title: Reduction of atlantoaxial subluxation causes airway stenosis.
abstract: METHODS
  A cross-sectional study.
  
  
  OBJECTIVE
  The purpose of this study was to investigate the effect of reduction of anterior atlantoaxial subluxation (AAS) on the oropharyngeal airway space.
  
  
  BACKGROUND
  Our previous studies have shown that reduction of the occipito-C2 angle (O-C2A) makes the mandible shift posteriorly, resulting in oropharyngeal airway stenosis, which occasionally causes postoperative dysphagia after occipitocervical fusion. Based on this background, we hypothesized that reduction of AAS would also cause oropharyngeal airway stenosis independent of the O-C2A, because it also shifts the mandible posteriorly. To our knowledge, there are no data demonstrating an association between reduction of AAS and the oropharyngeal airway space.
  
  
  METHODS
  The authors prospectively evaluated 64 patients with rheumatoid arthritis. We analyzed lateral cervical plain radiographs of 5 different positions (neutral, flexion, extension, retraction, and protrusion), and measured the O-C2A, C2-C6 angle, anterior atlantodental interval, anteroposterior distance of the narrowest oropharyngeal airway space (nPAS), and so on. The subjects were classified into 2 groups: group R comprised patients with a "reducible AAS" in dynamic cervical movement, and group N comprised "patients without AAS" patients.
  
  
  RESULTS
  In the multiple regression analysis, the change in the O-C2A was the only significant independent variable related to the percentage change in the nPAS from the neutral position in group N. On the contrary, the change in the anterior atlantodental interval and change in the O-C2A were significantly related to the percentage change in the nPAS in group R. No cases in group N and 7 cases (28%) in group R showed a paradoxical decrease in the nPAS in extension, in which the O-C2A is largest and reduction of AAS is obtained.
  
  
  CONCLUSIONS
  Reduction of AAS has a negative effect on the oropharyngeal airway space. Therefore, reduction of AAS during occipitocervical fusion may cause postoperative dysphagia despite maintenance of the O-C2A.
authors: *Department of Orthopaedic Surgery †Department of the Control for Rheumatic Diseases, and ‡Department of Human Health Science, Graduate School of Medicine, Kyoto University, Japan §Department of Orthopaedic Surgery, Osaka Medical College, Japan ¶Faculty of Health Science, Department of Physical Therapy, Kyoto Tachibana University, Japan; and ‖Human Care Research Team, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan.
authors: Masanori
authors: M
authors: Izeki
authors: Masashi
authors: M
authors: Neo
authors: Hiromu
authors: H
authors: Ito
authors: Koutatsu
authors: K
authors: Nagai
authors: Tatsuro
authors: T
authors: Ishizaki
authors: Takeshi
authors: T
authors: Okamoto
authors: Shunsuke
authors: S
authors: Fujibayashi
authors: Mitsuru
authors: M
authors: Takemoto
authors: Hiroyuki
authors: H
authors: Yoshitomi
authors: Tomoki
authors: T
authors: Aoyama
authors: Shuichi
authors: S
authors: Matsuda
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000402:Airway Obstruction / Q000000981:diagnostic imaging / Q000209:etiology*; D001172:Arthritis, Rheumatoid / Q000150:complications / Q000000981:diagnostic imaging / Q000601:surgery; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging / Q000601:surgery*; D003251:Constriction, Pathologic / Q000000981:diagnostic imaging / Q000209:etiology; D003430:Cross-Sectional Studies; D003680:Deglutition Disorders / Q000000981:diagnostic imaging / Q000209:etiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010614:Pharynx / Q000000981:diagnostic imaging* / Q000601:surgery; D011183:Postoperative Complications / Q000000981:diagnostic imaging / Q000209:etiology*; D011446:Prospective Studies; D011859:Radiography