Fig. 1From: Transforaminal endoscopic lumbar discectomy with two-segment foraminoplasty for the treatment of very highly migrated lumbar disc herniation: a retrospective analysisIllustration for the classification of migrated LDH by Lee et al. [4]; line a, b, and c indicates the boundary for upward very-highly, highly, and moderately migrated herniation, respectively (the distance between the line a and b is 3Â mm; d indicates the intervertebral disc level; line e, f, and g indicates the boundary for moderately, highly, and very-highly downward herniation, respectivelyBack to article page