The Anterior Ethmoidal “Genu”: A Newly Appreciated Anatomic Landmark for Endoscopic Sinus Surgery

Human sinonasal anatomy varies widely between patients, challenging surgeons operating in the sinuses. Ethmoid sinus anatomy is so variable it has been referred to as a labyrinth. Accordingly, reliable, consistent anatomic landmarks aid surgeons operating in this region. The goal of this investigation was to explore our observations and hypothesis that the ethmoidal bulla and the uncinate process are not entirely separate structures but rather attach, and the attachment could potentially provide a landmark for surgeons performing ethmoid and frontal recess surgery. Ethmoid sinus anatomy was studied in 57 sinonasal complexes through a variety of methods including gross anatomic dissection, endoscopic dissection and 3D CT stereoscopic imaging. The uncinate process and ethmoidal bulla were noted to fuse at the superior aspect of the hiatus semilunaris in 57/57 cases, forming a genu-like feature in the anterior ethmoid. This consistent anatomic feature related closely to the frontal sinus drainage pathway, which drained medial to it in 44/57 (77%) cases. The anterior ethmoidal “genu” appears to be an excellent anatomic feature that surgeons can use during ethmoid and frontal recess surgery. High resolution 3D stereoscopic CT scan is capable of demonstrating sinonasal anatomy in a detailed fashion previously only achieved by cadaveric dissection. This technology can potentially allow for a virtual dissection of a patient's anatomy prior to surgery and could improve minimally invasive procedures and reduce complications. Clin. Anat. 32:534–540, 2019.