Fig. 1. Measurement of lumbar lordosis, segmental angle, disc height and contralateral foraminal area. A : Lumbar lordosis : the angle between L1 and S1 upper endplates. B : Segmental angle : the angle between the upper and lower endplates at the disc space where surgery was done. C : Disc height: the distance between the upper and lower endplates at the center of the disc space at the surgical site from the sagittal view in the plain radiograph. Foraminal area : the area of bony neural foramen.