Grand Rounds-Sagittal Imbalance and Minimally Invasive Spine Surgery
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- Good morning. Hi, this is Joe Chang with Vanderbilt University, and it's a pleasure to introduce this session of Operative Grand Rounds for the AANS. Now with us today is Dr. Charlie Branch, who's currently a Professor and Chairman of the Department of Neurosurgery at Wake Forest University. Some of the things that we do with minimally invasive surgery regarding sagittal balance are things that we take for granted. Personally, I've seen a lot of cases where patients who've undergone a minimally invasive surgery end up in slight kyphosis with the adjacent segment problems due to that issue and I hope Dr. Branch will be able to give us some insight into how we can avoid this. With that I'd like to introduce Dr. Branch, Charlie.
- Thank you, Joe. Good morning to you and I guess everyone who's listening. This particular lecture is actually a continuation of one that we finished earlier that looked at a hybrid, many open or minimally invasive technique for lumbar fusion. And certainly I'd encourage you to take a look at that and hear some of our thoughts there, because this will build on that. And today I'd like to really look at that the concept that preserving or correcting lumbar lordosis. Even in the degenerate patient really begins at that first fused segment. And so how can we not only embrace MIS, but really embrace the concept of lumbar lordosis or spinal deformity correction preservation at every level. So I hope this will be of some value to you. Let's move on into it. First things first, I guess my disclosures are I function as a consultant in educational and product development consultant for Medtronic and some of the devices you'll see in these lectures, I've actually received royalty payments for them through my work with Wake Forest University. We've had talked about minimally invasive spine surgery, and there's not a clear definition. Everyone's got a bit of a personal bias of percutaneous, endoscopic, tubular retractors navigation. But frankly, I think we can all agree that the goals of contemporary spine surgery are much more germane. We need to minimize tissue disruption. We must maximize the therapeutic benefit or value as we talk about it. Minimize the radiation exposure to the surgeon and the team. Minimize blood loss. Minimize inefficiencies in the operating room or with resources in the hospital and last but maybe even first, optimize their learning curve so that an older guy like me can learn a new or new technique add value to my patient without having to go through a protracted period exposing myself or patients to maybe some increased risk of learning. Now, MIS has a really sort of snowballed in its popularity I guess, over the last decade as technology and interest is great gain. Is there a benefit in these older patients that we all take care of? I think the concept of reduced blood loss, reduced infection rate, reduced hospital stays and even in these large patients who are deconditioned, there's growing evidence that there's value with the minimally invasive techniques, especially if we look at our VAS and ODI scores postoperatively. So I think that concept is valid although we'll talk a little bit about when and how we should use it. But I've got to add to that, the fact that these MIS techniques should not just accomplish those goals but they really should restore and maintain lumbar lordosis or correct a coronal and sagittal deformity and maintain spinal balance until fusion. In addition to these inefficiencies and learning curve opportunities. Does this resonate with you Joe at this point?
- Yeah absolutely, one of the things that we had talked about previously was a lot of my practice actually is revision surgeries. And so in the past we've seen so many people who have undergone minimally invasive surgery replace on say Wilson or Andrews frame in lordosis to make placing the tubes and the K wires easier, say for an L4 and S1 fusion and inadvertently fuse, really with a flat back with loss of lordosis and not recognizing that about two thirds of a lordosis actually is within that L4 to S1 area. So I think this is an important concept that not only can we do things minimally invasive, we need to kind of think about the overall global picture of the patient and settle balance, I think it's the key. I totally agree with you Charlie.
