title: Surgical management of symptomatic os odontoideum with posterior screw fixation performed using the magerl and harms techniques with intraoperative 3-dimensional fluoroscopy-based navigation.
abstract: METHODS
  Retrospective case series.
  
  
  OBJECTIVE
  To evaluate the accuracy of screw fixation using intraoperative three-dimensional fluoroscopy-based navigation (ITFN) and to assess the clinical outcomes of this treatment regimen.
  
  
  BACKGROUND
  The surgical management of symptomatic os odontoideum poses considerable difficulties due to the highly variable anatomy of the upper cervical spine and surrounding neurovascular structures. Various methods have been described for the treatment of symptomatic os odontoideum, all of which have limitations.
  
  
  METHODS
  Nineteen patients with symptomatic os odontoideum were investigated. Pain scores were assessed using the visual analogue scale. Myelopathy was assessed using the Nurick scale and Odom's criteria. Radiological imaging was carried out in all patients for diagnosis and to assess the atlantodens interval, space available for cord, and presence of intramedullary hyperintensity signals on T2-weighted images at the C1-C2 level. Posterior stabilization was performed for all patients by using ITFN.
  
  
  RESULTS
  The mean Nurick score improved from 2.3 before surgery to 0.7 at the time of follow-up. The mean follow-up period was 34.7 months (range, 12-65 mo). According to Odom's criteria, outcomes were as follows: excellent, 47%; good, 37%; fair, 11%; and poor, 5%. All patients with preoperative neck pain had symptom relief or improvement, with all of these patients having more than 83.7% improvement in visual analogue scale scores. The mean preoperative space available for cord value of 9.3 mm improved to 17.7 mm. Solid fusion and reduction of atlantoaxial dislocation were achieved in every patient without screw failure. Sixty screws were placed in 19 patients. Two C2 polyaxial screws in 2 patients and 1 transarticular screw in 1 patient slightly penetrated the transverse foramen with no vascular injury and clinical sequelae.
  
  
  CONCLUSIONS
  ITFN is a safe, accurate, and effective tool for screw placement in patients with symptomatic os odontoideum.
authors.affiliation: Department of Spine Surgery, Peking University Fourth Clinical Medical College, Beijing Jishuitan Hospital, Beijing, PR China.
authors.forename: Chong
authors.initials: C
authors.lastname: Weng
authors.forename: Wei
authors.initials: W
authors.lastname: Tian
authors.forename: Zhi-Yu
authors.initials: ZY
authors.lastname: Li
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
authors.forename: Qin
authors.initials: Q
authors.lastname: Li
authors.forename: Yong-Qing
authors.initials: YQ
authors.lastname: Wang
authors.forename: Yu-Zhen
authors.initials: YZ
authors.lastname: Sun
mesh_terms: D000293:Adolescent; D000328:Adult; D001863:Bone Screws; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery; D005260:Female; D005471:Fluoroscopy; D006801:Humans; D008297:Male; D008875:Middle Aged; D009809:Odontoid Process / Q000002:abnormalities* / Q000601:surgery*; D017063:Outcome Assessment, Health Care; D010147:Pain Measurement / Q000379:methods; D015203:Reproducibility of Results; D012189:Retrospective Studies; D013118:Spinal Cord Diseases / Q000175:diagnosis / Q000000981:diagnostic imaging; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D055815:Young Adult