Revision sinus surgery depends on knowing constant bony anatomical landmarks that are unaltered by prior surgery or advanced pathology. • A wide maxillary antrostomy exposes the posterior lamellae and the medial orbital floor (MOF). • The superior margin of the maxillary sinusotomy (junction of the inferior aspect of the lamina papyracea and MOF) forms a bony ridge, which delineates the anterior ethmoid cells (medially) from the orbital floor (laterally). • The posterior margin of the maxillary sinusotomy (posterior fontanelle remnant), delineates the middle turbinate/sphenopalatine foramen (medially) from the posterior wall of the maxillary sinus (laterally). • The relationship between the MOF and adjacent structures can help guide the surgeon. • The posterior ethmoid cells lie superior to the posterior orbital floor adjacent and medial to the ridge of the antrostomy. • The sphenoid sinus lies inferior to the MOF, adjacent to the nasal septum, approximately 7 cm from the columella. • The nasolacrimal duct runs anterior, but parallel to the direction of the frontal recess and infundibulum.
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