title: Subaxial sagittal alignment after atlantoaxial fixation techniques.
abstract: METHODS
  A retrospective clinical case series.
  
  
  OBJECTIVE
  To evaluate the association between C1-C2 fixation angle and postoperative C2-C7 alignment in the sagittal plane after C1 lateral mass screw with C2 pedicle screw fixation (C1-LMS) or Magerl with wiring technique.
  
  
  BACKGROUND
  Various techniques for posterior correction and fusion, such as the Magerl procedure with posterior wiring and C1-LMS procedures, are used for treating atlantoaxial instability. However, only few studies investigating the relationship between postoperative C1-C2 angle and C2-C7 sagittal alignment change after C1-C2 fixation have been reported.
  
  
  METHODS
  We retrospectively followed up 42 patients who underwent the C1-LMS (22 patients) or Magerl with wiring procedure (20 patients) to treat C1-C2 instability for >2 years. The atlantodental interval, space available for the spinal cord, and O-C1, C1-C2, C2-C3, and C2-C7 angles were measured.
  
  
  RESULTS
  Significant reduction in atlantodental interval and increase in space available for the spinal cord were observed in both groups. Although the preoperative C1-C2 angles were similar, the angle at the final follow-up was higher in the Magerl with wiring group than in the C1-LMS group (P<0.01). The C1-C2 fixation and postoperative C2-C7 angles were negatively correlated in both groups (C1-LMS group, r=-0.55, P<0.01; Magerl with wiring, r=-0.62, P<0.01).
  
  
  CONCLUSIONS
  Increased lordotic change in the C1-C2 angle was associated with increased kyphotic changes in the C2-C7 angle after both procedures. The C1-LMS procedure effectively controlled C1-C2 sagittal alignment during surgery. To decrease the risk of postoperative subaxial kyphotic changes, the C1-C2 fixation angle should be carefully determined.
authors.affiliation: *Hokkaido Orthopaedic Memorial Hospital †Department of Advanced Medicine for Spine and Spinal Cord Disorders, Hokkaido University Graduate School of Medicine ‡Sapporo Orthopaedic Hospital, Sapporo, Hokkaido, Japan.
authors.forename: Shigeki
authors.initials: S
authors.lastname: Oshima
authors.forename: Hideki
authors.initials: H
authors.lastname: Sudo
authors.forename: Manabu
authors.initials: M
authors.lastname: Ito
authors.forename: Kuniyoshi
authors.initials: K
authors.lastname: Abumi
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery; D003710:Demography; D005260:Female; D005500:Follow-Up Studies; D005592:Fracture Fixation / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011182:Postoperative Care; D011184:Postoperative Period; D011300:Preoperative Care; D011859:Radiography; D055815:Young Adult