Robot-assisted mandibular angle osteotomy using electromagnetic navigation.

BACKGROUND: To explore the potential of electromagnetic (EM) navigation technology in the field of robot-assisted surgery, we set up a maxillofacial surgical robotic system (MSRS) guided by an EM navigation tool. Mandibular angle osteotomy was used to analyze the feasibility in confined surgical areas. METHODS: Model and animal experiments were implemented to validate the system precision. Before the experiment, a customized dental splint was made and then fixed with a standard navigation part. An accurate 3D surgical plan was designed based on the preoperative CT scan. During the experiment, the splint was rigidly mounted on teeth for navigation registration, so the robot could position a specially designed template to guide the accurate osteotomy according to the preoperative plan. For the model experiment, a Coordinate Measuring Machine was used to measure the template's position and angle. For the animal experiment, surgeons completed the surgery by moving a saw along the template, while a postoperative CT scan was carried out to calculate the precision. RESULTS: All procedures were successfully completed, with no complications in any of the experimental animals. In the model experiment, the accuracy of the navigation position and angle was 0.44±0.19 mm and 3.5°±2.1°, respectively. In the animal experiment, the lateral osteotomy line error was 0.83±0.62 mm, the interior error was 1.06±1.03 mm, and the angle between the actual cutting plane and preoperative planning plane was 5.9°±4.7°. CONCLUSIONS: Robot-assisted surgery with EM navigation resulted feasible in the real operating environment. Moreover, this system's precision could meet clinical needs, while the proposed procedure was safe and easy on animals. Consequently, this approach has the potential to be applied to clinical craniomaxillofacial practice in the near future.

Early hemi-mandibular lengthening by distraction osteogenesis contributes to compensatory maxillary growth.

Mandibular distraction osteogenesis at an early age is the standard hemifacial microsomia treatment. Nevertheless, the recurrence rate remains high and the definition of early age is controversial. We explored the optimal timing for mandibular distraction, when the surrounding skeleton, such as maxilla, can grow compensatory, to reduce recurrence. Hemifacial microsomia patients were prospectively divided into Groups A (1-3 years old) and B (4-6 years old), according to maxillary and mandibular growth curves. Computed tomography scans were obtained before distractor implantation and after removal surgery. Maxillary volume increase percentage was the main outcome indicator; other indicators (maxillary symmetry and complications) were secondary outcomes. Fifty-eight patients were enrolled and all but one patient in Group A (failed distraction) completed the study. Two patients had facial nerve injury and another two had mouth-opening limitation, which was relieved after coracoid resection. The difference in percentage increase in maxillary volume between the affected and unaffected sides was 5.06 ± 2.73% and 3.18 ± 1.99% in Groups A and B, respectively, suggesting better compensatory growth in younger patients (P = 0.004). Maxillary symmetry was apparently elevated after mandibular distraction. Mandibular distraction osteogenesis was confirmed to be feasible and safe at age <4 years.

Computer-assisted surgery in therapeutic strategy distraction osteogenesis of hemifacial microsomia: Accuracy and predictability.

BACKGROUND: Distraction osteogenesis can be used to treat hemifacial microsomia in patients of any age group. Application of three-dimensional (3D) technology in the surgical planning of distraction osteogenesis allows the placement of an intraoral distractor to define the cutting line and help predict the outcome of surgery. AIM: This study compared the results of distraction osteogenesis performed, using computer-assisted surgery, on OMENS-plus-classified M2A, M2B, and M3 type patients. Comparisons were in terms of either accuracy or predictability. METHODS: 40 patients were selected to participate in the 8-month study. Preoperative image data from 3D-CT scans of the 40 patients were translated into DICOM format 3D cephalometrics, run using the computer software MIMICS version 18, and based on eight reference anatomical landmark points, five lines of measurement, and the midline of the mandibular plane. The distraction vector for the affected side of mandible was selected and the elongation process simulated repeatedly until satisfactory results were obtained. The surgical guide was created using CAD/CAM-RP technology. The distraction osteogenesis procedure was then performed using the surgical guides. Follow-up for all patients continued until 8 months postoperatively. Accuracy with and without computer-assisted surgery was assessed linearly and volumetrically. Simple mean comparisons and paired t-tests were conducted using IBM SPSS V21. RESULTS: In those patients who received computer-assisted surgery, distraction in the M2A type mandible showed accuracy of around 97.77% ± 7.92% (p > 0.05) for height and 97.91% ± 10.23% (p > 0.05) for length of the mandible. Meanwhile, the M2B type mandible presented accuracy of around 93.85% ± 8.07% (p > 0.05) for height and 95.85% ± 10.16% (p > 0.05) for length. For the M3 type mandible accuracy was around 98.42% ± 6.58% (p > 0.05) for height and 97.14% ± 11.45% (p > 0.05) for length. These measurements showed no significant differences between preoperative design and real outcome. CONCLUSIONS: Individualized guides improve the accuracy of distraction osteogenesis. They help the surgeon to identify the mandibular defect and ensure the desired outcome after the operation.