Radiological classification of migrated disc herniation according to Lee et al.55
| Zone | Direction | Range of Distance |
| Zone 1 | Far-upward | From the inferior margin of the upper pedicle to 3 mm below the inferior margin of the upper pedicle |
| Zone 2 | Near-upward | From 3 mm below the inferior margin of the upper pedicle to the inferior margin of the upper vertebral body |
| Zone 3 | Near-downward | From the superior margin of the lower vertebral body to the center of the lower pedicle |
| Zone 4 | Far-downward | From the center of the lower pedicle of the lower vertebral body to the inferior margin of the lower pedicle |