Fig. 1

The sagittal section images of L2-L3 spinal segment with different grades of disc degeneration. a Grade 0: healthy disc with the leading edge height of lumbar 10.27 mm and the trailing edge height 8.30 mm, b Grade 1: mildly degenerated disc with the leading edge height of lumbar 7.44 mm and the trailing edge height 3.80 mm, c Grade 2: moderately degenerated disc with the leading edge height of lumbar 6.21 mm and the trailing edge height 4.60 mm, the osteophytes were between 2.97 mm and 3.45 mm, d Grade 3: seriously degenerated disc with the leading edge height of lumbar 6.33 mm and the trailing edge height 2.82 mm, and the maximum osteophyte was 14.92 mm