title: Subaxial sagittal alignment and adjacent-segment degeneration after atlantoaxial fixation performed using C-1 lateral mass and C-2 pedicle screws or transarticular screws.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the effect of a fixed atlantoaxial angle on subaxial sagittal alignment, and that of atlantoaxial fixation on adjacent-segment motion and degeneration.
  
  
  METHODS
  The authors retrospectively reviewed 65 patients in whom atlantoaxial instability was treated with atlantoaxial fixation by C-1 lateral mass and C-2 pedicle screw fixation (30 patients, Goel-Harms [GH] group) or a combination of transarticular screw fixation and posterior wiring (35 patients, Magerl-Brooks [MB] group). Angles of Oc–C1, C1–2, C2–3, and C2–7 were determined based on an upright lateral radiograph in flexion, neutral, and extension positions. The range of motion (ROM) at Oc–C1 and C2–3 was also determined. All patients were examined before and 2 years after surgery.
  
  
  RESULTS
  The mean preoperative atlantoaxial angles in the GH and MB groups were 20.9 ± 8.3° and 18.3 ± 7.2°, respectively, and the mean postoperative atlantoaxial angles in the same groups were 23.5 ± 5.6° and 29.7 ± 6.3°, respectively, with a statistically significant difference between the 2 groups (p < 0.05). The mean preoperative angles of C2–7 in the GH and MB groups were 15.4 ± 7.8° and 13.7 ± 9.5°, respectively, and after surgery, the angles were 11.8 ± 12° and 2.48 ± 12°, respectively, with a statistically significant difference between the 2 groups (p < 0.05). The postoperative angle of C1–2 showed a negative correlation with the extent of change observed in the C2–7 angle pre- and postoperatively in each of these 2 surgical procedures. The Oc–C1 ROM increased after surgery in both groups, but the difference was not statistically significant (p = 0.38). The C2–3 ROM decreased after surgery in both groups, and the difference was statistically significant (p < 0.05).
  
  
  CONCLUSIONS
  Atlantoaxial fixation in a hyperlordotic position produced kyphotic sagittal alignment after surgery in both GH and MB groups. Reduction of the atlantoaxial joint can be easily achieved through screw fixation at an optimal angle, thereby ameliorating the risk for subsequent subaxial kyphosis. Degeneration of lower adjacent segments appeared to be less with this procedure compared with using a combination of transarticular screw fixation and posterior wiring.
authors.affiliation: Department of Spine and Orthopedic Center, Konan Kosei Hospital, Aichi, Japan. goy@K6.dion.ne.jp
authors.forename: Go
authors.initials: G
authors.lastname: Yoshida
authors.forename: Mituhiro
authors.initials: M
authors.lastname: Kamiya
authors.forename: Hisatake
authors.initials: H
authors.lastname: Yoshihara
authors.forename: Tokumi
authors.initials: T
authors.lastname: Kanemura
authors.forename: Fumihiko
authors.initials: F
authors.lastname: Kato
authors.forename: Yasutugu
authors.initials: Y
authors.lastname: Yukawa
authors.forename: Keigo
authors.initials: K
authors.lastname: Ito
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Matsuyama
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Sakai
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D053587:Arthrometry, Articular; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D001847:Bone Diseases / Q000209:etiology; D001863:Bone Screws; D001864:Bone Wires; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging / Q000601:surgery*; D002648:Child; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000601:surgery*; D007738:Kyphosis / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D019637:Orthopedic Procedures / Q000009:adverse effects / Q000379:methods; D011859:Radiography; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D055815:Young Adult