There are two main kinds of spinal fusion based on where the bone graft is placed. The first is a posterolateral fusion. Bone graft is placed along the back of the spine joining the transverse processes of two vertebrae. The transverse process is part of the bone that sticks out to the side and attaches to the rib.
Screws and rods are used most often to hold the vertebrae together while this type of fusion is healing.
The second type of fusion is called an interbody spine fusion. In this fusion, the bone graft is placed in between the vertebral bodies. The disc is taken out and the bone graft goes in its place. This fuses one vertebral body to the other.
The graft can be placed in between the vertebral bodies from the front or the back of the body. Using an incision in the abdomen to get to the spine is called an anterior approach or anterior lumbar interbody fusion (ALIF). The graft can also be placed from a posterior approach through the back. This approach is called a posterior lumbar interbody fusion or PLIF.
Using both kinds of fusion at the same time increases the chances for a solid fusion. This type of surgery is referred to as a 360-degree fusion. It's like using a belt and suspenders to hold the spine together.