Anatomical Variation in Maxillary Sinus Ostium Positioning: Implications for Nasal-Sinus Disease.

Among humans, superiorly located maxillary sinus ostia (MSO) result in drainage complications and maxillary sinus (MS) disease. While previous studies investigate maxillary sinusitis frequency or MSO-position relative to specific nasal landmarks, few explore MSO-position to overall MS dimensions. This study investigates whether MSO-position relates to MS size/shape and if sex-based differences exist. Twenty-nine landmarks, placed on magnetic resonance images (MRIs) of 109 individuals (males = 57; females = 52), captured maximum dimensions of the cranium, MS, nasal cavity, and MSO-position relative to the MS floor (MSO_MSF) and nasal floor (MSO_NCF). Landmark coordinates were used to calculate centroid sizes and 13 linear distances; distances were size standardized by cranial centroid-size. Principal components analysis (PCA) on 3D-coordinates indicates that variation in MSO-position relates to superior-inferior MS positioning within the face (PC1 22% variance) and MS height (PC2 12% variance). Regression analyses indicate that MS size (r2 = 0.502; P < 0.001) and height (r2 = 0.589; P < 0.0001) strongly contribute to MSO_MSF: larger, taller MSs exhibit greater MSO_MSFs. Sex-based differences were not evident in PC shape-analyses nor among size-standardized dimensions. However, Mann-Whitney U-tests indicate females have absolutely smaller MSs (P = 0.001) and MSO_MSF distances (P = 0.001). Further, regressions indicate females exhibit lower MSO_MSFs for a similar MS height. Overall, MSOs superiorly placed relative to the MS floor correlate with larger, taller MSs and/or sinuses positioned inferiorly within the face. While craniofacial surgeons/clinicians should be aware of potential sex-based differences in MS size and MSO position, this study does not suggest that higher incidences of female-reported sinusitis relate to sex-based differences in MS anatomy. Anat Rec, 302:917-930, 2019. © 2018 Wiley Periodicals, Inc.