Supraorbital keyhole approach and frontal sinus pneumatization: a radioanatomical study of surgical corridors and safety margins

The supraorbital keyhole approach (SKA) is a minimally invasive corridor to the anterior skull base. However, inadvertent frontal sinus (FS) entry remains a primary complication. This study aims to quantify the relationship between surgical landmarks and FS morphometry to establish safety thresholds. Analysis was performed on 120 patients (53 males, 67 females; 48.5 ± 14.5 years old) using high-resolution computed tomography (CT) scans. Distances from the supraorbital notch (SON) and superior temporal line (STL) to the lateral FS border were measured. Statistical analysis was performed according to sides, sexes and FS pneumatization types. Receiver operating characteristic (ROC) curves and the 95% safety rule (5th percentile) were utilized to identify predictive morphometric thresholds and safe surgical corridors. Morphometric analysis recorded significant sexual dimorphism, with males exhibiting larger FS dimensions and more hyperplastic patterns (p < 0.001 and p = 0.013, respectively). Distances of surgical landmarks (SON, STL) from the FS lateral border were significantly different between the FS pneumatization patterns (p < 0.001). These distances were also statistically significant correlated with FS morphometric dimensions. The 95% safety rule established that the FS lateral border remains within 9.20 mm lateral to the SON, while a minimum safe window of 9.13 mm is maintained medial to the STL. ROC analysis identified FS width larger than 28.57 mm (AUC = 0.81) and height more than 23.93 mm (AUC = 0.77) as robust predictors of lateral sinus involvement. The proposed ‘9-mm safety algorithm' provides a standardized framework to minimize FS breach. Preoperative screening for ipsilateral FS width exceeding 28.57 mm serves as a critical diagnostic finding and highlights the need for patient-specific risk stratification for the supraorbital corridor.