What is adjacent segment disease after spinal fusion?

Adjacent segment disease is new pain or nerve symptoms caused by wear and tear at the spinal level directly above or below a spinal fusion. It usually appears years after surgery, when the neighboring disc or joints break down, narrow the space around the nerves, or become unstable. It can happen after fusion in the neck (cervical) or the lower back (lumbar).

What is adjacent segment disease?

Adjacent segment disease is a symptomatic problem at a spinal level next to a fusion. A fusion joins two or more vertebrae so they heal into one solid piece of bone. That stops painful motion at the fused level, but the levels on either side now handle more of the bending and twisting.

Over time, those neighboring levels can develop disc degeneration, bone spurs, thickened ligaments, or slippage of one vertebra on another (spondylolisthesis). When these changes cause symptoms, doctors call it adjacent segment disease.

Is adjacent segment degeneration the same as adjacent segment disease?

No. The two terms describe different things, and mixing them up causes a lot of confusion.

	Adjacent segment degeneration	Adjacent segment disease
What it means	Wear seen on X-ray or MRI at the neighboring level	Wear at the neighboring level that causes symptoms
Symptoms	Often none	Pain, numbness, weakness, or walking problems
How common	Common on long-term imaging	Less common
Needs treatment?	Usually not on its own	Often, starting with non-surgical care

Many people have degeneration on a scan and feel fine. Some of that wear would likely have happened anyway with age.

What are the symptoms of adjacent segment disease?

The symptoms of adjacent segment disease usually look like the problem that led to the first surgery, just coming from a different level. They depend on where the fusion is.

After a lumbar (lower back) fusion, people may notice:

• Low back pain that returns after a period of relief
• Pain, numbness, or tingling that travels into the buttock or leg (sciatica)
• Leg heaviness or pain when walking or standing that eases with sitting or bending forward (neurogenic claudication)
• Weakness in the leg or foot

After a cervical (neck) fusion, people may notice:

• Neck pain or stiffness
• Pain, numbness, or tingling into the shoulder, arm, or hand
• Weakness in the arm or grip
• Clumsy hands, trouble with buttons or handwriting, or unsteady walking, which can be signs of spinal cord compression (myelopathy)

What does adjacent segment disease feel like?

Many patients describe it as "my old pain coming back" after months or years of feeling better. The pain may be in a slightly different spot, or on the other side, because a different nerve is involved.

Not every new ache after fusion is adjacent segment disease. Muscle strain, a fusion that did not fully heal, hardware problems, and hip or sacroiliac joint pain can feel similar, so an exam and imaging are needed.

How common is adjacent segment disease after spinal fusion?

Reported rates of adjacent segment disease vary widely between studies, so there is no single reliable number. Some studies count any change on imaging, others count only symptoms, and others count only patients who needed another operation. Follow-up also ranges from a couple of years to more than a decade.

What studies agree on is that imaging changes are more common than symptoms, and symptoms are more common than reoperation. Risk also builds slowly over time, which is why researchers often study it with survival analysis, a method that tracks how long people go before an event happens.

How long does adjacent segment disease take to develop?

Adjacent segment disease most often develops several years after fusion, though it can appear earlier. Because the extra stress on neighboring levels adds up gradually, the chance of developing it tends to rise the longer someone is followed after surgery.

Symptoms that start within weeks of surgery are usually from something else, such as nerve irritation, healing problems, or hardware position, and should be checked by the surgical team.

What raises the risk?

Several factors are commonly linked to a higher risk of adjacent segment disease:

• Existing wear at the neighboring level before surgery
• Longer fusions that span more levels, which put more stress on the ends
• Poor sagittal alignment, meaning the side-view curve of the spine is not well balanced. One common measure is PI-LL mismatch: the difference between pelvic incidence (a fixed angle set by the shape of the pelvis) and lumbar lordosis (the inward curve of the lower back). A mismatch over about 10 degrees is generally considered a sign of malalignment.
• Older age, and in some studies higher body weight
• Disruption of the neighboring joints or ligaments during surgery, for example from screw placement or removing bone at the adjacent level

How can you prevent adjacent segment disease after spinal fusion?

There is no guaranteed way to prevent adjacent segment disease, but some steps may lower the risk. Much of it comes down to surgical planning. Surgeons try to restore a balanced spinal curve, fuse only the levels that need it, and protect the joints and ligaments at the neighboring levels.

In the neck, artificial disc replacement keeps some motion and is an alternative to fusion for selected patients. Whether it meaningfully lowers adjacent level problems over the long term is still being studied.

After surgery, patients can support their spine by:

• Following the rehabilitation plan and building core and back strength
• Staying active with low-impact exercise such as walking or swimming
• Keeping a healthy weight
• Not smoking, since smoking harms bone healing and disc health

The right plan depends on the individual, so these choices are best made with the care team.

What is the treatment for adjacent segment disease?

Treatment for adjacent segment disease usually starts with non-surgical care. Options include physical therapy, anti-inflammatory or nerve pain medicines, activity changes, and spinal injections to calm an irritated nerve. Many people improve enough with these to avoid more surgery.

Surgery may be considered when symptoms are severe, keep coming back despite treatment, or cause weakness or spinal cord compression. Depending on the problem, it may involve:

• Decompression to remove bone or tissue pressing on the nerves
• Extending the fusion to include the affected level
• Disc replacement at the new level in selected cervical cases

The decision depends on the person's symptoms, imaging, overall health, and goals. Researchers are also building models that estimate an individual patient's risk over time, such as this adjacent segment disease risk model.

When to seek emergency care

Get emergency care right away if you have had spinal fusion and develop any of these:

• New loss of bladder or bowel control, or trouble passing urine
• Numbness in the groin, inner thighs, or buttocks (the "saddle" area)
• Rapidly worsening weakness in the legs or arms
• Sudden loss of balance or hand function
• Fever with severe back pain or wound drainage

These can be signs of serious nerve or spinal cord compression or infection.

Frequently asked questions

How long does spinal fusion last?

A spinal fusion is meant to be permanent. Once the bone has healed solidly, the fused levels stay joined for life. What can change over time is the health of the levels above and below the fusion, which is why adjacent segment disease is a long-term consideration.

Can adjacent segment disease happen after cervical fusion?

Yes. Adjacent segment disease after cervical fusion is well recognized and can cause neck pain, arm symptoms, or spinal cord compression at the level next to the fusion. It is managed much like the lumbar form, with non-surgical care first and surgery when needed.

Does everyone with a spinal fusion get adjacent segment disease?

No. Many people never develop symptoms at the neighboring levels. Imaging changes are fairly common over the years, but most of them do not cause problems.