title: [Analysis of 160 cases of C1 lateral mass screw fixation in patients with atlas occipitalization and occipito-cervical instability].
abstract: OBJECTIVE
  To summarize the clinical effect of C1 lateral mass screw fixation in patients with atlas occipitalization and occipito-cervical instability (OCI).
  
  
  METHODS
  Patients of atlas occipitalization and OCI from June 2007 to October 2013 which had been treated by C1 lateral mass fixation in our institution were retrospective analyzed. The clinical neurologic function improvement rate and bone fusion rate were investigated at follow-ups. The nuances of the C1 lateral mass insertion were summarized.
  
  
  RESULTS
  Among the 160 patients, 1 patient died, 1 got worse, 1 was stable, 155 got recovery and 2 lost to follow-up. Among the 157 cases within 12-52 months follow-up (mean 34 months), 147 cases got reduction and release from the cervico-medullary junction compression and 10 got no effective reduction which were resumed to anterior decompression at second surgery.At one year follow-up, 155 cases had solid bony fusion and 2 had no evident fusion.The entry point for C1 screw was located at the midpoint of the posterior surface of C1 facet and the screw was directed approximately between 0-40° cephalad and approximately between 0-20° medially.
  
  
  CONCLUSIONS
  C1 lateral mass screw fixation is a safe and feasible method and could provide solid stability in patients with atlas occipitalization and OCI. The risk of placement of C1 screw could be decreased to a low rate after the preoperative evaluation and trajectory design.
authors.affiliation: Department of Neurosurgery, PLA General Hospital, Beijing 100853, China.
authors.forename: Chong
authors.initials: C
authors.lastname: Li
authors.affiliation: Department of Neurosurgery, PLA General Hospital, Beijing 100853, China.
authors.forename: Yiheng
authors.initials: Y
authors.lastname: Yin
authors.affiliation: Department of Neurosurgery, PLA General Hospital, Beijing 100853, China.
authors.forename: Guangyu
authors.initials: G
authors.lastname: Qiao
authors.affiliation: Department of Neurosurgery, PLA General Hospital, Beijing 100853, China.
authors.forename: Huaiyu
authors.initials: H
authors.lastname: Tong
authors.affiliation: Department of Neurosurgery, PLA General Hospital, Beijing 100853, China; Email: xg_yu@aliyun.com.
authors.forename: Xinguang
authors.initials: X
authors.lastname: Yu
mesh_terms: D001268:Atlanto-Axial Joint; D001863:Bone Screws; D001270:Cervical Atlas; D019299:Decompression, Surgical; D006801:Humans; D019651:Plastic Surgery Procedures; D012189:Retrospective Studies