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Update on Adjacent Segment Degeneration

There remains considerable controversy on the nature of Adjacent Segment Degeneration after lumbar fusion.  To the non-spine surgeons,  the issue is the theory that a fusion operation places more stress on the levels above or below the fusion,  and will lead to accelerated degeneration and subsequent surgery.  In fact,  most surgeons will tell patients about the risk for potential future surgery after lumbar fusion.

The skeptic will say the surgeon is just setting up a biase towards future surgery.   Some will say lumbar fusions are not great surgery,  and the rate of future surgery is so great that the primary lumbar spine fusion surgery should be avoided.   Several studies have showed a rate of additional future lumbar spine surgery after fusion at 10-15% over 10 years in the US population.  Spine surgeons like me,  need some guidance,  so we can appropriately discuss the effects of lumbar spinal fusion,  and the potential for increasing back pain,  and subsequent surgery after the fusion.

Recently,  there has been much interest in the so called Minimally Invasive Spine Surgery (MIS),  and potential benefits of this approach in lumbar fusions.  The major advantage,  according to the researchers on MIS is the sparing of the lumbar multifidus muscle.  It turns out the multifidus is probably the main stabilizing muscle of the spine,  and preservation may indeed also prevent the development of the Adjacent Segment Degeneration associated with lumbar fusion.

The most relevant study regarding was recently published in the August 1, 2014 Spine,  was the ISSLS Prize Winner and is titled “Long Term Follow-up Suggests Spinal Fusion is Associated With Increased Adjacent Segment Disc Degeneration But without Influence on Clinical Outcome: Results of a Combined Follow-up from 4 Randomized Control Trials” and authored by Anne F. Mannion, PhD, et al.     To summarize,  four sites,  representing locations in the United Kingdom,  Norway and Sweden followed patients for an average of 13 years randomized to surgery or non-surgery for painful lumbar disk degeneration.   Pre-operative x-rays were obtained.  The patients themselves had chronic LBP for more than a year,  with the suspected cause of the pain secondary to degenerative disk disease.   Inclusion criteria for the randomization included the use of several disability scales including the Oswestry Disability Index. Long term followup was obtained in 272 fusion patients,  and 92 non-surgical patients.   The results of the comparison of fusion vs non-fusion is another topic.  This paper looked a the effects of fusions on development of Adjacent Segment Degeneration.

X-rays were compared between the groups.  In both groups,  there was development of disk space narrowing.  In other words,  with or without surgery,  both groups had degeneration of the disks that were compared.  The study also showed the disk narrowing of the surgical patients were of a great magnitude.   But after statistical analysis,  there were no evidence that the increased degeneration associated with the fusion patients led to any difference in clinical outcomes.   In otherwords,  the difference in the amount of degeneration between the fusion,  and non surgery group did not cause any more disability or back pain.  Based on the prospective nature of this study,  I can conclude that adjacent Segment degeneration after spine surgery does not lead to more surgery secondary to the fusion.  This may or may not be what Surgeons want to counsel,  but it looks like it is the truth.  Based on latest research,  Surgeons can say  Spine Surgery is always a possibility for any spine patient, but the need for additional surgery  most likely is not related to a prior Lumbar Fusion.

