A laminectomy or laminotomy (a partial laminectomy) is sometimes called a decompression procedure. The procedure is used to access the spinal canal from the back of the spine, or posteriorly. After an incision is made in the midline of the neck or back, the muscle is moved away to expose the lamina, which are the bony shingles that overlay the neural (nerve) elements. The lamina form a roof over the neural canal. The lamina can be removed in whole or in part to expose a single nerve root or more of the neural elements as needed. In the case of a lumbar disc herniation, a laminotomy, or partial removal of the lamina is usually sufficient to gain access to the affected nerve root. The nerve root will usually be visible just beneath the lamina, with a disc herniation underneath it. The nerve root is gently held out of the way with a retractor and the disc herniation can be accessed. In the case of spinal stenosis, a more extensive laminectomy is performed and may require removal of an entire lamina on both sides of the midline, and including the spinous process where the lamina from both sides meet. This permits the surgeon to uncover the canal containing the nerves and to extend the decompression laminectomy to the area of the facet joints, where bony spurs can be removed. In some cases, it is necessary to remove the entire lamina and a portion of the facet joint (through the same exposure). If the surgeon is concerned that instability will occur, a fusion may be performed in addition.