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Spine and Back Health

Spinal fusions

02/18/2008

Question:

What are the pros and cons between cage fusion, bone fusion and artificial disc replacements?

Answer:

Hello, thank you for your question. You have asked a question with a very complex answer. I have given lectures 60-90 minutes long on this subject.

Fusions - In essence, the advantages of fusion are that we have a long track record with it - we understand a lot about how it works, and how it performs in the long-term. If a person fuses successfully, it's also permanent and you don't have to worry about it later. Fusion is also applicable to a much larger group of patients, many of whom do not qualify for an artificial disc.

Cages have some advantages over bone fusion alone - especially with the current materials (PEEK or carbon fiber instead of titanium), but there is no clear-cut winner between the two. Sometimes it's surgeon preference/experience.

The downside to fusion is, first and foremost the patient has to fuse. If you don't successfully heal the bone, you will end up with a "failed fusion", also called "pseudoarthrosis", and this often leads to repeated attempts to obtain successful fusion. Secondly, you have to restrict activities a little longer with the fusion, to allow the bone to heal, even after the pain of surgery is resolving. Third, there is a phenomenon called "adjacent segment degeneration" in which it is thought that over many years, the rigid fused part of the spine leads to more stress on adjacent discs, causing them to wear out - sort of a "domino effect".

Artificial discs - the advantage is possibly avoiding adjacent segment degeneration. This remains unproven, but is likely. Studies have shown slightly faster return-to-work time, since you're not waiting for bone to heal. Of course, the concept of avoiding fusion is instinctively appealing, but there is no proof that the overall success rate or eventual outcome for the patient is any better than fusion.

The downsides are that we don't really know how they hold up in the long term (10, 20 years or even longer), they have to be implanted through the abdomen, and there are some concerns that revising or replacing them may be dangerous. Keep in mind, they've only been around in the U.S. for about 7 years (only available on the market and FDA approved for 3.5 years), and for about 24 years in Europe, so there's limited experience here in this country. Also, remember, many patients are not appropriate candidates for artificial discs.

This is a very brief summary of some of the issues. In the end, the decision of which operation is right for each individual patient must be made between the patient and their surgeon.

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Response by:

David J Hart, MD David J Hart, MD
Associate Professor of Neurosurgery
School of Medicine
Case Western Reserve University