title: The biomechanical effects of a sagittal split ramus osteotomy on the relationship of the mandible, the hyoid bone, and the cervical spine.
abstract: The effects of a sagittal split ramus osteotomy in correcting mandibular retrognathism and prognathism were studied cephalometrically in a group of 25 patients. The patients were divided into two groups, 18 patients with retrognathic mandibles and 7 patients with prognathic mandibles to be corrected by means of a sagittal split ramus osteotomy according to Obwegeser Dal Pont. The major complications of this type of surgical intervention have been documented in literature and are known as (1) a certain degree of relapse, i.e., mandibular instability and (2) the development of a permanently disturbed head balance. The displacement of the dental, skeletal, and neuromuscular components within the craniomandibular complex requires a large adaptive capacity and suggests that the patient will develop a forward head posture (anteroposition of the head) after both types of surgical intervention. In mandibular advancement, however, the initiating mechanism to develop a forward head posture starts in the cervicothoracic transition (C6-C7-T1-T2). In mandibular set-back, the discussed mechanism will start in the upper cervical area (C0-C1-C2-C3). The different pattern of movement of C2 and C3 in mandibular advancement and mandibular set-back, respectively, confirmed the conclusion that the initiating mechanisms, may be found in the cervicothoracic transition and the upper cervical region, respectively.
authors.forename: J W
authors.initials: JW
authors.lastname: Valk
authors.forename: A J
authors.initials: AJ
authors.lastname: Zonnenberg
authors.forename: C J
authors.initials: CJ
authors.lastname: van Maanen
authors.forename: O G
authors.initials: OG
authors.lastname: van Wonderen
mesh_terms: D000293:Adolescent; D000328:Adult; D002508:Cephalometry; D002574:Cervical Vertebrae / Q000503:physiopathology*; D005260:Female; D006801:Humans; D006928:Hyoid Bone / Q000503:physiopathology*; D008297:Male; D008334:Mandible / Q000002:abnormalities / Q000601:surgery*; D009334:Neck Muscles / Q000503:physiopathology*; D010027:Osteotomy / Q000009:adverse effects*; D011187:Posture; D011378:Prognathism / Q000601:surgery; D063173:Retrognathia / Q000601:surgery; D013122:Spinal Diseases / Q000209:etiology