A method for determining the size and placement of the screw within the vertebral pedicle in the selected region, to produce a truly three-dimensional image of the spine in the selected spinal area using a computer; Removing the spine from the 3-D image in the selected cortical wall thickness by using a computer; Phase by using a computer to determine the narrowest cross-section (isthmus) within each of the pedicle; Is arranged by extending in the opposite direction, starting at the center of the cheek using a computer to concentrically within the pedicle without touching the pedicle wall, it ends at a predetermined distance from a front inner cortical wall of the in the vertebra body, the direction opposite step extending toward the outside to generate a straight line to penetrate the posterior pedicle cortex; To the small cross-sectional size than the cross-section of a straight line isthmus by using a computer to extend concentrically with and radially, in which part of the line the exception posterior pedicle cortex and in contact with the internal cortical wall of the vertebral body trick removed step to extend the growing stops when cylinder; And using a computer includes a step of calculating the ideal pedicle screw diameter, length and quadrature jeolseon of the resulting cylinder for each pedicle.