A simple decompression aims to relieve the pressure on the nerves or spinal cord by removing any bone or disc tissue which is causing the compression. This leaves most of the bony architecture of the spine intact, so the spine remains stable. 

Sometimes so much bone has to be removed or the spine is already unstable that along with decompressing the spine it has to be stabilised. This would be in the form of a fusion using special screws and rods called a pedicle screw system as a form of scaffold to allow bone to grow from one level to the other one or two levels.