Sagittal computerized tomography reconstruction of the lateral nasal wall for functional endoscopic sinus surgery

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.

Frontal Angle: A New Predictor of Difficulty in Endoscopic Frontal Sinus Surgery-A Preliminary Computed Tomography Study

OBJECTIVES

The possibility of visualization of the frontal sinus during endoscopic surgery depends on 3-dimensional configuration of the frontal sinus opening (FSO). We aimed to determine the prevalence of unfavorable angulation of the lower part of the posterior wall of the frontal sinus and its relation to FSO diameter.

METHODS

One hundred and twenty-eight computed tomography (CT) scans were retrospectively reviewed to measure (1) the angle between the nasal floor and the plane tangent to the posterior table of the frontal sinus above the most posterior aspect of the anterior buttress (frontal angle, FA) and (2) dimensions of the FSO.

RESULTS

The FA ranged from below 30° to 90°. Nearly 13% of sinuses (16.4% of patients) showed FA about 90°, which should enable good visualization of the sinus with the 30° scope after opening and clearing the frontal recess, while 4% (6.25% of patients) showed FA ≤ 30°. The anterior-posterior diameter (A-PD) was below 5 mm in 17.6% of sinuses (26.6% of patients). There was a significant correlation between FA and A-PD. Unfavorable combination of FA and A-PD (<45°, <5 mm) was present in 5.2% of sinuses (8.6% of patients), and extremely unfavorable combination (<30°, <5 mm) in 0.8% (0.8% of patients).

CONCLUSIONS

The FA shows great interindividual variability, which is very likely to reflect the possibility of inspection of the frontal sinus. This implies a need for further prospective clinical studies to validate FA as a predictor of difficulty in frontal sinus surgery.

Frontal Ostium Grade (FOG): A New Computer Tomography Grading System for Endoscopic Frontal Sinus Surgery

Objective

The location and size of the frontal sinus ostium are critical in determining surgical difficulty. The more anterior the ostium, the more difficult is the surgical access. We propose a novel computed tomography (CT) grading specific to the anatomical position of the frontal ostium.

Study Design

Observational study followed by a prospective part.

Settings

Tertiary rhinology practice

Subject and Methods

On a specified sagittal CT cut, a vertical line was drawn through the posterior edge of the frontal process of the maxilla (frontal buttress/beak) along its vertical axis (reference [R-] line). A second (S-) line was placed at the point of upturn of the skull base. Based on if the S-line was posterior or anterior to the R-line, the frontal ostium was graded positive and more easily accessible or negative and thereby more challenging, respectively. If both lines overlapped, then a neutral (0) grading existed.

Results

A total of 297 CTs (594 ostia) were analyzed. In total, 394 (65%) ostia were grade positive, 52 (8.75%) were grade negative, and 103 (17.3%) were grade neutral. Ninety frontal sinusotomies were then performed using this grading system: 48 were positive, 21 negative, and 21 neutral. The average time to complete a frontal sinusotomy was 9.96 minutes for grade positive compared to 11.4 minutes for neutral and 16.05 minutes for grade negative ( P < .005).

Conclusion

This novel anatomical CT grading system is designed to be useful in planning and predicting the level of difficulty in endoscopic frontal sinus surgery.

Analysis of the Agger nasi cell and frontal sinus ostium sizes using computed tomography of the paranasal sinuses

The Agger nasi cell (ANC) and the frontal sinus ostium (FO) are important structures that can influence the anatomy and physiology of the frontal recess. The aim of this study was to evaluate the presence and size of ANC and the FO and correlate them according to gender, race and among themselves.

Method

A prospective study with 40 patients who underwent CT of the paranasal sinuses with sagittal reconstruction. Measurements: ANC (APAN) anteroposterior diameter, ANC (CCAN) craniocaudal diameter, ANC (LLAN) side-to-side diameter, anteroposterior diameter of the FO (APFO) and side-to-side diameter of the FO (LLFO).

Results

Twenty-two patients were male and 18 females, mean age 33.7 years. Most patients were white (45%), followed by browns (32.5%), blacks (20%) and asians (2.5%). The ANC was present in 98.7% of patients. There was statistical difference for APAN on females and LLAN on females and on the total sample. There were no differences for all measurements regarding gender, as well as the race. ANC and FO measurements showed positive correlation, but poor or very poor.

Conclusion

The prevalence of ANC in our sample was high and did not show a statistically significant difference for most measurements. The correlation between measurements of ANC and the FO was poor or very poor.

Anatomical variation of the nasal septum: Correlation among septal components

The nasal septum consists of multiple components with various developmental origins and is considered a mosaic structure. Few studies have focused on anatomical relationships among the components of the nasal septum, even though they are essential for clinical assessments of morphological abnormalities in the nasal septum. This study was performed to evaluate anatomical correlations among components of the nasal septum using computed tomography (CT) of the paranasal sinus. We studied images from CT scans of 168 paranasal sinuses collected at a secondary referral hospital between July 2008 and February 2009. The area of each component of the nasal septum was measured using median sagittal images of CT scans after three-dimensional reconstruction using computer software. The area of the cartilaginous septum decreased with age, whereas the area of the total nasal septum remained constant. The area of the perpendicular plate of ethmoid increased with age at the expense of the area of the septal cartilage.