- The literature several years ago really started to expose us to the potential benefits in this paper from Los Angeles, reviewed the complications and outcomes and how you could actually reduce some of the accepted complications in older people in particular with MIS techniques. Here in 2008, this whole concept was sort of started and many others know that Rick Fessler is kind of championed this. So I think the literature has pushed us down the path of can we, should we look at minimally invasive options for deformity correction? And yet it was here in this paper in 2010 in neurosurgical focus where Mike Wang and Praveen Mummaneni really started to remind us that, cob correction and lordosis improvement were concepts that we really got to start focusing on, not just can I get a pedicle screw in the right position with a minimally invasive technique. And so I think as the literature has developed, we're seeing that there's some things that we can and maybe should do. We can get some corrections, we can get great outcomes. And most recently, although I don't have it here in my slide deck in neurosurgical focus in May of 2014, I would encourage everyone here to really look at that particular issue, that the neurosurgical focus, which provides a great collection of resources, articles and even an algorithm for when the MIS techniques can and should be considered in spinal deformity. So with that sort of preamble, let's accept that there is a potential deformity correction advantage and I think we've got to begin with a what is sagittal balance? What is sagittal alignment? Our younger surgeons and trainees are much more familiar with this vocabulary and some of us older people are, but it's critical. There's a plumb line that goes from C7 T1 midsection and intersects with the posterior-superior corner of the S1 vertebra. And now we're going to call that the sagittal vertebral line and sagittal alignment, okay? Is best if it's within five centimeters of that line. Now a normal thoracic kyphosis is about 30 degrees and normal lumbar lordosis is about 60 degrees. And so for us to truly have sagittal alignment, we've got to make sure that this lumbar lordosis is about 30 degrees greater than the thoracic kyphosis, because that's just how we're built. Here's a nice illustration of that and this is elementary. And again, I'd encourage all of you to really look at this and study it further if this is not something you're familiar with. So our goals, the sagittal alignment. Again, our SVA has less than five centimeters. Pelvic tilt is actually how our pelvis accommodates this lumbar thoracic kyphosis lordosis to help us maintain vertical alignment and it needs to be less than 25 degrees. And even a more critical measure as we're getting into outcome assessment is this pelvic incidents to lumbar lordosis ratio or difference, okay? I think there's pretty good evidence now that if the pelvic incidence to lumbar lordosis difference is greater and plus, or minus nine degrees, the patient outcomes are just not as good. And this is a, I think a number that everybody needs to really get embedded in their knowledge base. Let me just sort of remind you for those of you that aren't familiar. Again, pelvic incidence is measured from the midpoint of the femoral head to that mid position of the sacral endplate, and then that perpendicular to that drives the incidents number. Sacral slope, again, as you see here, sacral endplate with the horizontal, and then pelvic tilt the vertical off that central femoral head to the midpoint of the endplate. Again, these are readily available and ought to be part of your knowledge development. So in humans as we get older, there are some changes, pelvic incidence is relatively fixed. And so pelvic incidence is effectively a fixed number that doesn't really change whether you're standing or laying down or whether you're young or whether you're older. On the other hand, pelvic tilt as you can see, increases as we get older, and that sacrum kind of tilts backward to accommodate our degenerating spine and sacral slope as you can see here tends to go down as we get older as well. So these are just realities of life, but are important as we start to try to fix people as their spine ages and these are some illustrations. Again, while pelvic incidence may be measured in a supine x-ray that may not even require a three foot standing film, sacral slope and pelvic tilt, really, and even really quality measures of lumbar and thoracic kyphosis and lordosis need to be measured in those standing three foot films. So enough of the sort of basic education, and let's get into a very practical frame of mind, okay? Joe, have you ever seen one of these? Great fusion, L4 to S1, maybe an older fixation plate or the old cliff and plate concept looks great, did well for a few years and now they're back in the office with the neurogenic claudication and back pain when standing and a picture that shows an almost complete block at that adjacent segment. Is this a common occurrence in your practice now?
- It is when fusions are commonly revised in my practice, yes.
- And I'll just be honest a few years ago, I was not, really thinking okay, well, my thought a few years ago was okay, how do I get this? Can I get this fixed without doing a fusion? Can I get away with just a decompression? If I've got to do a fusion how do I hook up this new segmental fixation to this hardware? And those are all very hard concepts. What I'd like to ask everyone today to consider is equally or more important to the success of not just this operation, but the degeneration of the adjacent one is to what degree do we need to restore lordosis at this level to ensure the best outcome for our patients? How do we do that? Well, let's take some of the parameters and metrics that we just discussed and apply them to this patient. If we are now believe that the optimal pelvic incidence to lumbar lordosis difference is about nine degrees. And in this case, the L1, S1 lordosis is about 45 degrees. Sorry for the typo here, this is actually 56 degrees, okay? Instead of 46. Well, now we we already know that we're at that 10 centimeter differential or mismatch, and that to get a good lordosis correction, we've got to add eight to 10 degrees. At this level to really get that patient's lumbar lordosis back into a more normal range. So it's not just about getting a good fusion anymore, it's really about getting the right lordosis. Any thoughts, anything you want to add on that, Joe?
