The dural sac cross-sectiona area of the pre - compressed spine was 100 ± 18.2 mm after compressed scanning was 87.1 ± 2.3 mm; the anteroposterior diameter before the compressed MRI was 9.9 ± 1.1 mm after the axial loading MRI was 8.9 ± 1.1 mm; thickness of ligamentum flavum changed with pre - compressed 3.05 ± 0.5 mm, post-compression 4.2 ± 0.5 mm; disc bulge changed with pre-compressed 2.2 ± 0.1 mm, post-compressed 2.3 ± 0.1 mm.