Measurements of neural foraminal dimensions (NFD) in the intact state and after 1 mm, 2 mm, 3 mm, 4 mm, or 5 mm pedicle-lengthening at L4 and/or L5: a) the original NFD of control, canal stenosis (CCS), lateral recess stenosis (LRS) and foraminal stenosis (FS) group, NFD was significantly larger in the control group compared with the three LSS groups, p < 0.001; b) increased percentage of NFD of control, CCS, LRS and FS group after gradual lengthening of the L4 pedicle by 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, the percentage increase was FS>control>LRS>CCS at 1 mm and FS>CCS>LRS>control at 2 mm to 5 mm, p < 0.001 for all lengthening distance; c) increased percentage of NFD of control, CCS, LRS and FS group after gradual lengthening of the L5 pedicle by 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, the percentage increase was control>LRS>CCS>FS at 1 mm and CCS>LRS>control>FS at 2 mm to 5 mm, p = 0.04 at 1 mm, p = 0.001 at 2 mm, p < 0.001 at 3 mm to 5 mm; d) increased percentage of NFD of control, CCS, LRS and FS group after gradual lengthening of the L4 and L5 pedicle by 1 mm, 2 mm, 3 mm, 4 mm, 5 mm, the percentage increase FS>CCS>LRS>control, p < 0.001 at 1 mm, p = 0.045 at 2 mm, p = 0.04 at 3 mm, p = 0.004 at 4 mm, p = 0.006 at 5 mm.