- Hell no, I think you've hit the nail on the head. Kind of just looking at these parameters. If you look at S1, you can see how flat it is. And I agree with you that it's more than just adding an extra set of screws and going up another level. If we don't take care of why this happened in the first place, that is what, the adjacent segment stresses due to the deformity issues. Then I agree, I think we're gonna end up propagating this problem. And so I think what you're talking about is just the white on.
- And how much attention do we use to focus on the hardware, either the screw, the screw position, the plate, was it a plate or a rod, or where it's that encroachment on this fossette, I think we blamed a lot of adjacent level degeneration on either the hardware, the stiffness, a lot of things, and really just didn't focus on whether we've done a good job fixing lordosis or not. So, let's be real. One and two level lumbar fusions are the most common. Fusion and kyphosis is going to lead to premature adjacent level degeneration, or maybe even less than optimal symptomatic relief and sequential fusions are going to impair the overall balance and probably start that fusion cascade on up. So I think this is a principle that we need to really focus on. I'm wanna show you this morning again, some literature that would validate that we actually can get good lordosis at a single level in the lumbar spine with a TLIF or PLIF antibody fusion technique, while there is some increasing evidence that the direct lateral approaches can do this as well. I'm gonna focus on the posterior approach today. In this article, by Dave Polly and his colleagues, a journal on neurosurgery spine 2012. They really wanted to determine, what degree of lordosis correction they could get with a bilateral TLIF approach. And it was this comparable to sort of subtraction osteotomy. And in this cohort of patients where they measured the pre-op and post-op segmental lordosis. They found that they could get seven to eight degrees of segmental correction. That again was probably contributing to that minimally clinically important difference that the patient experience. Their largest gain was at five one where they got 10 degrees of correction, which would make sense, given the normal anatomical configuration at five one. And so here's what they looked at, they said could we know that with the Smith-Peterson osteotomy, that you can actually get pretty significant deformity correction, could we do the same thing with this bilateral TLIF placed way up front? And so that's really what this study confirmed for us. Again, one cage versus two, okay? There's I think, there's a lot of people who use sort of a one cage technique. Joe, I think you're a unilateral TLIF guy, or that's your preference, is that correct?
- It is.
- And then this is not uncommon. I think the cost of implants and a host of things are going to force us all into what's the best. This study from Japan is an interesting one because they looked at a unilateral pedicle screw in one cage versus bilateral pedicle screws in two cages. And found that yes, in this group of patients with degenerative spondylosis. That there was no difference in segmental lordosis accomplishment with the one versus two, but the fusion rate and actually the VAS and leg pain scores were actually better with the bilateral group. So food for thought, I think we're gonna be wrestling with this value equation. Cost, time, effort versus outcomes as we move forward. I had to throw that in for you Joe because it's a concept that we all wrestle with. But...
- I agree. I think also the, if you're going to do a single cage, the idea carpentry is gonna be important. Kind of like what you're noticing here, where the inner body graph is pushed up to the front to restore lordosis versus a lot of the TLIFs I see where people are putting in a cage obliquely, and you're never really gonna be able to load restore lordosis with an oblique cage. And you'll probably talk about that here in a little bit.
