title: Treatment of primary basilar invagination by cervical traction and posterior instrumented reduction together with occipitocervical fusion.
abstract: METHODS
  This retrospective study was conducted to analyze the radiographic and clinical results in seven patients with primary basilar invagination who accepted a combination of continuous cervical traction before operation and posterior screw/rod system reduction together with occipitocervical fusion.
  
  
  OBJECTIVE
  To evaluate the radiographic and clinical outcomes of this treatment regimen in combination of continuous cervical traction and posterior instrumented reduction with pedicle screw/rod system.
  
  
  BACKGROUND
  Primary basilar invagination poses considerable difficulties in the surgical management regarding surgical approach, reduction, and decompression. A variety of methods have been described to treat primary basilar invagination and all methods existed limits.
  
  
  METHODS
  There were four male and three female patients, and the ages ranged from 12 to 40 years (average age, 22.3 yr). Six patients presented neurologic deficits. The Nurick scale was from 1 grade to 4 grades (average, 2.7 grades). The distance of the odontoid tip in relation to Wackenheim line, atlantodental interval, Klaus height index, craniospinal angle, modified Omega angle, and cervicomedullary angle were measured pretreated and after surgery. When the tip of odontoid process was inferior or approximate to Wackenheim line and McRae line after cervical traction, the operation of reduction and fixation should be accepted.
  
  
  RESULTS
  After surgery, the mean Wackenheim value and atlantodental distance were reduced 9.3 mm and 2.0 mm, respectively. The mean Klaus height index, craniospinal angle, Omega angle, and cervicomedullary angle improved 6.5 mm, 17.0°, 11.6°, and 27.4°, respectively. All postoperative data had a significance compared with pretreatment data (P < 0.05). There was a tendency that younger patients were able to obtain more ideal reduction than adults. Of six patients with neurologic symptoms, five patients were normal or nearly normal. All patients achieved solid fusion.
  
  
  CONCLUSIONS
  This case series demonstrates a safe, easy, and effective treatment regimen for the patients with primary basilar invagination.
authors.affiliation: Spine Section/Department of Orthopaedic Surgery, First Affiliated Hospital of Sun Yat-sen University, Guangzhou, China.
authors.forename: Xinsheng
authors.initials: X
authors.lastname: Peng
authors.forename: Liyan
authors.initials: L
authors.lastname: Chen
authors.forename: Yong
authors.initials: Y
authors.lastname: Wan
authors.forename: Xuenong
authors.initials: X
authors.lastname: Zou
mesh_terms: D000293:Adolescent; D000328:Adult; D001139:Arnold-Chiari Malformation / Q000150:complications / Q000601:surgery; D001268:Atlanto-Axial Joint / Q000601:surgery; D001863:Bone Screws; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D002648:Child; D003131:Combined Modality Therapy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D004204:Joint Dislocations / Q000150:complications / Q000601:surgery; D008297:Male; D009777:Occipital Bone / Q000601:surgery*; D009809:Odontoid Process / Q000601:surgery; D010985:Platybasia / Q000150:complications / Q000000981:diagnostic imaging / Q000601:surgery*; D011859:Radiography; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000295:instrumentation / Q000379:methods*; D014143:Traction / Q000379:methods*; D016896:Treatment Outcome; D055815:Young Adult