title: [C(2) trans-laminar screws for atlantoaxial instability: preliminary clinical report of nine cases].
abstract: OBJECTIVE
  C(2) pedicle screw is the classic instrumentation for posterior C(2) fixation. But it could be dangerous in case of anatomical variation, such as high riding vertebral artery and small C(2) pedicle. C(2) trans-laminar screw could be an alternative choice. This retrospective study is to evaluate the feasibility of C(2) trans-laminar screw for atlantoaxial instability with anatomical variation.
  
  
  METHODS
  In our clinical work, we had nine atlantoaxial instability cases with C(2) pedicle malformation. If the malformation is unilateral, we inserted one C(2) trans-laminar screw and one C(2) pedicle screw in the normal pedicle; if the malformation is bilateral, bilateral trans-laminar screws were used. Then C(2) instrumentation could be connected with C(1) lateral mass screw or occipital screw in cases with C(1) occipitalization. Then atlantoaxial or occipitocervical fusion could be done with morselized autogenous cancellous iliac grafts.
  
  
  RESULTS
  Nine cases had C(2) trans-laminar screw, including 2 atlantoaxial fusion and 7 occipitocervical fusion. Six cases had unilateral trans-laminar screw and 3 had bilateral trans-laminar screw. Radiographs demonstrated all the screws were placed satisfactorily except one. There was no neurological deterioration or vertebral artery injury. All the cases had an average follow-up of 9 months (4 - 13 months). All patients attained solid fusion without screw failure. In the 8 cases with neurological deficit, 3 were excellent, 1 was good, 2 were fair and 2 had no change.
  
  
  CONCLUSIONS
  C(2) trans-laminar screw fixation could provide sufficient stability. This technique could be an alternative to standard C(2) pedicle screw in cases with pedicle malformation and high riding vertebral artery. It is safe and simple in experienced hands.
authors.affiliation: Department of Orthopaedics, Third Hospital of Peking University, Beijing 100083, China. drwangpku@Gmail.com
authors.forename: Chao
authors.initials: C
authors.lastname: WANG
authors.forename: Sheng-lin
authors.initials: SL
authors.lastname: WANG
authors.forename: Ming
authors.initials: M
authors.lastname: YAN
mesh_terms: D000293:Adolescent; D000328:Adult; D001268:Atlanto-Axial Joint; D001368:Axis, Cervical Vertebra / Q000601:surgery; D001863:Bone Screws; D002648:Child; D005240:Feasibility Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007593:Joint Instability / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*