The Maxillary Sinus Ostium: Demystifying Middle Meatal Antrostomy

Locating the maxillary sinus ostium can be a problem in endoscopic middle meatal antrostomy. Patients requiring revision sinus surgery may be found to have the maxillary sinus ostium obstructed, or the previous antrostomy placed in the wrong location. The intricate lateral nasal wall anatomy can be difficult to translate into the two-dimensional endoscopic view. It is therefore understandable how finding the maxillary sinus ostium at times can be tedious. Inability to accurately identify the maxillary sinus ostium may preclude an appropriate middle meatal antrostomy, and predispose the patient to persistent sinus disease. The primary landmarks for identifying the maxillary sinus ostium are the uncinate process and the ethmoid bulla. The initial surgical step in endoscopic ethmoidectomy is uncinectomy. This is usually followed immediately by removal of the bulla, frequently before the maxillary ostium has been accurately identified. After evaluating CT scans of 61 revision sinus surgery patients, and observing a large number of sinus surgeon training in the OR and the dissection lab, we have noted that uncinate removal is often incomplete. An uncinate remnant is commonly left inferiorly. This may lie against the lateral nasal wall obscuring the maxillary sinus ostium. This coupled with loss of the ethmoid bulla, the primary surgical landmark, may make identification of the maxillary ostium quite difficult. We feel that the key to successful middle meatal antrostomy (MMA) and avoidance of persistent maxillary sinus disease is positive visual maxillary ostium identification immediately after removal of the uncinate process. The residual inferior uncinate process typical after incomplete uncinectomy, and its subsequent removal, are demonstrated. An alternate technique is presented for complete uncinate removal, simplifying maxillary ostium identification.