Spinal stenosis after surgery. Coloured X-rays of the lumbar spine of a 64-year-old patient after lumbar decompressive laminectomy surgery to relieve spinal stenosis. Spinal stenosis is an abnormal narrowing (stenosis) of the spinal canal. This causes a restriction to the spinal canal and affects neurological function. Lumbar decompressive laminectomy involves the removal of the roof of bone overlying the spinal canal and thickened ligaments in order to decompress the nerves.