Intraoperative surgical navigation for endoscopic sinus surgery: rationale and indications

Semi-Quantitative Assessment of Surgical Navigation Accuracy During Endoscopic Sinus Surgery in a Real-World Environment

INTRODUCTION

Although surgical navigation is commonly used in rhinologic surgery, data on real world performance are sparse because of difficulties in collecting measurements for target registration error (TRE). Despite publications showing submillimeter TRE, surgeons do report TRE of >3 mm. We describe a novel method for assessing TRE during surgery and report findings with this technique.

METHODS

The TruDi navigation system (Acclarent, Irving, CA) was registered using a contour-based protocol. The surgeon estimated target registration error (e-TRE) at up to 8 points (anatomic regions of interest [ROI]) during endoscopic sinus surgery (ESS). System logs were used to simulate the localization for quantitative assessment of TRE (q-TRE).

RESULTS

We performed 98 localizations in 20 patients. The ROI in the sinuses were ethmoid (33 sites), maxillary (28 sites), frontal (17 sites), and sphenoid (22 sites). For localizations, mean qTRE and eTRE were 0.93 and 0.84 mm (P = .56). Notably, 80% of qTRE and 81% of eTRE were 1 mm or less. Mean qTRE and eTRE were less for attending-performed registrations at the maxillary, frontal and sphenoid.

CONCLUSION

Surgical navigation accuracy, as measured by qTRE and eTRE, approaches 1 mm or better at all sinus sites in a real-world setting for 80% of localizations. The qTRE method provides a unique approach for assessing TRE. Surgeons underestimate TRE (overstate navigation accuracy), but this difference does not seem to be statistically significant. Registration performed by trainees yields higher TRE than registration performed by attendings. These data may be used to guide navigation optimization.

The Role of Augmented Reality Neuronavigation in Transsphenoidal Surgery: A Systematic Review

In the field of minimally invasive neurosurgery, microscopic transsphenoidal surgery (MTS) and endoscopic transsphenoidal surgery (ETS) have been widely accepted as a safe approach for pituitary lesions and, more recently, their indications have been extended to lesions at various skull base regions. It is mandatory during transsphenoidal surgery (TS) to identify key anatomical landmarks in the sphenoid sinus and distinguish them from the lesion. Over the years, many intraoperative tools have been introduced to improve the neuronavigation systems aiming to achieve safer and more accurate neurosurgical interventions. However, traditional neuronavigation systems may lose the accuracy of real-time location due to the discrepancy between the actual surgical field and the preoperative 2D images. To deal with this, augmented reality (AR)-a new sophisticated 3D technology that superimposes computer-generated virtual objects onto the user's view of the real world-has been considered a promising tool. Particularly, in the field of TS, AR can minimize the anatomic challenges of traditional endoscopic or microscopic surgery, aiding in surgical training, preoperative planning and intra-operative orientation. The aim of this systematic review is to analyze the potential future role of augmented reality, both in endoscopic and microscopic transsphenoidal surgeries.

Artificial intelligence directed development of a digital twin to measure soft tissue shift during head and neck surgery

Digital twins derived from 3D scanning data were developed to measure soft tissue deformation in head and neck surgery by an artificial intelligence approach. This framework was applied suggesting feasibility of soft tissue shift detection as a hitherto unsolved problem. In a pig head cadaver model 104 soft tissue resection had been performed. The surface of the removed soft tissue (RTP) and the corresponding resection cavity (RC) was scanned (N = 416) to train an artificial intelligence (AI) with two different 3D object detectors (HoloLens 2; ArtecEva). An artificial tissue shift (TS) was created by changing the tissue temperature from 7,91±4,1°C to 36,37±1,28°C. Digital twins of RTP and RC in cold and warm conditions had been generated and volumes were calculated based on 3D surface meshes. Significant differences in number of vertices created by the different 3D scanners (HoloLens2 51313 vs. ArtecEva 21694, p<0.0001) hence result in differences in volume measurement of the RTC (p = 0.0015). A significant TS could be induced by changing the temperature of the tissue of RC (p = 0.0027) and RTP (p = <0.0001). RC showed more correlation in TS by heating than RTP with a volume increase of 3.1 μl or 9.09% (p = 0.449). Cadaver models are suitable for training a machine learning model for deformable registration through creation of a digital twin. Despite different point cloud densities, HoloLens and ArtecEva provide only slightly different estimates of volume. This means that both devices can be used for the task.TS can be simulated and measured by temperature change, in which RC and RTP react differently. This corresponds to the clinical behaviour of tumour and resection cavity during surgeries, which could be used for frozen section management and a range of other clinical applications.

Endoscopic Orientation of Juxta-pituitary Carotid in Transsphenoidal Approaches: Critical Considerations for Clinical Applications

Introduction  In sphenoid sinuses with ill-defined carotid bony landmarks, accidental injury of the internal carotid artery (ICA) remains one of the most challenging complications, which is particularly reported in the endoscopic endonasal transsphenoidal approaches (EETAs). Objectives  To describe an anatomical model for the endoscopic orientation of the juxta-pituitary segment of the ICA in relation to the lateral opticocarotid recess (OCR) as a nearby bony landmark. Methods  Dissection was performed progressively, simulating the EETA, in twenty fresh adult cadavers. After reducing the posterior and lateral walls of the sphenoid sinuses, various measurements were taken from both lateral OCRs to "contact points" on the juxta-pituitary segment of the ICA and lateral margins of the pituitary gland. Results  The current results have enabled us to divide the region between the lateral OCRs into 3 compartments: 2 lateral parasellar compartments contain juxta-pituitary segments of the ICA with a mean width of 8 mm and a narrow range from 7 mm to 10 mm; and a central intercarotid sellar compartment represents the safe region for bone drilling, showing widely variable widths ranging from 9 mm to 20mm. In all specimens, the variation in the width of the intercarotid compartment correlated with the distance between both lateral OCRs. Conclusion  The present study improves surgeon awareness of the variations in the course of the ICA through the EETA along sphenoid sinuses with ill-defined bony landmarks. An appreciation of the measurements taken in the present study can help in operative training, and can also provide a base for future studies to confirm ICA courses associated with a higher risk of injury.

Optimal Usability Test Procedure Generation for Medical Devices

Medical device usability testing offers many benefits, including finding medical device usage errors and providing safety to users. As usability testing becomes mandatory for medical devices, manufacturers are increasing the cost burden. In order to perform a high-quality usability test, it is important to implement a usability test procedure, but guidelines for this are lacking. In this paper, we propose a method to systematically design and implement a usability test procedure. We propose methods to reduce test time-costs and apply them to implement the final procedure. Next, by applying the proposed method to sinus surgical navigation system, it is shown that the total time was reduced by 21% compared to the usability summative test procedure previously used in the same system.

[BIOPASS hybrid navigation for endoscopic sinus surgery - an assistance system]

Previous navigation systems can determine the position of the "tracked" surgical instrument in CT images in the context of functional endoscopic sinus surgery (FESS), but do not provide any assistance directly in the video endoscopic image of the surgeon. Developing this direct assistance for intraoperative orientation and risk reduction was the goal of the BIOPASS project (Bild Ontologie und prozessgestütztes Assistenzsystem). The Project pursues the development of a novel navigation system for FESS without markers. BIOPASS describes a hybrid system that integrates various sensor data and makes it available. The goal is to abandon tracking and exclusively provide navigation information directly in the video image. This paper describes the first step of the development by collecting and structuring the surgical phases (workflows), the video endoscopic landmarks and a first clinical evaluation of the model version. The results provide the important basis and platform for the next step of the project.

