How Long Does Pain Last After Spinal Fusion?

The question of how long does pain last after spinal fusion is not a simple one. It’s as complex as the spine itself, and therefore will take some time and background information to answer.

The Big Picture

When scans like MRI, CT, and ultrasound first came on the market, it was thought they’d herald a new golden age of surgery. All you had to do is look at a scan, see which joints, tendons or discs were damaged, and do an operation to fix them.

And for a time, this was how the surgical industry operated. The only problem with this approach is that the results were far from stellar. What ‘should’ have worked often didn’t. And then researchers started looking at scans were people had a lot of wear and tear, degeneration and stenosis…but very little pain.

Awkward questions were asked, like “How do you know, just by looking at as can of that worn disc, that’s it’s definitely the only thing causing this person’s diffuse back pain?”

The short answer is that in most cases, you can’t. Which is unfortunate, because back pain is a huge problem, and surgeries like spinal fusion were meant to solve it.

The big issue is that essentially, spinal fusions are not a good operation. They should really only be used as a last resort because the operation itself is a destructive one.

To do a fusion, you’re destroying the disc and taking bone (usually from the person’s pelvis,) to help fuse the vertebrae. There are many things that can go wrong, and it’s only after looking at these that we can answer the question: how long does pain last after spinal fusion?

A model of the vertebrae of the spine, with discs in between each segment. The yellow structure is the spinal cord and nerves which branch off it. In a human, the right-hand side of the spine faces outwards. This is important, as you can see it makes it harder to get to the disc, and the branching nerves have to be pulled aside to do this.

The (Many) Problems with Spinal Fusions

Doing a spinal fusion means removing the disc completely. This has been a standard operation for the last 30 years. What everyone would like for a disc problem is the ability to replace the disc with something which behaves just like a healthy disc.

The disc has a very important job, which is to act as a shock absorber and provide movement between each spinal segment. However, technology is not yet at that stage.

When you do a fusion, you’re stopping the fused segment from ever moving again. It’s an irreversible operation that changes the biomechanics of your spine.

At its most basic, the operation is reducing the ability of your body to work and move properly. More than this though is the problem of the adjacent segments. Because you’ve fused two segments of the spine, the segments above and below the fusion have to do extra work under more pressure. 

Back Pain Years after Spinal Fusion Surgery

Over time, there’s an increasing proportion of people where the segments above and below the fusion quickly become worn. If these people then get back pain in the adjacent segments to the fusion, you’re faced with a difficult problem.

Do you then fuse the next segments above or below? This will further increase the pressure for the next adjacent segments and could create a domino effect with the levels each side of the fusion again become painful. The bigger the length of the fused spine, the more work the joints above and below it have to do. And the more rapid the degeneration will be.

This is sometimes called adjacent-segment disease. However, it’s not a disease, it’s a mechanical failure of the spine after forces become concentrated in a particular area due to the inflexibility of a fused joint.

The Fusion Operation

The other problems with a spinal fusion become clear when you look at what’s involved in doing a fusion.

To do this operation, surgeons remove the disc and fill the space between the vertebrae with small pieces of bone. This is not a straight forward procedure. To remove the disc you have to go in and pull the nerves aside and remove some bone which is part of the arch of the back of the spine. 

Once you’ve removed some of the bone of the arch and pulled the nerve out of the way, you can then go in and scrape out the contents of the disc and remove the wall of the disc. Another difficulty is that the area furthest back, the most posterior aspect of the disc is the most difficult part to remove. It’s also the part that is most commonly affected as it has the most nerve endings.

Scan of a Spinal Fusion

Once the disc removal (diskectomy) is complete, you put a cage in. It’s usually a small metal cage you squeeze together to insert between the vertebrae. Once you have it in place, you release it and the cage pops open.

The next step is to pack bone chips into the space where the disc was. Surgeons often remove bone from the top of the patient’s pelvis for this purpose. Sometimes, they take bone from a cadaver.

The surgeon slips that bone into the cage filling the space between vertebrae. Because bone is living, the hope is it will start to grow, and fill the space with living bone.

The reason that you use bone is that bone is amazingly strong because your body constantly is renewing it. The bone is, in fact, the real fusion element, and the bits of metal which look so impressive are in fact just the splint to help the bony graft to take.

Lastly, you put in screws to hold everything in place. This is how you do a spinal fusion with metal splinting.

Difficulties of Back Pain Diagnosis

A significant problem with spinal fusions is the difficulty of sorting out exactly which disc is causing your pain. 

Often, this isn’t done very accurately, with specialists and surgeons relying solely on scans to diagnose. Many large, well-researched studies have shown that relying solely on scans to diagnose the cause of pain is hugely inaccurate.

In addition to discs, back pain can come from facet joints, deep muscles, tendons, nerves, and other structures.

You can’t diagnose which disc is the painful disc by doing imaging. You can see on an MRI a disc and quite a lot of detail. But as we get older, the disks wear. You may have three or four discs, one above the other, all of which are worn and only one of which is causing your pain.

Our ability to discriminate which one it is unfortunately as much luck as anything. Therefore, one of the reasons spinal fusion fails is that the surgeon has removed the wrong disc.

So far, that’s two reasons why spinal fusions are not a good operation. Firstly, it’s very difficult to discriminate which disc is causing pain. The second is you’re changing the biomechanics forever of the area and creating increased pressure in the segments above and below the fusion. The third problem is that you’re not at all guaranteed that the fusion is going to take. 

