title: Retrospective study on change in pharyngeal airway space and hyoid bone position after mandibular setback surgery.
abstract: OBJECTIVE
  The purpose of this study was to evaluate changes in the pharyngeal airway space and hyoid bone position after mandibular setback surgery with bilateral sagittal split ramus osteotomy (BSSRO) and to analyze the correlation between the amount of mandibular setback and the amount of change in pharyngeal airway space or hyoid bone position.
  
  
  METHODS
  From January 2010 to February 2013, a total of 30 patients who were diagnosed with skeletal class III malocclusion and underwent the same surgery (BSSRO) and fixation method in the Division of Oral and Maxillofacial Surgery, Department of Dentistry at the Ajou University School of Medicine (Suwon, Korea) were included in this study. Lateral cephalograms of the 30 patients were assessed preoperatively (T1), immediately postoperatively (T2), and 6 months postoperatively (T3) to investigate the significance of changes by time and the correlation between the amount of mandibular setback and the amount of change in the airway space and hyoid bone position.
  
  
  RESULTS
  Three regions of the nasopharynx, oropharynx, and hypopharynx were measured and only the oropharynx showed a statistically significant decrease (P<0.01). A significant posterior and inferior displacement of the hyoid bone was found 6 months after surgery (P<0.01). Analysis of the correlation between the amount of mandibular setback and the amount of final change in the airway space and hyoid bone position with Pearson's correlation showed no significant correlation.
  
  
  CONCLUSIONS
  In this study, the oropharynx significantly decreased after mandibular setback surgery, and changes in the surrounding structures were identified through posteroinferior movement of the hyoid bone during long-term follow-up. Therefore, postoperative obstructive sleep apnea should be considered in patients who plan to undergo mandibular setback surgery, and necessary modifications to the treatment plan should also be considered.
authors.affiliation: Division of Oral and Maxillofacial Surgery, Department of Dentistry, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Sung Woon
authors.initials: SW
authors.lastname: On
authors.affiliation: Department of Dentistry, Gumdan Top General Hospital, Incheon, Korea.
authors.forename: Min Woo
authors.initials: MW
authors.lastname: Han
authors.affiliation: Division of Oral and Maxillofacial Surgery, Department of Dentistry, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Doo Yeon
authors.initials: DY
authors.lastname: Hwang
authors.affiliation: Division of Oral and Maxillofacial Surgery, Department of Dentistry, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Seung Il
authors.initials: SI
authors.lastname: Song
keywords: Hyoid bone position; Mandibular setback surgery; Obstructive sleep apnea; Pharyngeal airway space