Reliability and accuracy of dynamic navigation for zygomatic implant placement

Objectives

To assess the accuracy of a real‐time dynamic navigation system applied in zygomatic implant (ZI) surgery and summarize device‐related negative events and their management.

Material and methods

Patients who presented with severely maxillary atrophy or maxillary defects and received dynamic navigation‐supported ZI surgery were included. The deviations of entry, exit, and angle were measured after image data fusion. A linear mixed‐effects model was used. Statistical significance was defined as p < .05. Device‐related negative events and their management were also recorded and analyzed.

Results

Two hundred and thirty‐one zygomatic implants (ZIs) with navigation‐guided placement were planned in 74 consecutive patients between Jan 2015 and Aug 2020. Among them, 71 patients with 221 ZIs received navigation‐guided surgery finally. The deviations in entry, exit, and angle were 1.57 ± 0.71 mm, 2.1 ± 0.94 mm and 2.68 ± 1.25 degrees, respectively. Significant differences were found in entry and exit deviation according to the number of ZIs in the zygomata (p = .03 and .00, respectively). Patients with atrophic maxillary or maxillary defects showed a significant difference in exit deviation (p = .01). A total of 28 device‐related negative events occurred, and one resulted in 2 ZI failures due to implant malposition. The overall survival rate of ZIs was 98.64%, and the mean follow‐up time was 24.11 months (Standard Deviation [SD]: 12.62).

Conclusions

The navigation‐supported ZI implantation is an accurate and reliable surgical approach. However, relevant technical negative events in the navigation process are worthy of attention.

A systematic review of common landmarks in navigated endoscopic sinus surgery (NESS)

BACKGROUND

Navigation brought about a tremendous improvement in functional endoscopic sinus surgery (FESS). When upgraded accordingly, FESS becomes navigated endoscopic sinus surgery (NESS). Indications for intraoperative use of navigation can be broadened to almost any FESS case. NESS in advanced sinus surgery is currently still not used routinely and requires systematic practice guidelines.

PURPOSE

The purpose of this paper is to report on commonly identified landmarks while performing advanced NESS according to evidence-based medicine (EBM) principles.

MATERIAL AND METHODS

This review paper has been assembled following PRISMA guidelines. A PubMed and Scopus (EMBASE) search on anatomical landmarks in functional endoscopic and navigated sinus surgery resulted in 47 results. Of these, only 14 (29.8%) contained original data, constituting the synthesis of best-quality available evidence.

RESULTS

Anatomical landmarks are considered to be the most important points of orientation for optimal use of navigation systems during FESS surgery. The most commonly identified significant landmarks are as follows: (1) Maxillary sinus ostium; (2) Orbital wall; (3) Frontal recess; (4) Skull base; (5) Ground lamella; (6) Fovea posterior; (7) Sphenoid sinus ostium. Conclusions: Establishing common landmarks are essential in performing NESS. This is true for advanced and novice surgeons alike and offers a possibility to use navigation systems systematically, taking advantage of all the benefits of endoscopic navigated surgery.

Endoscopic Orientation of Juxta-Pituitary Carotid in Transsphenoidal Approaches: Critical Considerations for Clinical Applications

Accidental injury of the internal carotid artery (ICA) remains one of the most challenging complications reported in the endoscopic endonasal transsphenoidal approaches (EETA) particularly, in sphenoid sinuses with ill-defined carotid bony landmarks. The purpose of this study was to describe an anatomical model for the endoscopic orientation of juxta-pituitary segment of ICA in relation to the lateral optico-carotid recess (OCR) as a nearby bony landmark. Cadaveric dissection was conducted progressively in twenty fresh adult cadavers simulating the EETA. After reducing posterior and lateral walls of sphenoid sinuses, various measurements were taken from both lateral OCRs to "contact points" of the juxta-pituitary segment of ICA and lateral margins of the pituitary gland. Current results have enabled us to divide the region between lateral OCRs into three compartments. Two lateral parasellar compartments contain juxta-pituitary segments of ICA showing a mean width of 8 mm; with a narrow range of 7-10 mm; and a central inter-carotid sellar compartment represents the safe region for bone drilling showing widely variable widths ranging between 9 to 20 mm. In all specimens; variation in the width of the inter-carotid compartment correlated with the distance between both lateral OCRs. This study improves surgeons' awareness of the ICA course variations in the EETA through sphenoid sinuses with ill-defined bony landmarks. An appreciation of the measurements gathered from this study can help in operative training, and can also provide a base for future studies to confirm ICA courses associated with higher risk of injury.

Automated atlas-based segmentation for skull base surgical planning

PURPOSE

Computational surgical planning tools could help develop novel skull base surgical approaches that improve safety and patient outcomes. This defines a need for automated skull base segmentation to improve the usability of surgical planning software. The objective of this work was to design and validate an algorithm for atlas-based automated segmentation of skull base structures in individual image sets for skull base surgical planning.

METHODS

Advanced Normalization Tools software was used to construct a synthetic CT template from 6 subjects, and skull base structures were manually segmented to create a reference atlas. Landmark registration followed by Elastix deformable registration was applied to the template to register it to each of the 30 trusted reference image sets. Dice coefficient, average Hausdorff distance, and clinical usability scoring were used to compare the atlas segmentations to those of the trusted reference image sets.

RESULTS

The mean for average Hausdorff distance for all structures was less than 2 mm (mean for 95th percentile Hausdorff distance was less than 5 mm). For structures greater than 2.5 mL in volume, the average Dice coefficient was 0.73 (range 0.59-0.82), and for structures less than 2.5 mL in volume the Dice coefficient was less than 0.7. The usability scoring survey was completed by three experts, and all structures met the criteria for acceptable effort except for the foramen spinosum, rotundum, and carotid artery, which required more than minor corrections.

CONCLUSION

Currently available open-source algorithms, such as the Elastix deformable algorithm, can be used for automated atlas-based segmentation of skull base structures with acceptable clinical accuracy and minimal corrections with the use of the proposed atlas. The first publicly available CT template and anterior skull base segmentation atlas being released (available at this link: http://hdl.handle.net/1773/46259 ) with this paper will allow for general use of automated atlas-based segmentation of the skull base.

A Review of Training and Guidance Systems in Medical Surgery

In this paper, a map of the state of the art of recent medical simulators that provide evaluation and guidance for surgical procedures is performed. The systems are reviewed and compared from the viewpoint of the used technology, force feedback, learning evaluation, didactic and visual aid, guidance, data collection and storage, and type of solution (commercial or non-commercial). The works’ assessment was made to identify if—(1) current applications can provide assistance and track performance in training, and (2) virtual environments are more suitable for practicing than physical applications. Automatic analysis of the papers was performed to minimize subjective bias. It was found that some works limit themselves to recording the session data to evaluate them internally, while others assess it and provide immediate user feedback. However, it was found that few works are currently implementing guidance, aid during sessions, and assessment. Current trends suggest that the evaluation process’s automation could reduce the workload of experts and let them focus on improving the curriculum covered in medical education. Lastly, this paper also draws several conclusions, observations per area, and suggestions for future work.

Augmented reality-enhanced navigation in endoscopic sinus surgery: A prospective, randomized, controlled clinical trial

OBJECTIVE

Endoscopic sinus surgery represents the gold standard for surgical treatment of chronic sinus diseases. Thereby, navigation systems can be of distinct use. In our study, we tested the recently developed KARL STORZ NAV1 SinusTracker navigation software that incorporates elements of augmented reality (AR) to provide a better preoperative planning and guidance during the surgical procedure.

METHODS

One hundred patients with chronic sinus disease were operated on using either a conventional navigation software (n = 52, non-AR, control group) or a navigation software incorporating AR elements (n = 48, AR, intervention group). Incidence of postoperative complications, duration of surgery, surgeon-reported benefit from the navigation system and patient-reported postoperative rehabilitation were assessed.

