title: [An analysis of surgical outcome and influencing factors in patients of congenital basilar invagination with atlantal-axial dislocation: report of 120 cases].
abstract: OBJECTIVE
  To investigate the surgical outcome and its influencing factors in patients of congenital basilar invagination (BI) with atlanto-axial dislocation (AAD).
  
  
  METHODS
  From May 2004 to August 2010, 120 patients who had BI with AAD were surgically treated with direct posterior intraoperative distraction-reduction and fixation technique, 93 patients were successfully followed up by means of questionnaire survey, telephone and clinical evaluation. Pre- and postoperative dynamic cervical X-rays, computed tomographic scans, 3-dimentional reconstruction views and magnetic resonance imaging were performed. Pre- and postoperative Japanese Orthopaedic Association (JOA) score, distance between odontoid tip and Chamberlain's line and atlantodental interval were measured to evaluate the surgical result. Statistical analysis was performed by means of paired t test and Pearson Correlation analysis.
  
  
  RESULTS
  There were 93 cases were followed up for 24-99 months with an average of 46.5 months. Until the final follow-up, clinical symptoms were improved in 79 patients (84.9%), and were stable in 7 patients (7.5%) and deteriorated in 4 patients (4.3%). Three patients died postoperatively (3.2%). Patients without intramedullary signal intensity change (ISIC) had better surgical outcome. Patients with compression from anterior odontoid tip and posterior bone margin of occipital foramen had the worst surgical outcome (F = 3.987, P < 0.01). Overall, good decompression and bone fusion were shown on postoperative image in 87 patients (93.5%). There were 3 deaths in this series because of basilar artery thrombosis, posterior fossa hematoma and unknown reasons each.
  
  
  CONCLUSIONS
  The direct posterior intraoperative distraction-reduction and fixation technique is an effective simple and safe method for the treatment of BI with AAD. Anterior compression from odontoid tip and posterior compression from bone margin of occipital foramen-atlantal posterior arch play important roles in its developing mechanism. ISIC on MRI is a predictive factor for the worse surgical outcome.
authors.affiliation: Department of Neurosurgery, Xuanwu Hospital, Capital Medical University, Beijing 100053, China.
authors.forename: Xing-wen
authors.initials: XW
authors.lastname: Wang
authors.forename: Feng-zeng
authors.initials: FZ
authors.lastname: Jian
authors.forename: Zan
authors.initials: Z
authors.lastname: Chen
authors.forename: Hao
authors.initials: H
authors.lastname: Wu
authors.forename: Yu-hai
authors.initials: YH
authors.lastname: Bao
mesh_terms: D000293:Adolescent; D000328:Adult; D001268:Atlanto-Axial Joint / Q000601:surgery*; D001863:Bone Screws; D002648:Child; D019299:Decompression, Surgical; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D004204:Joint Dislocations / Q000150:complications / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D010985:Platybasia / Q000150:complications / Q000601:surgery*; D060891:Root Cause Analysis; D013123:Spinal Fusion / Q000379:methods*; D055815:Young Adult