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from the American Academy of Orthopaedic Surgeons

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Posterolateral Lumbar Fusion

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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. Spinal fusion is a treatment option when motion is the source of the pain—the theory being that if the painful vertebrae do not move, they should not hurt.

There are several different types of spinal fusion surgery; your doctor will talk with you about which one is appropriate in your situation. This article focuses on posterolateral lumbar fusion—the most common type of spinal fusion—and discusses only the surgical component of the procedure.

For a complete overview of spinal fusion, including approaches, bone grafting, complications, and rehabilitation, please go to Spinal Fusion.

Posterolateral Fusion

In a posterior approach to lumbar fusion, the surgeon makes an incision down the middle of the lower back.  To see the vertebrae, the surgeon will pull back the muscles that surround the spine.

incision site for lumbar spine surgery

A posterior approach to lumbar surgery. An incision is made down the middle of the lower back, over the vertebrae to be fused.

In many cases, the surgeon will remove arthritic bone and any other structures, such as a herniated disk, that may be putting pressure on spinal nerves. This procedure is called a decompression, or laminectomy.

After the decompression, the surgeon will place graft material along the sides of the vertebrae to stimulate bone growth. The bone graft material is typically placed over the transverse processes of the vertebrae.  This is called a posterolateral fusion.

Titanium screws and rods are often used to provide immediate stability to the spine until a solid fusion has been achieved. These screws typically are not removed even after the bone graft has healed.

lumbar spine decompression and bone graft placement

(Left) Muscles surrounding the spine are pulled back to expose the bone. (Right) After a decompression procedure, bone graft material is placed over the transverse processes and screws are placed to provide stability to the spine. 

Back and side views of posterolateral fusion with screws.

These x-rays show front  and side  views of posterolateral lumbar fusion. 

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Last Reviewed

February 2018

Contributed and/or Updated by

Daniel K. Park, MD

Peer-Reviewed by

Stuart J. Fischer, MD

AAOS does not endorse any treatments, procedures, products, or physicians referenced herein. This information is provided as an educational service and is not intended to serve as medical advice. Anyone seeking specific orthopaedic advice or assistance should consult his or her orthopaedic surgeon, or locate one in your area through the AAOS Find an Orthopaedist program on this website.