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There are many reasons why someone may have chronic neck pain after cervical fusion. The key to unraveling this lies in understanding the effects of the fusion, and what can go wrong with the operation.
A cervical spine fusion is an operation that’s been around for probably 30 years. The procedure of fusion is that the surgeon goes in and destroys the disc which sits between two vertebrae.
That’s a one-level fusion. If you do a two-level fusion, there’ll be two discs that are destroyed by the surgeon. You can do a three-level fusion or even a four-level fusion.
The reason fusions are done is that the surgeon has made a clinical decision that a disc in the neck is the primary cause of the person’s neck pain. This may or may not be correct.
In the neck, the disk itself carries about 50% of the weight of the head. The facet joints are relatively big and they carry the rest of the load. This is different from the lumbar (back) spine, where the disc is proportionately much bigger.
In the back, the disc carries about 85% of the weight and the facet joint only 15% of the way. This makes lumbar spine discs more likely to be the primary cause of back pain.
However, the disc in the neck, even though it starts to look worn or damaged, is less likely to be a cause of chronic neck pain, because it carries less load.
The fusion operation itself involves destroying the disc and replacing it with bone fragments that are usually harvested from the patient’s own iliac crest (a large bone in the pelvis.)
During the operation, the surgeon will take this bone and crumble it into the space that is left behind by the disc. They’ll put a spacer in to widen and create the correct distance between the vertebrae so that the nerves can come up more easily. The spacer is usually a cage which will contain the bony fragments.
The difference in the neck and the lumbar spine is that the front of the neck is much easier to get to than in the spine. The procedure itself is technically easier to do than a lumbar spine fusion.
However, opening the front of the neck is not a benign procedure. There are whole lot of structures there that are incredibly important for life. Things like the carotid artery and huge veins run in the neck. There are also important nerves like the vagus nerve and structures like the esophagus and the trachea which you breathe through.
The surgeon has to very carefully move these aside so they can get to the front of the spine. Then they use an instrument to destroy the disc and replace it with bone. The aftermath should be just be a small scar.
As long as the surgeon does everything correctly, the operation should be fairly quick.
Issue #1
The first problem with this operation is that in the neck, it is less likely that the disc is the cause of the patient’s pain.
You may have a disc removed that looked abnormal on an MRI scan. But if it isn’t actually the cause of the patient’s pain, then they will wake up from the operation with the original pain plus the pain from the fusion.
The big issue is that it’s very hard to diagnose whether a disc is causing pain. Invariably you will get wear and tear in the discs. Seeing wear and tear, or even an abnormal disc does not always mean it is the problem.
In short, a disc not looking normal does not equal causing pain.
In the neck the cause of the pain is more likely to come from the facet joints, as these are carrying more of the person’s weight than the disc. This is why it’s often more sensible to do medial branch blocks before a fusion operation.
Medial branch blocks temporarily turn off the tiny little nerves that supply the facet joints. In this way, you can rule out the facet joints as the cause of neck pain, without the risks of unnecessary surgery.
This is very important, as chronic neck pain following a cervical spinal fusion in the neck is a significant issue. Sometimes the disc that was removed was actually working quite well, and the primary cause of the pain has been left untouched.
Issue #2
The second problem can occur when the fusion itself does not take. The bony graft that’s packed into the spacer cage doesn’t always grow.
After a fusion, even if the disc was the cause of pain, you still have to wait for bone graft to grow and the fusion to firm up. This can take many months.
It is not uncommon to have pain in the neck following fusion surgery which slowly gets better over 12 to 18 months. If you have pain early on, that can actually just be part of the operation. It’s a slow healing process, but in the end, the operation may end up being successful.
But you can’t know this for sure until almost a year has passed.
If the fusion doesn’t take, then what you have is a group of crumbly bones sitting in a hard metal cage. This cage can then push into the vertebrae above and below the fusion.
The metal cage is not structurally strong enough to provide support for your spine. This comes from the bone growth. If the bone doesn’t grow, this can cause pseudo arthrosis, a fairly common cause of chronic neck pain following a cervical neck fusion.
Issue #3
The third risk is that something goes wrong in the surgery. You may have some structural damage or you may introduce infection.
With a fusion, you’re putting a foreign body (the cage) into an important structure of the body. If the area becomes infected, it can be very hard to settle.
A primary reason to do surgery on the neck is not neck pain, but nerve pain arising from the neck (radicular pain.)
If you have pain shooting down into your arm or hand, this can be caused by an obvious compression, irritation, and inflammation of a nerve root exiting the spine in the neck.
This type of pain can get better on its own. However, if it’s not getting better, then this is a good reason to have surgery on your neck.
Decompression surgery is very different from a cervical fusion. It’s a less destructive operation to open the space for the nerve so that it can run more freely and reduce pressure. It leaves the disc and the basic structure of your neck intact.
This surgery has a much greater chance of success because you can be much more confident about the cause of pain. If you look at nerves, and one is much more compressed than the others, it is more likely to be the cause of pain than a worn or slightly bulging disc.
You can also work out anatomically which nerve is irritated. This is because if you squeeze a certain nerve, it will cause pain in a specific area of your body.
Therefore you can work backward from effect to cause. For instance, a different nerve supplies the middle finger of your hand than the one that supplies your thumb.
With this type of analysis, you can be much more confident that you have the correct cause of the person’s pain. When you’re dealing with structures in the neck like the disc, the process is much less specific, the spine level is harder to define and the actual structure is much harder to determine. It often comes down to ‘best guess’ and this is not ideal for a destructive and irreversible operation.
Next Steps
If you have chronic pain after a cervical fusion there are things you can do to improve your pain which do not rely on surgery. Find out more here: