Evaluation of dynamic morphologic changes in the masseter muscle in patients undergoing mandibular angle sagittal split osteotomy: a report of 130 cases.

摘要

OBJECTIVE: To evaluate the dynamic morphologic changes in the masseter muscle after mandibular angle sagittal split osteotomy (MASO). METHODS: Computed tomographic (CT) examinations were performed on 130 patients treated with MASO before surgery and at 3, 6, 12, and 18 months after surgery. These CT images were stored and a 3-dimensional reconstruction was made for calculating the volume of masseter muscle using Mimics 10.01 software. The cross-sectional area of masseter muscle was evaluated preoperatively and postoperatively using 3-dimensional CT images observed from 3 selected slice levels, which paralleled the Frankfurt horizontal plane. RESULTS: Following treatment, the reduction of the volume and cross-sectional area of masseter muscle were calculated. The volume of the masseter muscle was reduced by 28.18%, 39.58%, 33.37%, and 31.18% at 3, 6, 12, and 18 months postoperatively, respectively. The cross-sectional area of 3 slices were reduced, but the sectional area of the lower slice had the sharpest decline, with reductions of 79.27%, 84.39%, 84.02%, and 83.57% at 3, 6, 12, and 18 months postoperatively, respectively. CONCLUSIONS: The results showed that the masseter muscle undergoes significant atrophy after mandibular osteotomy, and these changes could be considered as a guide for the design and simulation of MASO before surgery.