Surgical and topographic anatomy of the maxillary line: an important landmark for endoscopic nasal surgery.

The maxillary line is an important surgical landmark in the lateral nasal cavity. We investigated its location, variation, and relation to other landmarks in 47 formalin fixed cadaveric half-heads dissected in steps. Measurements and observations were made to describe the topography of the maxillary line, maxillary line midpoint (M-point), and their relationship with surgically important structures. The mean curved length of the maxillary line was 15 mm (SD 3.5) and can be classified into three types. The M-point had a mean vertical distance of 0.8mm (SD 2.9) below the nasolacrimal sac-duct junction. It was found below, above, or on the same level as the nasolacrimal sac-duct junction in 57.4%, 38.3%, and 4.3% of specimens, respectively. In 51.1% the M-point was anterior to the nasolacrimal duct axis and 48.9% overlapping the lacrimal apparatus. The maxillary line and its M-point are useful surgical landmarks for localizing the nasolacrimal duct segments.