- Sure and I think this is... I use this picture as my prototype because, we all know that a normal five one really has about a 15 to 18 degree, 20 degrees in some cases lordosis as its normal configuration. And so it's not just about height restoration and foraminal restoration and stabilization of the segment it's, can we restore the lordosis if we don't, we're starting down the trail to a flat, flat back. The techniques I use are really focused on the device itself, you know. Getting interbody devices that give us upfront 12 or 18 degrees of lordosis that now sort of facilitate the correction as opposed to just, forcing us to get a grand as far up front as we can, and then put as much compressive force posteriorly as we can. What this technique that I'm using now actually allows me to not just insert a device sideways and rotate it and restore height, but to be able to actually visualize getting this device up front, rotating and in position and then with this minimally invasive midline technique that I showed you on my last video, get a segmental fixation with lots of graft using a posterior, either unilateral or bilateral technique where a good lordotic, 18 degrees of lordosis is accomplished even before we put in our segmental fixation. And you're at the risk of not being, making this a commercial thing, I will use the names and products, but this is a technique that is available and growing in its acceptance. I think all of the companies that provide devices now are looking at either expandable or fixed lordotic techniques. And I believe this is something we should all seriously consider because the concept of getting good interbody fusion or grafting, a good decompression, either unilaterally or bilaterally, but then getting a lordotic segmental fixation is something that we would just need to be focused on. Any thoughts on that before I go into these cases?
- Actually Charlie, what's the largest amount of correction that you can actually get with these cage devices, you know as far as the angles?
- Well, in theory, if 18 degrees is the most correction, I think putting a short device way up front means you can even tilt a little more, I'll show you some cases here. The most I've been able to actually demonstrate is about a 15 degree correction, even with an 18 degree device, because it's settles into that concavity of the endplate. But again, I think as, as I'm coming to learn more, if I can get seven or eight degrees of correction, that's infinitely better than either zero degrees or worse, putting somebody in kyphosis, which I'm afraid I did with some of my rectangular devices that I was using years ago.
- And when did you decide to use this technique compared to a standard Ponte osteotomy with Chevron osteotomy?
- Well for most people who's, I think we'll go back to the when should you use an interbody fusion in the patient who's got a highly mobile well-preserved displace, but a highly unstable segment, getting that inner body device in helps again preserve lordosis and eliminate motion and preserve foraminal height. Again the person who's got a collapsed disc space, that's kind of flat getting to doing the osteotomy and kind of creating that wedge, may actually make more sense than going through the process of trying to get a interbody device in. Although I'll show you here in a minute that even some of these bone on bone on deformities, especially at five one. That the capacity to get the height, the disc height restored and lordosis corrected is something that once you've done it, I've done it in a few cases then you realize it's almost, it's almost compelling you to do it every time, but that's the challenge of surgery, isn't it?
- Okay, well, let's show some cases and we can learn a little bit more about your approach to this.
- And this is a lady that I believe is not uncommon. She's near 60. She's had years of exertional back pain that we treated non-operatively. And now she presents with neurogenic claudication that's accelerated over months and is resistant to non-operative therapy. Her imaging study shows a relatively well-preserved disc spaces, but here at four five, there's obviously a synovial cyst here on this sagittal view that becomes more obvious on the axial. And then as we look at the five one level, there's almost this exposed a bridge of disc or buckled disc with some foraminal considerations here that makes me concerned that something's going on at five one that just doesn't appear on the sagittal view. Of course, the fossette degeneration, and even maybe fissuring in the fossette tells me that this is a bad joint. Sure enough, on the flection and extension views, when she bends forward, there's several millimeters of translation at both levels worse at five one and four five, and a almost lateral listhesis or coronal deformity when she stands on these ap views. The measurement to it, sure enough, almost eight millimeters of slip here at four five, nine and a half millimeters of slip at five one. So my perspective here was this is a lady who has a highly mobile, hyper mobile unstable spine here with a synovial cyst at four or five and correcting this really means fixing this entire, both these motion segments. And because of this configuration, this is someone who's at high risk of getting fixed as a flat back, if I don't really pay attention to the lordosis correction potential here. Do you agree with me so far?
- I do.
