Modelling the effects of middle meatal synechiae post-endoscopic sinus surgery using computational fluid dynamics (CFD) and virtual surgery

Chronic rhinosinusitis (CRS) is a common sinonasal condition carrying a significant disease burden. Functional endoscopic sinus surgery (FESS) is often indicated where medical management fails. Middle turbinate lateralisation and adhesion formation (MiTLAF) is a common cause of failed FESS. Various MiTLAF prevention techniques have been described in the literature; however, no studies objectively analyse the physiological sequelae. This thesis reviews the literature regarding MiTLAF prevention techniques to determine the most efficacious and safe technique(s). As a proof of concept, computational fluid dynamics (CFD) analysis was employed to model aerodynamic changes occurring in the presence of MT synechiae. Systematic review was performed following the PRISMA guidelines. The effects of post-operative MT synechiae on airflow velocity and streamlines, temperature, and relative humidity levels were done using CFD. A three-dimensional sinonasal model was segmented from the data, and virtual surgery was performed to simulate a full-house functional endoscopic sinus surgery. Multiple synechiae models were virtually created in locations to reflect those most commonly seen in clinical practice. CFD analysis was performed on each model, in comparison with a control model without synechiae. Mass-weighted averages for airflow velocity, relative humidity and mucosal temperature were recorded to assess for dynamic changes in the presence of synechiae. The reviewed literature suggests that silastic splints and conchopexy are most safe and effective in MiTLAF prevention. CFD analysis demonstrated aberrant downstream airflow in all models. There was reduced airflow and increased air temperature/humidity in ipsilateral frontal, ethmoid and sphenoid sinuses with increased airflow velocity and reduced air/mucosal surface temperature in a concentrated central “jet” in the middle meatus. Effects were more significant with larger synechia. Bulk inspired airflow at the nasopharynx was largely unaffected. These findings may explain the persistent symptoms seen in post-FESS CRS patients with MT synechiae and reinforce the importance of prevention and adhesiolysis. Further studies with multiple models of actual post-FESS patients with synechiae are required to validate these findings