Predictability and Accuracy between 3D Virtual Surgical Planning and Actual Outcomes in Orthognathic Surgery

Abstract

Introduction: We are living a paradigm shift in orthognathic surgery. Several tools and technological advances are being implemented to help improve surgical experience and to offer better functional and aesthetical results. Virtual surgical planning is a revolutionary tool which helps us design the surgical plan preoperatively and establish a surgical protocol specifically designed for that patient. In this study, our goal is to validate the predictability of virtual surgical planning in orthognathic surgery, comparing the final results with the virtual plan. Material and methods: We performed an ICP based super imposition of 3D models of the virtual planning preoperatively designed and the 3D model of the postoperative CBCT using free software (Slicer) in patients who underwent bimaxillary orthognathic surgery. The results of the super imposition were saved on the postoperative model and presented as a color-coded map. This was generated as a .vtk file that was exported to another free software that displayed the difference in mm in relevant cephalometric points (point A, point B, pogonion, left and right gonion and first upper molars) in the three axis (x, y and z) between the postoperative result and the virtual plan. Then, we registered these results for all patients and analysed these data. Results: A total of 41 patients were included. The median of the differences in mm between virtual planning and postoperative results were less than 1mm for all cephalometric points, except for both gonion, where greater than 1mm differences were found in the mediolateral (horizontal) direction. For the rest of landmarks, the highest differences were found at A point and pogonion in the anteroposterior direction (0,83mm and 0,78mm, respectively). Conclusions: We found overall small and tolerable differences (<1mm) between the planned movements and the postoperative results. The highest were found at the gonion in the mediolateral direction and mandibular rami, which could be explained by the torque of the proximal segment. The differences in A point and pogonion in the anteroposterior direction were the highest among the rest, which may be related to inaccuracy of the splint in this direction.