title: Retrospective study of changes in pharyngeal airway space and position of hyoid bone after mandibular setback surgery by cephalometric analysis.
abstract: BACKGROUND
  The posterior movement of mandible was known as the main cause of the changes in the pharyngeal airway space (PAS) and the postoperative obstructive sleep apnea (OSA). The purpose of this study was to know the changes of PAS and position of hyoid bone.
  
  
  METHODS
  Lateral cephalographies of 13 patients who had undergone sagittal split ramus osteotomy (SSRO) setback surgery were taken preoperatively (T1), postoperatively within 2 months (T2), and follow-up after 6 months or more (T3). On the basis of F-H plane, diameters of nasopharynx, oropharynx, and hypopharynx were measured. The movements of the soft palate, tongue, and hyoid bone were also measured.
  
  
  RESULTS
  The amount of mandible setback was 7.5 ± 3.8 mm. In the measurements of PAS, there was a statistically significant decrease of 2.8 ± 2.5 mm in nasopharynx (P < 0.01), and 1.7 ± 2.4 mm in oropharynx (P < 0.01) were observed after surgery. The hypopharynx decreased 1.0 ± 2.1 mm after surgery and continuously decreased 1.0 ± 2.8 mm at follow-up. The changes in hyoid bone position showed the posterior movement only after surgery and posteroinferior movement at follow-up.
  
  
  CONCLUSIONS
  The PAS such as nasopharynx, oropharynx, and hypopharynx showed relatively high correlation with the amount of mandibular setback. The change of resistance in upper airway may be important for the prevention of OSA after mandibular setback surgery.
authors.affiliation: Department of Oral and Maxillofacial Surgery, College of Medicine, Inha University, #7-206, 3rd St. Shinheung-dong, Choong-gu, Incheon, 400-711 South Korea.
authors.forename: Hyun-Woo
authors.initials: HW
authors.lastname: Cho
authors.affiliation: Department of Oral and Maxillofacial Surgery, College of Medicine, Inha University, #7-206, 3rd St. Shinheung-dong, Choong-gu, Incheon, 400-711 South Korea.
authors.forename: Il-Kyu
authors.initials: IK
authors.lastname: Kim
authors.affiliation: Department of Oral and Maxillofacial Surgery, College of Medicine, Inha University, #7-206, 3rd St. Shinheung-dong, Choong-gu, Incheon, 400-711 South Korea.
authors.forename: Hyun-Young
authors.initials: HY
authors.lastname: Cho
authors.affiliation: Department of Oral and Maxillofacial Surgery, College of Medicine, Inha University, #7-206, 3rd St. Shinheung-dong, Choong-gu, Incheon, 400-711 South Korea.
authors.forename: Ji-Hoon
authors.initials: JH
authors.lastname: Seo
authors.affiliation: Department of Oral and Maxillofacial Surgery, College of Medicine, Inha University, #7-206, 3rd St. Shinheung-dong, Choong-gu, Incheon, 400-711 South Korea.
authors.forename: Dong-Hwan
authors.initials: DH
authors.lastname: Lee
authors.affiliation: Department of Oral and Maxillofacial Surgery, International St. Mary's Hospital, Catholic Kwandong University College of Medicine, Incheon, South Korea.
authors.forename: Seung-Hoon
authors.initials: SH
authors.lastname: Park
keywords: Cephalometric; Hyoid bone; Mandibular setback; Pharyngeal airway space