title: Effect of a reduction of the atlanto-axial angle on the cranio-cervical and subaxial angles following atlanto-axial arthrodesis in rheumatoid arthritis.
abstract: OBJECTIVE
  We retrospectively investigated the radiographic findings in patients with atlanto-axial subluxation (AAS) due to rheumatoid arthritis, and clarified the effect of reduction of the atlanto-axial angle (AAA) on the cranio-cervical and subaxial angles.
  
  
  METHODS
  Forty-one patients, consisting of 29 females and 12 males, with AAS treated by surgery were reviewed. The average patient age at surgery was 61.0 years, and the average follow-up period was 4.0 years. We investigated the AAA at the neutral position in lateral cervical radiographs before surgery and at the last follow-up. In addition, we also investigated the clivo-axial angle (CAA) and the subaxial angle (SAA) at the neutral position before and after surgery.
  
  
  RESULTS
  Due to pre-operative AAA, the patients were classified into three groups as follows: (1) the kyphotic group (K group), (2) the neutral group (N group), and (3) the lordotic group (L group). The average AAA values at the neutral position in the K group before and after surgery were 6.0° and 18.1°, respectively (P < 0.001). In the N group 19.7° and 21.7°, respectively (P < 0.05), and in the L group 31.6° and 27.0°, respectively (P < 0.01). However, no significant differences in the average CAA values were found before and after surgery in all groups. Furthermore, no significant differences in the SAA values were seen before and after surgery in all groups.
  
  
  CONCLUSIONS
  A proper reduction of the AAA did not affect the cranial angles or induce kyphotic malalignment of the subaxial region after atlanto-axial arthrodesis. However, if we can obtain a significant and large reduction of AAA in patients showing kyphosis before surgery, then this reduction will be offset in the atlanto-occipital joint and we should therefore pay special attention to its morphology after surgery.
authors.affiliation: Department of Orthopedic Surgery, Gunma University Graduate School of Medicine, 3-39-22 Showa, Maebashi, Gunma, 371-8511, Japan. ihaku@showa.gunma-u.ac.jp
authors.forename: Haku
authors.initials: H
authors.lastname: Iizuka
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Iizuka
authors.forename: Ryoichi
authors.initials: R
authors.lastname: Kobayashi
authors.forename: Yasuhiko
authors.initials: Y
authors.lastname: Takechi
authors.forename: Masahiro
authors.initials: M
authors.lastname: Nishinome
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Ara
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Sorimachi
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakajima
authors.forename: Kenji
authors.initials: K
authors.lastname: Takagishi
mesh_terms: D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000000981:diagnostic imaging / Q000601:surgery*; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D001269:Atlanto-Occipital Joint / Q000000981:diagnostic imaging / Q000601:surgery; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011859:Radiography; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000379:methods*; D016896:Treatment Outcome