Fusion methods include Posterior Lumbar Inter-Body Fusion (PLIF),  which involves the placement of rigid stabilizing lag screws into the spine, linked by inter-locking rods.  A wide area of the dorsal arch of bone, or lamina, is also removed to reduce constricting pressures on the nerves within.  And bone graft material is layered across the gaps removed by earlier, which in time will fuse together to strength the bonds between bones.

BAK Cage implants can also be positioned between the vertebrae, which serves to rigidly separate the individual bones of the spine and to ensure proper gapping between the bones for safe passage of transiting nerve structures.  Small holes are drilled into the bony vertebrae and then the implants are inserted, and screwed into place.

And technologies are now underway for Artificial Disc Replacement. The latter is still fairly experimental, and is only authorized for patients with a single disc injury (not multiple disc injuries).  Theoretically the artificial disc could replace the damaged or incompetent disc, but the drawback is that a lot of surgery/tissue injury is removed in exposing the disc spaces to perform this operation