Fabrication of cranio-facial soft tissue model by rapid prototyping and its clinical application.

1.目的为了改善颌骨畸形患者的功能和美观，正颌外科手术得到了广泛的应用。我们应用快速成型(RP)技术，从3D-CT数据中建立了三维颅面骨模型，并将其用于术前模拟。然而，术后复发通常是由于扭曲的软组织和肌肉造成的紧张。因此，本研究的目的是制作包括软组织在内的模拟模型，以评估手术前后软组织的变化。材料和方法由于咀嚼肌，尤其是咬肌，被认为对术后复发有很大的影响，所以对咬肌进行了模拟。在接受矢状劈开或垂直升支截骨术的患者中，符合以下标准的患者为研究对象：1)不做上颌骨手术或对颧骨和鼻骨进行有限的打击，2)生长期结束后进行术前CT检查，术后6个月内进行CT检查。从每一层CT切片中提取咬肌数据。咬肌长轴定义为咬肌重心在每个层面上的回归线。3.结果术后咬肌长轴略向后倾斜。然而，如果考虑到关于扫描角度和参考轴确定的技术误差，可以得出结论，咬肌的变形是最小的。当手术前后CT扫描角度相差较大时，本研究采用的方法是不准确的。因此，为了更准确地评估软组织的变化，可能有必要严格规范手术前后的CT扫描条件。

1. ObjectiveOrthognathic surgery has been widely performed to improve function and esthetics of patients suffering from jaw deformity. We have applied rapid prototyping (RP) technology to fabricate 3-dimensional cranio-facial bone models from 3D-CT data and the models have been used for presurgical simulation. However, post-operative relapse usually takes place due to tension from distorted soft tissues and muscles. Therefore, the purpose of this study was to fabricate simulation models including soft tissue in order to evaluate soft tissue change before and after surgery.2. Materials and MethodsThe masseter was modelled because masticatory muscles, especially the masseter, are supposed to have strong influence on postoperative relapse. Among patients underwent sagittal split or vertical ramus osteotomy, those who met the following criteria were included as subjects ; 1)no maxillary surgery or limited blow the zygomatic and nasal bones, 2)Preoperative CT taken after growth period was over and postoperative CT taken within 6 months after surgery are available. The masseter data was extracted from each CT slice. The long axis of the masseter was defined as a regression line of the center of gravity of the masseter on each slice. The change of the masseter muscle angluation was evaluated by the angle between the reference axes before and after the surgery.3.ResultsThe long axis of the masseter muscles tended to tilt slightly to the posterior direction after surgery. However, if the technical errors regarding the scanning angle and the reference axes determination are taken into account, it can be concluded that the distortion of the masseter muscles, was minimal. The method used in this study would be inaccurate when the difference between the CT scanning angles taken pre and postoperatively was large. Therefore, in order to evaluate soft tissue changes more accurately, it may be necessary to strictly standardize pre and postoperative CT scanning conditions.