Hi, I'm Pete Angivine, Associate Professor of Neurological Surgery at Columbia University, and today as part of the breakfast seminar on adult scoliosis, I'm going to talk about the role of osteotomies in degenerative scoliosis surgery. I don't have any relationships or potential conflicts to disclose, but I do have several biases that are worth mentioning as it adds some context to my talk. First is that I do virtually all of my surgery as open surgery. I do very little minimally invasive surgery for a few different reasons, one of which is that I believe that there's no such thing as a free lunch, and by that I mean that all of these operations, osteotomies, inner bodies, minimally invasive, open, have pros and cons, and a lot of surgical decision-making is about weighing the risks and the benefits of the various approaches. Most of my patients, perhaps because I'm a neurosurgeon, who have degenerative lumbar scoliosis, also have neurological symptoms or dysfunction, and that also affects many of the surgeries that I plan in that a wide decompression is part of most of the operations that I perform. And finally, I do prefer to perform surgery through a single posterior incision. I do relatively little lateral surgery and relatively little interior surgery. The outline of my talk, first I'll talk a little bit about the purpose of osteotomies, briefly about the types of the osteotomies, some of the specific considerations of degenerative scoliosis, osteotomy and level selection, and briefly about complications. So degenerative scoliosis, these tend to be small to moderate-sized curves. They tend to be localized to the lumbar and thoracolumbar region. Sometimes of course it's difficult to differentiate, and sometimes it's not important to differentiate whether a patient had a pre-existing adolescent idiopathic scoliosis, developed into adult idiopathic scoliosis, and then had superimposed degeneration. Oftentimes the degree of rotation, the magnitude of the curve, gives us some hints, of course, in addition to the history of the patient. These symptomatic lesions are typically or often associated with stenosis. That stenosis tends, except in the most severe cases, to be in the lateral recess or foraminal locations rather than central stenosis, although that can occur. These patients generally are over 60 years old, which brings some other medical issues to bear. They tend to be more females than males. And the sagittal alignment issues are usually limited or related to thoracolumbar kyphosis and degenerative dysthysia in the lumbar spine with relative hypolordosis. The purpose of osteotomies fundamentally is to create or enhance the flexibility of the spine, generally in the region of the deformity, to allow for correction and restoration of the functional alignment. I say generally in the region of the deformity because occasionally, although less and less often, we'll do osteotomies adjacent to the area of deformity for various reasons to allow for global realignment without trying to get absolute segmental correction. So the basics of osteotomies. This paper from 2014, published by Frank Schwab and co-authors, does a nice job, I think, of outlining some of the general subtypes of osteotomies. And just some nomenclature here, a PCO, posterior column osteotomy, and that would be a, on this diagram, a type II, essentially, osteotomy, a tricolumnar osteotomy, now this can include actually the traditional pedicle subtraction osteotomy, shown in figure number three here, or vertebral column resection, shown in figure five. Any osteotomy that extends through all three columns, as the name implies, can be considered a tricolumnar osteotomy, and that, of course, produces the greatest degree of flexibility in the spine. Posterior column osteotomies adopted this term to avoid the often misunderstood distinctions between a Ponte osteotomy and a Smith-Peterson osteotomy, sorry about the misspelling there. These have also been called Chevron osteotomies because of the location of the bony resection posteriorly, you can see that on the figure on the right-hand side. Typically, in the degenerative scoliosis patients, we perform multiple PCOs centered on the apex of the scoliosis and or the kyphosis to allow for gradual sort of anatomic realignment of the spine. Tricolumnar osteotomies, this includes, as I mentioned, the pedicle subtraction osteotomies and also the vertebral column resection and the variants, including one or more discs adjacent to the level of the osteotomy. Typically these are used, at least in my practice, for revision surgery in the setting of a solid arthrodesis. It's very rare that we perform a tricolumnar osteotomy in a patient who hasn't had a previous fusion or doesn't have a spontaneous arthrodesis of the spine. And so most, if not all, primary degenerative scoliosis patients can be managed effectively, meaning achieving neural decompression, sagittal and coronal balance with posterior column osteotomies, perhaps in combination with inner body fusions and posterior instrumentation, at least in my experience. We do encounter situations such as this with the interlateral osteophyte formation fusion through the apex of the lumbar curve. And this can be quite a difficult situation to correct directly because of that large osteophyte, the dissection there can be somewhat fraught if you try to work lateral to that. Oftentimes that strips less safely and easily than the typical subperiosteal dissection. We can eggshell that out, but oftentimes it's easier, safer, and just as effective to achieve correction through a disc such as the one shown down below that level, that segment of spontaneous fusion where there's the vacuum disc and obviously going to be quite a bit of flexibility, perhaps just with a posterior column osteotomy and maybe an inner body fusion at that level. So considering all of these options is important when planning surgery. So thinking about planning the surgery, first is understanding the patient's symptoms, whether they have back end or leg pain, whether they have complaints of coronal imbalance or sagittal imbalance, and also assessing whether either of those might