Sublabial Anterior Maxillectomy or Endoscopic Denker Approach: Comparative Analysis of Two Minimally Invasive Approaches to the Infratemporal Fossa

Introduction: Surgical resection of lesions in the infratemporal fossa (ITF) is technically challenging. Adequate visualization and maneuverability of the instruments are of paramount importance for the successful resection in this deep-seated area with a high density of vital neurovascular structures. Traditional open approaches meet these requirements by mobilizing or resecting large volumes of tissue. The philosophy behind minimally invasive implies smaller or no incisions and minimal or no bone removal. Illumination/visualization is provided by a microscope (external source) or an endoscope (internal source).

This study attempts to compare two minimally invasive approaches, the endoscopic endonasal Denker approach, and the endoscopic-assisted sublabial anterior maxillectomy to access targets in the ITF. Although the sublabial anterior maxillectomy approach has been extensively studied and serves as the standard for comparison, there is a dearth of literature on the endoscopic endonasal Denker approach. In this study, the parameters used for comparison of the surgical field included the maximum radial access and area of exposure of the posterior wall of maxilla. Surgical freedom, an objective measure of the ease of maneuverability of instrument was also used for comparison.

Methods: A total of five latex-injected cadaveric heads were dissected bilaterally performing an endoscopic Denker approach on the left side and an endoscopic-assisted sublabial anterior maxillectomy on the right side. Computed tomography (CT) scans were obtained before dissection. A surgical navigation device was used to compute the lateral access, area of exposure, and surgical freedom with both the approaches. The radius of surgical access was calculated with the probe of the neuronavigator placed in alignment with the line-of-sight of the endoscope (0 degrees). The area of exposure (surgical field) was calculated as the area of bone removed from the posterior wall of the maxillary sinus. Surgical freedom was computed using the stereotactic probe as the working area at the proximal end of the instrument (surgical gate) with the distal tip of the instrument at a fixed anatomical target. Surgical freedom was computed at the following four targets vidian canal, foramen rotundum, foramen ovale, and the mandibular condyle.

Results: The lateral access of both approaches was similar (p > 0.05): 53.14 + 4.67 degrees for the Denker approach and 53.42 + 3.99 degrees for the endoscopic-assisted sublabial anterior maxillectomy. Similarly, the area of exposure with the Denker approach 8.46 + 1.56 cm², although higher compared with that of the endoscopic-assisted sublabial anterior maxillectomy (7.97 + 1.71 cm²) was not significant statistically. The Denker approach offered superior surgical freedom compared with endoscopic-assisted sublabial anterior maxillectomy at all the target points (Table 1). However, this higher surgical freedom was not statistically significant (p > 0.05).

Conclusion: This study demonstrates that, in a cadaveric model, the endoscopic Denker approach offers similar radial access to that of the endoscopic-assisted sublabial anterior maxillectomy approach. Both approaches offered similar and complete exposure of the ITF. The ease of instrument maneuverability as measured by the surgical freedom for Denker approach was similar to the endoscopic-assisted sublabial anterior maxillectomy approach.