Quantitative Analysis of the Working Windows for Sitting and Park Bench Positions Through the Retrosigmoid Approach Evaluated in a Cadaver Model.

Abstract

Background and objectives: The choice of the optimal surgical position in the treatment of posterior fossa lesions still remains a controversial and debated issue. Morphometric data on the different perspective of vision offered by different surgical position are scarce. This article investigated the differences due to the vision perspectives provided by the sitting and park bench positions.

Methods: The study was conducted using 4 fixed cadaver heads. A standardized retrosigmoid approach was performed on each side of each head. Three operators collected anatomic observation and 2 separate measurements each, for all the sides and diagonals of the projections of 2 areas delimited by the cranial nerves in the cerebellopontine angle (defined as working windows ABCD and ABEF). The collection of the measurements was repeated for each side of each head, both in the sitting and in the park bench positions. The average areas of the working windows were calculated for each position and then compared by statistical analysis.

Results: The park bench position is associated to larger areas for both working windows (P = .0013 for ABCD; P < .001 for ABEF) compared with the sitting position. These measures allow to quantify the differences of the working windows that are an indirect expression of the different angle of vision of each position.

Conclusion: Our cadaveric study shows that there is a better vision perspective offered by the park bench position for lesions that do not modify the course of the cranial nerves in the cerebellopontine angle. However, different positioning of patients presents different advantages and limitations for surgeon based on size of the tumor and lesion location. In our opinion, choice of patient positioning could be tailored to lesion's peculiarities more than on surgical habits.