Frontal sinus outflow anatomy.

Most of the studies of frontal sinus anatomy were completed 50 to 70 years ago. The information they provide is not necessarily relevant or helpful to the modern rhinologic surgeon who approaches the frontal sinus transnasally and endoscopically. We performed anatomical dissections of the outflow tract of 82 frontal sinuses in 41 cadaver heads to illustrate the various drainage patterns from the frontal sinus to the nose and to correlate these drainage sites with the distance and angle from the pyriform aperture. We found that the frontal sinus drained anterior to the uncinate process in 24 specimens (29.3%) with an average distance of 3.65 cm from the pyriform aperture and 58 degrees from the nasal floor. The frontal sinus drained posterior to the uncinate process in 56 specimens (68.3%) with an average distance of 4.10 cm and 65 degrees from the nasal floor. In this latter group, most of the sinuses (51 specimens) drained into the ethmoid infundibulum. Two of the specimens had a hypoplastic frontal sinus with no outflow tract at all. These findings are different from those described in the early 20th century.