You can put the bone chips in, but in a proportion of people, the bone does not grow or does not grow adequately. The vertebrae continue to move and you get what’s called a pseudoarthrosis.

If the bone does not grow around the cage, the cage starts to press down and wear away the bone above and below. The bone gets worn away and you end up with a space around this piece of metal where the vertebra wobbles backward and forwards using this as a pivot.

The bone in the vertebra is being worn away. There’s too much movement around the screws and you start getting lysis – the bone wears away around the screws themselves. This is the third reason why the operation fails.

Nerve Pain After a Spinal Fusion

There are also risks with the surgery itself because it’s a highly technical operation. To get access to the disc, you need to pull nerves aside.

What may happen is that the person goes in with back pain and ends up with back pain and nerve pain, because the nerves were stretched or damaged during the operation.

There are also some people who end up with as much pain from the area the surgeon has removed the bone from. What you’ve done is you’ve gone with a hammer and chisel and chipped backbone.

I had a patient once who had a problem with her neck. She had the fusion done in her neck and the surgeon took too much bone from her pelvis. This caused her to have a pelvic fracture soon after the operation.

These are some of the risks of the spinal fusion operation, and why it’s never something to be entered into lightly.

When to Get A Spinal Fusion?

With all these risks, when is it actually a good idea to get a fusion? 

It’s a very difficult question. The problem is that there is a very small proportion who do need to have their disc removed. The issue, at present, is that the only way to diagnose this is after the fact.

If you have internal disc disruption, the only way to absolutely know this is to remove the disc and send it away for analysis.

You can do a discogram, but the results are not always conclusive, and it’s a provocative procedure, meaning it can inflame the disc and cause its own problems, as well as a lot of pain. (A discogram is when you use a needle to inject dye into a disc and look at it under a CT scan.)

How Long Does Pain Last After Spinal Fusion?

When people are recovering, how long do they usually take?

This really depends on whether the pain was truly coming from your disc and not some other structure. Assuming the correct disc was taken out, below are the different possibilities.

Some people wake up and find their pain is worse because they’ve had a destructive operation on a disc and had bone taken from their pelvis. There’s a lot of healing that needs to take place before they can be sure of how much pain relief they’ve gained from the operation.

Occasionally somebody wakes up feeling a lot better. That’s great, but it’s incredibly rare. 

Usually, by two to three months, the pain is starting to improve (if the correct disc has been taken out) and the bone graft is starting to take.

By three to four months, those that are going to be a lot better are well on the way. But there are quite a proportion of people who are not a lot better, in fact, their pain continues on unchecked.

On scans, you can see bone appear and grow in the fused segment over the next 12 to 18 months. As this carries on, you may still improve, but as the months go by, the proportion of people that are actually going to get better gets smaller and smaller. 

The Surgery Recovery Stats

The overall picture is that in good hands where the operation is appropriate, around 65 to 70% of people end up with adequate pain relief.

However, it’s not that common to be pain-free. There may still be some discomfort, and the operation needs a long rehab period.

The unfortunate thing is that many people have fusions when they would be better served by having a less invasive operation. Sometimes, as well, the wrong disc is removed, so they don’t get the pain relief they were hoping for.

A spinal fusion is the kind of operation that hopefully in a few years we’ll look back and say “I can’t believe we used to do this. We have something so much better.” However, we’re not there yet, and for a very small proportion of people with back pain, this is the right option.

Other, Less Invasive Back Pain Operations

Probably the best back operation in terms of outcomes is the one used to treat spinal stenosis. This operation’s purpose is to relieve pressure on a nerve.

The thing about spinal stenosis is that it doesn’t usually cause pain in your back. It causes pain down your legs or arms. The pain it can cause shooting down your legs is called sciatica, and this tends to be worse when you’re standing up or leaning backwards. 

Spinal stenosis is a narrowing of the central canal in your spine where all the nerves run. This is often a natural process as we age. When you get wear and tear of the vertebrae, you get an overgrowth of bone to stabilize the joints.

Bony overgrowth will reduce the size of the foramen (the hole that the nerve has to go through.) These bony changes can press on the nerve.

It’s also possible to have a bulging disc reducing the space for the nerve. Finally, there’s a ligament called the ligamentum flavum which runs down the back of the spine and can bulge forward and press on the nerve.

The surgery’s purpose is to decompress the nerve by trimming back the disc, or chipping back the bone, and cutting back the ligamentum flavum.

If you can decompress the nerve is this way, the results are often good. The main problem is if you have to remove so much bone that you destabilize the joint and then you’re into the same problem, which is now you need to fuse that segment. 

Another operation to relieve sciatica where you have a disc prolapse irritating a nerve is a micro diskectomy. This is where you trim the disc back and clean up the segment, but you don’t do a fusion.

Cortisone injections also are also a good option, as quite a high proportion of people get better, given time. A transforaminal cortisone injection or a nerve sleeve cortisone injection is worth doing to see if this will settle things and allow you to avoid surgery.

If You’re Still in Pain Many Months After a Spinal Fusion

The first thing to be aware of is that surgery, especially a spinal fusion, should only be done after all other options are exhausted. If you’re contemplating having a spinal fusion, it’s a good idea to get a second or even third opinion from different surgeons, and also investigate less invasive solutions.

If you’ve had a spinal fusion already, you may be in the fortunate proportion of people for whom this operation works.

However, if you’ve had a fusion, and you’re still in pain, there are things you can do to alleviate this. If you’ve had pain for a long time, and want to find out things you can do yourself (without surgery) to get relief.

This is where things can become quite technical. To get educated on your options, here’s where to take the next step.