Intraoperative Image-Guided Navigation in Craniofacial Surgery: Review and Grading of the Current Literature

Augmented Reality Navigation in Craniomaxillofacial/Head and Neck Surgery

Objective

This study aims to (1) develop an augmented reality (AR) navigation platform for craniomaxillofacial (CMF) and head and neck surgery; (2) apply it to a range of surgical cases; and (3) evaluate the advantages, disadvantages, and clinical opportunities for AR navigation.

Study Design

A multi-center retrospective case series.

Setting

Four tertiary care academic centers.

Methods

A novel AR navigation platform was collaboratively developed with Xironetic and deployed intraoperatively using only a head-mounted display (Microsoft HoloLens 2). Virtual surgical plans were generated from computed tomography/magnetic resonance imaging data and uploaded onto the AR platform. A reference array was mounted to the patient, and the virtual plan was registered to the patient intraoperatively. A retrospective review of all AR-navigated CMF cases since September 2023 was performed.

Results

Thirty-three cases were reviewed and classified as either trauma, orthognathic, tumor, or craniofacial. The AR platform had several advantages over traditional navigation including real-time 3D visualization of the surgical plan, identification of critical structures, and real-time tracking. Furthermore, this case series presents the first-known examples of (1) AR instrument tracking for midface osteotomies, (2) AR tracking of the zygomaticomaxillary complex during fracture reduction, (3) mandibular tracking in orthognathic surgery, (4) AR fibula cutting guides for mandibular reconstruction, and (5) integration of real-time infrared visualization in an AR headset for vasculature identification.

Conclusion

While still a developing technology, AR navigation provides several advantages over traditional navigation for CMF and head and neck surgery, including heads up, interactive 3D visualization of the surgical plan, identification of critical anatomy, and real-time tracking.

Navigation-guided orbital medial wall fracture reconstruction

BACKGROUND

Orbital medial wall fractures, which are more common than inferior wall fractures, have traditionally been difficult to diagnose with conventional radiography. As the fracture extends deep into the bony orbit, accurately visualizing internal structures becomes challenging, increasing the risk of optic nerve compression. In a previous study, the author introduced a technique for treating medial orbital wall fractures using a combined transethmoidal and transcaruncular approach. In this study, the authors hypothesized that the use of surgical navigation could enhance precision, safety, and anatomical reconstruction in this approach and employed navigation during surgery for medial orbital wall fractures and evaluated whether it improved postoperative functional and anatomical outcomes while minimizing complications.

METHODS

From September 2021 to November 2023, 48 patients with isolated medial wall fractures underwent surgical treatment using a combined transcaruncular approach and transethmoidal packing to repair the orbital fracture. Of these patients, 23 underwent surgery with the use of intraoperative navigation, while the other 25 did not. Intraoperative navigation was employed to facilitate precise fracture reduction and reduce the risk of optic nerve injury. The outcomes were compared by dividing the patients into two groups. Preoperative and postoperative assessments included ophthalmologic evaluations, Hertel exophthalmometry, and computed tomography-based orbital volume measurements.

RESULTS

The surgical approach with intraoperative navigation was successfully performed in all patients. Postoperative outcomes showed full recovery without residual symptoms or complications. Orbital volume measurements indicated a significant reduction in the preoperative orbital volume ratio from 109.03% to 104.80% postoperatively (p< 0.001). However, changes in the Hertel scale were not statistically significant (p = 0.086).

CONCLUSION

The integration of intraoperative navigation in medial orbital wall fracture surgery enhances the precision of medial orbital wall restoration and minimizes postoperative complications, supporting its use in the surgical management of medial orbital fractures.

Reduction of giant parietooccipital fibrous dysplasia using dynamic mirror image guidance: a case report and review of the literature

BACKGROUND

Craniofacial fibrous dysplasia (CFD) typically occurs in the facial bones and anterior cranial vault and can produce both disfigurement and functional limitations for patients disfigurement. Treatment consists of reducing the abnormal bone. Bone contouring can become challenging when the exposure does not extend to the corresponding normal contralateral structures for comparison or when normal landmarks are not available, which may compromise the overall aesthetic outcome. We describe a technique using dynamic mirroring to accurately contour the involved part of the cranium in a case of giant CFD.

