Confusion about Back Fusion
Doctors and researchers are still unsure about the best way of doing spinal fusion. Using special devices called fusion cages to support the bones has become very popular. The implanted cages are usually placed next to each other in the disc space (after the disc is removed).

One way to put the cages in place is a surgical procedure called posterior lumbar interbody fusion (PLIF). "Posterior" means the operation is done by opening the spine from the back. "Interbody" is the disc space between the vertebral body above and below. The surgeon removes a small piece of bone off the back of the vertebral column, making it easier to get the disc out and the cages in.

But taking out part of the bone can cause weakness in a spine that already needs more stability. Studies have compared the use of one cage instead of two. A single cage placed at an angle inside the disc space results in greater stiffness after the operation. Increased stiffness or loss of motion is actually the goal of a fusion.

The authors of this study used the posterior approach with one cage for spinal fusion. A minimum amount of bone was removed to make room for the cage. Screws and rods called instrumentation were also used to support the spine at that level.

A single cage lowers the risk of nerve damage. It's an easier way to do the operation. Other good things about a single-cage PLIF are less blood loss, less time in surgery, and a shorter hospital stay.

These authors conclude that a single cage with instrumentation is a good choice for fusing two vertebrae in the low back. This method shows better results than doing a PLIF with two cages.
References
Jie Zhao, et al. Posterior Lumbar Interbody Fusion Using One Diagonal Fusion Cage With Transpedicular Screw/Rod Fixation. In European Spine Journal. April 2003. Vol. 12. No. 2. Pp. 173-177.