Hi, this is Dr. John Shim. Today, I'm here with Jason Mazza, orthopedic assistant. Jason's been working with me for over 20 years, and one of his functions is to look at the literature, and to make sure we're staying abreast of what's going on in the orthopedic and spine research arena. Today we're going to talk about a very interesting topic called adjacent disc degeneration Jason, have you had a chance to kind of review an article and maybe a present that article to our audience? Yes. The article we're going to discuss today is titled Adjacent Disc Degeneration After Lumbar Disc Replacement or Non-Operative Treatment. This was a study that was produced in in Spine here in late December of 2018. Very interesting study out of Norway. This was a randomized control multicenter trial. Involved 5 University hospitals in which patients were followed for eight years. The goals of the study, as defined by the authors, was twofold. First and foremost, to assess the long term development of adjacent disc degeneration after total disc replacement or non-operative treatment, and secondly, they looked to analyze the association between adjacent disc degeneration development and clinical outcomes. For the purpose of the study there were two treatment groups. There were 126 patients that were randomized into either lumbar disc replacement group or a non-operative group. The non-operative group, as described by the authors, went through a program of cognitive and physical therapy for a three to five week period. The results of the study may be surprising to some. Adjacent disc degeneration was increased in 40% in the non operative group and 42% in the total disk replacement group over the course of eight years. These numbers were not statistically significant. Again, looking at the secondary measures, there was no association between adjacent disc degeneration and clinical outcome. While we can't say there were certainly some flaws with the study, we can pick them apart, but for the purposes of our discussion the treatment groups in this case were very similar in the demographics presented, and in their overall characteristics. So, Dr. Shim, to help our viewers. Can you tell us a little bit more about what is adjacent disc disease? Sure, so adjacent disc disease is a fancy medical way of saying it your discs wear out over time. We know that there's an aging process. The aging process of discs start at a relatively early age. By the time you're in your 20s about twenty to twenty-five percent of people will have disc degeneration identified on studies such as MRIs. By the time you're in your 40s, it's more than 50 percent. You could imagine what it's like when you're in your 60s. The numbers keep growing. So, we know adjacent disc degeneration is the process of aging and process of wear and tear. The interesting thing is, just because you have these adjacent disc disease findings doesn't necessarily mean you're going to have pain. So, the difficulty for doctors, surgeons, clinicians is to find out; is this degeneration that we see on the MRI or a CAT scan or x-ray actually the source of the pain, and then from the perspective of your study the reason why this study was very important to doctors who perform lumbar fusions and lumbar disc replacements is we want to know if there's a different outcome when we do these two different operations. For this study what's important for me as a clinician, Is this study supports that if we use artificial disc replacements for the lower back it does not necessarily change or increase the development of disc degeneration. So, as you talked about with adjacent disc disease, we've kind of combed through the literature and we have found that the rates of adjacent disc disease after any type of lumbar surgery vary from about five percent up to as high as 100 percent. A lot of unanswered questions about this again that doesn't necessarily imply that there's pain associated with this. So, my next question to you again as a surgeon, and you kind of just headed in that direction a minute ago, but what is your main takeaway from this study, and does the results of the study change your thinking at all with adjacent disc disease? So, we know that there's very important structures at the back of the spine. There's various muscles and ligaments, and one of the most important muscles is something called the multifidus muscle. And if you do a dissection of the spine to do your fusion operation or diskectomy operation, and you have to adjust or move or cut into that muscle, it may potentially lead to more instability or more problems down the road. We also know that if you do traditional lumbar fusion surgeries, but have some issues where you had to remove a little bit of the facet joint or the ligaments around the capsule of the facet joint above your fusion you may accelerate the development of disc degeneration of adjacent level disease. So, there's been studies that show that if you go through the front or anteriorly, where you don't do anything to the back of the spine, you may not develop this adjacent level disease from surgery. So this this study in a way supports that if you do surgery from the front anteriorly where most artificial disc replacements are performed, perhaps you decrease the rate or you don't change the rate of adjacent level disease. I think this study is supportive of using more anterior technique, support of it supportive of using artificial disc replacements in terms of disc degeneration. The other part though, which is the this a half glass half-full glass half-empty issue is - does this actually improve your clinical outcome? Fortunately, the study also showed there was no difference in a clinical outcome in terms of what happens to these adjacent disc degenerations. We get them naturally. Did getting an artificial disc replacement improve your clinical outcome from that perspective, and the answer was no. So, it was helpful that it doesn't cause more degeneration, but it's not helpful in that you're better. So it's kind of a 50/50 type of outcome, but it is important because now we can counsel patients about this. Yeah, and the last question and perhaps the most important. What does this mean for patients? So, as I stated before that patients are not experiments they're patients. They have individual desires, individual needs, individual goals, but this gives us a little bit more information during the discussion. If you had an anterior procedure, perhaps you'll not have as much degeneration or the levels above. Compared to if you had to posterior procedure. If you have an artificial disc replacement to the lower back, perhaps you won't develop some of these adjacent degenerations as that some of the other fusion type operations may have. So, there is some pros to it, but the con still is does it actually change your long-term outcome your clinical outcome? Are you better? Do you feel better? The results aren't that supportive. So, as an individual, as a patient, you need to have this information so you can have the right decision points before you can decide: what kind of surgery, if I want surgery, what are my goals of my surgery? So, I thought it was helpful. So this is Dr. John Shim along with Jason Mazza, discussing adjacent level disease. We hope you had the opportunity to review our video and we hope that we provided some information that might help you make your decisions on how to take care of your back, and if you ever have to have a surgical discussion to bring up points to discuss with your surgeon in anticipation of making a decision about surgery. Thank you for listening. Take care.

Last modified: December 13, 2019

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