Effect of the Supine Position and Anesthesia on Nasal Anthropometric Measurements in Rhinoplasty Patients

<b>Background:</b> Body position and anesthesia may alter nasal anthropometric measurements, potentially affecting both preoperative assessment and intraoperative decisions in rhinoplasty. Quantifying these effects is essential for the accurate evaluation of nasal morphology. <b>Methods:</b> Thirty-five patients (28 females, 7 males; mean age 27.9 ± 6.95 years) undergoing primary rhinoplasty were prospectively included. Standardized lateral photographs were obtained in three conditions: upright, preanesthetic supine, and postanesthetic supine. Linear distances were measured using a digital caliper in a position replicating the photographic setup, and angular parameters were calculated from the photographs using ImageJ software (version 1.53, National Institutes of Health, Bethesda, MD, USA). Statistical analyses were performed to compare nasal measurements among the three positions. <b>Results:</b> The nasion-pronasale distance increased in the preanesthetic supine compared with the upright position (<i>p</i> < 0.001), while the pronasale-alar curvature distance remained unchanged (<i>p</i> = 0.984). The nasofrontal angle was higher upright (<i>p</i> < 0.001), whereas the nasolabial (<i>p</i> < 0.001) and nasomental (<i>p</i> = 0.010) angles were greater in the preanesthetic supine position. After anesthesia, both nasion-pronasale (<i>p</i> < 0.001) and pronasale-alar curvature (<i>p</i> = 0.001) distances increased further, while the nasofrontal angle remained higher upright (<i>p</i> < 0.001). <b>Conclusions:</b> Supine positioning and anesthesia significantly modify nasal profile parameters. Awareness of these predictable morphologic changes can help surgeons avoid misinterpretation and improve the accuracy of preoperative planning, intraoperative evaluation, and postoperative assessment.