3D CT evaluation of masseter muscle morphology after setback osteotomy for mandibular prognathism.
OBJECTIVE
Following mandibular setback osteotomy, changes in the direction, length, and cross-sectional area of the masseter muscle were studied by means of computerized tomography (CT) images generated with a 3-dimensional (3D) reconstructive technique.


METHODS
Pre- and postoperative CT examinations were performed on 17 prognathic patients treated by sagittal split ramus osteotomy with rigid osteosynthesis and 13 patients treated by intraoral vertical ramus osteotomy without osteosynthesis. The pre- and postoperative masseter muscle direction and length were evaluated using 3D CT images observed from a lateral viewing angle. The cross-sectional area of the masseter muscle was first measured on an axial CT image of a selected slice level, following which the right-angle cross-sectional area of the muscle was revised using the measured area from the axial image.


RESULTS
Postoperatively, anterior tilting of the masseter muscle was observed; however, masseter muscle length was unchanged. Three months postoperatively, a significant reduction in the cross-sectional area of the masseter muscle was seen. A tendency to revert back to the normal dimension was seen between 6 months and 1 year postoperatively. No significant difference was noted between the 2 surgical techniques.


CONCLUSIONS
Three-dimensional computed tomography is an adequate imaging modality for masseter muscle evaluation. The results of this study suggest the masseter muscle may undergo reversible atrophy after mandibular setback osteotomy.
Department of Oral Radiology, Asahi University School of Dentistry, Gifu, Japan. kawamata@dent.asahi-u.ac.jp
Akitoshi
A
Katsumata
Masami
M
Fujishita
Yoshiko
Y
Ariji
Eiichiro
E
Ariji
Robert P
RP
Langlais
D000293:Adolescent; D000328:Adult; D002508:Cephalometry; D005260:Female; D005593:Fracture Fixation, Internal; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional / Q000379:methods*; D008297:Male; D008334:Mandible / Q000000981:diagnostic imaging* / Q000601:surgery; D008406:Masseter Muscle / Q000033:anatomy & histology*; D009133:Muscular Atrophy / Q000000981:diagnostic imaging*; D019340:Osteotomy, Le Fort / Q000379:methods*; D011378:Prognathism / Q000601:surgery; D014057:Tomography, X-Ray Computed / Q000379:methods*