RESULTS

The surgeons reported a higher benefit during surgery, used the navigation system for more surgical steps and spent longer time with preoperative image analysis when using the AR system as compared with the non-AR system. No significant differences were seen in terms of postoperative complications, target registration error, operation time and postoperative rehabilitation.

CONCLUSION

The AR enhanced navigation software shows a high acceptance by sinus surgeons in different stages of surgical training and offers potential benefits during surgery without affecting the duration of the operation or the incidence of postoperative complications.

LEVEL OF EVIDENCE

1b.

A 16-Year Study on Incidence and Progression of Diseased Sphenoethmoidal (Onodi) Cell

Traumatic operative injury of the optic nerve in an endoscopic sinus surgery may cause immediate or delayed blindness. It should be cautioned when operating in a sphenoethmoidal cell, or known as Onodi cell, with contact or bulge of the optic canal. It remains unclear how frequent progression to visual loss occurs and how long it progresses to visual loss because of a diseased sphenoethmoidal cell. Research to discuss these questions is expected to help decision making to treat diseased sphenoethmoidal cells. From July 2001 to June 2017, 216 patients received conservative endoscopic sinus surgery without opening a diseased sphenoethmoidal cell. We used their computed tomography images of paranasal sinuses to identify diseased sphenoethmoidal cells that could be associated with progression to visual loss. Among the 216 patients, 52.3% had at least one sphenoethmoidal cell, and 14.8% developed at least one diseased sphenoethmoidal cell. One patient developed acute visual loss 4412 days after the first computed tomography. Our results show that over half of the patients have a sphenoethmoidal cell but suggest a rare incidence of a diseased sphenoethmoidal cell progressing to visual loss during the follow-up period.

Evaluating an Image-Guided Operating Room with Cone Beam CT for Skull Base Surgery

Importance  Skull base surgery requires precise preoperative assessment and intraoperative management of the patient. Surgical navigation is routinely used for complex skull base cases; however, the image guidance is commonly based on preoperative scans alone. Objective  The primary objective of this study was to assess the image quality of intraoperative cone-beam computed tomography (CBCT) within anatomical landmarks used in sinus and skull base surgery. The secondary objective was to assess the registration error of a surgical navigation system based on intraoperative CBCT. Design  Present study is a retrospective case series of image quality after intraoperative cone beam CT. Setting  The study was conducted at Toronto General Hospital and Princess Margaret Cancer Centre, University Health Network, Toronto. Participants  A total of 46 intraoperative scans (34 patients, 21 skull base, 13 head and neck) were studied. Main Outcome and Measures  Thirty anatomical landmarks (vascular, soft tissue, and bony) within the sinuses and anterior skull base were evaluated for general image quality characteristics: (1) bony detail visualization; (2) soft-tissue visualization; (3) vascular visualization; and (4) freedom from artifacts (e.g., metal). Levels of intravenous (IV) contrast enhancement were quantified in Hounsfield's units (HU). Standard paired-point registration between imaging and tracker coordinates was performed using 6 to 8 skin fiducial markers and the corresponding fiducial registration error (FRE) was measured. Results  Median score for bony detail on CBCT was 5, remaining at 5 after administration of IV contrast. Median soft-tissue score was 2 for both pre- and postcontrast. Median vascular score was 1 precontrast and 3 postcontrast. Median score for artifacts on CBCT were 2 for both pre-and postcontrast, and metal objects were noted to be the most significant source of artifact. Intraoperative CBCT allowed preresection images and immediate postresection images to be available to the skull base surgeon. There was a significant improvement in mean (standard deviation [SD]) CT intensity in the left carotid artery postcontrast 334 HU (67 HU) ( p  < 10 ^-10 ). The mean FRE was 1.8 mm (0.45 mm). Conclusion  Intraoperative CBCT in complex skull base procedures provides high-resolution bony detail allowing immediate assessment of complex resections. The use of IV contrast with CBCT improves the visualization of vasculature. Image-guidance based on CBCT yields registration errors consistent with standard techniques.

Multi-modal Framework for Image-guided Trans-oral Surgery with Intraoperative Imaging and Deformation Modeling

Treatment of throat cancers have improved due to minimally-invasive trans-oral approaches. Surgeons rely on preoperative imaging to guide their resection; however, large tissue deformations occur during trans-oral procedures due to placement of necessary retractors and laryngoscopes which hinders the surgeon's ability to accurately assess tumor extent and location of critical structures. We propose an image-guided framework utilizing intraoperative imaging and deformation modeling to improve surgeon accuracy and confidence. A CT-compatible laryngoscopy system previously developed was evaluated in this framework. Intraoperative images were acquired during laryngoscopy; force-sensing capabilities were enabled in the laryngoscope; and tracking of the scope and anatomic features was trialed. Tissue deformation and displacement were quantified and determined to be extensive, with values <; 4.6 cm in the tongue, <; 1.8 cm in bony structures, and <; 108.9 cm³ in airway volume change. Surgical navigation using intraoperative imaging and tracking was evaluated. Preliminary assessment of deformation modeling showed potential to supplement intraoperative imaging. Future work will involve streamlined integration of the components of this framework.

Use of Mixed Reality Visualization in Endoscopic Endonasal Skull Base Surgery

BACKGROUND

Neuronavigation systems assist with spatial orientation during endoscopic transnasal skull base surgery, but they require a correlation of 3-dimensional (3D) views with 2-dimensional (2D) radiology studies.

OBJECTIVE

To outline an initial experience with a novel technology platform that provides intraoperative navigation using 3D reconstructions of patient anatomy for endoscopic surgery.

METHODS

A retrospective study of endoscopic anterior skull base and complex paranasal procedures was performed. Data from preoperative computed tomography and magnetic resonance imaging scans were fused to create 3D digital models of patient anatomy. Using the technology developed by Surgical Theater (Mayfield Village, Ohio), these reconstructions were designed to highlight particular anatomic regions of interest. The models were studied to guide the surgical approach and anticipate critical structures.

The reconstructions were linked with the navigational technology created by Brainlab (Munich, Germany) during endoscopic surgery. A dynamic image of the reconstruction was displayed alongside a matching endoscopic camera view. These 2 views could be overlaid to provide an immersive, mixed reality image of the patient's anatomy.

RESULTS

A total of 134 cases were performed. The pathologies included tumors of the anterior skull base or sinonasal cavity, inflammatory sinus disease, and cerebrospinal fluid leaks. Specific anatomic structures, such as the internal carotid arteries and optic nerves, were chosen for enhancement. Surgeons felt that the technology helped to guide the extent of bony dissection and to identify critical structures.

CONCLUSION

We describe the first clinical series of complex skull base pathologies treated using a novel mixed reality platform.

Missed paranasal sinus compartments in sinus surgery with and without image-guidance systems: a pilot feasibility study

PURPOSE

Image-guidance systems (IGS) have gained widespread use in endoscopic sinus surgery (ESS) and have been thoroughly analysed. In this study, we looked for a new parameter to determine if patients could directly benefit from the use of IGS during primary ESS. We questioned if IGS could improve the quality of ESS in chronic rhinosinusitis (CRS) patients via allowing a more comprehensive treatment of all involved sinus compartments.

METHODS

In a pilot feasibility study, we evaluated uncomplicated CRS patients following primary ESS with and without IGS between January 2011 and June 2012 using preoperative and postoperative CT scans. The preoperative CT scans identified the sinus compartments requiring surgery. The postoperative CT scans were used to evaluate the treatment effect in these compartments. From these data, we calculated a missing ratio (missed compartments/compartments requiring surgery) for each patient.

