Planar geometrical analysis for design of the shortest incision to open the dura mater: technical note.

Quadrilateral dural window is opened with a conventional incision design, such as a pair of diagonal lines or a rectangular shape, but the total cutting length is not the shortest possible. Shorter incision length will have a lower risk of dysraphia associated with cerebrospinal fluid (CSF) liquorrhea or related CSF infection. We propose a new and effective dural incision design with the shortest cutting length for quadrilateral dural openings. We investigated the design of the dural incision using a simple planar geometrical figure. We discovered the shortest network design to connect the four vertices of the quadrilateral. The shortest network design was formed of five line segments with two three-pronged interconnections (TPIs) with the same angle of 2π/3 between any two lines (2π/3-TPI). In practice, first we must draw a quadrilateral W horizontally then add two equilateral triangles outside W. Using a 2π/3-bent wire, the 2π/3-TPIs are traced on the path connecting the outward vertices of the equilateral triangles. Using this method, we can reduce the incision length by 10% from conventional designs using a pair of diagonal lines.