Approach to the Orbital Surface of the Greater Wing of the Sphenoid through the Inferior Orbital Fissure

Background: The inferior orbital fissure (IOF) is between the lateral wall and the orbital floor, and it is anterior and inferior to the orbital surface of the greater wing of the sphenoid (GWS). Tumors arising from the pterygopalatine fossa, such as juvenile nasopharyngeal angiofibroma, nasopharyngeal carcinoma, and other neurocentric tumors may grow through the IOF and invade the orbital surface of the GWS. The IOF and the orbital surface of GWS can be reached by endoscopic endonasal approach (EEA) with medial maxillectomy and Caldwell–Luc transmaxillary approach (CLTM) via different trajectories. The aim of this study was to compare the length of the IOF exposure, and the area of access to the orbital surface of the GWS between EEA with medial maxillectomy with or without CLTM approach.

Methods: Using CT registration, five cadavers (10-sides) were dissected. The length of the IOF from the maxillary strut to the most anterior aspect of the fissure was measured. The maxillary strut, the most superolateral point of the SOF, the most anterolateral point of the IOF, and the most superolateral point of the orbital surface of the GWS at the three-suture junction (frontozygomatic suture, frontosphenoid suture, and sphenozygomatic suture) were used to calculate the area of the GWS. These measurements were calculated in (1) EEA with medial maxillectomy and (2) with the addition of a CLTM approach.

Results: The length of the IOF was 29.78 ± 1.39 mm. The length of the posteromedial part, middle part, and anterolateral part of IOF were 18.51 ± 0.85, 4.38 ± 0.71, and 6.89 ± 1.27 mm, respectively. The length of the IOF exposure was 23.53 ± 1.63 mm by EEA with medial maxillectomy, almost equal to the summation of posteromedial and middle parts of the IOF. It was 32.79 ± 1.88 mm by CLTM approach, even greater than the total length of IOF and significantly greater (p < 0.0001) than EEA ([Fig. 1A]). The area of access to the GWS was also significantly greater (p < 0.0001) by CLTM approach (428.84 ± 36.21 mm², 82.8%) than EEA with medial maxillectomy (159.08 ± 22.96 mm², 30.7%; [Fig. 1B]). Because of the limitation of orbital retraction, access to the GWS via EEA is limited to 1-cm superior to the IOF.

Conclusion: The length of IOF exposure and the area of access to the GWS are significantly greater via CLTM approach than EEA. For lesions extending to the anterolateral part of the IOF or more than 1-cm superiorly to the IOF, EEA with medial maxillectomy alone is not sufficient and a CLTM approach is needed.

Fig. 1 (A) The length of IOF exposure by EEA with medial maxillectomy (red) and CLTM (green; purple: total length). (B) The area of access to the orbital surface of the GWS by EEA with medial maxillectomy (red) and CLTM (green; purple: total area).

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
12 February 2021