A spinal fusion is when two or more vertebrae in the low back are fused together to create a solid bridge of bone between the vertebrae and across the disc space. A fusion is usually performed to eliminate movement between vertebrae and stabilize a painful or unstable segment of the spine. A posterior spine fusion approaches the spine through the back to accomplish the fusion.
Posterior spinal fusion has high success rates in patients with spondylolisthesis or scoliosis. Sometimes patients with spinal stenosis also benefit from a fusion if a disc is collapsed and the neural foramen, or exiting space for the nerve, needs to be spread open. Posterior fusion for dark, or worn-out, discs is less reliable than when other conditions such as those listed above are also present.
After general anesthesia, an incision is made over your lower back and your muscles are gently pulled away from your spine to expose the lumbar vertebrae. If your nerves are under any pressure they are decompressed. The surgeon takes small pieces of bone from the outside part of the back of your pelvis and these pieces are used to stimulate the fusion. The bone on the lower part of your spine is then roughened up and the graft is then placed closely against the roughened-up bony surfaces to help produce fusion. Many times, the surgeon also performs an interbody fusion in which the disc is removed and replaced with either solid bone from a cadaver or a carbon fiber cage packed with your own bone. This increases the chances of successful fusion.
Screws, plates, and rods (also known as hardware) are used to immobilize the spine which enhances the healing process. Hardware acts as an internal splint, or, like a rebar in concrete, and increases the chances of fusion. Hardware also allows for the correction of deformity in the spine.
One of the two most common complications of posterior lumbar fusion is a spinal fluid leak. This occurs in about 3% of patients who have never had prior surgery and up to 10% of patients who have had prior surgery. Spinal fluid leaks are repaired but may add 1–2 days to the hospital stay.
Nonunion, or failure of the vertebrae to fuse, occurs in up to 5% of nonsmokers for a one-level fusion and up to 20% of smokers. Nonunion rates rise with the number of levels of the spine to be fused. Nonunions can require more surgery.
Infection rates average 1-2% and may require further surgery and antibiotics. Nerve damage is rare and is generally limited to one nerve going to one leg and is not a cause of paralysis.
Complications associated with the placement of the screws include bone breakage and nerve damage. Dr. Button uses live x-ray imaging to help minimize risks associated with hardware placement.
Epidural hematomas are collections of blood that can put pressure on the nerves and cause severe pain. They occur in less than 1% of cases and are usually recognized in the hospital and resolve with another surgery to evacuate the blood collection. The surgeon will place drains during surgery to minimize the chance of an epidural hematoma.
Fusion rates in non-smokers are usually greater than 95% for one-level fusions. Significant pain relief is seen in about 85% of patients with spondylolisthesis or scoliosis as the cause of their pain.
Most patients are ready to go home by the second or third day after surgery. Within the first few weeks following discharge, we encourage you to begin walking for one half hour to two hours each day. If you were given a brace, you must wear it during the day although you can remove it to sleep or shower. You should be able to go up and down stairs, drive, and perform basic daily activities without too much of a problem. Activity limitations and other details are found in Dr. Button’s aftercare instructions.
Spine fusion is generally an elective surgery. Therefore, it is your choice to proceed based on your current level of discomfort and disability. We recommend that you do not have surgery if you can live with your current level of pain or can make changes in your lifestyle to decrease the pain. If you have made a valiant effort and the pain still persists, surgery may be your next step.