fig1
From: Minimal laminectomy using the interlaminar approach for percutaneous endoscopic lumbar discectomy
Figure 1. Preoperative radiographic findings on the migration and shape of the upper vertebral laminae. The extent of migration was evaluated by using T2-weighted sagittal magnetic resonance imaging. (A) Low-grade migration: defined as a migration extent smaller than the height of the disc space (case 2); (B) high-grade migration: defined as a migration extent exceeding the height of the disc space (case 11); (C) concave (-): caudal margin of the upper vertebral laminae (CM-UVL) is straight, as evaluated by using three-dimensional computed tomography (case 8); (D) concave (+): CM-UVL has a measurable concave and the superior articular process is easy to access (case 9)
