The normal uncinate process: histology and clinical relevance

In this three-center, prospective, non-randomized, controlled trial, we performed a qualitative and quantitative histological and morphometric assessment of the normal uncinate process (UP). The soft tissue and bony elements of the normal UP of 16 adults were investigated and compared with 28 age- and gender-matched archival reference-group samples of neighboring structures of the inferior and middle turbinates. A series of measurements were taken and included the thickness of the mucosal layers and bone, epithelial height, basement membrane thickness, number of lamina propria inflammatory cells, and the area fraction (AF) of the epithelium, connective tissue, glands, veins and arteries. The data showed that the medial and lateral mucosal layers are built of loose connective tissue and harbor various inflammatory cell population, abundant glands, and thin-walled small-caliber venules. In-between, there is a thin lamellar compact bone (≤ 80 μm) or a significantly thicker cancellous bone (110-400 μm; P < 0.001). Both mucosal layers are similar in thickness, epithelial height, basement membrane thickness, and AF of soft-tissue constituents. A comparison with the lateral aspect of the inferior and middle turbinates showed that the AF of the connective tissue, total submucosal glands, submucosal serous and mucous glands, and veins of the lateral mucosa are significantly different (all P < 0.001). This diversity may point to different physiological roles for the UP and the inferior and middle turbinates. The UP rich glandular network, which is probably responsible for drainage and ventilation of the maxillary sinus into the ethmoid infundibulum laterally and the frontal sinus into the middle meatus medially, supports the argument that it is preferable, particularly for the less complicated cases, to keep the normal physiology of the ethmoid infundibulum and use bone- and mucosa-sparing techniques for the management of refractory chronic sinus disease.