title: Do the changes in muscle mass, muscle direction, and rotations of the condyles that occur after sagittal split advancement osteotomies play a role in the aetiology of progressive condylar resorption?
abstract: Changes in cross-sectional area (CSA), volume (indicating muscle strength), and direction of the masseter and medial pterygoid muscles after surgical mandibular advancement were measured, along with the rotation of the condyles after bilateral sagittal split osteotomies (BSSOs) to advance the mandible. Measurements were done on magnetic resonance images obtained before and 2 years after surgery. CSA and volume were measured in five short-face and seven long-face patients (five males, seven females). Muscle direction was calculated in eight short-face and eight long-face patients (eight males, eight females). Short-face patients underwent BSSO only; long-face patients underwent combined BSSO and Le Fort I osteotomies. The CSA and volume decreased significantly (mean 18%) in all patients after surgery. The postoperative muscle direction was significantly more vertical (9°) in long-face patients. Rotations of the proximal segments (condyles) were minimal after 2 years. The results of this study showed that, after BSSO advancement surgery, changes in the masseter and medial pterygoid muscles are not likely to cause increased pressure on the condyles and nor are the minimal rotations of the condyles. It is concluded that neither increased muscle traction nor condylar rotations can be held responsible for progressive condylar resorption after advancement BSSO.
authors: Department of Oral and Maxillofacial Surgery/Pathology, Academic Centre for Dentistry Amsterdam (ACTA) and VU University Medical Centre, Amsterdam, Netherlands; Elkerliek Hospital, Helmond, Netherlands. Electronic address: dicker@xs4all.nl.
authors: G J
authors: GJ
authors: Dicker
authors: Department of Radiology, VU University Medical Centre, Amsterdam, Netherlands.
authors: J A
authors: JA
authors: Castelijns
authors: Department of Oral and Maxillofacial Surgery/Pathology, Academic Centre for Dentistry Amsterdam (ACTA) and VU University Medical Centre, Amsterdam, Netherlands.
authors: D B
authors: DB
authors: Tuinzing
authors: Department of Oral and Maxillofacial Surgery, Radboud University Medical Centre, Nijmegen, Netherlands; Department of Cranio-maxillofacial Surgery, Maastricht University Medical Centre, Netherlands.
authors: P J W
authors: PJ
authors: Stoelinga
mesh_terms: D000293:Adolescent; D000328:Adult; D001862:Bone Resorption / Q000473:pathology*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008335:Mandibular Condyle / Q000473:pathology* / Q000601:surgery*; D008406:Masseter Muscle / Q000473:pathology* / Q000601:surgery*; D008875:Middle Aged; D053580:Muscle Strength; D019340:Osteotomy, Le Fort; D059229:Osteotomy, Sagittal Split Ramus; D011626:Pterygoid Muscles / Q000473:pathology* / Q000601:surgery*; D016896:Treatment Outcome
keywords: Bilateral sagittal split osteotomy; Condylar position; Magnetic resonance imaging; Masseter muscle; Medial pterygoid muscle; Muscle direction; Muscle size; Progressive condylar resorption; Relapse; Surgical mandibular advancement