Adjacent Segment Disease and Back Pain

Adjacent segment disease, a known complication of spinal fusion, can also be caused by degenerative changes in the back and neck.

Adjacent segment disease (ASD) is a spinal disorder that may develop after spinal fusion (eg, instrumentation, bone graft). Although ASD is widely known to be a potential complication of spinal fusion, it can also be caused by natural degenerative changes that occur in the spine due to aging. ASD is also known as adjacent segment syndrome, transitional syndrome, and adjacent segment degeneration.
Illustration of vertebrae with instrumentation,rods and screws.Adjacent segment disease may develop after spinal fusion performed to stabilize a section of the spine using rods and screws. Photo Credit: the aging population in the United States continues to increase, so, too, will the rate of spinal fusion.1 The increasing rate of spinal fusion has led spine surgeons and researchers to delve deeper into the connection between fusion and adjacent segment disease.

What are the symptoms of adjacent segment disease?

ASD may produce symptoms like those that led you to spine surgery in the first place.

So, if your surgery was in your lumbar spine (low back), you may feel:

  • Low back pain
  • Pain that radiates from your low back down into one or both legs and/or feet
  • Neurological symptoms (tingling, numbness, or weakness) in your lower extremities
  • Pain while walking and/or difficulty standing

If your surgery was in your cervical spine (neck), you may feel:

  • Neck pain
  • Pain that radiates from your neck down into your shoulders, arms, and/or hands
  • Neurological symptoms (tingling, numbness, or weakness) in your neck and upper extremities

Symptoms depend on the degenerative changes related to ASD and where they occur on your spine (eg, cervical versus lumbar). For example, if your ASD causes spondylosis (spinal osteoarthritis), you may feel a different set of symptoms than if your ASD is related to spinal stenosis.

In some cases, a person may have adjacent segment disease and not even know it—this is called asymptomatic adjacent segment disease. It is most likely to be detected on magnetic resonance imaging (MRI). MRI most clearly shows the degenerative changes associated with ASD, as it produces detailed pictures of abnormalities in your soft tissues (eg, spinal nerves and intervertebral discs). A plain x-ray, for example, often isn’t sensitive enough to pick up these soft tissue problems, as it better highlights bone disorders.

How does ASD become a complication of spinal fusion?

The spinal column is made up of motion segments—basically, one intervertebral disc, the vertebrae above and below the disc, facet joints and supporting soft tissues (eg, ligaments). Motion segments work together to absorb and distribute forces during activity and at rest—like the links in a chain or hinges on a door. If one of those links or hinges is artificially attached to an adjacent link it changes the way the whole chain moves.

Similarly, when one or more motion segments in the spine is fused and no longer moves, the motion segments above and below the spinal fusion compensate for lost motion at the fused level(s). As the adjacent segments’ mobility increases, they take on additional stress—this accelerated wear and tear may lead to adjacent segment disease.

ASD may lead to several degenerative disorders in the adjacent spinal segments, including:

  • Bulging or herniated discs
  • Spinal stenosis
  • Spondylosis (spinal osteoarthritis)
  • Spondylolisthesis
  • Scoliosis

Because adjacent segment disease is a potential complication of spinal fusion, many people assume their spine surgery failed if ASD occurs. This is not necessarily the case. The spinal fusion itself may be a success, but ASD appears a consequence of degenerative changes involving many factors (eg, biomechanical stress, age).

Are there other causes of adjacent segment disease?

Spinal fusion isn’t the sole cause of adjacent segment disease. Degenerative changes in your spine, such as those related to aging, may also cause the condition.

In some cases, the spinal disc(s) and joints in the adjacent segment(s) may have a history of degenerative changes (eg, spondylosis or a bulging disc). That is, the segments around the area of fusion may have already begun degenerating before the fusion surgery itself. The older you are, the more likely your spine may have progressed in the degenerative process, and that can increase your risk for degenerative spinal disorders associated with ASD.

Are there specific risk factors for adjacent segment disease?

Knowing ASD’s risk factors is important, as it can help guide pre-surgery conversations with your doctor to help understand how these factors apply to you. Researchers have connected the following risk factors to adjacent segment disease:

  • Older age
  • Tobacco use
  • Having a degenerative spinal disorder prior to undergoing spinal fusion (eg, previous herniated disc)
  • Multi-level spinal fusion
  • Being female
  • Undergoing an open, or traditional, fusion (research shows that minimally invasive spine surgery bears a smaller risk of ASD2)

Treating and Preventing Adjacent Segment Disease

Your doctor will work with you to decide the best course of action to manage your adjacent segment disease. Milder forms of ASD that are not causing spinal instability, pain or nerve problems may be treated non-surgically. Physical therapy may help improve body mechanics, and medications and spinal injections can help ease inflammation and pain.

Severe cases of ASD—those that compromise the stability of your spine and/or nerve health—may require a second surgery. In most cases this will be another fusion.

In an effort to reduce the risk of ASD, artificial disc replacement was been developed, which is approved for use in both the cervical and lumbar spine, and allows for movement in the injured or diseased segment (unlike fusion, which strives to eliminate movement). This preserved mobility may help prevent ASD, but more long-term data is needed to understand if artificial disc replacement is the solution to preventing surgery-related ASD. Many patients with advanced arthritis or instability of the spine are not candidates for artificial disc replacement.

The decision to undergo spine surgery—and the type of surgery used—is a personal decision between you and your medical team. Some patients may benefit from a second spinal fusion to treat adjacent segment disease, while others may be candidates for artificial disc replacement or a different procedure. As with any spine surgery, revision or second surgery bear risks that you should understand before undergoing the procedure. Weighing those risks against the potential benefits will help you confidently move forward with your care plan.

Updated on: 02/09/21
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