title: Surgical treatment of chronic C1-C2 dislocation with absence of odontoid process using C1 hooks with C2 pedicle screws: a case report and review of literature.
abstract: METHODS
  A case report. OBJECTIVE.: A rare case of chronic C1-C2 dislocation with absence of odontoid process that underwent posterior C1-C2 arthrodesis using C1 hooks and C2 pedicle screws.
  
  
  BACKGROUND
  C1-C2 dislocation is a rare but fatal upper cervical injury. To date, there have been many reports about C1-C2 dislocation of traumatic origin. However, very few C1-C2 dislocation cases of congenital odontoid deformities had been presented. This was particularly the case when the odontoid process was absent.
  
  
  METHODS
  Plain radiograph of his cervical spine revealed a C1-C2 dislocation, and subsequent computed tomographic scan as well as magnetic resonance imaging (MRI) detected absence of odontoid process and cord compression. Upon admission, the patient was placed on skull traction and the weight increased from 3.5 to 5.5 kg. After 10 days of traction, reduction was achieved radiographically and the posterior C1-C2 arthrodesis by C1 hooks with C2 pedicle screws was performed.
  
  
  RESULTS
  After surgery, the patient showed significant improvement in gait function despite slightly raised muscle tone in his lower extremities. Four-month postoperative radiographs indicated restoration of C1-C2 alignment and bony fusion. No residual cord compression was present.
  
  
  CONCLUSIONS
  In clinical evaluation of patients who present with neck pain and limited cervical motion with or without neurologic deficits, C1-C2 dislocation should be considered. If the patient has no history of trauma or infection, congenital C1-C2 deformity, especially odontoid malformation, has to be included as a possible factor. Once the diagnosis is confirmed, posterior C1-C2 arthrodesis may become necessary for stabilizing C1-C2 and preventing it from deterioration or new development of neurologic symptoms.
authors.affiliation: Orthopedics Department, The First Affiliated hospital of Soochow University, Suzhou, China.
authors.forename: Xue Feng
authors.initials: XF
authors.lastname: Li
authors.forename: Wei Min
authors.initials: WM
authors.lastname: Jiang
authors.forename: Hui Lin
authors.initials: HL
authors.lastname: Yang
authors.forename: Tian Si
authors.initials: TS
authors.lastname: Tang
authors.forename: Xiao Hong
authors.initials: XH
authors.lastname: Gong
authors.forename: Jing
authors.initials: J
authors.lastname: Yuan
authors.forename: Genlin
authors.initials: G
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D001863:Bone Screws; D002574:Cervical Vertebrae / Q000293:injuries / Q000601:surgery; D002908:Chronic Disease; D006801:Humans; D004204:Joint Dislocations / Q000000981:diagnostic imaging / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D009809:Odontoid Process / Q000002:abnormalities*; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome