title: Skeletal changes after modified intraoral vertical ramus osteotomy for correction of mandibular prognathism.
abstract: BACKGROUND
  Orthognathic surgery is widely used to correct congenital and acquired dentofacial discrepancies. Various surgical procedures have been advocated for correction of mandibular prognathism. In this study, a modified intraoral vertical ramus osteotomy has been developed for surgical correction of mandibular prognathism. The aim of this study is to identify contributing factors to skeletal change by analysing cephalometric changes after modified intraoral vertical ramus osteotomy.
  
  
  METHODS
  Forty-one patients, treated for absolute mandibular prognathism by bilateral modified intraoral vertical ramus osteotomy, were evaluated cephalometrically with reference to the menton point. A set of four standardised lateral cephalograms were obtained from each subject preoperatively (T1) and immediately postoperatively (T2), prior to removal of maxillomandibular fixation (T3), and at 1-year postoperatively (T4). The mean setback of the menton was 12.4 mm in the horizontal direction. Relapse was defined as forward movement of the menton during the 1-year follow-up.
  
  
  RESULTS
  The highly significant backward movements in a horizontal direction were observed during the maxillomandibular fixation period (T3-T2). Moreover, highly significant forward movement was observed following the maxillomandibular fixation period (T4-T3). After 1-year follow-up (T4-T2), the mean changes of the menton were 0.1 mm backward in the horizontal direction.
  
  
  CONCLUSIONS
  In this series, the mean skeletal change compared with the amount of setback was less than 1% (0.1/12.4 mm) in backward movement. The results suggest that the modified intraoral vertical ramus osteotomy technique is useful and the more stable approach for correction of severe mandibular prognathism.
authors.affiliation: Department of Oral Maxillofacial Surgery, Kaohsiung Medical University, No. 100, Shih-chuan 1st Road, Kaohsiung 807, Taiwan.
authors.forename: Steven Sheng-Tsung
authors.initials: SS
authors.lastname: Lai
authors.forename: Yu-Chuan
authors.initials: YC
authors.lastname: Tseng
authors.forename: I-Yueh
authors.initials: IY
authors.lastname: Huang
authors.forename: Yi-Hsin
authors.initials: YH
authors.lastname: Yang
authors.forename: Yee-Shyong
authors.initials: YS
authors.lastname: Shen
authors.forename: Chun-Ming
authors.initials: CM
authors.lastname: Chen
mesh_terms: D000293:Adolescent; D000328:Adult; D002508:Cephalometry / Q000379:methods; D005260:Female; D006801:Humans; D019248:Jaw Fixation Techniques; D007574:Jaw Relation Record / Q000379:methods; D008297:Male; D008313:Malocclusion, Angle Class III / Q000473:pathology; D008334:Mandible / Q000473:pathology / Q000601:surgery; D008335:Mandibular Condyle / Q000473:pathology; D008437:Maxilla / Q000473:pathology / Q000601:surgery; D010027:Osteotomy / Q000379:methods*; D011184:Postoperative Period; D011378:Prognathism / Q000473:pathology / Q000601:surgery*; D016896:Treatment Outcome; D014716:Vertical Dimension