Accuracy of Maxillary Repositioning by Using Surgical Navigation System

Abstract

　The results of virtual surgery performed using simulation software based on acquired CBCT image data were transferred to actual two-jaw surgery using a navigation system to treat seven patients with deformities. Osteotomy was applied and the accuracy of navigation surgery was investigated.
　Patients with congenital anomalies such as cleft lip and palate were excluded. An impression of the dentition was prepared for each of the patients about 14 days before surgery and a splint was prepared. Another splint with reference points for navigation registration was prepared by adding references to the first splint using contrast-enhancing resin. The patients were fitted with the splint and CBCT images of centric occlusion were acquired. Simulation proceeded using preoperative CBCT image data, and then the osteotomy line, as well as the direction and distance of bone segment movement, were set. Standard registration was achieved using the splint with the reference points to match the three-dimensional CT image with positional information about the patient. Surgery then proceeded following the standard method. The position of the osteotomy line and the direction of maxillary movement were confirmed while also confirming the three-dimensional position using a navigation pointer. The mandible was moved according to the maxillary position. We investigated errors of maxillary position between the position set on the simulation and that after movement in actual surgery as follows. The preoperative simulation image and postoperative three-dimensional CT image were superimposed, and anteroposterior, vertical, and horizontal errors were measured at five points. When the maxilla had moved forward, the error between the maxillary positions on simulation and after actual surgery was within 2mm at most measurement points, and highly accurate, but the errors were relatively large when facial asymmetry required movement in three dimensions.
　Therefore, to clarify the usefulness of orthognathic surgery through a linkage between simulation and navigation, close analysis involving many cases might be necessary to establish a method of addressing three-dimensional movement of the maxilla.