The lumbar laminectomy or laminotomy procedure is a roto-rooter job to open a pathway for a nerve or group of nerves that are being compressed. The spinal canal is like a house with a roof. The floor is made up of the disc and vertebral body. The sides are made up of the internal edges of the facets. The roof is made up of ligamentum flavum and lamina.
With stenosis or narrowing of the central canal, there are bone spurs that grow from the facet and disc edges into the spinal canal from the floor and sides. There occasionally is also a disc bulge or herniation that also crowds out the canal from the floor. From the roof, the ligamentum flavum thickens and pushes down from the top of the canal.
During the lumbar laminectomy or laminotomy procedure, to remedy this overcrowding, a portion of the lamina (the roof of the house) is removed along with the ligamentum flavum. Any spurs off the facets that are crowding in from the sides are also removed. If there is a disc herniation, it is removed and some disc spurs may be compressed back into the body of the vertebra. The canal is irrigated and a Valsalva maneuver is performed to make sure there is no dural leak. The incision is closed and the patient sent to recovery.
There are times that this procedure is done on a level that already has a vertebral slip (see degenerative spondylolysthesis elsewhere in the web site). If the slip is not unstable (does not move on flexion and extension x-rays) and the amount of slip is not significant, this laminectomy can be performed without stabilization (fusion). It should be noted that there are occasions that removing the spurs from the facets can lead to more slip or instability. Remember that the spurs developing off the facets formed to try and make the vertebra more stable. Removal has between a 15-30% chance of creating more slip. These numbers do not pertain to any level that has no slip.