Determination of significant parameters of the pyriform aperture in functional and surgical aspects. Part 2: reference range of parameters in the pyriform aperture region

In medicine, a reference range (RR) is a range of values considered normal for physiological parameters in healthy individuals, with parameters within the RR considered within the normal range. A reference limit is a value mathematically derived from a reference distribution, defined such that a specified proportion of reference values lie above or below it. Currently, there are no established standards for reference ranges and limits for the parameters of the pyriform aperture region. Objective. To determine the reference ranges and limits of the parameters of the pyriform aperture region. Material and methods. The reference range and limits of the present study were determined for the following parameters of the piriformis width measured using cone beam computed tomography data in 577 individuals of the Central European type of Caucasian race (≥18 years, 273 men and 304 women) divided into age groups (18–44, 45–59, 60–74, ≥75 years): maximum width of the pyriform aperture (WPA), width of the nasal cavity at the level of the attachment of the anterior bony end of the inferior nasal turbinates (WNCp), width of the pyriform aperture in the projection of the attachment of the anterior bony end of the inferior turbinates (WPAp), length of the pyriform ridge (LPR) and angle of the pyriform ridge (APR). The lower reference limits (LRL), calculated in mm as μ (mean value) ± 1.96σ (standard deviation) and μ±3σ, were used as an anatomical reference for the relative and absolute narrowness of the parameters of the width of the pyriform aperture region. Results. For men, regardless of age, the LRLs are respectively: WPA — 20.82 and 19.06; WNCp — 19.15 and 17.18; WPAp — 19.28 and 17.34. For women, regardless of age, the LRLs are respectively: WPA — 19.34 and 17.57; WNCp — 18.74 and 16.78; WPAp — 18.79 and 16.96. For women in the younger age group (18–44 years), the LRLs are respectively: WPA — 18.29 and 16.32; WNCp — 17.7 and 15.6; WPAp — 17.88 and 15.92. The reference range for the length and angle of the piriformis ridge is written as the lower and upper reference limits for men and women, respectively: LPR in mm ([0; 4.36] and [0; 4.22]), APR in degrees ([70.8; 113.05] and [69.76; 108.69]). Conclusions. The results of the study should be used in a possible surgical algorithm for the treatment of chronic nasal obstruction as a reference range and limits for the parameters of the piriformis region.