Spinal fusion is a surgical procedure used to correct problems with the small bones in the spine (vertebrae). It is essentially a "welding" process. The basic idea is to fuse together the painful vertebrae so that they heal into a single, solid bone.

This article focuses on just the surgical component of posterior lumbar interbody fusion and transforaminal lumbar interbody fusion. For a complete overview of spinal fusion, including approaches, bone grafting, complications, and rehabilitation, please go to Spinal FusionSpinal Fusion (topic.cfm?topic=A00348).

Another method of fusing the lumbar spine involves removing the intervertebral disk. When the disk space has been cleared out, a metal, plastic, or bone spacer is implanted between the two adjoining vertebrae.

These spacers, or "cages", usually contain bone graft material. This promotes bone healing and facilitates the fusion. After the cage is inserted, surgeons often use metal screws, plates, and rods to further stabilize the spine.

An interbody fusion can be performed using a variety of different approaches.

Posterior lumbar interbody fusion (PLIF). A spacer may be inserted from the back of the spine. With this approach, your surgeon gains access to your spine by removing the bone (lamina) and retracting the nerves. Then the back of the disk can be removed and a spacer inserted.

The weakened intervertebral disk is removed during a posterior lumbar interbody fusion. It is replaced with a cage, or spacer.

Transforaminal lumbar interbody fusion (TLIF). With this technique, the surgeon approaches the spine a little bit from the side. This requires less movement of the nerve roots. More recently, it has even been possible to take a direct side approach and center the incision over the patient's flank. With this approach, the surgeon can reach the disk without moving the nerves and opening the back muscles.

In these front and side views of a TLIF procedure, note the screws in the back of the vertebrae. The cage can only be seen by the white metal markers. Bone graft is in the disk space inside and around the cage.