Comparative analysis of surgical freedom and angle of attack of two minimal-access endoscopic transmaxillary approaches to the anterolateral skull base.

OBJECTIVE: 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.

METHODS: 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.

RESULTS: 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).

CONCLUSIONS: 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.