[CT observation of retromaxillary posterior ethmoid].

To investigate the morphologic characteristics of the retromaxillary posterior ethmoid.A total of 103 outpatients encountered in our hospital during March 2012 and December 2012,who completed paranasal sinus CT examination,were included in this study.Patients had no sinus trauma,surgery or tumor history.Their paranasal sinus CT scans were analyzed from scheduled axial and coronal plane.The incidence and imaging features of the retromaxillary posterior ethmoid were observed.The retromaxillary posterior ethmoid(RMPE)was the posterior ethmoid cell that expanded along the lamina papyracea toward the infraorbital region.RMPE was located behind the posterior wall of the maxillary sinus and under the orbital floor.The occurrence rate of the RMPE was 74.3%.The ethmomaxillary septum is the bony septum the between the maxillary sinus and posterior ethmoid.Anatomical confirmation of RMPE is based mainly on the presence of the ethmomaxillary septum.RMPE is located at the back of ethmomaxillary septum.The sagittal angulation of the ethmomaxillary septum ranged from 22 to 87 degrees,with an average of(50.34±12.10)degrees.The ethmomaxillary septum is important for anatomic recognition of the RMPE.Accurate identification of the RMPE before ESS can help improve the removal of the posterior ethmoid sinus.