Comparative Analysis of Surgical Freedom and Angle of Attack of Two Minimal-Access Endoscopic Transmaxillary Approaches to the Anterolateral Skull Base

Abstract

Surgical freedom and the angle of attack influence approach selection for open cranial base approaches, but these concepts have not been well studied in minimal-access endoscopic approaches. We therefore developed a methodology to study surgical freedom and angle of attack in two endoscopic transmaxillary transpterygoid approaches, the endonasal ipsilateral uninostril medial maxillotomy and the sublabial Caldwell-Luc anterior maxillotomy. Dissections were performed bilaterally in three formalin-fixed cadaver heads (six sides). For each approach, three progressively lateral and posterior anatomic targets were identified. Utilizing frameless stereotaxy, surgical freedom using the vector cross-product method was calculated for both approaches for each target. The mean and maximum possible angles of attack were calculated in the axial and sagittal planes. Compared to the endoscopic endonasal-transmaxillary approach, the endoscopic Caldwell-Luc approach offered significantly greater surgical freedom to the genu of the internal carotid artery (P=0.02), foramen rotundum (P=0.03), and foramen ovale (P=0.03). Mean and maximum possible angles of attack were also significantly different between the two approaches for each target. The Caldwell-Luc approach offered a more bottom-up approach in the sagittal plane and a more head-on approach in the axial plane to each target (P<0.05). We have successfully developed a model for comparing endoscopic skull base approaches. Both the endonasal medial maxillotomy approach and Caldwell-Luc approach provided endoscopic access to each target. However, the sublabial Caldwell-Luc approach offered greater surgical freedom and a more head-on approach than the endonasal medial maxillotomy. These differences in surgical freedom and angles of attack may be useful to consider when planning minimal-access approaches.