OBSERVATIONS

A 49-year-old male presented with a giant deforming fibrous dysplasia of the right mastoid and parieto-temporo-occiput that was causing functional limitations due to the size of the bony mass. This was managed with multidisciplinary bony reduction. Several neurovascular structures were in proximity to the areas of planned drilling of the expansile lesion, and dynamic mirroring of the uninvolved left skull was utilized to maximize safety and symmetry of reduction. High-speed drilling of the right occipital bone was performed until the navigation system alerted the surgeon that symmetric depth had been achieved. There were no complications from the procedure and this technique maximized the limits of symmetric reduction without significantly increasing surgical complexity or duration.

LESSONS

Dynamic mirroring of bony structures in the posterior cranium is not commonly employed in neurosurgical practice. This technique may help improve the aesthetic outcomes of bony reduction in craniofacial dysplasia and a variety of similarly managed bony lesions, contour cranioplasties, and in unilateral craniosynostosis surgery.

Intraoperative navigation in craniofacial surgery

Craniofacial surgery requires comprehensive anatomical knowledge of the head and neck to ensure patient safety and surgical precision. Over recent decades, there have been significant advancements in imaging techniques and the development of real-time surgical navigation systems. Intraoperative navigation technology aligns surgical instruments with imaging-derived information on patient anatomy, enabling surgeons to closely follow preoperative plans. This system functions as a radiologic map, improving the accuracy of instrument placement and minimizing surgical complications. The introduction of first-generation navigation systems in the early 1990s revolutionized surgical procedures by enabling real-time tracking of instruments using preoperative imaging. Initially utilized in neurosurgery, intraoperative navigation has since become standard practice in otolaryngology, cranio-maxillofacial surgery, and orthopedics. Since the 2000s, second-generation navigation systems have been developed to meet the growing demand for precision across various surgical specialties. The adoption of these systems in craniofacial surgery has been slower, but their use is increasing, particularly in procedures such as foreign body removal, facial bone fracture reconstruction, tumor resection, and craniofacial reconstruction and implantation. In Korea, insurance coverage for navigation in craniofacial surgery began in 2021, and new medical technologies for orbital wall fracture treatment were approved in August 2022. These technologies have only recently become clinically available, but are expected to play an increasingly important role in craniofacial surgery. Intraoperative navigation enhances operative insight, improves target localization, and increases surgical safety. Although these systems have a steep learning curve and initially prolong surgery, efficiency improves with experience. Calibration issues, registration errors, and soft tissue deformation can introduce inaccuracies. Nonetheless, navigation technology is evolving, and the integration of intraoperative computed tomography data holds promise for further enhancements of surgical accuracy. This paper discusses the various types and applications of navigation employed in craniofacial surgery, highlighting their benefits and limitations.

Customized orbital implant versus 3D preformed titanium mesh for orbital fracture repair: A retrospective comparative analysis of orbital reconstruction accuracy

This study aimed to compare the accuracy of inferomedial orbital fracture restoration using customized orbital implant versus 3D preformed titanium mesh. Patients were divided into two groups. Group 1 underwent surgery with customized orbital implants and intraoperative navigation, while group 2 was treated using 3D preformed titanium meshes with preoperative virtual surgical planning (VSP) and intraoperative navigation. Reconstruction accuracy was assessed by: (1) comparing the postoperative reconstruction mesh position with the preoperative VSP; and (2) measuring the difference between the reconstructed and unaffected orbital volume. Pre- and postoperative diplopia and enophthalmos were also evaluated. Fifty-two patients were enrolled (25 in group 1 vs 27 in group 2). The mean difference between final plate position and ideal digital plan was 0.62 mm (SD = 0.235) in group 1 and 0.69 mm (SD = 0.246) in group 2, with no statistical difference between the groups (p = 0.282). The mean volume differences between the reconstructed and unaffected orbits were 0.95 ml and 1.02 ml in group 1 and group 2, respectively, with no significant difference between the groups (p = 0.860). Overall clinical improvements, as well as complications, were similar. 3D preformed titanium meshes can reconstruct inferomedial fractures with the same accuracy as customized implants. Therefore, in clinical practice, it is recommended to use 3D preformed meshes for this type of fracture due to their excellent results and the potential for reducing time and costs.

