A common fusion method used to hold the vertebrae together from the outside uses two things: (1) bone chips from the hip and (2) metal screws and plates. Research has come up with interbody fusion as a new way to fuse the bones together from the inside out.
A special sponge with bone growth protein is put inside a titanium cage. The cage is placed between the vertebrae where the disc used to be. Bone cells start to grow and fill in and around the cage.
The advantages of the interbody fusion are:
full load put on them through the spine.