RESULTS

Of the 169 ESS patients who were treated, ten patients were retrospectively identified as complying with the inclusion and exclusion criteria following ESS with IGS. Ten patients treated without IGS were then randomly chosen. The median missing ratio for non-IGS patients was 36%, and for IGS patients, the median missing ratio was 0% (p = 0.046). However, the missing ratio was depended on the number of compartments requiring surgery. Stratification of the number of compartments requiring surgery resulted in an exact p value of 0.13.

CONCLUSIONS

IGS could help the surgeon to more completely address diseased sinus compartments. For better scientific merit, a comparative study of ESS with and without IGS seems feasible, using the proposed failing score missed compartments/compartments requiring surgery as the primary outcome parameter.

Computed tomography-guided navigation assisted drainage for inaccessible deep neck abscess: A case report

RATIONALE

Deep neck infections (DNIs) in the head and neck area are difficult to treat due to the anatomical complexity of the cervical region. Since inflammation causes changes in anatomy, it is often difficult to find the exact location of the abscess, which leads to failed surgical drainage.

PATIENT CONCERN

A 76-year-old female patient was referred to our clinic with trismus and right-side facial swelling. After extraction of her lower third molar 2 weeks ago, due to chronic periodontitis, her trismus had aggravated and her maximal mouth opening was 20 mm.

DIAGNOSES

Computed tomography (CT) revealed an approximately 2.5 cm-sized abscess pocket with cellulitis in the right pterygomandibular space.

INTERVENTIONS

Since the first surgical drainage attempt using the intraoral approach under general anesthesia had failed and conservative antibiotic treatment was also ineffective, a second surgical procedure with a CT-guided navigation system was performed and the pus was successfully evacuated.

OUTCOMES

After drainage with CT-guided navigation, the clinical symptoms and septic conditions of the patient showed remarkable improvement, and there was no recurrence of infection within a year after the procedure.

LESSONS

Drainage with CT-guided navigation can be used as a successful surgical tool to aid in the surgery of patients with DNI when it is difficult to accurately target the abscess due to inflammation.

Initial experience with image-guided surgical navigation in transoral surgery

BACKGROUND

Surgical navigation using image guidance may improve the safety and efficacy of transoral surgery (TOS); however, preoperative imaging cannot be accurately registered to the intraoperative state due to deformations resulting from placement of the laryngoscope or retractor. This proof of concept study explores feasibility and registration accuracy of surgical navigation for TOS by utilizing intraoperative imaging.

METHODS

Four patients undergoing TOS were recruited. Suspension laryngoscopy was performed with a CT-compatible laryngoscope. An intraoperative contrast enhanced CT scan was obtained and registered to fiducials placed on the neck, face, and laryngoscope.

RESULTS

All patients were successfully scanned and registered. Registration accuracy within the pharynx and larynx was 1 mm or less. Target registration was confirmed by localizing endoscopic and surface structures to the CT images. Successful tracking was performed in all 4 patients.

CONCLUSION

For surgical navigation during TOS, although a high level of registration accuracy can be achieved by utilizing intraoperative imaging, significant limitations of the existing technology have been identified. These limitations, as well as areas for future investigation, are discussed.

Endoscopic sinus surgery with and without computer assisted navigation: A retrospective study

OBJECTIVE

In the last years endoscopic sinus surgery (ESS) is improved with the introduction of computer assisted navigation (CAN). In this retrospective study we evaluated the usefulness of CAN in endoscopic sinus surgery and studied its advantages over conventional endoscopic sinus surgery.

METHODS

We retrospectively reviewed the records of 96 patients with chronic rhinosinusitis (CRS). 48 patients undergoing endoscopic sinus surgery with surgical navigation (A group) and other 48 without navigation (B group). Data about percentage of complications, olfactory function (Visual Analogue Scale), Sino-nasal Outcomes Test (SNOT-22), Rhinosinusitis Quality of Life (RhinoQoL), recurrence (CT Lund-Mackay score), total nasal resistance (rhinomanometry) and duration of the intervention were collected and analyzed.

RESULTS

A group evidenced a decrease of recurrence rate (p=0.009), a reduction of total nasal resistance (p=0.007), of frontal recess stenosis (p=0.04) and of nasal symptomatology (p=0.008). QoL had a better improvement in group A. Rate of other complications and olfactory function did not show statistically significant differences between the two groups. The average calibration time was approximately 11min in the A group. Total time of surgical procedure does not evidenced statistically significant difference between the two groups (p>0.05) but if it is considered only the time of the surgical intervention, the difference of duration is significant reduced statistically (p<0.05) in CAN surgery.

CONCLUSION

Computer assisted navigation in ESS can be useful for the most experienced surgeons, especially in the frontal recess surgery, decreasing the recurrence rate and reducing the total nasal resistance.

Total intravenous versus inhaled anesthesia in transsphenoidal tumor surgery

PURPOSE

Visualization of the surgical field is essential for patient safety during endoscopic transsphenoidal tumor surgery. In this retrospective chart review and data analysis of patients undergoing endoscopic transsphenoidal resection of pituitary tumors under general anesthesia we sought to determine if total intravenous anesthesia with propofol and remifentanil leads to decreased bleeding, surgical duration, time to extubation and/or length of stay in the recovery room compared to inhaled anesthesia with sevoflurane or desflurane.

METHODS

After IRB approval, chart reviews of 193 American Society of Anesthesiologists class 1 to 3 patients were conducted who had undergone transsphenoidal, endonasal resections of pituitary tumors under total intravenous or inhaled anesthesia at an academic teaching hospital in the United States over a seven-year time period. One hundred four patients fulfilled the inclusion criteria and were further reviewed. Primary outcome was intraoperative blood loss; secondary outcomes were surgical duration, time to extubation and length of stay in the recovery room.

RESULTS

Gender, age, and Lund-Mackay-Scores were equally distributed between the two anesthetic groups. We found no significant effect of the anesthetic technique, age, gender, or Lund Mackay score on any of the primary or secondary outcomes. The only significant predictor for recovery room length of stay was intraoperative blood loss.

CONCLUSION

Our study shows no evidence that total intravenous anesthesia is superior to inhaled anesthesia or vice versa during endoscopic transsphenoidal sinus surgery with regard to relevant clinical outcome parameters.

A novel approach to skull-base and orbital osteotomies through virtual planning and navigation

OBJECTIVE

Computer-assisted planning of osteotomy lines, coupled with navigation-guided performance of planned osteotomies, is a highly innovative approach to skull-base and orbital surgery. The aim of this pilot study is to provide an assessment of the accuracy of this novel approach in guiding the correct positioning of osteotomy lines in frontal, temporal, and orbital regions, defining the agreement between the spatial position of the planned and performed osteotomies.

METHODS

Fifteen patients with orbital, frontal sinus, and lateral skull-base diseases underwent virtual surgical planning. Osteotomies to access the orbit, frontal sinus, and lateral skull base were planned on computer tomography-based three-dimensional models. The planned osteotomies were reproduced on the operating field using a navigation system. The positions of the performed and planned osteotomies were compared. The results were described as the mean positional difference between planned and performed osteotomies and as Lin's concordance coefficient, and Bland-Altman limits of agreement were also defined.

RESULTS

The overall mean difference was 0.719 mm (95% confidence interval [CI]: 0.472 to 0.965 mm). Overall, Lin's concordance coefficient was 0.997 (95% CI: 0.996 to 0.998), and overall Bland-Altman limits of agreement ranged from -1.407 to 2.844 mm. The smallest mean difference (0.587 mm, 95% CI: 0.244 to 0.931 mm) was calculated in the orbit group, whereas the highest mean difference (0.904 mm, 95% CI: 0.428 to 1.379 mm) was described in the lateral skull-base group.