Mixed Reality Combined with Surgical Navigation in Resection of Micro- and Mini-Tumors of the Parotid Gland: A Pilot Study

OBJECTIVE

This study aimed to evaluate the feasibility and outcomes of mixed reality combined with surgical navigation (MRSN) in the resection of parotid micro- and mini-tumors.

METHODS

Eighteen patients who underwent parotid tumor resection between December 2020 and November 2022 were included. Six patients were enrolled in MRSN group, and the surgeons performed the surgery with the help of MRSN technology. The surgical procedures include virtual planning, data transfer between mixed reality and surgical navigation, tumor localization and resection assisted by surgical navigation under mixed reality environment. Twelve patients were enrolled in control group, and intraoperative tumor localization and resection were performed according to the experience of the surgeon. Total surgery time and intraoperative bleeding were recorded. Perioperative complications were recorded during follow-up.

RESULTS

The mean surgery time of MRSN group (76.7 ± 14.0 min) and control group (65.4 ± 21.3 min) showed no significant difference (p = 0.220), so did the intraoperative bleeding of MRSN group (16.0 ± 8.0 mL) and control group (16.7 ± 6.6 mL) (p = 0.825). None of the patient in MRSN group underwent any complication, although one patient in control group suffered temporary facial paralysis. The mean deviation between the virtually marked and the intraoperative actual outermost point of tumor was 3.03 ± 0.83 mm.

CONCLUSION

MRSN technology can realize real-time three-dimensional visualization of the tumor, and it has the potential of enhancing the safety and accuracy of resection of micro- and mini-tumors of parotid gland.

LEVEL OF EVIDENCE

4 Laryngoscope, 134:1670-1678, 2024.

Deep Learning: A Primer for Neurosurgeons

This chapter explores the transformative impact of deep learning (DL) on neurosurgery, elucidating its pivotal role in enhancing diagnostic performance, surgical planning, execution, and postoperative assessment. It delves into various deep learning architectures, including convolutional and recurrent neural networks, and their applications in analyzing neuroimaging data for brain tumors, spinal cord injuries, and other neurological conditions. The integration of DL in neurosurgical robotics and the potential for fully autonomous surgical procedures are discussed, highlighting advancements in surgical precision and patient outcomes. The chapter also examines the challenges of data privacy, quality, and interpretability that accompany the implementation of DL in neurosurgery. The potential for DL to revolutionize neurosurgical practices through improved diagnostics, patient-specific surgical planning, and the advent of intelligent surgical robots is underscored, promising a future where technology and healthcare converge to offer unprecedented solutions in neurosurgery.

Modern Image-Guided Surgery: A Narrative Review of Medical Image Processing and Visualization

Medical image analysis forms the basis of image-guided surgery (IGS) and many of its fundamental tasks. Driven by the growing number of medical imaging modalities, the research community of medical imaging has developed methods and achieved functionality breakthroughs. However, with the overwhelming pool of information in the literature, it has become increasingly challenging for researchers to extract context-relevant information for specific applications, especially when many widely used methods exist in a variety of versions optimized for their respective application domains. By being further equipped with sophisticated three-dimensional (3D) medical image visualization and digital reality technology, medical experts could enhance their performance capabilities in IGS by multiple folds. The goal of this narrative review is to organize the key components of IGS in the aspects of medical image processing and visualization with a new perspective and insights. The literature search was conducted using mainstream academic search engines with a combination of keywords relevant to the field up until mid-2022. This survey systemically summarizes the basic, mainstream, and state-of-the-art medical image processing methods as well as how visualization technology like augmented/mixed/virtual reality (AR/MR/VR) are enhancing performance in IGS. Further, we hope that this survey will shed some light on the future of IGS in the face of challenges and opportunities for the research directions of medical image processing and visualization.

