Lateral View and posterior view of lumbar spine after (A) laminectomy and (B) bilateral laminotomy. In laminectomy, the lamina and spinous processes of lower L4 and upper L5 are removed by rongeur and Kerrison clamp. The ligamentum flavum and supraspinous ligament of L4–L5 are removed. In laminotomy, fenestration is made on both sides. The inferior margin of L4 lamina and superior margin of L5 lamina are removed by burr. The L4–L5 ligamentum flavum is removed.