Department of Biomedical Radiation Sciences (Head: Sung-Joon Ye, PhD), Graduate School of Convergence Science and Technology, Seoul National University, South Korea.
Orthognathic Surgery Center (Head: Soon Jung Hwang, DDS, MD, PhD), Seoul National University Dental Hospital, South Korea.
J Craniomaxillofac Surg. 2019 Jan;47(1):127-137. doi: 10.1016/j.jcms.2018.10.016. Epub 2018 Oct 26.
It is essential to reposition the mandibular proximal segment (MPS) as close to its original position as possible during orthognathic surgery. Conventional methods cannot pinpoint the exact position of the condyle in the fossa in real time during repositioning. In this study, based on an improved registration method and a separable electromagnetic tracking tool, we developed a real-time, augmented, model-guided method for MPS surgery to reposition the condyle into its original position more accurately. After virtual surgery planning, using a complex maxillomandibular model, the final position of the virtual MPS model was simulated via 3D rotations. The displacements resulting from the MPS simulation were applied to the MPS landmarks to indicate their final postoperative positions. We designed a new registration body with 24 fiducial points for registration, and determined the optimal point group on the registration body through a phantom study. The registration between the patient's CT image and physical spaces was performed preoperatively using the optimal points. We also developed a separable frame for installing the electromagnetic tracking tool on the patient's MPS. During MPS surgery, the electromagnetic tracking tool was repeatedly attached to, and separated from, the MPS using the separable frame. The MPS movement resulting from the surgeon's manipulation was tracked by the electromagnetic tracking system. The augmented condyle model and its landmarks were visualized continuously in real time with respect to the simulated model and landmarks. Our method also provides augmented 3D coronal and sagittal views of the fossa and condyle, to allow the surgeon to examine the 3D condyle-fossa positional relationship more accurately. The root mean square differences between the simulated and intraoperative MPS models, and between the simulated and postoperative CT models, were 1.71 ± 0.63 mm and 1.89 ± 0.22 mm respectively at three condylar landmarks. Thus, the surgeons could perform MPS repositioning conveniently and accurately based on real-time augmented model guidance on the 3D condyle positional relationship with respect to the glenoid fossa, using augmented and simulated models and landmarks.
在正颌手术中，将下颌近段（MPS）重新定位到尽可能接近其原始位置是至关重要的。传统方法在重新定位过程中无法实时精确定位髁突在窝中的位置。在这项研究中，我们基于改进的配准方法和可分离的电磁跟踪工具，开发了一种用于 MPS 手术的实时、增强、模型引导方法，以更准确地将髁突重新定位到其原始位置。在虚拟手术规划后，使用复杂的上下颌模型，通过 3D 旋转模拟虚拟 MPS 模型的最终位置。将 MPS 模拟产生的位移应用于 MPS 标志点，以指示其最终术后位置。我们设计了一个带有 24 个基准点的新配准体，通过体模研究确定了配准体上的最佳点组。术前使用最佳点在患者的 CT 图像和物理空间之间进行配准。我们还开发了一个可分离的框架，用于在患者的 MPS 上安装电磁跟踪工具。在 MPS 手术过程中，使用可分离框架将电磁跟踪工具反复附着和分离于 MPS。外科医生操作引起的 MPS 运动由电磁跟踪系统跟踪。通过电磁跟踪系统，连续实时地可视化增强的髁突模型及其标志点相对于模拟模型和标志点的位置。我们的方法还提供了增强的窝和髁突冠状位和矢状位的 3D 视图，使外科医生能够更准确地检查 3D 髁突-窝位置关系。三个髁突标志点处模拟和术中 MPS 模型之间以及模拟和术后 CT 模型之间的均方根差分别为 1.71±0.63mm 和 1.89±0.22mm。因此，外科医生可以根据增强和模拟模型以及标志点相对于关节窝的 3D 髁突位置关系，使用实时增强模型引导，方便、准确地进行 MPS 复位。
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