Sacrum following laminectomy. Composite 2D and 3D frontal computed tomography (CT) scans of the sacrum (base of spine) and lower lumbar vertebrae (L4 to S1) of a 64-year-old female patient following laminectomy. A laminectomy is a surgical procedure that removes a portion of the vertebra bone (backbone) called the lamina, which is the roof of the spinal canal. Here the procedure was carried out due to the presence of radicular pain, possibly caused by hernia or narrowing of the lumbar spinal canal.