Orbital Fractures: A New CT-Based Protocol to Guide the Surgical Approach and Reconstruction Material Decision-Making

Preoperative computer-assisted planning and intraoperative navigation are becoming popular for orbital fracture treatment. However, not all institutions currently have access to these computer-aided applications. The authors present a simple and intuitive operative algorithm to guide orbital fracture reconstructions. The operative algorithm was based on linear measurements of orbital defects on high-resolution Computer tomography (CT) scans using specific axial, coronal, and sagittal plane images. The fractures were then divided into 3 types based on site and defect-size area. For each type, the authors suggested a surgical approach and material reconstruction. Between February 2022 and January 2023, 57 patients were treated according to the described CT-based protocol. The quality of reconstruction was classified as ideal, satisfactory, acceptable, and poor based on postoperative CT. Diplopia, enophthalmos, and postoperative complications were assessed. Fifty-seven patients were included. Forty-four (77.2%) patients were included in the type 1 group, 4 (7.01%) in the type 2 group, and 9 (15.79%) in the type 3 group. The reconstruction was considered ideal in 54 (94.7%) cases, satisfactory in 2 (3.5%), and acceptable in 1 (1.8%). No revision surgery was required. In all cases, preoperative diplopia was settled out, and only 1 patient reported postoperative enophthalmos. No complications occurred, with good clinical results and orbital symmetry. The linear CT measurement-based protocol is a simple and reliable workflow to guide the surgeon's choice of reconstruction material and surgical approach for primary orbital reconstruction. It allows good management of orbital trauma and could help standardize treatment decisions with an imaging technique available in all institutions.

Computer assisted skull base surgery: a contemporary review

Skull base surgery has evolved significantly since Harvey Cushing's first descriptions in the early 1900s. Computer aided surgery (CAS) applications continue to expand; they include virtual surgical planning, augmented and virtual reality, 3D printing of models/cutting guides/implants, surgical navigation, and intraoperative imaging. The authors will review the current skull base CAS literature and propose a computer aided surgical workflow categorizing these applications into 3 phases: 1) Virtual planning, 2) Surgical execution, 3) Intraoperative verification.

Reducing Risks for Midface and Mandible Fracture Repair

The midface skeleton provides structural scaffolding to the middle third of the face. Complications associated with fracture repair in these regions can result from incomplete, inaccurate, or delayed assessment, poor initial and subsequent reduction and fixation, infection, uncontrolled hemorrhage, hardware failure and associated soft tissue injuries. A systematic approach to managing the patient with facial trauma that includes Acute Trauma Life Support principles, early reconstruction, and precise reduction and fixation is essential to reducing the short-term and long-term risks of complications.

Target registration errors in navigation-assisted mandibular surgery according to the tracking methods and the type of markers: experiments using human dry mandibular bone

OBJECTIVES

This study was conducted to evaluate the accuracy of navigation process according to the type of tracking methods and registration markers. The target registration errors (TREs) were measured at seven anatomical landmarks of the mandible.

METHODS

Four different experiments were performed to obtain the TREs using two tracking methods, the optical tracker (Polaris) and the electromagnetic (EM) tracker (Aurora), and two types of registration markers, invasive and noninvasive markers. All comparisons of TREs were statistically analyzed using SPSS and Python-based statistical package.

RESULTS

The average TRE values obtained from the four experiments were as follows: (1) 0.85 mm (± 0.07) using invasive marker and Aurora, (2) 1.06 mm (± 0.12) using invasive marker and Polaris, (3) 1.43 mm (± 0.15) using noninvasive marker and Aurora, and (4) 1.57 mm (± 0.23) using noninvasive marker and Polaris. Comparisons between all the experimental results revealed statistically significant differences except for the type of tracking system. Although the comparison between the modality of the tracking system showed no significant differences, the EM-based approach consistently demonstrated better performances than the optical type in all comparisons.