- All right so, the beauty of these lordotic devices that I just shared means now I can actually not just, get a good decompression dorsally and get rid of that synovial cyst and use my little hybrid cortical and bone trajectory technique to get her fixed, but I've been able to preserve, or even augment inner body height, pyramidal surface area, get good graft in the disc space and still preserve the lordosis, or maybe augment it with a minimally invasive or midline hybrid technique. To validate this, I've taken a 33 degree lordosis with her fully extended, okay? Note that previous picture, I didn't show you the lordosis when she was flexing forward with both of these slip was about 20 degrees, okay? So this is the best I could get in her ambient state. And now I have fixed her in a lordotic position that's better than she was before. And so I'm, again, I'm pretty proud of this, right? Because instead of actually flattening her out, I've put her back where she should be, or even better without going through my standard posterior and midline approach. Let me show you another one, maybe a little less exciting. This is a degenerative spondy at four or five. Older lady, a little large, unresponsive to non-operative therapy. Pretty typical picture on our imaging, where we've got our, collapsed, slipped, disc foraminal stenosis, a lateral recess stenosis, bad joints on both sides. I think this is a typical picture and segments above and below that are that are not as healthy, she's 70 and large. She's got a seven millimeter slip that gets a little bit worse, a couple of millimeters when she stands. And she's got a 13 degrees segmental lordosis with some lateral collapse. So I think this is a picture of segmental instability with the potential for me, if I'm not careful to flatten this out, decompressing and fusing, or maybe even decompressing and not fusing, I think there is that risk. So the goal is, restore the height, stabilize the segment, line and back up if you can, but even more important, turn this 13 degree lordosis into a 20 degree lordosis at this segment, which is now stable. In this case, I used an 18 degree device that was 14 millimeters high and 22 millimeters long seated up against the anterior element of the annuals. And again, the technique is well illustrated in that video that we did I think earlier. Any comments or critiques on this one?
- Yeah. Is there a way for the average surgeon to be able to predict how much correction they will have based on the cage angle. I mean in your situation use an 18 degree cage, but when only seven degrees in your correction from 13 to 20, does that average for you? Or what do you typically see with these lordotic cages?
- Well, and that's what, and that's, it is. And this is I think the disconcerting thing, because in many of the products we're seeing now, have eight degrees of lordosis or 10 degrees of lordosis built into the device. And you come to realize that with those devices, you just don't get much correction. In fact, the lordosis corrections about half of the lordosis in the device itself. I just think that's just because of the configuration of the endplate in inner space. So my thought now is, I'm gonna get about half of the lordosis of my interbody device. So if I really need eight or 10 degrees, I've got to put in an 18 degree device. If I only need five or six degrees, well, maybe a 12 degree lordosis device is adequate. That to answer your question on that?
- It does.
- How about a lytic spondy? And these are tough, these are notoriously tough because most of these people, either are at grade one, two slip or the very parallel endplate. Sometimes even bone on bone, I'll show you one here in a minute, that's even worse than that. But getting these people corrected, we argue over fusion in sight to how much correction to get. I think that the real challenge is can we... so often we go in and fuse them and we've either fixed, we've flattened them out or fixed them in a way that accelerates the degeneration up here at four five, if it isn't already case. My goal here is, you know I'm gonna have a pretty sizable spondylolisthesis because of this ridging here. I've got a fairly mobile segment here because it preserved disc. So this is someone I need to stop the movement, restore the height and restore lordosis. Again, pretty typical picture. Foraminal obliteration bilaterally with a mobile segment and a lytic pars and this patient is uncomfortable. Now historically, the devices we used were biconcave. I think for years, I've used the biconcave device, put it in, try to get as tall one as I could push it way up front and then put the screw plate construct under compression posteriorly and that was sort of how I got my lordosis. And you say, we've almost got that pars back to the leading edge if there's one. And again, if I'm thinking and I'm doing a good job, I can actually get the deformity correction here that I want. The problem I've run into in this technique is often when I'll put compression posterially, I'll end up putting the squeeze back on the foraminal even losing some of my correction because as I pull the, the screws together, my fives sort of shifts back forward, and then I've sort of lost something. So the beauty of a lordotic device now lets me actually get the correction done before I start manipulating hardware. And in this case, you can see here at 17 degree correction 17 degree preop lordosis can be corrected to a 24 degree with really nice height preservation, alignment, and good segmental fixation. So I think this goes along with my principal, I'm getting eight seven, eight degrees of correction, but it's taking me an 18 degree lordosis on my device to do that. But now I don't have to put these screws next to each other on this rod the fixation is a fixation, not a stressed out compression construct. What do you think of that?
- That was a good idea. Is there ever a time where you wouldn't do an interbody fusion to restore lordosis, or do you think an interbody cage is really important for restoration of lordosis especially for these shorter segment constructs?
