Résumé
Objectives To investigate the changes in the masseter muscle following osteotomy of the prominent mandibular angle using real-time three-dimensional (3D) ultrasonography, and to supply guidance for resection of the mandibular angle. Methods Real-time 3D ultrasonography was applied preand post-operatively (over a 6-month follow-up period) to 10 patients who underwent curved osteotomy with the following objectives: (1) to reconstruct the morphological changes of the masseter under different conditions; (2) to assess masseter muscle volume changes, and (3) to obtain the dynamic morphological changes of masseter during mouth opening and closing. Results The reconstructed 3D images revealed that longitudinal diameters of masseter muscle decreased and angle regions changed to be arc-shaped with significant thinning 6 months after operation. The mean volume of masseter muscle was (18. 222 ±3. 028) cm36 months post-operatively, compared with the pre-operation mass of (25. 480 ± 7. 113) cm3,the statistical difference was significant (P＜0.01). Transverse and longitudinal changes of the thickest masseter muscle section 6 months post-operatively were of no statistic difference (P＞0. 01) compared with pre-operation status during mouth opening and closing motions. Conclusion A certain extent of atrophy occurs primarily in the angle region of masseter muscle after mandibular angle ostectomy. However, these changes do not significantly impair masseter muscle function. Real-time 3D ultrasonography offers a novel, safe, and convenient technique for masseter muscle reconstruction and observation of masseter muscle movement.