Ostiomeatal complex

The ostiomeatal complex (OMC) or ostiomeatal unit (OMU), sometimes less correctly spelled as osteomeatal complex, is a common channel that links the frontal sinus, anterior ethmoid air cells and the maxillary sinus to the middle meatus, allowing airflow and mucociliary drainage. 

Gross anatomy

The ostiomeatal complex is composed of five structures:

1. maxillary ostium: drainage channel of the maxillary sinus
2. infundibulum: common channel that drains the ostia of the maxillary antra and anterior ethmoid air cells to the hiatus semilunaris
3. ethmoid bulla: usually a single air cell that projects over the hiatus semilunaris
4. uncinate process: hook-like process that arises from the posteromedial aspect of the nasolacrimal duct and forms the anterior boundary of the hiatus semilunaris
5. hiatus semilunaris: final drainage passage; a region between the ethmoid bulla superiorly and free-edge of the uncinate process

Variant anatomy

There is a wide range of anatomical variants that affect the many structures that compose the ostiomeatal complex and are not pathological in themselves but their presence can result in disease. See main article, ostiomeatal narrowing due to nasal anatomical variation, for the complete list. 

Related pathology

• silent sinus syndrome