CT-Based Quantification of Chronic Sinonasal Osteitis: Relationship Between Global Osteitis Scoring Scale and Hounsfield Unit

Technical Summary: CT-Based Quantification of Chronic Sinonasal Osteitis

Problem Statement
Chronic rhinosinusitis (CRS) is a persistent inflammatory condition that frequently extends beyond the mucosa to induce osteitis, characterized by the thickening of paranasal sinus walls. While High-Resolution Computed Tomography (HRCT) is the standard imaging modality for assessing this condition, current radiological evaluation relies heavily on the Global Osteitis Scoring Scale (GOSS). The GOSS system quantifies osteitis based on the thickness and extent of sinus wall involvement. However, the authors note that this thickness-based approach captures morphological changes but fails to account for alterations in bone mineral density. Since chronic inflammation triggers complex bone remodeling processes—including osteoblastic activity, osteoclastic resorption, and neo-osteogenesis—relying solely on wall thickness may not adequately reflect the true complexity of the disease. The relationship between structural thickening (GOSS) and bone density (measured in Hounsfield Units, HU) remains poorly understood, creating a gap in the radiologic characterization of CRS-related osteitis.

Methodology
This study employed a retrospective cross-sectional design involving 32 adult patients diagnosed with CRS according to the 2020 EPOS criteria. Subjects were recruited from Dr. Saiful Anwar General Hospital and underwent sinonasal-focused HRCT scans without contrast.

• Exclusion Criteria: Patients with a history of functional endoscopic sinus surgery (FESS), recent corticosteroid or antibiotic use (within four weeks), sinonasal malignancy, or sinus trauma were excluded.
• Data Acquisition: CT scans were performed using a 128-slice scanner with bone window settings and a slice thickness of 1–3 mm.
• Measurement Protocol:
  • GOSS Scoring: Each paranasal sinus (maxillary, anterior/posterior ethmoid, sphenoid, and frontal) was independently scored from 0 to 5 based on wall thickening and extent of involvement.
  • HU Measurement: Mean Hounsfield Unit values were measured at standardized locations on the sinus walls to quantify bone mineralization.
  • Reliability: Scoring and measurements were conducted by a head and neck subspecialist radiologist and an ENT-Head and Neck subspecialist rhinologist.
• Statistical Analysis: The correlation between GOSS scores and HU values was analyzed using Spearman's rank correlation test (α = 0.05) for both the total dataset and individual sinus locations.

Key Results
The study analyzed 156 osteitis-positive sinuses across the 32 patients. The most frequent location for osteitis was the right anterior ethmoid sinus (16.7%).

• Overall Correlation: A statistically significant but very weak positive correlation was found between GOSS scores and HU values across the total dataset (Spearman's r = 0.167; p = 0.038). This suggests a slight tendency for bone density to increase as wall thickness increases, but the association is minimal.
• Sinus-Specific Findings: When analyzed individually, no significant correlation was observed between GOSS scores and HU values for any specific sinus (p > 0.05).
• Density Patterns: Notably, the highest mean HU values were observed in sinuses with a GOSS score of 0 (no wall thickening). In sinuses with higher GOSS scores (1–5), HU values varied significantly. In certain sinuses, such as the maxillary and sphenoid sinuses, a negative correlation trend was observed, where increased thickness was associated with lower HU values.

Key Contributions
The primary contribution of this work is the empirical demonstration that bone thickness (GOSS) and bone density (HU) represent distinct imaging characteristics of osteitic remodeling in CRS. The study challenges the assumption that increased wall thickness necessarily correlates with increased bone mineralization. By showing that sinuses without thickening can possess the highest density, and that thickened sinuses exhibit heterogeneous density patterns, the paper highlights the limitations of using GOSS as a sole indicator of bone remodeling severity.

Significance and Claims
The authors conclude that the assessment of chronic sinonasal osteitis should integrate both structural (thickness-based) and densitometric (HU-based) CT parameters. They assert that thickness-based scoring alone is insufficient to reflect the complexity of inflammatory bone remodeling, which may involve simultaneous phases of resorption and neo-osteogenesis resulting in heterogeneous bone density.

The paper modestly claims that this combined approach may improve the radiologic characterization of CRS-related osteitis and support more accurate disease assessment. It does not propose a new clinical protocol or specific HU thresholds but suggests that future research with larger, multicenter samples is required to clarify the correlation between these parameters and to establish accurate HU threshold values for radiological evaluation. The study emphasizes that understanding the distinct nature of these parameters is a necessary step toward better defining the pathophysiology of osteitis in CRS.