Surgical anatomy of the natural ostium of the sphenoid sinus

OBJECTIVES: This study was undertaken to measure the distance and the angle between the anterior part of nasal cavity and the natural ostium of the sphenoid sinus. The anatomical location of the natural ostium according to the direction of surgeon's operating view toward the anterior wall of the sphenoid sinus was also analyzed. STUDY DESIGN: This study used careful cadaver dissection under a surgical microscope. METHODS: One hundred sagittally sectioned adult cadaveric heads were used. We measured the distances and angles for identifying the natural ostium of the sphenoid sinus using several reference points such as the limen nasi, the sill, and the posteroinferior end of the superior turbinate. In addition, we tried to identify whether the location of the natural ostium is medial or lateral to the posterior end of the superior turbinate. RESULTS: The natural ostium of the sphenoid sinus was located at an angle of 35.9 degrees with a distance of 56.5 mm from limen nasi and at an angle of 34.3 degrees with a distance of 62.7 mm from nasal sill. It was located approximately 1 cm above the posteroinferior end of the superior turbinate and at a medial aspect to the posterior end of the superior turbinate in 83% of specimens. CONCLUSIONS: We speculate that the posteroinferior end of the superior turbinate is the best landmark for identifying the natural ostium of the sphenoid sinus. Furthermore, the natural ostium should ideally be searched from a superior and medial aspect in relation to the posteroinferior end of the superior turbinate.