Fig. 1

The classification of Pfirrmann grade. On T2-weighted image, grade I—the structure of the disk and disk height are normal, with a bright white signal intensity. Grade II—the structure of the disk is abnormal and the disk height is normal, with a white signal and a clear distinction between nucleus and anulus. Grade III—the structure of the disk is abnormal and the disk height is normal or slightly decreased, with an average gray signal intensity and an unclear distinction between nucleus and anulus. Grade IV—the structure of the disk is abnormal and the disk height is normal or moderately decreased, with a dark gray signal intensity and a lost distinction between nucleus and anulus. Grade V—the structure of the disk is abnormal and the disk space is collapsed. The distinction between nucleus and anulus is lost