Orthognathic treatment of asymmetry: two cases of “waferless” stereotactic maxillary positioning

Accurate transfer of bimaxillary orthognathic surgical plans using computer-aided intraoperative navigation

Objective

To examine the accuracy of computer-aided intraoperative navigation (Ci-Navi) in bimaxillary orthognathic surgery by comparing preoperative planning and postoperative outcome.

Methods

The study comprised 45 patients with congenital dentomaxillofacial deformities who were scheduled to undergo bimaxillary orthognathic surgery. Virtual bimaxillary orthognathic surgery was simulated using Mimics software. Intraoperatively, a Le Fort I osteotomy of the maxilla was performed using osteotomy guide plates. After the Le Fort I osteotomy and bilateral sagittal split ramus osteotomy of the mandible, the mobilized maxilla and the distal mandibular segment were fixed using an occlusal splint, forming the maxillomandibular complex (MMC). Realtime Ci-Navi was used to lead the MMC in the designated direction. Osteoplasty of the inferior border of the mandible was performed using Ci-Navi when facial symmetry and skeletal harmony were of concern. Linear and angular distinctions between preoperative planning and postoperative outcomes were calculated.

Results

The mean linear difference was 0.79 mm (maxilla: 0.62 mm, mandible: 0.88 mm) and the overall mean angular difference was 1.20°. The observed difference in the upper incisor point to the Frankfort horizontal plane, midfacial sagittal plane, and coronal plane was < 1 mm in 40 cases.

Conclusions

This study demonstrates the role of Ci-Navi in the accurate positioning of bone segments during bimaxillary orthognathic surgery. Ci-Navi was found to be a reliable method for the accurate transfer of the surgical plan during an operation.

Randomized Controlled Clinical Trial to Assess the Utility of Computer-Aided Intraoperative Navigation in Bimaxillary Orthognathic Surgery

ABSTRACT

Accurate application of the preoperative surgical plan in actual surgical settings is of paramount importance in orthognathic surgery. This randomized controlled clinical trial aimed to evaluate the accuracy of computer-aided intraoperative navigation (Ci-Navi) compared with that of conventional navigation methods in bimaxillary orthognathic surgery. Fifty-two patients were randomly divided into 2 groups. Group A (n = 26) patients underwent surgery assisted with Ci-Navi and group B (n = 26) patients underwent surgery assisted with conventional intraoperative navigation methods. During the operation, after LeFort I osteotomy, the mobile maxilla was repositioned to the designated position either using assistance from real-time Ci-Navi (group A) or using an intermediate splint (group B). Intra- and intergroup linear and angular differences between preoperative planning and postoperative outcomes were calculated. In group A, the overall mean linear difference was 0.79 mm (0.62 mm for the maxilla and 0.88 mm for the mandible) and the overall mean angular difference was 1.20°. In 23 cases, the difference from the upper incisor point to the Frankfort horizontal plane, midfacial sagittal plane, and coronal plane was less than 1 mm. In group B, the overall mean linear difference was 1.98 mm (1.76 mm for the maxilla and 2.02 mm for the mandible) and the overall mean angular difference was 2.08°. The difference from the upper incisor point to the Frankfort horizontal plane, midfacial sagittal plane, and coronal plane was less than 1 mm in 15 cases. This study demonstrates the utility of Ci-Navi is superior to the conventional methods in aiding the accurate repositioning of bony segments in bimaxillary orthognathic surgery.

Design, development and clinical validation of computer-aided surgical simulation system for streamlined orthognathic surgical planning

PURPOSE

There are many proven problems associated with traditional surgical planning methods for orthognathic surgery. To address these problems, we developed a computer-aided surgical simulation (CASS) system, the AnatomicAligner, to plan orthognathic surgery following our streamlined clinical protocol.

METHODS

The system includes six modules: image segmentation and three-dimensional (3D) reconstruction, registration and reorientation of models to neutral head posture, 3D cephalometric analysis, virtual osteotomy, surgical simulation, and surgical splint generation. The accuracy of the system was validated in a stepwise fashion: first to evaluate the accuracy of AnatomicAligner using 30 sets of patient data, then to evaluate the fitting of splints generated by AnatomicAligner using 10 sets of patient data. The industrial gold standard system, Mimics, was used as the reference.

RESULT

When comparing the results of segmentation, virtual osteotomy and transformation achieved with AnatomicAligner to the ones achieved with Mimics, the absolute deviation between the two systems was clinically insignificant. The average surface deviation between the two models after 3D model reconstruction in AnatomicAligner and Mimics was 0.3 mm with a standard deviation (SD) of 0.03 mm. All the average surface deviations between the two models after virtual osteotomy and transformations were smaller than 0.01 mm with a SD of 0.01 mm. In addition, the fitting of splints generated by AnatomicAligner was at least as good as the ones generated by Mimics.

CONCLUSION

We successfully developed a CASS system, the AnatomicAligner, for planning orthognathic surgery following the streamlined planning protocol. The system has been proven accurate. AnatomicAligner will soon be available freely to the boarder clinical and research communities.

Combined use of rapid-prototyping model and surgical guide in correction of mandibular asymmetry malformation patients with normal occlusal relationship

OBJECTIVE

The aim of this study is to discuss the application of rapid-prototyping model and surgical guide in the treatment of mandibular asymmetry malformation with normal occlusal relationship.

STUDY DESIGN

Twenty-four mandibular asymmetry malformation patients with relatively normal occlusal relationship were included in this study. Surgical 3-dimensional rapid-prototyping mandibular models were made for all patients from the computed tomography (CT) DICOM data. The presurgical plan was designed on the model, and the surgical guiders for the osteotomy lines were manufactured. Genioplasty and/or mandibular osteotomy based on the presurgical plan were performed on these patients with the combined use of the rapid-prototyping model and surgical guides. All patients underwent postoperative CT scan and had at least 3-month follow-up.

RESULT

All patients were satisfied with the final results. According to the postoperative CT images and 3-month follow-up, all patients' mandibular asymmetry malformation was significantly improved, and the operation time was distinctly shortened relative to the conventional method.

CONCLUSION

Rapid-prototyping model and surgical guide are viable auxiliary devices for the treatment of mandibular asymmetry malformation with relatively normal occlusal relationship. Combined use of them can make precise preoperative design, improve effects of operation, and shorten operating time.

Keyhole System: A Computer-Assisted Designed and Computer-Assisted Manufactured Maxillomandibular Complex Repositioner in Orthognathic Surgery

Currently, virtual orthognathic surgery using the CAD/CAM program and three-dimensional printing technology has provided a valuable tool supporting accurate surgical planning and precise surgery. However, despite the advancements in CAD/CAM virtual surgical planning, accurately reproducing surgical planning from a virtual surgery to the operating field is still challenging. Here, we report the Keyhole system as a method that has constantly provided us with consistent results during double-jaw surgery, especially during this age of ever increasing aesthetic demand from patients.

Review of orthognathic surgery and related papers published in the British Journal of Oral and Maxillofacial Surgery 2011-2012

This review summarises all orthognathic and related papers published between January 2011 and December 2012 in the British Journal of Oral and Maxillofacial Surgery (BJOMS). A total of 36 articles were published, a high proportion of which (78%) were full-length papers. The remainder consisted of short communications and technical notes. The topics included operative planning and postoperative outcomes, and there was a strong focus on distraction osteogenesis. There were fewer orthognathic articles published in BJOMS than articles on other subspecialties such as trauma or head and neck oncology. Only 8 (29%) of the full-length articles were prospective studies or randomised trials, which highlights a need for well-designed clinical studies in orthognathic research.