Application of computer-aided navigation in combined bimaxillary orthognathic surgery and mandibular contouring osteoplasty for craniofacial deformities

Mandibular asymmetry often persists after bimaxillary orthognathic surgery combined with mandibular contouring osteoplasty (MCO). This study aimed to evaluate the accuracy of computer-aided navigation (CAN) in transferring virtual surgical plans during combined bimaxillary orthognathic surgery and mandibular contouring osteoplasty (MCO), and to assess the postoperative mandibular symmetry achieved through this navigation-guided protocol. A prospective single-arm cohort study was conducted on 30 adult patients (13 males, 17 females; mean age 24.2 years) who underwent bimaxillary orthognathic surgery (Le Fort I osteotomy and bilateral sagittal split ramus osteotomy) followed by navigated MCO. Preoperative virtual surgical planning was performed using Mimics software. Intraoperatively, the maxillomandibular complex was repositioned under real-time CAN guidance (AccuNav-A system), and MCO was performed using a custom-designed percutaneous navigation probe. Mandibular symmetry was assessed pre- and postoperatively by measuring linear distances from bilateral reference points on the inferior mandibular border, as well as from maxillary and mandibular dental landmarks, to the Frankfort horizontal plane (FHP), mid-sagittal plane (MSP), and coronal plane (CP). The overall mean linear discrepancy between the virtual plan and the 12-month postoperative outcome was 1.92 mm, with angular deviations of 1.27° for the occlusal plane and 1.42° for the mandibular plane. For dental landmarks, maxillary points showed smaller deviations (mean 0.76 mm) than mandibular points (mean 0.98 mm), and deviations were smallest in the MSP (0.68 mm) and largest in the CP (1.03 mm). The 95% confidence intervals of the mean discrepancies included zero for all landmark–plane combinations, and no statistically significant systematic deviation was detected (all P > 0.05). The magnitude of the observed discrepancies, rather than the non-significant P -values, provides the basis for judging accuracy. In this single-arm cohort, accurate transfer of the virtual surgical plan was achieved under a CAN-guided protocol in bimaxillary orthognathic surgery combined with MCO, with an overall mean linear discrepancy below the 2-mm reference threshold. However, this threshold was not met uniformly across all landmarks: upper 95% confidence limits remained below 2 mm for maxillary dental landmarks, whereas several mandibular skeletal landmarks showed mean discrepancies exceeding 2 mm. Maxillary positioning was more accurate than mandibular positioning, and deviations increased progressively along the craniofacial axis. These findings support the feasibility of precise, controlled execution of this complex combined procedure under a navigation-guided protocol; however, the absence of a control group means that superiority over conventional techniques cannot be established.