Figure 2.

Methods for calculating the herniation index (HI) in the axial plane of the magnetic resonance imaging (MRI) scan. AB: the maximal anteroposterior disc length, which is the diameter of the herniated disc material extended maximally from the posterior border of the vertebral body. CD: the width of the herniated disc material at the level of the middle AB distance of the herniated disc material from the coronal plane of the MRI scan. EF: the maximal anteroposterior canal length. GH: mid-AB distance. HI was calculated using the following formula: