Hi, I am Dr. Tony Mork, author, speaker, endoscopic spine specialist. Today I am going to do part II of lumbar foraminal stenosis, the treatment. In here I am going to recap on the anatomy, and I am going to show you two different ways that you can approach lumbar foraminal stenosis from a surgical point of view. I hope you enjoy this.
What is Lumbar Foraminal Stenosis?
The foraminal canal is a short canal that provides protection for the exiting nerve root as it branches off the spinal cord. The exiting nerve root branches off the spinal cord and exits out of the spinal canal via the foraminal canal. After the nerve gets out of the foraminal canal, it goes down to the buttock, thigh, leg, or foot and provides sensation as well as motor function. This is the anatomy that was seen in the previous foraminal stenosis video of the normal anatomy of the foraminal canal. We can see the borders of the disc on the front, the ascending facet in the back, the tip, which is the troublemaker; the little guillotine called the superior articular process. The descending facet is also on the back as well. So this is the foraminal canal with the nerve divided so that you can get a better look at the foraminal canal.
What Causes Lumbar Foraminal Stenosis?
What is the problem? It is stenosis, or narrowing. And the exiting nerve root gets pinched in the foraminal canal. This can happen for a number of reasons. The main reason that the exiting nerve root can get pinched is the superior articular process of the ascending facet where it actually is able to press on or indent the exiting nerve root as seen here in this slide. Really anything that changes the dimensions of the foraminal canal, such as a disc herniation, soft tissues from the facet joint like a synovial cyst, the tip of the facet, the superior articular process or SAP, or even loss of disc height that causes narrowing of the canal can contribute to foraminal stenosis and pressure on the nerve.
In this slide we can see pressure being exerted by the disc pushing backward from the facet joint capsule pushing forward, and the nerve which is flattened and squashed in between and is very symptomatic as a result. Pressure on the nerve causes pain, numbness; could be needles and pins, and/or weakness or atrophy such as a footdrop in extreme examples. The goal of treatment is to get pressure off the nerve so that its blood supply and circulation can be reestablished and the symptoms resolved. So the goal of the treatment is to get the pressure off the nerve, which seems straightforward enough. Essentially what we want to do is make the canal bigger, and there are really two ways or approaches.
The Two Treatment Options
There are really two treatment options. One is indirect decompression, and this can be achieved with a fusion or a spacer. There is also direct decompression. This refers to an endoscopic approach or a foraminotomy. I guess in the vernacular, there are two ways to treat the problem. One is to jack the disc space open, or two, remove the problem.
Let’s talk about option #1, jacking the disc space open. Well, this can be achieved in one of two ways. Either put an implant in the disc space and open the foraminal canal like that, or put an implant between the spinous processes. I think it is important to realize that if you put an implant in the disc space, you are getting a fusion. Here is an example of an implant being utilized in the disc space to jack open the foraminal canal. So this is a fusion; this is an implant between the vertebral bodies, usually supplemented by some bone graft; and this represents a fusion. You notice that when you open this up wider that the foraminal canal here is also widened and may resolve the foraminal stenosis issue. But it is doing it indirectly. Remember, the SAP, this little tip here, is the big problem; and this is not being removed or addressed. It is just that the foraminal canal has been made larger by wedging in this implant.
In this case we have a spacer located between two of the spinous processes, so the spinous process of the vertebra above and the spinous process of the vertebra below is actually stretched out by a spacer. Common spacers would be like a CoFlex or an X-STOP. Again, if you widen this space enough, you would expect that the foraminal canal would get wider. The restraints on this, of course, are the capsule of the facet joint which is just going to let it go so far. So I think you can get some improvement here, but it is not exactly like dealing with the problem itself which is, again, most of the time the ascending facet and the superior articular process of the ascending facet.
Well, a spacer may not actually address the actual problem, as it is only used to just jack open the anatomy that exists; and it may cause long-term problems like adjacent disc disease, which is a commonly known long-term complication of fusions.
Foraminotomy, The Second Option
Option two is to actually treat the problem. What is it that is causing the foraminal stenosis? Is it a disc herniation? Bony stenosis from the superior articular process? Or some soft tissue growth into the foraminal canal like a synovial cyst or overgrowth of the capsule of the facet joint? Well, there could be some challenges. It is already a tight, small canal. The offending structures are small, and the nerve is at risk, which is being compressed in the foraminal canal. So, direct decompression, or what is referred to as a foraminotomy, can be approached from the outside in or the inside out.
SLIDE 21: If you go from the outside in, it can be done open surgery or with a tubular retractor such as a Metrex tube. In my experience, it is hard to identify the anatomy. The facet joint is violated, and really this type of procedure just cuts a slot into the facet so that there is some room for the nerve to exist in the foraminal canal.
When doing the foraminotomy from the inside out, using the endoscopic approach like I advocate, it is an elegant type of procedure. It preserves the anatomy. The facet joint remains intact. There is a great view, as we are going to see shortly to see the problem. And, you can address the problem under direct vision. Plus, you are only treating what needs to be treated; nothing more. With an endoscopic decompression, you can trim the bone, remove overgrowth of soft tissue, or remove a disc herniation.
Here we see the picture of an endoscope used for foraminal decompression, and we can see the light cord which is grey and going down. The instrument that is being pushed to the center of the endoscope is actually some of the tools to perform this surgery, as you are going to see shortly. Here just for size is demonstrating the size of the endoscope being used. So a 7-mm endoscope here is compared to the size of a dime. This is the smallest Metrex tube I have ever seen used, which is a 14. Most of the time people are using 20 and 22’s, on up from there; but just to show you that this is really half the diameter of the smallest Metrex tube you could ever imagine using. So this small endoscope fits into the foraminal canal, whereas you can see that the Metrex tube probably would not.
This is a view inside the foraminal canal. As we talked about before, this is one of the borders, the ascending facet. In this case there is a dramatic superior articular process which I call the shark tooth or little guillotine right here, and where it is pushing into is the nerve root. So you can see the nerve root right here, and as its passes under some of the soft tissue and protected by this fat, but you can see that it passes right under here, so it is coming out of the spinal canal behind the SAP, travels down,; and this is going to go out to one’s buttock, thigh, leg, foot, etc. Just as an orientation, this is the left side of the patient. The head is to our left. The foot is to the right, and the nerve root is coming out from the spinal canal, out here. But you can see how this is digging into the exiting nerve root and causing all the pain and symptoms this person is having.
Here we are inside the foraminal canal at lumbar 4-5 with a Richard Wolf endoscope. We are going to probe the superior articular process which looks like a shark’s tooth, before we start to burr it down. This is a high-speed diamond burr tip that is effective to remove the bone but does not involve the soft tissue. Below the shark’s tooth we can see something that looks like gold foam. This gold foam is really fat that surrounds and protects the exiting nerve root as it passes through the foraminal canal. This is a sealed water environment with continuous irrigation, and we are using Richard Wolf endoscope to give us this crystal-clear view.
People always ask, what happens to the bone dust or debris? And the answer is that the continuous irrigation just washes it away. When the bone is sufficiently removed, I can use a Kerrison bone cutting tool to continue removing the shark’s tooth. Next we are going to use a Richard Wolf articulating low-speed burr. If you watch carefully, you will see that I can tilt or angle it upward to remove eve more of the bone that was putting pressure on the nerve. Note that I am always directing the burr away from the nerve. You can also see some small chunks of white tissue being removed by the burr. These are pieces of the facet joint capsule. Since the capsule of the facet joint can also take up space in the foraminal canal, it is a good idea to remove some of this as well.
Please note how well these tools work to remove this hard bone. For all the discussion about laser spine surgery, the laser works best for soft tissues, not for bone removal, which is required here. Notice how the shark’s tooth is gone and how much space there is now between the ascending facet and the fat surrounding the exiting nerve root. The view just doesn’t get any better than this.
I am now using a Kerrison bone cutting instrument to remove the tip of the superior articular process, and this is followed with a hooded oval burr to contour and remove any rough edges. The exiting nerve root is covered in fat and is seen and to the right.
This is the postop picture after removing the tip of the superior articular process. We can see in the model as it normally would be, this tip has the potential and actually in the previous surgery was actually was digging into the exiting nerve root as it’s coming off the spinal cord.
In this x-ray you can see that the whole tip here has been removed. This is flat now; no longer pointed, so this has been a successful removal of the tip of the superior articular process. This just happens to be the scope with the burr inside of it. So this is how the x-ray would like postoperative with the SAP no longer pushing into the exiting nerve root. Thus, problem solved.
Why Doesn’t Everyone Perform This Type of Surgery?
So, for the big question: If endoscopic spine surgery for foraminal stenosis is so great, why doesn’t everyone do it? Well, there are four main answers.
- Not enough arthroscopy experience. The anatomy is confusing in a small foraminal canal and does not look like any anatomy I have ever seen in any anatomy book.
- This tough anatomy requires people to have a lot of arthroscopy experience to perform this operation safely. It is not an easy orientation. The nerve is in tight quarters here and must not be injured.
- It takes a lot of practice to do this safely, a lot more practice than doing a fusion.
- It requires expensive German arthroscopic equipment.
The Benefits of Foraminal Decompression
Well, what are the main benefits of endoscopic foraminal decompression? There are three main benefits:
- No fusion or spacers, and so there are no long-term consequences like adjacent disc disease which is common at the bookends if a fusion is performed.
- It doesn’t disturb the normal anatomy. As you can see from the video, we’re only shaving off a spur or a shark’s tooth, so to speak, or just some overgrowth of bone and soft tissue. But the main portion of the anatomy, it is restoring the foraminal canal to its normal dimensions.
- This treatment approach only addresses the problem. It doesn’t create any problems.
So as I like to say, refuse to fuse when possible. I just think the body has such great potential to heal itself and doesn’t need a fusion for the majority of problems that I get to see.
Hi, Dr. Tony Mork here. Thanks for watching. I hope you enjoyed the treatment of lumbar foraminal stenosis. If you have any questions, feel free to give me a call at the office.