be improved or as, or more importantly, worsened through possible surgery. It's important, and this is really the key for thinking about osteotomies, it's important to thoroughly evaluate the nature and the severity of the patient's deformity. How big is it? Where is it? And how flexible is it? Because as I mentioned earlier, the osteotomy is really to enhance or create flexibility in a region of the spine where we need to get correction. And then we want to plan strategically. Where are we going to decompress? What type and where are we going to do the osteotomies? And oftentimes those two levels happily coincide in the lumbar spine, in degenerative lumbar scoliosis. What kind of inner body type are we going to use and where are we going to do that? And how are we going to order these procedures? With any spinal deformity surgery, I think it's important to plan for the possibility that you may have to shorten the day and come back for another day. Fortunately, that's pretty rare, but having a logical order of procedures so that if you need to stop, you can do so safely and come back another day, either within a short period of time or in a delayed fashion. So looking at a few different patients and some issues. So here's a patient who comes in in his 70s, doesn't have any significant leg pain, but has significant back pain, but more importantly, is really unhappy with his posture. He has a very difficult time standing up, he has a difficult time walking, he feels like he looks like a turtle and feels as though he's just sinking down into his pelvis. This is the, we have the long cassettes on the left-hand side. The supine films are critical for evaluating flexibility, in my opinion. Oftentimes the supine x-rays, at least in our institution, don't show the bony detail all that clearly. And as a proxy for that, I'll often use the scout views from the CAT scan, which has the additional benefit. Usually the patient has been lying there for at least a few minutes. So the sagittal and coronal reconstructions can be useful, and the MRIs can be useful. And there, of course, the patient's generally been lying for even a longer period of time. So it gives the curve the greatest chance to relax and spontaneously correct. And here we see on the sagittal reconstructions that there's significant disc degeneration, vacuum discs, these spaces open up, and so we know that we can employ that degree of flexibility to help us get correction of this curve, likely just with posterior column osteotomies. And so looking at the upright films, we know we need to reduce that thoracolumbar kyphosis, and so multiple posterior column osteotomies in that region will help achieve that. And then we need to work on the coronal malalignment in addition to the sagittal malalignment, and so some distal osteotomies there. So posterior column osteotomies from T10 to L5 allow us to achieve good correction. Oftentimes with these curves, we'll do multiple iterations of correction. Multiple rods are useful for that, and you can see there on the right-hand side of the post-op image the use of the kickstand rod, which I'll talk a little bit about in a few minutes. I think it's important to try, when possible, to level L4 off. I think that that's a critical rough landmark for achieving overall coronal balance. Getting a relatively level L4 seems to be key, and so oftentimes I use an L4-5 PCO with a T-lift at that level to achieve that, and when I do T-lifts in these patients, particularly if they have significant stenosis, I do it almost like the old PLIF approach, bilateral complete facetectomies, bilateral annular resections, and working in the disc space from both sides, ultimately just putting in a single T-lift cage from one side from a more lateral approach, trying to get it ventrally in the midline, but really taking apart the disc to maximize the degree of correction, the exposure, and, of course, also the decompression for those patients who have stenosis, and we can see that again here. Here we needed to do more upper lumbar posterior column osteotomies, in this case L1-2 and L2-3 to allow for some more angular correction through those levels in concert with an L4-5 T-lift, again, to try to level off the L4 body. Here's a patient with combined coronal and sagittal deformity again. In this case, the PCOs overlapped that we needed, both in the coronal and the sagittal plane. He actually was fairly flexible distally, which is nice when that occurs, but they can't always plan on that, but T11 to L2 PCOs here allow for correction of the sagittal coronal plane. With these patients with these sweeping kyphoses, and there have been a couple of these here, my tendency is to extend the instrumentation up to the upper thoracic spine. I think although we could have and did correct the thoracolumbar junction pretty well here, that correction really extends right up to the T10-11 level. I think stopping, at least in my hand, stopping this construct at that level carries with it an increased risk of proximal junctional kyphoses. Of course, you can't avoid PJK, at least I can't seem to, at any specific level, but I found it occurs less often in these circumstances with proximal extension. Now, on the other hand, look at this sagittal film, probably overcorrected this patient a little bit, and this patient may well develop proximal junctional kyphoses eventually in the upper thoracic spine. It's one of the bugaboos of spinal deformity surgery, in particular in the patient 60 or older. Here's another patient with a lot of these considerations, back and leg pain, spontaneous fusion of a couple of levels due to these anterior osteophytes, but vacuum discs down below, fair degree of spontaneous correction when lying supine, although not so much in the coronal plane, seen on the coronal reconstruction of the CT scan. Patient has very tight stenosis, L3-4 and L4-5, with symptoms at those levels. So doing, in this case, planning for posterior osteotomies at the levels that are not spontaneously fused, so above and below, the spontaneous fusion. And then the use here of the kickstand rod, which we'll talk about in just a minute, to help maintain