Abstract
Using a special software program we measured spinopelvic parameters on digitised radiographs of the entire spine and the pelvis of 50 patients with lumbar disc herniation and compared these with the same measurements on 30 healthy subjects. In the disc hernia group the patients had a relatively straight spine in the sagittal plane. The sacrum was more vertical, and the value of the lumbar lordosis was lower, as was the amplitude of the spinal curvatures, when compared with those of the healthy group. This results in a higher gravitational compressive force which may, in turn, lead to progressive degeneration of the discs. The anterior shift of the line of gravity may cause spinopelvic instability, and contraction of the posterior spinal muscles in trying to balance this disturbed spatial relationship may produce back pain.