- Well, I think as we've talked and as I think Polly's article would show, if you are willing to, if there's adequate anterior release of an annulus an adequate posterior sort of osteotomy or partial vertebrae section, you can actually get good correction. But if in fact stiff up front and you've done a decompression and the disc was already collapsed, you're just not gonna get more than a couple of degrees of correction, unless you either restore the anterior height or whittle off bone posteriorly to give yourself more of an angle. In which case you better be sure you've done a good dorsal decompression, or you're going to pinch that nerve in the brain.
- Yeah. I think that's a word of caution that I think is, needs to be out there more. I've seen a lot of people who try to do Smith-Peterson osteotomy by getting the posterior wall sort of the vertebral bodies together. And then they can flare out the anterior wall for correction, but they end up losing or really injuring that nerve posteriorly without thinking about how much compression you have when you start reducing it that way. So I think you make an excellent point.
- This is a tougher one because quite often we'll see these people at our premises. This is a young lady, who's just been disabled for years now. A lot of efforts at non-surgical therapy that just didn't get her where she wanted to be. And we've seen the picture right? The grade two plus latex bonding with deformity of the sacral and lumbosacral disk, but a degenerated four five segment with sort of this retro listhesis of four on five or five slipped out from under four, whatever you want to call it, congenital sort of defect here. How do you... What's your sort of approach to fixing this problem? Actually you've kind of come to realize you're gonna have to, you're gonna have to fix this lady because she's not gonna get better with the non-operative therapist.
- Yeah, these are tough. I mean these are patients that they typically have to get L4 in order to get good purchase and then trying to get a reduction on there. But you're right, it's challenging, especially challenging is actually an inner body at that L5, S1 region without doing some type of, almost like a dome osteotomy, the best one to get my cages in. I'm sure you have a better technique for me to use after this.
- Well no, I mean you said it all right. This patient requires removal of this dysplastic, five one element here. But once you've done that and visualize the five routes, kind of trying to trim off his dome so that now you can actually get height correction, is something that I think we ought to aspire to do, it's not a big deal to take this little spur off here and kind of create and flatten this out with an osteotome with careful techniques and intraoperative C-arm, you can do that. But I'm not gonna get this lady fixed unless I get this height restored or a dramatic decompression of this deformed . And so I think here's an opportunity to take this segmental correction concept where we smooth off the endplate, got an lordotic device up front, restore the height, not only at five one, but at four or five, corrected her or enhanced or maintained her lumbar lordosis, but we're able to do it through a mini open or hybrid technique that accomplishes our goals without putting her through a major ordeal. Again, to reinforce the concept, here's a lady who's pretty much got an eight degree segmental lordosis with a 15 millimeter slip that post-operatively, we can actually get 20 degrees segmental lordosis at five one. So I actually got 12 on this one with my 18 degree, but that's because of the configuration. And I think if we go on up, you'll see that the, that the lordosis in this lady looks normal even without measurement lines, as opposed to getting fused pitched forward, which I'm afraid I would have done and did years ago. I hope this has been a productive session for everybody. We kinda covered the thoughts of, there's some MIS or hybrid techniques that are certainly relevant for deformity correction, but for most of us deformity correction starts at that one or two levels, segmental fusion in the lumbar or lumbosacral spine. And these cases that are the bread and butter or norm cases that we see and I think focusing on these and getting these done well and using the new technologies that have lordosis built into them is something that we ought to certainly investigate and I believe ought to embrace. Joe, let you have the closing thoughts here.
- Good Charlie. I wanna thank you again for taking the time out this morning to share these really important concepts with us. I think some of the fundamentals that you've discussed about sagittal balance and how we approach the surgical planning is something that I think every surgeon should know. Again, I wanna thank you for taking the time to do this. I also want to thank Anna Lisa Rodriguez, one of your residents at Wake Forest, who has put in so much effort to help us coordinate this session. So certainly she deserves a lot of credit with that. With that, I wanna thank our viewers for watching this session of the Operative Grand Rounds, the AANS Operative Grand Rounds. And please tune in again for another session in the future. Thank you very much.
- Thank you.
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