CONCLUSION

This study's results support the use of this novel planning and navigation protocol for guiding osteotomy in anterior and lateral skull-base surgery, providing a clinical validation of this technique.

LEVEL OF EVIDENCE

4 Laryngoscope, 00:1-9, 2018 Laryngoscope, 129:823-831, 2019.

Navigation accuracy after automatic- and hybrid-surface registration in sinus and skull base surgery

Objective

Computer-aided-surgery in ENT surgery is mainly used for sinus surgery but navigation accuracy still reaches its limits for skull base procedures. Knowledge of navigation accuracy in distinct anatomical regions is therefore mandatory. This study examined whether navigation accuracy can be improved in specific anatomical localizations by using hybrid registration technique.

Study design

Experimental phantom study.

Setting

Operating room.

Subjects and methods

The gold standard of screw registration was compared with automatic LED-mask-registration alone, and in combination with additional surface matching. 3D-printer-based skull models with individual fabricated silicone skin were used for the experiments. Overall navigation accuracy considering 26 target fiducials distributed over each skull was measured as well as the accuracy on selected anatomic localizations.

Results

Overall navigation accuracy was <1.0 mm in all cases, showing the significantly lowest values after screw registration (0.66 ± 0.08 mm), followed by hybrid registration (0.83± 0.08 mm), and sole mask registration (0.92 ± 0.13 mm).On selected anatomic localizations screw registration was significantly superior on the sphenoid sinus and on the internal auditory canal. However, mask registration showed significantly better accuracy results on the midface. Navigation accuracy on skull base localizations could be significantly improved by the combination of mask registration and additional surface matching.

Conclusion

Overall navigation accuracy gives no sufficient information regarding navigation accuracy in a distinct anatomic area. The non-invasive LED-mask-registration proved to be an alternative in clinical routine showing best accuracy results on the midface. For challenging skull base procedures a hybrid registration technique is recommendable which improves navigation accuracy significantly in this operating field. Invasive registration procedures are reserved for selected challenging skull base operations where the required high precision warrants the invasiveness.

Implementation of a miniaturised navigation system in head and neck surgery for the detection and removal of foreign bodies

The removal of embedded blast-generated fragments from soft tissue is very difficult, especially in the head and neck regions. First, because many retained foreign materials are non-metallic and can, therefore, not be detected by fluoroscopy, and second, because a broad exploration of the soft tissue is not possible in the facial area for functional and cosmetic reasons. Intraoperative navigation computer-assisted surgery (CAS) may facilitate the retrieval of foreign bodies and reduce exploration trauma. In a blind trial, five test specimens of different materials (glass, metal, wood, plastic, and stone) were inserted on the left and right sides of the head and neck of ten body donors through an intraoral incision. A second physician then detected and removed the foreign bodies from one side of the body without and from the other side of the body with navigation. We measured the duration of surgery, the extent of tissue trauma caused during surgery, the time it took to remove the foreign bodies, and the subjective evaluation of the usefulness of navigation. With the aid of the navigation system, the various foreign bodies were detected after an average of 26.7 (±35.1) s (p < 0.0001) and removed after an average of 79.1 (±66.2) s (p = 0.0239), with an average incision length of 10.0 (±3.5) mm. Without the navigation system, the foreign bodies were located after an average of 86.5 (±77.7) s and removed after an average of 74.1 (±45.9) s, with an average incision length of 13.0 mm (±3.6) mm (=0.0007). Intraoperative navigation systems are a valuable tool for removing foreign bodies from the soft tissue of the face and neck. Both the duration of surgery and the incision length can be reduced using navigation systems. Depending on the material of the foreign bodies and the signal intensity in the CT/MRI scanner, however, the detection reliability varies. All in all, navigation is considered to be a useful tool.

Prospects and limitations of different registration modalities in electromagnetic ENT navigation

The present study examined electromagnetic tracking technology for ENT navigation. Five different registration modalities were compared and navigation accuracy was assessed. Four skull models were individually fabricated with a three-dimensional printer, based on patients' computer tomography datasets. Individual silicone masks were fitted for skin and soft tissue simulation. Five registration modalities were examined: (1) invasive marker, (2) automatic, (3) surface matching (AccuMatch), (4) anatomic landmarks, and (5) oral splint registration. Overall navigation accuracy and accuracy on selected anatomic locations were assessed by targeting 26 titanium screws previously placed over the skull. Overall navigation accuracy differed significantly between all registration modalities. The target registration error was 0.94 ± 0.06 mm (quadratic mean ± standard deviation) for the invasive marker registration, 1.41 ± 0.04 mm for the automatic registration, 1.59 ± 0.14 mm for the surface matching registration, and 5.15 ± 0.66 mm (four landmarks) and 4.37 ± 0.73 mm (five landmarks) for the anatomic landmark registration. Oral splint registration proved itself to be inapplicable to this navigation system. Invasive marker registration was superior on most selected anatomic locations. However, on the ethmoid and sphenoid sinus the automatic registration process revealed significantly lower target registration error values. Only automatic and surface registration met the accuracy requirements for noninvasive registration. Particularly, the automatic image-to-world registration reaches target registration error values on the anterior skull base which are comparable with the gold standard of invasive screw registration.

A Novel Augmented Reality Navigation System for Endoscopic Sinus and Skull Base Surgery: A Feasibility Study

Objective

To verify the reliability and clinical feasibility of a self-developed navigation system based on an augmented reality technique for endoscopic sinus and skull base surgery.

Materials and Methods

In this study we performed a head phantom and cadaver experiment to determine the display effect and accuracy of our navigational system. We compared cadaver head-based simulated operations, the target registration error, operation time, and National Aeronautics and Space Administration Task Load Index scores of our navigation system to conventional navigation systems.

Results

The navigation system developed in this study has a novel display mode capable of fusing endoscopic images to three-dimensional (3-D) virtual images. In the cadaver head experiment, the target registration error was 1.28 ± 0.45 mm, which met the accepted standards of a navigation system used for nasal endoscopic surgery. Compared with conventional navigation systems, the new system was more effective in terms of operation time and the mental workload of surgeons, which is especially important for less experienced surgeons.

Conclusion

The self-developed augmented reality navigation system for endoscopic sinus and skull base surgery appears to have advantages that outweigh those of conventional navigation systems. We conclude that this navigational system will provide rhinologists with more intuitive and more detailed imaging information, thus reducing the judgment time and mental workload of surgeons when performing complex sinus and skull base surgeries. Ultimately, this new navigational system has potential to increase the quality of surgeries. In addition, the augmented reality navigational system could be of interest to junior doctors being trained in endoscopic techniques because it could speed up their learning. However, it should be noted that the navigation system serves as an adjunct to a surgeon’s skills and knowledge, not as a substitute.

Does Image-Guided Surgery Reduce Complications?

Image-guided surgery (IGS) is progressively used in endoscopic sinus surgery (ESS), and surgeon comfort with the technology has increased. It remains a challenge to determine if the use of IGS in ESS leads to a reduction in surgical complications and improved outcomes. Current literature does not show a clear reduction in surgical complications. The routine use of IGS in ESS as a deterrent to medicolegal liability is not substantiated by recent reported data. There are particular situations in which IGS may be helpful, but its use is likely not required for routine ESS and seems best left to surgeon discretion.

Comparison of 3D C-arm-based registration to conventional pair-point registration regarding navigation accuracy in ENT surgery

OBJECTIVE

Navigation surgery on the skull base requires high navigation accuracy. The registration process is related to the main loss in accuracy. This study compared titanium screw registration with an inbuilt registration process of a 3-dimensional (3D) C-arm.

