Describe the anatomy osteomeatal complex.

The osteomeatal complex includes:

  • Bulla ethmodalis
  • Uncinate process
  • Maxillary turbinate
  • Ethmoid infundibulum.

It is important as ostium of frontal maxillary and anterior ethmoidal sinuses are present in this area.

Any anatomical variation mucosal swelling of osteomeatal complex can cause obstruction →stasis →repeated infection upstream sinuses.

Bulla ethmoidalis:

  • Largest, constant anterior ethmoidal cell
  • If not pneumatized, it may remain like a solid bony prominence.
  • It may extend superiorly to base of skull and posteriorly to ground lamella

Retrobulbar recess+suprabulbar recess= Lateral sinus of Grunwald.

Lateral→ lamina papyracea

superior→ skull base

Inferior →Bulla

Medially→Opens into middle meatus

Uncinate process:

  • Small thin lamina of ethmoid bone
  • Forms floor and medial wall of the ethmoidal influndibulum
  • Sickle shaped structure running from anterosuperior → posteroinferior direction.
2 borders2 ends
Posterosuperior: free, sharp and virus|| to anterior surface of bulla ethmoidalsPosteroinferior end: attached to inferior turbinate and divides lower membranous part of middle meatus into anterior and posterior fontanella.
anteroinferior border: altache to lateral nasal wall.Antero superior end: variable insection LP/skull base/MT accounts for the variation in the drainage of frontal sinus.

Middle turbinate:

  • Attach to the lateral wall through ground lamella.
  • Anterior 1/3 lie on sagittal plane →lateral edge of cribriform plate.
  • Middle 1/3 lie on frontal plane →Lamina papyracea
  • Posterior 1/3 runs horizontally →LP +medial wall of maxillary rimus.
  • Fracture of Middle Turbinate can damage cribriform plate and cause CSF rhinorrhea and anosmia
  • Paradoxical Middle Turbinate  can narrow middle meatus and affect ventilation
  • Concha bullosa (pneumatization of MT): 30%
    • Usually asymptomatic
    • drains into the frontal recess directly through agger nast cells
    • affect ventilation of OMC and resuts s/s.

Hiatus semilunaris: 2 dimentional gap b/w Uncinate process and Bulla Ethmoidalis .

Opens laterally into 3 dimentional funnel shaped face called enthmoidal influndibulum.

Ethmoidal infundibulum:

Frontal sinus →opens into the anterosuperior part of infundibulium just posterior to posterior wall of agger nasi cell.

Anterior ethmoidal opens into infundibulum

Maxillary sinus:

  • Natural ostium: opens in posterior infundibulum
  • Accessory ostium:  4-5% in normal but increased to 25 % in Chronic rhinosinusitis
  • Functional endoscopic sinus surgery(FESS) puts stress on this Osteomeatal comlex (OMC) and aims to restores normal sinus drainage and ventilation.


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