Computer-assisted Orthognathic Surgery Planning Based on Profile Classification Using Self-Organizing Map

在计划颌骨畸形手术时，可以参考先前接受手术的类似患者的面部轮廓来生成患者的术后轮廓。本研究的目的是开发一个计算机辅助的正颌手术计划系统，该系统可以搜索与新患者的轮廓相匹配的过去病例，生成新患者的术后轮廓，并计算美学评分。研究对象为37例接受正颌手术的颌骨畸形患者。使用术前和术后侧位头像，测量11个软组织轮廓（如面部凸度、鼻唇角和美学线（e线））。对于每个患者，使用自组织地图（SOM）对这些值进行分类，该地图根据相似度将数据排列在二维地图上。此外，根据手术引起的骨组织运动将SOM分类的每个簇划分为亚簇。在这个阶段，根据过去的案例为每个子簇分配一个美学值。该系统的分类结果与面部形态分类图的轮廓分类结果几乎完全匹配。因此，可以通过输入新病例的轮廓测量来搜索类似的过去病例。此外，通过参考亚群，可以确定达到高度美观结果的外科手术。本系统是支持颌骨畸形侧位诊断和手术计划、对侧位改变感到焦虑和兴奋的患者进行咨询和获得知情同意的有用工具。

When planning surgery for jaw deformity, it is possible to generate a postoperative profile of the patient by referring to the facial profile of similar patients who have previously undergone surgery. The objective of the present study was to develop a computer-assisted orthognathic surgery planning system that searches for past cases matching the profile of a new patient, generates the postoperative profiles of the new patient, and calculates an esthetic score.Subjects were 37 patients with jaw deformities who underwent orthognathic surgery. Using preoperative and postoperative lateral cephalograms, eleven soft tissue profile measurements were taken (such as facial convexity, nasolabial angle, and esthetic line (E-line)). For each patient, these values were classified using a self-organizing map (SOM) that arranges data on a two-dimensional map based on degree of similarity. Furthermore, each cluster classified by the SOM was divided into subclusters based on movement of bony tissue caused by surgery. At this stage, an esthetic value was assigned to each subcluster based on past cases.The results of classification by the present system almost completely matched profile classifications derived from the facial morphologic classification chart. Therefore, it is possible to search for similar past cases by inputting the profile measurements of a new case. Furthermore, by referring to subclusters, it is possible to identify a surgical procedure that achieves highly esthetic outcomes. The present system is a useful tool for supporting the profile diagnosis and surgery planning of jaw deformity, counseling patients who are anxious and excited about profile changes, and obtaining informed consent.