[INITIAL APPLICATION OF COMPUTER ASSISTED NAVIGATION SYSTEM IN RECONSTRUCTION OF MANDIBULAR DEFECTS].

OBJECTIVE: To evaluate the value of computer assisted navigation system (CANS) in the reconstruction of mandibular defects. METHODS: Between April 2012 and September 2014, 8 patients with mandibular defects were included in this study. There were 5 males and 3 females with an age range of 22-50 years (mean, 34.5 years), including 4 cases of ameloblastoma, 3 cases of odontogenic keratocyst, and 1 case of condylar osteoma. According to the CRABS (condyle, ramus, angle, body, symphysis) classification criteria based on the location of mandibular defect, there were 1 case of right CRAB type, 1 case of left RABS type, 1 case of left CR type, 1 case of right RAB type, 1 case of left C type, 1 case of right RABS+left S type, and 2 cases of right AB type. With the biteplate fixing mandible, maxillofacial CT and the donor site CT scan were done. Computer assisted design was made by using Surgicase CMF5.0 software and BrainLab Iplan software, included delineating the osteotomy lines for resection, ascertaining the normal anatomic structures for defect reconstruction, and determining the reconstructive morphology. With guide plates and the guidance of BrainLab navigation system, an en bloc tumor resection and simultaneous defect reconstruction were performed under the precise localization of mandibular angle and condyle. Preoperative and postoperative CT images were superimposed in Geomagic studio12.0 software system, and both were compared by three-dimensional (3D) objects and 2D slices. The complications and signs of recurrence were observed. RESULTS: Under the guidance of navigation, preoperative facial symmetry design, surgery simulation, and simultaneous navigation operation were performed successfully. The postoperative CT and postoperative 3D error analysis showed osteotomy lines and reconstruction contour had good matching with the preoperative planning. The error of important corresponding points (mandibular angle and external pole of condyle) in the reconstruction of mandibular defects were (1.83 +/- 0.19) mm and (1.61 +/- 0.24) mm. The patients were followed up 2-6 months (mean, 3.5 months). No complication was observed in the other patients except the patients undergoing rib transplantation who had mild limitation of mouth opening. Good facial symmetry was obtained, and no tumor recurrence was found. CONCLUSION: CANS can effectively increase the surgical precision in the reconstruction of mandibular defects and reduce complications, and recover facial symmetry. It is regarded as a valuable technique in this potentially complicated procedure.