Fig. 5.

With the morphological changes of the ligamentum flavum, A in the whole bulging type, the whole ligament bulged from the central canal to the intraforaminal zone centering on the subarticular zone (20 sites). B With the proximal bulging type, the cranial portion from the subarticular zone to the foraminal zone bulged like a boomerang (22 sites); C Erosion due to contact with disc (15 sites); D Fold (six sites); E Bone exposure of the tip of the superior articular process (three sites) was observed. The dotted lines of the schema show the zone classification. ( E extraforaminal zone, F foraminal zone, S subarticular zone, C central canal)