Experimental and Computational Analyses of Accessory Ostia Effects on Maxillary Sinus Ventilation

Background: Accessory ostia (AOs) can notably alter maxillary sinus ventilation, yet configuration-specific effects remain unclear. This study quantified how AO location and orientation regulate sinus ventilation using in vitro measurements and numerical analyses. Methods: One patient-specific sinonasal geometry (control) was used to reconstruct five models with varying AO numbers, locations, and orientations (AO-F, AO-FC, AO-F30, AO-B, AO-FB). E-vapor was used as a visual tracer for sinus clearance under breath-hold and quiet breathing conditions. Complementary simulations characterized flow dynamics and sinus ventilation rates. Results: Both inhalation and AO presence accelerate e-vapor clearance for all conditions considered. The e-vapor clearance time in AO-FB decreases from 51 s under breath-hold to 29 s under quiet breathing (1 m/s). Configuration-wise, posterior AO ventilates the sinus faster than anterior AO, with dual anterior–posterior ostia (AO-FB) consistently performing the best. Among the three anterior AO, an uptilt AO ventilates the sinus faster than a parallel one, which is in turn faster than an AO located closer to the natural ostium (NO), i.e., AO-F30 > AO-F > AO-FC. CFD predictions provide a mechanistic understanding of the configuration-specific differences observed in vitro. Flow patterns in the ostium–sinus region, as well as the ventilation rate and driving pressure, show high sensitivities to AO location and orientation. At 1 m/s, the predicted AO-NO pressure drop ranges 2–18 mPa, with the lowest in AO-FC and highest in AO-B. Conclusions: The high sensitivity of sinus ventilation to AO configurations underscores the clinical importance of examining NO-adjacent openings in surgical planning and physiological interpretation.