CONCLUSIONS

This study demonstrates that irrespective of the tracking modality, using invasive marker is a better choice in terms of accuracy. When using noninvasive marker, it is important to consider the increased TREs. In this study, the noninvasive marker caused a maximum increment of TREs of 0.81 mm compared with the invasive marker. Furthermore, using an EM-based tracker with invasive marker may result in the best accuracy for navigation.

Feasibility of a lung airway navigation system using fiber-Bragg shape sensing and artificial intelligence for early diagnosis of lung cancer

Currently early diagnosis of malignant lesions at the periphery of lung parenchyma requires guidance of the biopsy needle catheter from the bronchoscope into the smaller peripheral airways via harmful X-ray radiation. Previously, we developed an image-guided system, iMTECH which uses electromagnetic tracking and although it increases the precision of biopsy collection and minimizes the use of harmful X-ray radiation during the interventional procedures, it only traces the tip of the biopsy catheter leaving the remaining catheter untraceable in real time and therefore increasing image registration error. To address this issue, we developed a shape sensing guidance system containing a fiber-Bragg grating (FBG) catheter and an artificial intelligence (AI) software, AIrShape to track and guide the entire biopsy instrument inside the lung airways, without radiation or electromagnetic navigation. We used a FBG fiber with one central and three peripheral cores positioned at 120° from each other, an array of 25 draw tower gratings with 1cm/3nm spacing, 2 mm grating length, Ormocer-T coating, and a total outer diameter of 0.2 mm. The FBG fiber was placed in the working channel of a custom made three-lumen catheter with a tip bending mechanism (FBG catheter). The AIrShape software determines the position of the FBG catheter by superimposing its position to the lung airway center lines using an AI algorithm. The feasibility of the FBG system was tested in an anatomically accurate lung airway model and validated visually and with the iMTECH platform. The results prove a viable shape-sensing hardware and software navigation solution for flexible medical instruments to reach the peripheral airways. During future studies, the feasibility of FBG catheter will be tested in pre-clinical animal models.

Recent Trends in Orthognathic Surgery in Asia

Anatomy and standards of beauty are different between Asians and Westerners. Unlike Westerners, Asians have a wide and prominent jaw shape but prefer a slim and soft face shape. To achieve this goal, maxillary setback and/or posterior impaction surgeries are popular among upper jaw surgery, and various adjuvant surgeries are performed simultaneously on the mandible to obtain the so-called oval shape or V-line face. In addition, according to the development of virtual surgery software and orthodontic treatment techniques, the surgery-first approach is now accepted as a reliable option for orthognathic surgery if it is indicated.

Total Temporomandibular Joint Replacement and Simultaneous Orthognathic Surgery Using Computer-Assisted Surgery

Background

Disorders of the temporomandibular joint (TMJ) are frequent and are usually associated with other disorders of the facial skeleton. Surgery might be needed to correct TMJ anatomy and function and, in cases where pathologies coexist, a two-stage corrective surgery might be needed. However, the current fashion of single-stage procedures is feasible with the aid of new technologies such as computer-assisted surgery (CAS). This is a step forward toward performing complex procedures such as a TMJ replacement with simultaneous orthognathic surgery. CAS allows designing patient-fitted prosthesis and more predictable and accurate surgeries. Moreover, intraoperative development can be controlled in real time with intraoperative navigation, and postoperative results can be measured and compared afterwards.

Aims

The primary purpose of this article is to present the protocol used in our institution for orthognathic surgery associated with unilateral and bilateral TMJ replacement with patient-fitted prostheses guided with CAS.

Materials and methods

We present two cases to illustrate our protocol and its results.

