Zhu Ming, Chai Gang, Zhang Yan, Ma Xiao-Fei, Yu Zhe-Yuan, Mu Xiong-Zhen, Qi Zuo-Liang
Department of Plastic and Constructive, Ninth Hospital affiliated to Medical School of Shanghai Jiaotong University, Shanghai 200011, China.
Zhonghua Zheng Xing Wai Ke Za Zhi. 2010 Sep;26(5):340-4.
To evaluate the morphological change of masseter after the mandibular angle osteotomy.
Computerized tomography (CT) examination was performed on 120 patients treated by mandibular angle osteotomy before operation and at 3, 6, 12 months after operation, respectively. The pre- and postoperative masseter muscle thickness and cross-sectional area were evaluated using 3D CT images observed from 3 selected slice planes, which were paralleled with Frankfurt horizontal plane. These CT images were stored and three-dimensional reconstruction were made for calculation of masseter muscle volume through software.
After operation, the reduction of the masseter muscle volume and cross-sectional area was seen. The volume of the masseter at 3, 6, 12 months postoperatively decreased to 82.02%, 77.00% and 80.43% (P < 0.05). The cross-sectional area at 3, 6,12 months postoperatively decreased to 85.81%, 78.86% and 81.56% at A plane, 80.94%, 75.03% and 77.04% at B plane, and reached to 13.46%, 11.48% and 13.89% at C plane (P < 0.05, P < 0.05, P < 0.01). The masseter thickness after operation was significantly different from that before operation during the follow-up period, but not at 12 months after operation at A plane.
The masseter atrophy happens spontaneously after mandibular angle osteotomy, especially at the region of mandibular angle. It should be considered during surgical design.
评估下颌角截骨术后咬肌的形态变化。
对120例行下颌角截骨术的患者分别在术前及术后3、6、12个月进行计算机断层扫描（CT）检查。使用从3个与法兰克福水平面平行的选定切片平面观察到的三维CT图像评估术前及术后咬肌的厚度和横截面积。存储这些CT图像，并通过软件进行三维重建以计算咬肌体积。
术后可见咬肌体积和横截面积减小。术后3、6、12个月咬肌体积分别降至82.02%、77.00%和80.43%（P<0.05）。术后3、6、12个月A平面横截面积分别降至85.81%、78.86%和81.56%，B平面分别降至80.94%、75.03%和77.04%，C平面分别降至13.46%、11.48%和13.89%（P<0.05，P<0.05，P<0.01）。随访期间术后咬肌厚度与术前相比有显著差异，但术后12个月A平面除外。
下颌角截骨术后咬肌会自发萎缩，尤其是在下颌角区域。在手术设计时应予以考虑。
