neurosurgical Procedures / Q000009:adverse effects / Q000379:methods*; D010147:Pain Measurement; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome