The maxillary line: anatomic characterization and clinical utility of an important surgical landmark.

Objectives: The maxillary line is a mucosal projection along the lateral nasal wall that serves as a landmark for endoscopic sinus and orbital procedures. The anatomic relations of this structure are not well described. We sought to define the anatomy of the maxillary line and explore its clinical utility.

Study Design: Cadaver dissection/case series.

Methods: Twenty-five cadaveric nasal specimens were dissected. Extranasal and intranasal measurements of structures including the lacrimal crests, sac and duct, the suture line between the maxillary and lacrimal bones, and the maxillary sinus ostium were taken. The mid-point of the maxillary line, termed the "M point," was used for reference. The distance from the nasal sill to the M point was measured in 30 consecutive clinic patients.

Results: The maxillary line corresponded intranasally to the junction of the uncinate and maxilla and extranasally to the suture line between the lacrimal bone and maxilla within the lacrimal fossa. This suture was approximately half way between the anterior and posterior crests. Axially, the plane of the M point corresponded to the superior margin of the maxillary sinus ostium posteriorly (average 10 mm) and was just inferior to the lacrimal sac-duct junction anteriorly. In live subjects, the M point was approximately 3.9 cm from the nasal sill in women and 4.8 cm in men.

Conclusion: Understanding the conserved relationships of the maxillary line and M point with adjacent nasal and orbital structures will ensure the complete removal of the uncinate process during uncinectomy and promote safe and ample exposure of the lacrimal sac during endoscopic dacryocystorhinostomy.