During functional endoscopic sinus surgery (FESS), the surgeon must identify the 'key landmark' of the middle turbinate basal lamella (ground lamella). Surgeons must not violate this structure because it separates:

• A The ethmoid bulla from the hiatus semilunaris
• B The anterior ethmoidal sinuses from the posterior ethmoidal sinuses ✓
• C The maxillary sinus ostium from the nasolacrimal duct
• D The sphenoid sinus from the posterior ethmoids

Explanation

The basal lamella (ground lamella) of the middle turbinate is its horizontal insertion into the lateral nasal wall. Anterior to the basal lamella lie the anterior ethmoid cells (agger nasi, ethmoid bulla, infraorbital cells); posterior to it lie the posterior ethmoid cells. This anatomical boundary is critical in FESS to avoid inadvertent entry into posterior ethmoids when performing anterior ethmoidectomy, and to systematically approach posterior disease. Penetration into the skull base or orbit most commonly occurs during posterior ethmoid dissection.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.