# Multidimensional Morphology of the Ethmoid Roof and Anterior Ethmoidal Artery: A CT-Based Analysis and Proposal of the Akcan Classification

## TL;DR

This study introduces a new classification system for ethmoid roof anatomy that includes artery positioning, aiming to improve surgical planning for sinus and skull base procedures.

## Contribution

The Akcan Classification integrates anterior ethmoidal artery exit patterns with morphometric parameters, offering a more comprehensive anatomical framework than existing systems.

## Key findings

- Suspended AEA configurations correlate with wider ethmoid roofs, deeper lateral lamellae, steeper angles, and shorter AEA–lamella distances.
- Supraorbital ethmoid cells are more common in Type 3 AEA configurations.
- All morphometric measurements showed excellent interobserver reliability (ICC range 0.87–0.94).

## Abstract

Background/Objectives: Anatomical variation in the ethmoid roof and lateral lamella play an important role in anatomical vulnerability during endoscopic sinus and skull base surgery. However, widely used classifications, including the Keros system, primarily focus on vertical depth and may not fully reflect the complex geometric relationship between the ethmoid roof, lateral lamella, and the anterior ethmoidal artery (AEA). This study aimed to characterize ethmoid roof and lateral lamella anatomy using high-resolution CT and to propose a descriptive radiological framework—the Akcan Classification—that integrates AEA exit patterns with multiple morphometric parameters. Given the complexity of thin skull base structures, interobserver reproducibility of all morphometric parameters was additionally assessed to ensure measurement robustness. Methods: High-resolution paranasal sinus CT scans from 175 adults (350 sides) were retrospectively evaluated. Measurements included ethmoid roof width, lateral lamella depth, anterior–posterior length, lamellar angle, AEA–lamella distance, and sinonasal anatomical variations. Interobserver reliability was quantified using ICCs. AEA morphology was categorized as in-canal (Type 1), partially suspended (Type 2), or fully suspended (Type 3) based on radiological appearance of bony canalization. Appropriate statistical tests were used to compare morphometric features across groups. Results: Suspended AEA configurations demonstrated progressively wider ethmoid roofs, deeper lateral lamellae, steeper lamellar inclination, and shorter AEA–lamella distances (all p < 0.001). Supraorbital ethmoid cells were more frequently observed in Type 3 cases (p < 0.001). Other anatomical variations showed no significant association with ethmoid roof morphology. Interobserver reliability was excellent for all measurements (ICC range 0.87–0.94). Conclusions: The findings suggest that AEA configuration is associated with broader patterns of ethmoid roof and lateral lamella morphology. Rather than serving as a validated predictor of surgical outcomes, the Akcan Classification provides a structured anatomical and radiological descriptor that complements depth-based systems such as the Keros classification. The high reproducibility of measurements supports its potential utility for standardized anatomical assessment and preoperative radiological interpretation, while further studies incorporating surgical correlation are required.