Results

In the first case, the difference in millimeters between planning and surgical outcomes was 1.72 mm for the glenoid component and 2.16 mm for the condylar prosthesis; for the second case, differences in the right side were 2.59 mm for the glenoid component and 2.06 mm for the ramus, and in the left side, due to the anatomy the difference was a little greater, without clinical significance.

Conclusion

Combined surgery of the midface and mandible with total TMJ replacement is feasible and beneficial for the patient. CAS facilitates the planning and design of custom-fit prosthesis and execution of these procedures.

Proposal for the Fusion of Ultrasound and Computed Tomography Images for Image Shift Correction in Craniomaxillofacial Soft Tissue Surgery

ABSTRACT

Surgical navigation has greatly improved the accuracy of craniomaxillofacial bone surgery and is widely used in the clinic. However, during surgery, craniomaxillofacial soft tissue is always deformed due to traction and compression, which leads to intraoperative image drift. This, in turn, impacts navigation accuracy. In order to improve navigation accuracy, this technical note presents a preliminary proposal for fusion imaging technology, which combines ultrasound and computed tomography to address navigational image drift in craniomaxillofacial soft tissue surgery.

Virtual splint registration for electromagnetic and optical navigation in orbital and craniofacial surgery

In intra-operative navigation, a registration procedure is performed to register the patient's position to the pre-operative imaging data. The registration process is the main factor that determines accuracy of the navigation feedback. In this study, a novel registration protocol for craniofacial surgery is presented, that utilizes a virtual splint with marker points. The accuracy of the proposed method was evaluated by two observers in five human cadaver heads, for optical and electromagnetic navigation, and compared to maxillary bone-anchored fiducial registration (optical and electromagnetic) and surface-based registration (electromagnetic). The results showed minimal differences in accuracy compared to bone-anchored fiducials at the level of the infra-orbital rim. Both point-based techniques had lower error estimates at the infraorbital rim than surface-based registration, but surface-based registration had the lowest loss of accuracy over target distance. An advantage over existing point-based registration methods (bone-anchored fiducials, existing splint techniques) is that radiological imaging does not need to be repeated, since the need for physical fiducials to be present in the image volume is eradicated. Other advantages include reduction of invasiveness compared to bone-achnored fiducials and a possible reduction of human error in the registration process.

Surgical instrument to improve implant positioning in orbital reconstruction: a feasibility study

Adequate positioning of an orbital implant during orbital reconstruction surgery is essential for restoration of the pre-traumatised anatomy, but visual appraisal of its position is limited by the keyhole access and protruding soft tissues. A positioning instrument that attaches to the implant was designed to provide feedback outside the orbit. The goal of this study was to evaluate the accuracy of placement with the instrument and compare it with the accuracy of placement by visual appraisal. Ten orbits in five human cadaver heads were reconstructed twice: once using visual appraisal and once using the instrument workflow. No significant improvement was found for the roll (5.8° vs 3.4°, respectively, p=0.16), pitch (2.1° vs 1.5°, p=0.56), or translation (2.9 mm vs 3.3 mm, p=0.77), but the yaw was significantly reduced if the instrument workflow was used (15.3° vs 2.9°, p=0.02). The workflow is associated with low costs and low logistical demands, and may prevent outliers in implant positioning in a clinical setting when intraoperative navigation or patient-specific implants are not available.

Orbital Surgical Guidelines: Pediatric Considerations

Pediatric orbital and skull base surgery comprises a wide array of tumors. An understanding of the location of the lesion, nature of the disease, and surrounding anatomy is paramount to surgical planning in these small spaces. The goals of pediatric skull base surgery are to avoid injury to the surrounding structures, minimize cosmetic deformities, and remove some or all of the tumors based on anticipated pathology and biologic cost of removal. Safe surgery on many of these tumors requires an understanding of the location of the lesion relative to the optic nerve or orbit. This is particularly challenging because the dimensions of the orbital confines change continuously as one navigates from rostral to caudal. Management of these tumors may require a multidisciplinary approach including orbital surgery, neurosurgery, otolaryngology, oral maxillofacial surgery, plastic surgery, and interventional neuroradiology.