STUDY DESIGN

Experimental phantom study.

SETTING

Operating room.

SUBJECTS AND METHODS

Four skull models were fabricated with a 3D printer based on the patient's computed tomography (CT) data sets and fitted with an individually customized silicone skin. A 3D-isocentric C-arm fluoroscopic image intensifier system combined with a flat panel detector performed scans of petrous bones (PB) and paranasal sinuses (PS). The navigation accuracy of pair-point registration (PPR) with titanium screws was compared with C-arm-based registration.

RESULTS

Overall navigation accuracy was 1.53 ± 0.51 mm after PPR and 1.26 ± 0.12 mm after C-arm registration (P = .0259). PPR showed the best accuracy results on PS (1.28 ± 0.69 mm), followed by right PB (1.43 ± 0.52 mm) and left PB (1.74 ± 0.69 mm). A significant difference was seen only between PS and left PB (P = .0206). In contrast, C-arm registration revealed significantly lower target registration errors (TREs) on PB (0.99 ± 0.23 mm right PB, P < .0001; 1.2 ± 0.35 mm left PB, P = .0412) compared with PS. When comparing both registration modalities, C-arm registration was significantly superior on PB. With respect to specific anatomic locations, C-arm-based registration showed significantly lower TREs on the frontal and lateral skull base than PPR.

CONCLUSION

C-arm-based navigation shows higher navigation accuracy on the skull base compared with PPR. As the 3D C-arm allows real-time imaging and real-time navigation, it will be a helpful tool for skull base surgeons.

[CT-assisted navigation for retrosigmoidal implantation of the Bonebridge]

The Bonebridge is an active bone conduction implant (BCI) that is primarily indicated in patients with conductive and combined hearing loss. However, many of these patients present with a radical cavity as a result of previous surgery. In these cases, the implant should not be introduced into the mastoid region, but rather via a retrosigmoid approach to maintain separation from the pathological alteration. To ensure the best possible acoustic transduction, the Bone Conduction-Floating Mass Transducer (BC-FMT) should be positioned near to the cochlea. This requires precise identification of the sigmoid sinus, which cannot be achieved accurately enough using external anatomical landmarks. We thus report on two patients in whom the Bonebridge was implanted via a retrosigmoid approach using CT-guided navigation.

[Intraoperative navigation system in endoscopic sinus surgery]

Intraoperative navigation systems have been developed to increase the safety and efficiency of endoscopic sinus surgery. The objective of this study was to compare the application and utilization of optical and electromagnetical navigation systems in our own experience during the endoscopic surgery.

MATERIAL AND METHODS

An optical-based image guidance systems (MatrixPolar Navigation System, Xion, Germany; Karl Storz Surgical Cockpit Navigation Panel Unit, Karl Storz, Germany; Stryker Navigation CartII ENT, Stryker, USA) and electromagnetic (Fusion ENT Navigation System, Medtronic, USA; Fiagon, fiagon GmbH, Germany) was used to performed 40 sinonasal and skull base surgeries. We compared the precision and accuracy of both types of systems and additional time necessary for setting up the system and real operating room time. We also analysed the convenience of navigation according to possibilities of easy instruments manipulation and fluency of navigation process.

RESULTS

The mean measured accurancy of anatomical localization at start of the surgery for optical systems was 1.62 ± 0.4mm and for electromagnetic respectively 1.79 ± 0.39 mm. The time to set up the optical system was longer than for electromagnetic one (12 vs 5 minutes). Operating room time was increased for both systems, for optical to 22 vs 8 minutes for electromagnetic one. Surgeon's working comfort during operation was better for electromagnetic systems and allowed for fluently movements with instruments.

CONCLUSIONS

Intraoperative navigation systems assist the surgeon with anatomical localization during endoscopic sinus surgery and improve its safety and efficacy. The choice of optical or electromagnetic system should be compared of effective costs and surgeon's preferences.

Image guidance in rhinology and anterior skull base surgery: five-year single institution experience

OBJECTIVES

We examined our experience of image guidance surgery in rhinology, and compared image guidance surgery cases with non-image guidance cases. We also audited our practice against the American Academy of Otolaryngology-Head and Neck Surgery image guidance surgery guidelines.

METHOD

The study employed a single institution retrospective approach comprising 174 image guidance surgery patients (106 males and 68 females) and 134 non-image guidance surgery patients (75 males and 59 females).

RESULTS

In the image guidance surgery group, tumour operations represented 45 per cent of cases (55 per cent were non-neoplastic). Basic, intermediate and advanced (structured classification) procedures represented 19 per cent, 24 per cent and 61 per cent, respectively. Five minor complications were recorded. In non-image guidance surgery, tumour operations represented 8 per cent of cases (92 per cent were non-neoplastic). Basic, intermediate and advanced procedures represented 73 per cent, 12 per cent and 15 per cent, respectively. One minor complication was observed.

CONCLUSION

We report the largest series of image-guided ENT surgical procedures in the UK. In the cases we examined, image guidance surgery was predominantly used in advanced procedures and tumour surgery.

Transnasal endoscopic approach to symptomatic sinonasal osteomas

BACKGROUND

One of the most challenging benign tumors for the ear, nose, and throat (ENT) surgeon is represented by sinonasal osteomas. Surgical treatment should regard just symptomatic osteomas, because these tumors can provoke rhinosinusitis and mucoceles. Recently, new instruments have been applied in endoscopic sinus surgery (ESS). This study was designed to present our experience in the endoscopic management of osteomas of the paranasal sinuses. Clinical findings, preoperative imaging strategy, and surgical techniques are discussed.

METHODS

We retrospectively reviewed clinical records of patients who underwent ESS for sinonasal osteomas between 2003 and 2010 in our institutions.

RESULTS

We have treated with a transnasal endoscopic approach 29 patients affected by paranasal osteomas (13 men and 16 women; age range, 20-78 years; mean, 49.5 years). We found frontoethmoidal junction localization in 14 patients, frontal sinus in 6 patients, ethmoid in 6 patients, sphenoid in 1 patient, maxillary in 1 patient, and multiple osteomas in 1 patient. Initially, patients were treated by the cavitation technique with standard ESS instruments, whereas in more recent cases surgery was assisted by the use of ENT navigation system, curved drills, and ultrasound bone emulsifier. No major complications occurred. No radiological or endoscopic signs of recurrence (mean follow-up, 52 months; range, 6-89 months) have been observed.

CONCLUSION

Endoscopic removal of osteomas of the sinonasal region is feasible, taking into account the location and size of the lesion. Particular importance should be given to new instruments that have been applied in the last years in ESS.

Image-guided surgical navigation in otology

OBJECTIVES/HYPOTHESIS

To evaluate the efficacy of image-guided surgical navigation (IGSN) in otologic surgery and establish practice guidelines.

STUDY DESIGN

Prospective study.

METHODS

Between January 2003 and January 2010, all patients requiring complicated surgery for chronic otitis media, glomus jugulare, atresia, cerebrospinal fluid leak with or without encephalocele, and cholesterol granuloma of the petrous apex were offered IGSN. The accuracy of IGSN relative to pertinent pathology and 11 anatomic landmarks was established. Additionally IGSN-related operative time, complications, and surgical outcome were recorded.

RESULTS

In the study period there were 820 otologic procedures, among 94 patients (96 ears) with disease meeting proposed criteria. Thirteen patients (15 procedures) consented to the use of IGSN. All patients had a minimum 6 months of follow-up. The average additional operative time required was 36.7 minutes. The mean accuracy error was 1.1 mm laterally at the tragus but decreased to 0.8 mm medially at the level of the oval window. The mean accuracy of IGSN was within 1 mm in 10 of the 11 targeted surgical anatomic landmarks.

