title: Occipital Condyle-C1 Complex Screw for Fixation of Basilar Invagination Patients with Atlas Assimilation.
abstract: OBJECTIVE
  To investigate whether C1-occipital condyle complex (CC complex) screws can be safely and rapidly placed without guidance in basilar invagination patients with atlas assimilation.
  
  
  METHODS
  The occipital-cervical (OC) junction was fixed posteriorly in 8 basilar invagination patients with atlas assimilation using polyaxial titanium screws inserted unicortically into the CC complex and C2 pedicles and subsequent fixation to a 3-mm rod. Anatomic landmarks were used during the drilling. The screw angles and lengths of the CC complex were analyzed.
  
  
  RESULTS
  The width, length, and height values of the left-side CC complex were 7.96±2.23, 16.06±2.73, and 13.76±2.06 mm; those of the right-side CC complex were 7.84±1.38, 16.66±2.58, and 12.81±2.62 mm. The CC complex entry point was at the central point of posterior surface of the CC complex. The angle used for medialization was 10-15°, which was also the maximal superior screw angulation in the sagittal plane. The screw length required for unicortical purchase was 16-22 mm. The screw was not misplaced or poorly positioned, and no neurovascular complications associated with screw insertion were detected.
  
  
  CONCLUSIONS
  In patients with atlas assimilation, CC complex screws can be placed safely. The CC complex screws can be safely inserted assisted by microscope without image guidance.
authors.affiliation: Chinese PLA General Hospital, Department of Neurosurgery, Haidian District, Beijing 100853, China.
authors.forename: Huaiyu
authors.initials: H
authors.lastname: Tong
authors.forename: Lianfeng
authors.initials: L
authors.lastname: Li
authors.forename: Xin-Guang
authors.initials: XG
authors.lastname: Yu
authors.forename: Yuanzheng
authors.initials: Y
authors.lastname: Zhang
authors.forename: Wang
authors.initials: W
authors.lastname: Peng
mesh_terms: D001863:Bone Screws; D002574:Cervical Vertebrae / Q000601:surgery*; D006801:Humans; D009777:Occipital Bone / Q000601:surgery*; D010043:Outcome and Process Assessment, Health Care; D013122:Spinal Diseases / Q000601:surgery*; D013123:Spinal Fusion / Q000379:methods*