If you’ve done any internet research about spinal fusion or talked to someone who’s had it, it’s pretty clear that fusion is viewed in a negative light. But while most people are aware of its tarnished reputation—and may have even seen or heard horror stories from those who’ve experienced the surgery—not as many people are sure about the medical reasons behind it. The main reason why fusion doesn’t work in many cases is quite simple, actually—it’s called adjacent segment degeneration (ASD), and it can be avoided.
What is adjacent segment degeneration?
To understand adjacent segment degeneration (sometimes referred to as adjacent segment disease or adjacent segment syndrome), you first need to understand what happens during spinal fusion.
During fusion surgery, a surgeon removes a vertebral motion segment from your spine—made up of a disc and its accompanying facet joints—in its entirety, and fills in the gap with bone graft, rods, and spacers. The newly inserted material fuses with the vertebrae above and below to make one solid mass of bone. This procedure may temporarily relieve back and leg pain, but there are long-term consequences to removing a joint from your spine.
The absence of a vertebrae—and more specifically, the joint—changes the environment in which your spine operates. By stiffening a segment where there once was a joint, you create abnormal mechanical loads for the spine segments above and below the fusion. Those abnormal loads add stress to the nearby facet joints and discs and make them work harder, and as a result, they rapidly start to weaken, resulting in adjacent segment degeneration.
As time goes by, severe problems are likely to develop (like spinal stenosis or a herniated disc) and another fusion surgery may become necessary to correct the problem.
Hoping to avoid the fusion cycle? Learn more about a better alternative—BalancedBack® Total Joint Replacement.
Can adjacent segment degeneration be attributed entirely to fusion?
For a long time, there was some doubt as to whether this condition was due to the mechanical conditions created by fusion, or whether it was some combination of aging and/or genetics, but now the majority of evidence indicates ASD is due to biomechanics changes related to fusion.
Today, we know that most patients develop symptoms of adjacent segment degeneration five years after fusion. Symptoms start out as exclusively back pain, but they eventually progress to leg pain due to nerve compression. Some patients develop the condition sooner—as early as one year after fusion—while others take longer than five years.
How fast the condition develops also depends on how many fusions a patient has already had, and how many levels have been fused. The more levels are fused the greater the mechanical forces will be on the adjacent levels, so degeneration will happen faster. And if it’s a second or third fusion, it is also likely to happen even sooner than five years.
How can adjacent segment degeneration be avoided?
We now know that maintaining as little as five or six degrees of motion in your spine markedly lessens the magnitude of the mechanical forces, protecting your spine against adjacent segment degeneration.
At a 2017 presentation from the North American Spine Society annual meeting, data was shared showing that patients who underwent disc replacement—a procedure that replaces the disc only, and leaves the facet joints intact—instead of fusion showed a degeneration rate of 3 or 4 percent, simply because they were able to maintain motion in the joints of their spine. That data bears out in relation to adjacent segment degeneration of the cervical spine, as well; it occurs five times less in the neck now that disc arthroplasty is more commonly used than fusion.
But disc replacement surgery isn’t right for many patients, and there is another option that addresses the same issues and also preserves motion in the spine: BalancedBack® Total Joint Replacement.
BalancedBack® is the most complete solution for back and leg pain because it replaces the function of both the disc and facet joints with a total joint implant, allowing patients to keep moving as they normally would. The new, productive joint allows the levels above and below to move naturally, without additional stress on adjacent levels of your spine.
BalancedBack® also allows surgeons to address a wide range of problems that cause back and leg pain, including pinched nerves, spinal stenosis, arthritis in the facet joints, and sagittal imbalance. That means you’re able to solve the root cause of the problem and gain protection against adjacent segment degeneration at the same time.