title: O-C2 angle as a predictor of dyspnea and/or dysphagia after occipitocervical fusion.
abstract: METHODS
  A retrospective clinical study.
  
  
  OBJECTIVE
  To confirm the impact of the O-C2 angle on dyspnea and dysphagia after posterior occipitocervical (O-C) fusion.
  
  
  BACKGROUND
  Dyspnea and dysphagia are complications of posterior O-C fusion with malalignment, and may be prolonged or occasionally serious. However, it is difficult to select a safe alignment during surgery, and no indicators of the appropriate alignment have been available to preclude these complications.
  
  
  METHODS
  The authors retrospectively reviewed 29 consecutive patients who had undergone O-C or occipitocervicothoracic fusion between 2003 and 2008. Data were analyzed for O-C2 angles on plain radiographs and the axial computed tomographic cross-sectional areas of the oropharynx just cranial to the epiglottis before and after surgery. The patients were grouped according to whether they developed postoperative dyspnea and/or dysphagia (group A) or not (group B).
  
  
  RESULTS
  After surgery, 4 patients complained of dysphagia, and 1 patient had dyspnea and dysphagia, although they had all undergone short O-C fusions. The difference in the O-C2 angle (dOC2A = postoperative O-C2 angle--preoperative O-C2 angle) and the percentage change in the cross-sectional area of the oropharynx (S) before and after surgery (% dS) were linearly correlated. Both dOC2A and % dS were significantly lower in group A than in group B. All patients with dOC2A of less than -10 degrees showed % dS of less than -40%, and developed dyspnea and/or dysphagia after surgery. Conversely, no patients with positive dOC2A developed these complications.
  
  
  CONCLUSIONS
  The O-C2 angle has considerable impact on dyspnea and/or dysphagia after O-C fusion. The O-C2 angle is easily measured during surgery and can be a practical index with which to avoid postoperative dyspnea and dysphagia.
authors.affiliation: Department of Orthopaedic Surgery, Graduate School of Medicine, Kyoto University, Kyoto, Japan.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Miyata
authors.forename: Masashi
authors.initials: M
authors.lastname: Neo
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Fujibayashi
authors.forename: Hiromu
authors.initials: H
authors.lastname: Ito
authors.forename: Mitsuru
authors.initials: M
authors.lastname: Takemoto
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakamura
mesh_terms: D000328:Adult; D000368:Aged; D000402:Airway Obstruction / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D001172:Arthritis, Rheumatoid / Q000150:complications; D001268:Atlanto-Axial Joint / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D001269:Atlanto-Occipital Joint / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D001368:Axis, Cervical Vertebra / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D001859:Bone Neoplasms / Q000150:complications; D001270:Cervical Atlas / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D003680:Deglutition Disorders / Q000209:etiology / Q000503:physiopathology* / Q000517:prevention & control; D004417:Dyspnea / Q000209:etiology / Q000503:physiopathology* / Q000517:prevention & control; D005260:Female; D006801:Humans; D016268:Internal Fixators / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D009777:Occipital Bone / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D010614:Pharynx / Q000033:anatomy & histology / Q000293:injuries / Q000503:physiopathology; D011183:Postoperative Complications / Q000209:etiology / Q000503:physiopathology* / Q000517:prevention & control; D011859:Radiography; D012189:Retrospective Studies; D013123:Spinal Fusion / Q000009:adverse effects* / Q000379:methods; D014132:Trachea / Q000033:anatomy & histology / Q000293:injuries / Q000503:physiopathology