title: Feasibility of occipital condyle screw placement for occipitocervical fixation: a cadaveric study and description of a novel technique.
abstract: METHODS
  Occipital-cervical (OC) stabilization using occipital condyle fixation with a polyaxial screw-rod construct is described.
  
  
  OBJECTIVE
  To describe a novel technique and initial radiographic results for posterior OC fixation using the occipital condyles for cranial fixation.
  
  
  BACKGROUND
  Stabilization of the OC junction remains a challenge. Owing to the regional anatomy and the poor occipital bone purchase, multiple attachment points to the occipital bone are required to increase construct rigidity. To address these issues, we propose a novel OC fixation technique using polyaxial occipital condyle screws for cranial purchase.
  
  
  METHODS
  The OC junction was exposed posteriorly in silicone-injected cadaver heads. Polyaxial titanium screws (3.5 mm) were inserted bicortically solely into the occipital condyles; C1 lateral masses and C2 pedicles, or transarticularly through C1-C2, followed by fixation to a 3-mm rod. Drilling was guided by anatomic landmarks and fluoroscopy. Computerized tomography scans were obtained. Condylar screw angles and lengths were analyzed with respect to historical morphometric condyle measurements and with respect to neurovascular structures.
  
  
  RESULTS
  The condylar entry point was 4 to 5-mm lateral to the foramen magnum on the axial plane, and 1 to 2-mm rostral to the atlantooccipital joint. The mean angle of medialization was 17 degrees (range: 12 to 22 degrees). In the sagittal plane, the maximal superior screw angulation was 5 degrees. The mean screw length to obtain bicortical purchase was 22 mm (range: 20 to 24 mm). The hypoglossal canal was uninterrupted during its full course. The jugular bulb, carotid, and vertebral arteries were not injured by condyle screw placement. No fractures were identified.
  
  
  CONCLUSIONS
  Condyle screws can be placed without injury to neurovascular structures. OC junction fixation using polyaxial occipital condyle screws is feasible and can be considered a salvage technique or an alternative where other fixation techniques are not available.
authors.affiliation: Department of Neurosurgery, University of South Florida, Tampa, FL 33606, USA. juansuribe@gmail.com
authors.forename: Juan S
authors.initials: JS
authors.lastname: Uribe
authors.forename: Edwin
authors.initials: E
authors.lastname: Ramos
authors.forename: Fernando
authors.initials: F
authors.lastname: Vale
mesh_terms: D001269:Atlanto-Occipital Joint / Q000601:surgery*; D001863:Bone Screws; D002102:Cadaver; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005240:Feasibility Studies; D005593:Fracture Fixation, Internal / Q000295:instrumentation*; D006801:Humans; D007593:Joint Instability / Q000601:surgery*; D019919:Prosthesis Implantation / Q000379:methods*; D016059:Range of Motion, Articular; D013123:Spinal Fusion / Q000295:instrumentation*