Posterolateral Spinal Fusion

The spine is regulated and kept stable by three systems working in concert to enable and restrict movement.

The passive system includes the vertebrae, facet joints and ligaments, which all help to stabilize bending and twisting movements. The active system comprises muscles and tendons, which ensures stability when the movement is neutral and excludes bending or twisting. Finally, the neural system regulates muscles in the spine. If any of these three delicate systems is not functioning correctly, the others attempt to compensate to keep the spine stable. That is an imbalance that often leads to stress and injury.

Any exaggerated movement in the spine can cause pain, especially if the impact in the area pinches or irritates the nerves. Instability of the spine can often result in painful back spasms, which are the muscles’ way to compensate for extreme movement of the spine.

Your physician may recommend spinal fusion surgery, where the spinal vertebra and discs are connected with a bone.

During the procedure, surgeons place the bone graft on the transverse processes (the small bony projections off the right and left side of each vertebrae) in the back of the spine. The surgeon uses screws and rods to connect the two grafts on the outside of each vertebra. The grafts are then connected with a metal rod. Depending on the grade of the fusion, more or fewer screws and rods are used. Posterolateral Spinal Fusion (PSF), which has been practiced for many years, may be recommended for patients experiencing a variety of spinal conditions.

Conditions Treated by PSF:

  • Spondylolisthesis: This condition occurs when one vertebra slips forward on the adjacent vertebrae. It may be congenital (hereditary), the result of stress on the spine, or spinal degeneration. It may produce both a gradual deformity of the lower spine and a narrowing of the vertebral canal, which can cause back pain, leg pain and other symptoms.
  • Spinal Fractures: Unlike other injuries, this condition may not be evident immediately, but can cause unremitting back pain. Pain from this condition can be extreme, which is exacerbated by nearly any activity. Lifting objects or even simply standing in place can bring on searing pain.
  • Tumors: Spinal tumors usually emerge as a result of a tumor elsewhere in the body that travels to the spine via the bloodstream or lymph nodes. They can cause neurological issues and also have an effect on the vertebrae, causing pain in the back, perhaps radiating down the legs.
  • Infections: Neck and back pain could be an indication of meningitis, an infection of the linings of the brain and spinal cord. Other kinds of infections can have an impact on bone and discs.
  • Scoliosis: Abnormal sideways curvature of the spine instead of spinal alignment in a straight line.

Posterolateral Spinal Fusion Surgery

In a Posterolateral Spinal Fusion, the surgical approach to the spine is from the back through a midline incision that is approximately three to six inches long.

To begin, a bone graft is obtained from the pelvis (the iliac crest), although a bone graft substitute may also be used. Most spine surgeons work through the same incision to obtain the bone graft and to perform the fusion procedure.

Next, the harvested bone graft is laid out in the posterolateral portion of the spine. This region is on the outside of the spine and is a vascular area, which is important because the fusion needs blood to provide the necessary nutrients for it to grow.

Finally, a small extension of the vertebral body in this area (transverse process) is a bone that serves as a muscle attachment destination. The large back muscles that attach to the transverse processes are elevated to create a bed to lay the bone graft on. The muscles in the back are then laid back over the bone graft. This creates tension to hold the graft in place.