Tomographic assessment of anatomical boundaries in endoscopic frontal sinusotomy: retrospective radiologic analysis of Draf IIA and IIB approaches

• CT-based measurements guide safer and more effective frontal sinus surgeries. • First study to objectively measure drainage gain in Draf frontal sinusotomy. • Incomplete beak removal compromises surgical success in frontal sinusotomy. • Draf IIB is only effective with full frontal beak removal. • Complete removal of the frontal beak triples frontal sinus drainage pathway. The aim of this study was to evaluate the anatomical dimensions and boundaries involved in Draf IIA (DIIA) and Draf IIB (DIIB) frontal sinusotomies, and to determine how complete frontal beak removal affects the frontal sinus drainage pathway. Specifically, we compared the proportional increase in drainage area between DIIA and DIIB performed with and without complete frontal beak removal. This retrospective radiological anatomical study analyzed 296 hemifaces (from 148 patients) who underwent paranasal sinus Computed Tomography (CT). Individuals over 18-years of age without evidence of paranasal sinus disease were included. We measured the anatomical distances defining the frontal recess and estimated the differences in frontal recess area for three approaches: Draf type IIA (DIIA), Draf type IIB without complete removal of the frontal beak (DIIBwoFB), and Draf type IIB with complete removal of the frontal beak (DIIB). The measured areas of the frontal ostium were as follows: 59.00 ± 24.34 mm 2 (range: 0.55–160.00) for DIIA, 79.66 ± 30.29 mm 2 (range: 0.85–200.00) for DIIBwoFB, and 147.00 ± 35.25 mm 2 (range: 71.47–282.74) for DIIB. The proportional increase in drainage area was significantly higher when comparing DIIA to DIIB than to DIIBwoFB (3.64 ± 14.37 [range: 2.52–248.40] vs. 1.37 ± 0.18 [range: 1.00–2.64], respectively). Among the evaluated surgical approaches, the greatest proportional increase in anatomical drainage area was achieved with Draf IIB combined with complete frontal beak removal. These findings underscore the importance of frontal beak resection when considering the Draf IIB approach. IV.