A fusion entails one vertebral body (ex. L4) fusing to another (ex. L5). A fusion is bone growth connecting one bone to another. This provides stability and decreases pain from the facet joints and disc (ex. L4-5) in between the vertebral bodies. Fusion of the motion segment typically decreases nerve root irritation, as well. In other words, the fusion can decrease back pain from degeneration of the disc and facet joints, and decrease leg pain from nerve compression.
In order to obtain a solid fusion, the surgery must: stop the motion across the joints (like a cast), have sufficient surface area of bone to get bone to grow across it, have sufficient weight loading across the bone to get the body to make bone, and have the proper environment to facilitate the body to make bone.
For the majority of fusions we perform, we remove the disc and perform the fusion in the disc space. This is called an “interbody fusion” because we are trying to get bone to grow from one vertebral body to the other. The benefit of this type of fusion is that is fulfills the criteria outlined above. Putting a spacer in the disc space (made of bone or plastic) provides stability, removing the disc provides large surface area for bone growth, 80% of the weight bearing goes through the disc space, and the environment in the disc space is conducive to bone growth once the disc is removed.
We approach the spine from different directions in order to perform the interbody fusion across the disc space. The abbreviations for lumbar fusions are ALIF, DLIF/XLIF, TLIF, and PLIF. The first letter indicates the direction of the approach: anterior, direct lateral/extreme lateral, transforaminal, and posterior. The second letter is for lumbar. The last two letters is for interbody fusion. We decide which direction to approach from based on what is best for each individual patient.
For a description of the XLIF/DLIF, please click here
For a description of the TLIF, please click here
For a description of the PLIF, please click here.
We prefer a TLIF to a PLIF because we think it requires less nerve root retraction and is safer for the patient. They are very similar procedures, both done from the back.