A lumbar disk replacement is a type of back or spine surgery. Your spine is made up of bones called vertebrae that are stacked on top of each other. Disks between the vertebrae work like cushions to allow the vertebrae to rotate and move without the bones rubbing against each other. The lumbar vertebrae and disks are at the bottom of your spine. Lumbar disk replacement involves replacing a worn or degenerated disk in the lower part of your spine with an artificial disk made of metal or a combination of metal and plastic.