Tung-Yiu Wong1, Jia-Kuang Liu2, Jing-Jing Fang3, Tung-Chin Wu4, Yi-Hsuan Tu5. 1. Associate Professor, Division of Oral and Maxillofacial Surgery, Institute of Oral Medicine and Department of Stomatology, National Cheng Kung University Hospital, National Cheng Kung University College of Medicine, Tainan, Taiwan Republic of China. Electronic address: victortyw@yahoo.com.tw. 2. Associate Professor, Division of Orthodontics, Institute of Oral Medicine and Department of Stomatology, National Cheng Kung University Hospital, National Cheng Kung University College of Medicine, Tainan, Taiwan Republic of China. 3. Professor, Department of Mechanical Engineering, National Cheng Kung University College of Engineering, Tainan, Taiwan Republic of China. 4. Graduate Student, Department of Mechanical Engineering, National Cheng Kung University College of Engineering, Tainan, Taiwan Republic of China. 5. Assistant Professor, Department of Statistics, National Cheng Kung University, Tainan, Taiwan Republic of China.
Abstract
PURPOSE: A voxel-based median plane (optimal symmetry plane [OSP]) was developed to assess facial bone asymmetry. The purpose of the present study was to introduce a new method of planning surgical correction of facial asymmetry using the OSPs as guides and test its effectiveness. PATIENTS AND METHODS: A retrospective study was conducted of 20 facial asymmetry patients with a mandibular deviation of 4 mm or greater or 4° or more that required surgical correction. In the test group (n = 8), the plans for asymmetry correction were formulated using the matching OSP method, in which the OSPs of the facial bones are tracked and matched during the model surgery setup. In the control group (n = 12), traditional planning was conducted. The traditional plans were cross-checked for symmetry through tracking and revised as needed. The symmetry results of the plans were compared between the 2 groups and within the control group. The outcome measures were the deviation distances between the OSPs of the midface and mandible at the anterior or posterior mandible, the occlusal plane cant, and the angle formed by the 2 OSPs. Surgery was performed in accordance with the final plans, and the results were assessed for symmetry. RESULTS: The traditional plans left a major mandibular deviation in 5 of the 12 control subjects compared with none in the test group. The test group did significantly better than the control group. The revised plans were significantly better than the initial plans. Postoperatively, significant improvements in symmetry were observed. CONCLUSION: The new method resulted in surgical plans that brought about significantly less postoperative mandibular deviation while maintaining a reasonable occlusion.
PURPOSE: A voxel-based median plane (optimal symmetry plane [OSP]) was developed to assess facial bone asymmetry. The purpose of the present study was to introduce a new method of planning surgical correction of facial asymmetry using the OSPs as guides and test its effectiveness. PATIENTS AND METHODS: A retrospective study was conducted of 20 facial asymmetry patients with a mandibular deviation of 4 mm or greater or 4° or more that required surgical correction. In the test group (n = 8), the plans for asymmetry correction were formulated using the matching OSP method, in which the OSPs of the facial bones are tracked and matched during the model surgery setup. In the control group (n = 12), traditional planning was conducted. The traditional plans were cross-checked for symmetry through tracking and revised as needed. The symmetry results of the plans were compared between the 2 groups and within the control group. The outcome measures were the deviation distances between the OSPs of the midface and mandible at the anterior or posterior mandible, the occlusal plane cant, and the angle formed by the 2 OSPs. Surgery was performed in accordance with the final plans, and the results were assessed for symmetry. RESULTS: The traditional plans left a major mandibular deviation in 5 of the 12 control subjects compared with none in the test group. The test group did significantly better than the control group. The revised plans were significantly better than the initial plans. Postoperatively, significant improvements in symmetry were observed. CONCLUSION: The new method resulted in surgical plans that brought about significantly less postoperative mandibular deviation while maintaining a reasonable occlusion.