Effect of Incremental Maxillectomy on Exposure of the Pterygopalatine and Infratemporal Fossa: A Cadaveric Study with Comparative Analysis of Radial Access, Area of Exposure, and Surgical Freedom

Introduction: The lateral skull base, owing to its deep-seated location and complex neurovascular anatomy, presents a significant surgical challenge. A better understanding of its surgical anatomy, supplemented with the advent of intraoperative navigation, has allowed surgeons to access the lateral skull base endoscopically. However, the indications and intricacies regarding variations of the sinonasal corridor remain unsettled.

This study attempts to elucidate the benefits of incremental maxillectomies to access this region. We compared the access provided by the endoscopic medial maxillectomy (MM), anteriorly extended medial maxillectomy (EMM), and contralateral trans-septal and endoscopic Denker approaches. Exposure was assessed in terms of maximum radial access and area of exposure of the posterior wall of maxilla. Surgical freedom in terms of ease of instruments maneuverability was also assessed.

Methods: A total of five cadaveric specimens injected with a colored latex were dissected bilaterally. The dissection was carried in four progressive stages, documenting radial access, area of exposure, and surgical freedom for each stage. The maximum radius of surgical access was calculated with the navigation probe placed in alignment with the endoscopic line of sight (00). Area of exposure was calculated in terms of the area of bone removed from the posterior wall of the maxillary sinus. Surgical freedom was calculated using stereotactic navigation by computing the working area at the proximal end of the instrument (nostril/pyriform aperture) with the distal end fixed at a specific target. Fixed targets used for computing surgical freedom in the horizontal plane included the vidian canal, foramen ovale, and the superolateral aspect of the mandibular condyle. Targets in the vertical plane included the foramen rotundum and inferior point (IP), defined as the junction of the greater palatine vessel with the hard palate.

Results: The degree of lateral access significantly increased with the addition of a MM (30 + 3.62 degrees), EMM (40 + 2.34degrees), and contralateral trans-septal approach (48 + 4.52degrees). Adding a Denker approach, further increased the lateral access (mean angulation, 53.14 + 4.67degrees); however, this additional increase was not statistically significant when compared with the increase provided by a contralateral trans-septal approach.

Area of exposure provided by a MM (4.79 + 1.42 cm²) was significantly smaller than the areas exposed by the EMM, contralateral trans-septal, and Denker approaches (6.74 + 1.12 cm², 7.07 + 1.38 cm², and 8.46 + 1.56 cm², respectively, p < 0.05). The area of exposure after a Denker approach was significantly larger than that provided by the EMM (p < 0.05). In addition, a Denker approach offered superior surgical freedom at the level of foramen ovale and mandibular condyle (p < 0.05)

Conclusion: In a cadaveric model, extending the medial maxillectomy anteriorly to the pyriform aperture (EMM approach) or coming cross-court via the trans-septal approach increases both the area of exposure and the surgical freedom for instrument maneuverability. Moreover, the endoscopic Denker approach offers a superior radial access, area of exposure, and surgical freedom as compared with the MM, EMM, and contralateral trans-septal approaches.