CONCLUSIONS

Interactive image-guided surgical navigation during complex otologic surgery may improve surgical outcome and decrease morbidity by providing an accurate real-time display of surgical instrumentation relative to patient anatomy and pathology. In select cases, the extra cost of imaging immediately prior to surgery and extra operating room time may be compensated by enhancing the ability to distinguish distorted anatomy relative to disease, potentially improving surgical outcome. IGSN, although useful, does not replace surgical expertise and experience.

Intraoperative C-arm cone-beam computed tomography: quantitative analysis of surgical performance in skull base surgery

OBJECTIVES/HYPOTHESIS

To determine whether incorporation of intraoperative imaging via a new cone-beam computed tomography (CBCT) image-guidance system improves accuracy and facilitates resection in sinus and skull-base surgery through quantification of surgical performance.

STUDY DESIGN

Landmark identification and skull base ablation tasks were performed with a CBCT intraoperative image-guidance system in the experimental group and with image-guided surgery (IGS) alone based on preoperative computed tomography (CT) in the control group.

METHODS

Six cadaveric heads underwent preoperative CT imaging and surgical planning identifying surgical targets. Three types of surgical tasks were planned: landmark point identification, line contour identification, and volume drill-out. Key anatomic structures (carotid artery and optic nerve) were chosen for landmark identification and line contour tasks. Complete ethmoidectomy, vidian corridor drill-out, and clival resection were performed for volume ablation tasks. The CBCT guidance system was used in the experimental group and performance was assessed by metrics of target registration error, sensitivity, and specificity of excision.

RESULTS

Significant improvements were seen for point identification and line tracing tasks. Additional resection was performed in 67% of tasks in the CBCT group, and qualitative feedback indicated unequivocal improvement in confidence for all tasks. In review of tasks in the control group, additional resection would have been performed in 35% of tasks if an intraoperative image was available.

CONCLUSIONS

An experimental prototype C-arm CBCT guidance system was shown to improve surgical precision in the identification of skull base targets and increase accuracy in the ablation of surgical target volumes in comparison to using IGS alone.

A novel technique for tailoring frontal osteoplastic flaps using the ENT magnetic navigation system

CONCLUSION

The ENT magnetic navigation system is potentially useful and offers the most accurate technique for harvesting frontal osteoplastic flaps. It represents a valid tool in the wide range of instruments available to rhinologists.

OBJECTIVE

Precise delineation of the boundaries of the frontal sinus is a crucial step when harvesting a frontal osteoplastic flap. We present a novel technique using the ENT magnetic navigation system.

METHODS

Nineteen patients affected by different pathologies involving the frontal sinus underwent an osteoplastic flap procedure using the ENT magnetic navigation system between January 2009 and April 2011.

RESULTS

The ENT magnetic navigation system was found to be a safe and accurate tool for delineating the frontal sinus boundaries. No intraoperative complications occurred during the osteoplastic procedures.

A noncontact laser-guided system for endoscopic computer-assisted sinus surgery

The limited size of the nose leads to frequent instrument changes in navigated endonasal sinus surgery. Tracked instruments provide limited accuracy, and the pointer gives no navigation information during tissue removal. To overcome information loss, laser triangulation was integrated into navigation information. Accuracy and reliability of the laser-assisted distance-measuring system were evaluated within the distance of 0 and 20 mm. System accuracy of the laser endoscope was compared with a standard pointer using registration via bone screws and surface matching. Accuracy of the laser was 0.12 mm ± 0.12 mm with a reliability of 0.2 mm. The system accuracy of the laser endoscope was 0.59 mm ± 0.16 mm using bone screw registration and 0.64 mm ± 0.22 mm using surface matching. Additionally, laser endoscope is more accurate compared with the pointer using bone screw registration. Overall, navigation information was successfully integrated into an endoscope by laser triangulation with encouraging results.

Endoscopic orientation of the parasellar region in sphenoid sinus with ill-defined bony landmarks: an anatomic study

The sphenoid bony landmarks are important for endoscopic orientation in skull base surgery but show a wide range of variations. We aimed to describe an instructional model for the endoscopic parasellar anatomy in sphenoid sinuses with ill-defined bony landmarks. Five preserved injected cadaveric heads and four sides of dry skulls were studied endoscopically via transethmoid, transsphenoidal approach. The parasellar region was exposed by drilling along the maxillary nerve (V2) canal [the length of the foramen rotundum (FR) between the middle cranial fossa and the pterygopalatine fossa]. This was achieved by drilling in the inferior part of the lateral wall of posterior ethmoids immediately above the sphenopalatine foramen. Cavernous V2 was traced to the paraclival internal carotid artery (ICA). Cavernous sinus (CS) apex was exposed by drilling a triangle bounded by V2 and its canal inferiorly, bone between FR and superior orbital fissure (SOF) anteriorly, and ophthalmic nerve (V1) superiorly. Drilling was continued toward the annulus of Zinn (AZ) and optic nerve superiorly and over the intracavernous ICA posteriorly. Endoscopic measurements between V2, SOF, AZ, and opticocarotid recess were obtained. Endoscopic systematic orientation of parasellar anatomy is presented that can be helpful for approaching sphenoid sinus with ill-defined bony landmarks.

Prospective evaluation of intraoperative computed tomography imaging for endoscopic sinonasal and skull-base surgery

BACKGROUND

The objective of this study was to prospectively evaluate the clinical impact of intraoperative computed tomography (CT) imaging on endoscopic sinonasal and skull base procedures.

METHODS

A total of 49 patients were enrolled after informed consent from December 2009 to May 2010. Patients underwent intraoperative volume CT imaging (xCAT, Xoran Technologies, Ann Arbor, MI) at the conclusion of their proposed surgery.

RESULTS

The mean age was 48.6 years with male:female ratio of 1.3:1. Surgical procedures included revision or primary endoscopic sinonasal surgery (ESS) (36), endoscopic benign or malignant tumor resection (10), endoscopic mucocele drainage (2), and endoscopic tumor biopsy (1). The mean Lund-Mackay (L-M) score was 10.6 (range 1-21). The indications for intraoperative imaging included extent of paranasal sinus dissection in 38 (77.6%), extent of tumor resection in 11 (22.4%), adequacy of mucocele drainage in 3 (6.1%), and frontal stent position in 2 (4.1%) cases. Average acquisition time was 5.3 minutes. The CT acquisition quality was deemed excellent in 24 (49.0%), good in 15 (30.6%), fair in 5 (10.2%), and unattainable in 5 (10.2%) cases. Additional interventions were performed in 8 of 44 cases (18%) based on the intraoperative CT dataset. Analysis of predictive factors for additional intervention, including presence of polyps, presence of tumor, previous surgery, use of image guidance, and CT quality did not reach statistical significance.

CONCLUSION

Intraoperative CT scanning may hold important utility in selected endoscopic sinonasal and skull base procedures with additional interventions being performed in 18% of cases. The present study was unable to identify specific factors that would preoperatively predict the need for intraoperative imaging. Future clinical trials should include a multi-institutional design to better delineate these important variables.

Selecting the best approach to the frontal sinus

The Messerklinger technique is an endoscopic approach to sinus surgery designed to be minimally invasive and preserve mucosa and hence physiological function. More recently there have been advocates for more radical endoscopic approaches to the frontal sinus such as the Modified Lothrop. This review discusses different approaches to frontal sinus surgery including any advantages and disadvantages to each approach. After examining the evidence from the literature, meticulously performed endoscopic frontal sinusotomy with or without computer guidance appears to be the most effective minimally invasive procedure for treating chronic frontal sinusitis secondary to outflow tract obstruction. Properly performed, it is almost always effective in dealing with even the most diseased frontal sinus. It offers clear advantages in reducing complications and recurrence rates in frontal sinus disease, even for revision cases.

