METHODS FOR DETERMINING PEDICLE BASE CIRCUMFERENCE, PEDICLE ISTHMUS AND CENTER OF THE PEDICLE ISTHMUS FOR PEDICLE SCREW OR INSTRUMENT PLACEMENT IN SPINAL SURGERY

摘要

A method of determining the pedicle base circumference and the pedicle isthmus to facilitate screw placement in a pedicle of a vertebral body during spinal surgery, comprising providing a series of first lines tangential to the outer cortical surface of the vertebral body in and near the pedicle on a transverse section from a three-dimensional image of the vertebral body, providing a series of second lines extending through the vertebral body in and near the pedicle thereof in perpendicular relation to the series of first lines, identifying the pedicle base circumference as the areas of the outer cortical surface where adjacent second lines are at the greatest angle with respect to one another, and identifying the pedicle isthmus as the areas of the outer cortical surface where the second lines that are opposed to each other are closest to being parallel to one another. The center of the pedicle isthmus is identified from a cross- section thereof as the intersection of two lines derived from the centers of infinitesimal orthogonal second perpendicular lines from the outer cortical surface.