title: Changes of the Airway Space and the Position of Hyoid Bone after Mandibular Set Back Surgery Using Bilateral Sagittal Split Ramus Osteotomy Technique.
abstract: OBJECTIVE
  Although there have been several studies of reduced airway space after mandibular setback surgery using the sagittal split ramus osteotomy technique, research on the risk factors for changes of the airway space is lacking. Therefore, this study was performed to examine airway changes and the position of the hyoid bone after orthognathic surgery, and to assess possible risk factors.
  
  
  METHODS
  In this retrospective study, 50 patients who underwent posterior displacement of the mandible by the bilateral sagittal split ramus osteotomy technique were included. Changes of the position of the hyoid bone and the airway space were analyzed over various follow-up periods, using cephalometric radiography taken preoperatively, immediately after surgery, eight weeks after surgery, six months after surgery, and one year after surgery. To identify risk factors, multiple regression analysis of age, gender, body mass index (BMI), posterior mandibular movement, and the presence of genioplasty was performed.
  
  
  RESULTS
  Inferor and posterior movement of the hyoid bone was observed postoperatively, but subsequent observations showed regression towards the anterosuperior aspect. The airway space also significantly decreased after surgery (P <0.05), and increased slightly up until six months after surgery. The airway space significantly decreased (β=0.47, P <0.01) as the amount of mandibular setback increased. However, age, sex, BMI, and presence of genioplasty were not associated with airway reduction.
  
  
  CONCLUSIONS
  The amount of mandibular set back was significantly associated with postoperative reduction of airway space. It is necessary to establish a treatment plan considering this factor.
authors.affiliation: Department of Oral and Maxillofacial Surgery, Ewha Womans University Medical Center.
authors.forename: Sung-Keun
authors.initials: SK
authors.lastname: Choi
authors.affiliation: Department of Oral and Maxillofacial Surgery, Ewha Womans University Medical Center.
authors.forename: Ji-Eun
authors.initials: JE
authors.lastname: Yoon
authors.affiliation: Department of Oral and Maxillofacial Surgery, Ewha Womans University Medical Center.
authors.forename: Jung-Won
authors.initials: JW
authors.lastname: Cho
authors.affiliation: Department of Oral and Maxillofacial Surgery, Ewha Womans University Medical Center.
authors.forename: Jin-Woo
authors.initials: JW
authors.lastname: Kim
authors.affiliation: Department of Oral and Maxillofacial Surgery, Ewha Womans University Medical Center.
authors.forename: Sun-Jong
authors.initials: SJ
authors.lastname: Kim
authors.affiliation: Department of Oral and Maxillofacial Surgery, Ewha Womans University Medical Center.
authors.forename: Myung-Rae
authors.initials: MR
authors.lastname: Kim
keywords: Airway space; Orthognathic surgery; Prognathism; Saggital split ramus osteotomy