The More Low Back Levels You Have Fused the More Likely You Are to Need More Fusion
POSTED ON IN Research BY Christopher Centeno
Sometimes medicine isn't rocket science, but common sense. Take for example the idea that the more levels in a low back you fuse, the more damage can be done over time to surrounding structures. You don't need an MD or a PhD to see that this makes intuitive sense. However, despite this, we're seeing surgeons fuse more levels than ever. So this morning we'll go over recent research that throws some water on the multilevel fusion parade.
Defining Spine Structure and Back Fusion
The spine consists of a column of stacked bones called vertebrae, and the column stretches from the neck all the way down to the tailbone. There are five segments: cervical (7 bones), thoracic (12 bones), lumbar (5 bones), sacrum (5 fused bones), and coccyx (the 4 fused bones that make up the tailbone). Their purpose is to provide structure for the body and to protect the big bundle of nerves that threads through the middle of the column called the spinal cord. Between each vertebra, we have intervertebral discs, which cushion the vertebrae as we move and absorb shock.
While the terminology spinal column likely brings to mind a stick-straight structure, the spinal column is not straight. It actually has gentle snake-like curves to the front and back that provide counterbalance and aid with movement, balance, and shock absorption. In short, the spinal column is made for flexibility and movement.
The purpose of a spinal fusion, on the other hand, is to stop movement. A one-level fusion removes the disc between two vertebrae and uses screws and other hardware to force the two vertebrae together, which then fuse into one structure. A two-level fuses three vertebrae, three-level fuses four vertebrae, and so on. So is it really that big of a deal if we lose movement and flexibility in a few vertebrae? After all we have lots of vertebrae back there. Well, yes, it's a big problem. Let me explain.
Fusion Can Cause Adjacent Segment Disease
A fusion forces the adjacent vertebral segments (those above and below the fusion) to take on the extra stress and become overloaded with additional work they were never intended to do. When this occurs, this is called adjacent segment disease (ASD), and it may be accompanied by pain, bone spurs, arthritis, and so on. As it advances you are likely to start hearing your doctor throw out the F word again—another fusion. And next thing you know, you're chasing your ASD up or down your spine. So, yes, one fusion is one fusion too many. And if you've already had one fusion, this doesn't mean you have to say yes to another one. In fact, the long term fusion risk is that it will just create bigger and bigger problems down the road. See the video below for visuals and more information on ASD.
While I've highlighted many other studies on ASD following fusions, today's feature study takes this a step further, looking at the connections between the number of fused levels and the increased risk of more fusions resulting from ASD. Let's take a look .
Long-Term Fusion Risk: The More Levels Fused, the Greater the Risk for More Fusions
The new study investigated the occurrence of adjacent segment disease (ASD) following short lumbar fusion surgery. Specifically, how often does ASD following fusion result in additional fusions? The study defines “short fusion” as three or fewer fused levels. Researchers followed 479 subjects after short fusions. A total of 37 subjects (7.7%) underwent surgeries for ASD that developed after their initial fusion surgery.
The result? Subjects whose initial fusion included three segments were 2.7 times more likely to undergo ASD fusion surgery than those with one or two fused segments. So the more lumbar levels you have fused, the more likely you are to need additional fusions. Additionally, subjects with rheumatoid arthritis fared even worse, with a 4.5 times greater risk of more fusions.
Spinal Fusion is Irreversible: A Few More Reasons You Should Say No to Fusion
Adjacent segment disease aside, long term fusion risk includes many additional important issues. A few of these follow:
The upshot? Robert Heinlein once wrote that war was the last resort of the incompetent. Meaning that it was so awful that we needed to make sure that we place it in a special place in our minds so it never or only rarely happens. I would edit that for spine surgery and write that fusion is the last resort of the incompetent spine surgeon. Meaning that fusing a spine to treat pain is NEVER a good thing and that we need to make sure it occupies a special place in our minds so that we avoid it at all costs. If you have to fuse, then fuse one or two levels at most. However, given that we have surgeons fusing four, five, or six levels routinely, we have an awful lot of incompetent spine surgeons out there! So as a patient, please be smarter than your surgeon. Make sure he or she only gets to fuse one or, at maximum, two levels by refusing to have more than that fused! Or at the very least, get multiple opinions from both spine surgeons and nonsurgeons who don't know each other. In the end, avoid big fusions!
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