Three-dimensional computed tomography analysis to help define an endoscopic endonasal approach of the pterygopalatine fossa

Background: The pterygopalatine fossa (PPF) can be entered endoscopically, but the endoscopic landmarks to localize the bony structures in the PPF are not well described. This study aimed to investigate the anatomy of the sphenopalatine foramen (SPF), vidian canal (VC), and foramen rotundum (FR) with regard to an endoscopic endonasal approach to the PPF using three-dimensional reconstruction of computed tomography (CT) scans. Methods: The CT scans of 98 patients were retrospectively evaluated. The morphology of the SPF, VC, and FR as well as the spatial relationship between the SPF and VC were measured on a three-dimensional model. Results: The mean diameters of the SPF, VC, and FR were 5.3 ± 1.3 mm, 2.4 ± 0.7 mm, and 2.8 ± 0.5 mm, respectively. The mean distance between the VC and posteroinferior margin of SPF was 3.8 ± 1.0 mm. The mean vertical and horizontal distances on the surface plane of sphenoid bone between the VC and FR were 5.8 ± 1.9 mm and 8.5 ± 1.9 mm, respectively. The whole or partial margin of the VC was above the inferior margin of the SPF in 92% (180/196) of the VC and lateral to the posterior margin of the SPF in 98% (195/196) of the VC. The distance between the VC and SPF had a positive correlation with the distances between the VC and FR. Conclusion: The endoscopic endonasal approach to the PPF will be performed with greater accuracy and safety through comprehension of the spatial relationships between the SPF, VC, and FR.