Role of intraoperative CT-updates during image-guided endoscopic sinus surgery for sinonasal fibro-osseous lesions

Fibrous dysplasia, ossifying fibroma and osteomas are collectively known as fibro-osseous lesions. Occurrence in the sinonasal region is rare, and its management can be technically challenging. We report a case of an 8-year-old female with cemento-ossifying fibroma of the ethmoid sinus who underwent a two-staged, endoscopically assisted, transfacial resection of the lesion and a 31-year-old male with fibrous dysplasia of the ethmoid sinus who underwent endoscopic removal of the tumor. Both cases utilized intraoperative computed tomography (CT)-updated image-guided systems (IGS) to improve surgical precision. In the second patient, further resection was undertaken after CT-update in the same surgery. The postoperative courses were uneventful, and at 1-year follow-up no tumor recurrence was observed in either patient. Our experience suggested that the use of intraoperative CT-updated IGS in endoscopic or endoscopically assisted surgeries for sinonasal fibro-osseous lesions will lead to more optimal tumor control, which can translate into greater patient safety.

Influence of different registration modalities on navigation accuracy in ear, nose, and throat surgery depending on the surgical field

OBJECTIVES/HYPOTHESIS

Various invasive and noninvasive registration methods have been established in the past for intraoperative navigation. The present study compared the registration and navigation accuracy of three different registration modalities in anatomical locations of special interest for ear, nose, and throat surgery.

STUDY DESIGN

Prospective experimental phantom study.

METHODS

Four skull models were individually fabricated with a three-dimensional printer based on the patient's computed tomography data sets and fitted with an individual customized silicone skin. Three different registration modalities were examined: 1) invasive marker (IM), 2) oral splint (OS), and 3) laser scan (L). Accuracy measurements were assessed by targeting 26 titanium screws placed over the skull. The overall accuracy and the target registration error for eight selected anatomical locations were measured.

RESULTS

Mean accuracy was 0.67 + or - 0.1 mm (quadratic mean + or - standard deviation) for IM, 0.98 + or - 0.16 mm for OS, and 1.3 + or - 0.12 mm for L. The greatest differences in accuracy were found on the mastoid with best accuracy for IM (0.59 + or - 0.2 mm; P < .05 vs. OS and L), followed by OS (1.23 + or - 0.41 mm; P < .05 vs. L), and L (1.88 + or - 0.45 mm). In contrast, only small differences in accuracy were detected in the anterior skull base between the registration modalities (IM 0.75 + or - 0.21 mm, OS 0.71 + or - 0.27 mm, L 0.93 + or - 0.34 mm).

CONCLUSIONS

L and OS meet accuracy requirements in the midface and anterior skull base. OS is superior to L with navigation accuracies comparable to marker registration. However, neither method meets the high precision requirements for lateral skull base surgery. Laryngoscope, 2010.

Surgical interventions and local therapy for Wegener's granulomatosis

PURPOSE OF REVIEW

This review discusses the use of interventional procedures to treat manifestations of Wegener's granulomatosis caused by tissue damage and scarring. These manifestations include nasal and paranasal sinus disease, middle ear inflammation, nasolacrimal duct obstruction, orbital inflammatory masses, subglottic stenosis, tracheobronchial disease, and end-stage renal disease.

RECENT FINDINGS

Tissue damage caused by inflammation or a cicatricial process represents one of the major sources of morbidity for patients with Wegener's granulomatosis. Some of these manifestations require special interventions used alone or in combination with conventional medical treatment. These interventional procedures may include surgical or endoscopic repair of altered tissue, replacement of damaged organs, or the delivery of topical or injectable medications directly to the site of disease. Distinguishing symptoms caused by active disease from symptoms caused by tissue scarring is challenging and may play a critical role regarding the use of systemic immunosuppressive medications in combination with interventional therapy.

SUMMARY

Interventional procedures are indicated in certain manifestations of Wegener's granulomatosis. Distinguishing active Wegener's granulomatosis from inactive Wegener's granulomatosis and recognizing disease manifestations that may be amenable to local interventions can greatly improve the quality of life of patients. However, the evidence supporting the use of many of these interventions is based on small case series or individual reports.

Intraoperative imaging for otorhinolaryngology-head and neck surgery

The applications of endoscopic techniques have expanded beyond the treatment of inflammatory sinus disease and toward the resection of anterior and middle skull base lesions. Image-guided surgery has emerged as an important tool that compensates for the limitations of surgical endoscopy. The disadvantage of image-guided surgery, however, is its dependence on preoperative imaging data. Intraoperative imaging provides near real-time imaging that has the potential to improve surgical outcomes and reduce operative morbidity. The role of intraoperative imaging in endoscopic sinus and skull base surgery has demonstrated great promise in recent literature. It has had an impact on surgical decision-making during functional endoscopic sinus surgery and the resection of anterior skull base neoplasia. Advances in portable MRI and volumetric CT technology have enhanced the efficiency and safety of intraoperative imaging. Although further studies are required to quantify the precise utility of this new technology, it appears that intraoperative imaging will be an important tool for rhinologic surgery.

Outcome of computer-assisted surgery in patients with chronic rhinosinusitis

Objective:

To compare the complication rates and outcome of computer-assisted versus non-computer-assisted functional endoscopic sinus surgery.

Methods:

We reviewed retrospectively the medical records of 276 patients who had undergone sinus surgery for chronic rhinosinusitis with (n = 108) or without (n = 168) computer assistance, from 1996 to 2004, to determine the incidence of complications and need for revision surgery.

Results:

The incidence of complications was 6.5 per cent in the computer-assisted group and 6.0 per cent in the non-computer-assisted group (p = 1.00). In the computer-assisted group, 9.2 per cent needed revision surgery, compared with 10.7 per cent in the non-assisted group (p = 0.84).

Conclusions:

Although our study found no significant difference in complications or revision rates, computer-assisted surgery serves as an important orientation aid during functional endoscopic sinus surgery.

Image guidance systems for minimally invasive sinus and skull base surgery in children

OBJECTIVE

The use of image guidance for sinonasal and skull base surgery has been well-characterized in adults but there is limited information on the use of these systems in the pediatric population, despite their widespread use. The aim of this study is to evaluate the use of image guidance systems to facilitate an endoscopic minimally invasive approach to sinonasal and skull base surgery in a pediatric population.

METHODS

A retrospective cohort study was performed at a tertiary pediatric hospital. Thirty-three children presented with complications of sinusitis, tumors, traumatic, or congenital lesions of the skull base and underwent endoscopic surgery using image guidance from March 2000 to April 2007. Patient variables including diagnosis, extent of disease, and complications were extracted from paper and computer charts. Additional surgical variables including set-up time, accuracy, surgeon satisfaction index and number of uses per case were also reviewed.

RESULTS

Twenty-eight patients (85%) underwent sinonasal surgery and five (15%) underwent skull base surgery. Indications included infectious complications of acute sinusitis (N=15), neoplasms (N=12), choanal atresia (N=4), and cerebrospinal fluid leak (N=2). Thirty-one patients (94%) required only one procedure. No surgical complications were reported. Surgeon satisfaction, mean accuracy and number of uses per procedure increased over time (p<0.05).

CONCLUSIONS

Image guidance systems are safe and effective tools that facilitate a minimally invasive approach to sinonasal and skull base surgery in children. Consistent with adult literature, usage and surgeon comfort increased with experience. The additional anatomical information obtained by image guidance systems facilitates a minimally invasive endoscopic approach for sinonasal and skull base pathologies.