Drainage of the maxillary sinus: a comparative anatomy study in humans and goats

The maxillary sinuses are the most frequently infected paranasal sinuses in humans. It has been suggested that infection occurs relatively commonly in the maxillary sinuses owing to the position of their ostia high on their superomedial walls, which may be suboptimal for natural drainage. This may represent evolutionary lag, whereby the ostia remained in a quadrupedal position as bipedal humans evolved from their primate ancestors. This study examined the hypothesis that drainage of the maxillary sinus is optimal in the quadrupedal position.

The drainage of the human maxillary sinus and an analogous quadruped, the goat, was examined and compared in the upright, quadrupedal, and intermediate positions.

Department of Anatomy, King's College London.

Cadaveric human and goat maxillary sinuses were filled with saline in each position and the volume at which saline overflowed through the ostia was noted.

Volume at which spontaneous drainage occurred through ostia.

The volume of saline instilled before drainage was maximal in the upright position and reduced with each increase in anterior tilt, with drainage occurring most easily at 90° for both human and goat sinuses. Drainage was significantly better in the quadrupedal head position than upright in both species (p < .01).

This study demonstrated that human maxillary sinuses exhibit better passive drainage through their ostia when tilted anteriorly to mimic a quadrupedal head position. This may be an example of an evolutionary lag phenomenon and could be one etiologic factor in the prevalence of maxillary sinusitis in humans.