Augmented reality systems can combine virtual images with a real environment to ensure accurate surgery with lower risk. This study aimed to develop a novel registration and tracking technique to establish a navigation system based on augmented reality for maxillofacial surgery. Specifically, a virtual image is reconstructed from CT data using 3D software. The real environment is tracked by the augmented reality (AR) software. The novel registration strategy that we created uses an occlusal splint compounded with a fiducial marker (OSM) to establish a relationship between the virtual image and the real object. After the fiducial marker is recognized, the virtual image is superimposed onto the real environment, forming the “integrated image” on semi-transparent glass. Via the registration process, the integral image, which combines the virtual image with the real scene, is successfully presented on the semi-transparent helmet. The position error of this navigation system is 0.96 ± 0.51 mm. This augmented reality system was applied in the clinic and good surgical outcomes were obtained. The augmented reality system that we established for maxillofacial surgery has the advantages of easy manipulation and high accuracy, which can improve surgical outcomes. Thus, this system exhibits significant potential in clinical applications.

Augmented reality-based NS can provide precise navigation information by directly displaying a 3-dimensional individual anatomical virtual model onto the operative field in real time. It will allow rapid identification and safe dissection of a perforator in free flap transplantation surgery.

The authors have developed a novel augmented reality (AR)-based navigation system (NS) for craniofacial surgery. In this study, the authors aimed to measure the precision of the system and further analyze the primary influencing factors of the precision. The drilling of holes into the mandibles of ten beagle dogs was performed under the AR-based NS, and the precision was analyzed by comparing the deviation between the preoperational plan and the surgical outcome. The AR-based NS was successfully applied to quickly and precisely drill holes in the mandibles. The mean positional deviation between the preoperative design and intraoperative navigation was 1.29 ± 0.70 mm for the entry points and 2.47 ± 0.66 mm for the end points, and the angular deviation was 1.32° ± 1.17°. The precision linearly decreased with the distance from the marker. In conclusion, the precision of this system could satisfy clinical requirements, and this system may serve as a helpful tool for improving the precision in craniofacial surgery.

Background Vascular localization is crucial for perforator flap transfer. Augmented reality offers a novel method to seamlessly combine real information with virtual objects created by computed tomographic angiography to help the surgeon “see through” the skin and precisely localize the perforator. The head-mounted display augmented reality system HoloLens (Microsoft) could facilitate augmented reality–based perforator localization for a more convenient and safe procedure. Objective The aim of this study was to evaluate the precision of the HoloLens-based vascular localization system, as the most important performance indicator of a new localization system. Methods The precision of the HoloLens-based vascular localization system was tested in a simulated operating room under different conditions with a three-dimensional (3D) printed model. The coordinates of five pairs of points on the vascular map that could be easily identified on the 3D printed model and virtual model were detected by a probe, and the distance between the corresponding points was calculated as the navigation error. Results The mean errors were determined under different conditions, with a minimum error of 1.35 mm (SD 0.43) and maximum error of 3.18 mm (SD 1.32), which were within the clinically acceptable range. There were no significant differences in the errors obtained under different visual angles, different light intensities, or different states (static or motion). However, the error was larger when tested with light compared with that tested without light. Conclusions This precision evaluation demonstrated that the HoloLens system can precisely localize the perforator and potentially help the surgeon accomplish the operation. The authors recommend using HoloLens-based surgical navigation without light.

Objective: To summarize and analyze the postoperative complications of box-shift osteotomy performed at our center for Chinese orbital hypertelorism patients from 2008 to 2017. Method: This retrospective study reviews the records of 78 patients with complete medical records and at least 2 years of postoperative follow-up data. Both radiologic and anthropometric assessments were conducted before, 1 month after and 2 years after surgery to evaluate the bony and soft-tissue alterations. Postoperative complications were recorded during hospitalization and at each follow-up visit and divided into 3 groups: acute complications that occurred within 1 month after surgery; early complications that occurred within 6 months after surgery; and long-term complications that occurred within 2 years after surgery. Results: Both bony and soft-tissue alterations were significant at 1 month after surgery. The acute complications that occurred in our center included infection (12.8%), cerebrospinal fluid leakage (29.5%), epilepsy (2.6%), and nasal tip skin necrosis (1.3%). The early complications included strabismus (11.5%) and nasolacrimal duct obstruction (3.8%). The long-term complications included insufficient correction (55.1%), palpable metal implants (92.3%) and a drooping nasal tip (33.9%). Due to the insufficient correction and the continued growth of rib graft, the difference in the hypertelorism index and nasal length, between one month and 2 years postoperatively were statistically significant (P < 0.01). Other radiographic and anthropometric measurements changed with growth without a significance difference between 1 month and 2 years after surgery. Conclusion: In this study, we recorded all postoperative complications of box-shift osteotomy. The challenge of our future work is to identify methods for decreasing the incidence of these complications.

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HoloLens-based mixed-reality surgical navigation system (MR-SNS) technology has made great progress. However, the methodology for evaluating users’ perceptions concerning the safety, comfort, and efficiency of MR-SNS is still in its infancy. This study was intended to develop a method to systematically evaluate an existing MR-SNS system during actual clinical applications. This method differs from other existing methods currently used in industry, education, and device maintenance. Based on analytical hierarchy process theory and ergonomics evaluation methods, in this article, we propose a novel multicriteria evaluation model for a HoloLens-based MR-SNS. The model includes factors such as comfort, safety, and effectiveness, and is performed in an actual clinical application. A comprehensive experimental platform and scoring system that can analyze all indicators was built. The validation test showed no statistically significant differences in the accuracy of the 3 different movement patterns ( P = .95, P > .05). However, the static pattern showed the best accuracy. In addition, no significant difference ( P = .68, P > .05) in accuracy was found under 4 kinds of illuminance. A comparison of the results of this evaluation model and the input from experts who use the HoloLens-based MR-SNS in hospitals, indicated that this model has good precision (100%), recall (80%), and F1-measure (88.89%). The results highlighted the full efficacy of the proposed model in determining whether this system can be used in clinical trials to provide indicators for preliminary ex ante feasibility studies. This article describes the lessons learned from conducting this evaluation study of MR-SNS as part of the design process.

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