fig4

Figure 4. Upper half of the operative field is epidural space, lower half of that is disc spaces, and posterior longitudinal ligament (PLL) is consisting of the boundary of these spaces (A: PLL locates the tip of bipolar coagulator); (B) sharp dissection of the lateral margin of PLL is performed by beak forceps; (C) after that total removal of medial type lumbar disc herniation is achieved