truncal alignment, and again, nice control and correction of the thoracolumbar kyphosis with the extension of the instrumentation to the upper thoracic spine. Sometimes looking just at the posterior elements, one thinks that, one might think that there's complete fusion and that a tricolumnar osteotomy may be necessary, but looking at the middle panel, we see that these disc spaces are completely open, and so it's a long, difficult resection of all of that posterior bone at every level, basically pedicle to pedicle throughout that entire extent of the deformity. But having done that, the flexibility can be quite considerable, as shown here. So seven posterior column osteotomies, three distal lumbar lumbosacral inner body devices, a long construct extending to the upper thoracic spine. Some completely derotate this curve, and that's likely due to its magnitude, but also to the fact that this appears to be a degenerative lumbar scoliosis superimposed on an adult idiopathic curve because of the thoracic curve, but overall, acceptable sagittal and coronal correction. One thing we have to be careful of with this is the differential flexibility of the lumbar and lumbosacral fractional curves, either just due to the spondylosis or, in this case, due to prior fusion. The main lumbar curve is often the more flexible curve. It's up out of the pelvis, generally a greater degree of flexibility through that area. And if we're not careful and overcorrect that curve without adjusting for the, or adequately correcting the lumbosacral fractional curve, we're going to end up pushing the patients off and creating sagittal, or rather, coronal imbalance. And despite what had been said for years, I think we're now starting to realize that coronal imbalance is not particularly well tolerated by patients. Yes, they can accept a few centimeters, just as they can accept, oftentimes, a few centimeters of sagittal alignment, particularly as malalignment, particularly as patients get older. But if you have a patient who's four or five centimeters off to the side in coronal malalignment, particularly if their shoulders are off balance, they notice it, and they are not generally particularly happy with that. And so that's the reason in the indication for the kickstand rod, used, shown here. And its function is just, as its name implies, to sort of prop up the thorax. And you can think about doing this in the OR as either pushing down the hemipelvis, or pushing over the trunk, conceptually, it's just two ways of looking at the same mechanical process. But it's otherwise, without the kickstand rod, it's a difficult maneuver to perform, but an important one. Key intraoperatively, in my opinion, is to be able to get long cassette films on the table. We get digitally stitched sagittal and coronal films that show shoulders to pelvis, and those have been invaluable for assessing the global alignment in the coronal and sagittal plane. There are some workarounds with T-rods and so forth, but I do think that the best way to assess this is using a long cassette radiograph in the operating room. So to review the goals of surgery and decision-making process here, symptomatic improvement, of course, is the key goal of surgery through neural decompression and deformity correction. And assessing which of those goals is most important, or if they're equally important for each individual patient, helps us to plan the surgery. Looking at the type of the deformity, is it a global or is it a regional deformity, and what kind of correction is necessary? Is the curve or curves, are they rigid, are they flexible? It's very rare that there's a truly uniplanar curve, and assuming that there's a deformity solely in one plane risks creating deformity in another plane if you aren't careful. Also key, particularly for among neurosurgeons in general, who I think tend to see patients more often with signs or symptoms of nerve root compression is the need and location for decompression and where that is relative to the deformity. Just a couple of words about complications. These are, it's of course very difficult to isolate the effect of performing osteotomies on complication rate. These, of course, these studies are going to be confounded by all the other factors. Osteotomies add length, difficulty, technical procedures, differences to these operations, and therefore it shouldn't be any surprise that patients with posterior column osteotomies or tricolumnar osteotomies have higher rates of complications than patients who've not had osteotomies. And tricolumnar osteotomies tend to be associated with a greater degree and greater severity of complications than posterior column osteotomies alone. These are bigger operations, and so the risk of durotomy, neural injury, blood loss, or other complications goes up as surgery magnitude increases as well. So in conclusion, key to this, to osteotomy planning is a careful analysis of flexibility of the degenerative scoliosis to determine if osteotomies are even necessary. Happily, often the levels that require segmental correction are also stenotic, and therefore you get a little bit of a two for one. Do the decompression, you've done most of the osteotomy, and oftentimes that puts you right down or right next to the annulus, and therefore an inner body procedure from a posterior approach is facilitated. For coronal correction, I think that leveling the L4 segment is important, and again, maybe facilitate with an osteotomy at that level, as well as with inner body fusion. In my practice, in my experience, the posterior column osteotomies are really the workhorse osteotomy for degenerative scoliosis. The tricolumnar osteotomies, pedicle subtraction or vertebral column resection, are much less commonly necessary for a primary degenerative lumbar scoliosis. And keep in mind or have in your armamentarium the kickstand rod. Combined with a posterior release, it really helps to address or avoid coronal imbalance without the need for a tricolumnar osteotomy. Thank you very much for your attention.

Dr. Pete Angivine

Associate Professor

Neurological Surgery

Columbia University

osteotomies

degenerative scoliosis surgery