What is posterior spinal fusion with instrumentation surgery?

Lumbar fusion : Bridging the vertebral segments together in the spine. Should only be done if you have instability. Discogenic back pain without instability more controversial for fusions. Think of instrumentation as a temporary bridge (like a cast) until your bone heals over the site. The screws don't come out except in rare cases but become non essential once your bones fuse.

A type of spine : Surgery where implants which are usually several screws that attach to the bones of the spine and are then interconnected over one or more levels with usually a pair of metal rods -this is the instrumentation. A fusion is a healing together of two or more spine bones or vertebra with the use of bone material or synthetic substitutes.