1. Copyright © 2012 Lippincott Williams & Wilkins. Unauthorized commercial reproduction of this slide is prohibited Supplemental PowerPoint Slides Reduction of atlantoaxial subluxation causes airway stenosis Masanori Izeki, MD,* Masashi Neo, MD, PhD  ✝ Hiromu Ito, MD, PhD,** Koutatsu Nagai, PT, PhD, ✝ ✝ Tatsuro Ishizaki, MD, PhD, MPH§Takeshi Okamoto, MD, PhD,* Shunsuke Fujibayashi, MD, PhD,* Mitsuru Takemoto, MD, PhD,* Hiroyuki Yoshitomi, MD, PhD,* Tomoki Aoyama, MD, PhD, *** Shuichi Matsuda, MD, PhD*, *Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, Japan; **Department of the Control for Rheumatic Diseases, Graduate School of Medicine, Kyoto University, Japan; ***Department of Human Health Science, Graduate School of Medicine, Kyoto University, Japan; ✝ Department for Orthopaedic Surgery, Osaka Medical College, Japan; ✝✝ Faculty of Health Science, Department of Physical Therapy, Kyoto Tachibana University,Japan; §Human Care Research Team, Tokyo Metropolitan Institute of Gerontology, Tokyo, Japan;

2. Copyright © 2012 Lippincott Williams & Wilkins. Unauthorized commercial reproduction of this slide is prohibited Supplemental PowerPoint Slides Reduction of atlantoaxial subluxation causes airway stenosis 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 occipito-cervical fusion. Based on this background, we hypothesized that reduction of atlantoaxial subluxation (AAS) would also cause oropharyngeal airway stenosis independent of the O-C2A, because it also shifts the mandible posteriorly. U: uvula, E: epiglottis, M: mandible, T: tongue root, O: oropharynx, O-C2A: O-C2 angle, AADI: anterior atlantodental interval

3. Copyright © 2012 Lippincott Williams & Wilkins. Unauthorized commercial reproduction of this slide is prohibited Supplemental PowerPoint Slides The subjects were classified into two groups: “group R” comprised rheumatoid arthritis (RA) patients with a “reducible AAS” (n =25) “group N” comprised “non-AAS” RA patients (n = 39) ● No cases in group N and 7 cases (28%) in group R showed a paradoxical decrease in the narrowest oropharyngeal space (nPAS) in extension, in which the O-C2A is largest and reduction of AAS is obtained. (group R: 7 / 25, 28 %; group N: 0 / 39, 0%; two-tailed, Fisher exact test, P < 0.001). ● 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 (%dnPAS) in group N. On the contrary, the change in the AADI and the O-C2A were significantly related to the %dnPAS in group R.

4. Supplemental PowerPoint Slides Copyright © 2012 Lippincott Williams & Wilkins. Unauthorized commercial reproduction of this slide is prohibited Conclusion #1 Reduction of AAS correlated negatively with the oropharyngeal airway space in RA patients with AAS, perhaps because it was also accompanied by a posterior shift of the mandible. #2 Reduction of AAS during occipito-cervical fusion may cause postoperative dysphagia and/or dyspnea despite maintenance of the O-C2A. #3 Spine surgeons should pay attention not only to the reduced position but also to changes to the pharyngeal airway space when we perform occipito-cervical fusion with reduction of AAS.