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Grand Rounds-Spinal Deformity: Evaluation and Surgical Treatment - Part I

Tyler Koski and Jean-Pierre Mobasser

June 04, 2012


- Good afternoon and welcome to another session of the AAMS Operative Grand Rounds. And today we have Dr. Tyler Koski from Northwestern University discussing spinal deformity. Good afternoon, Tyler.

- Good afternoon, thanks for having me.

- Thanks for joining us today.

- My pleasure.

- This is a fairly interesting topic. Something that neurosurgeons, a lot of us aren't as comfortable with. Obviously this is traditionally been more orthopedic related, but that's changing with time. Do you agree?

- I certainly do. We're seeing more and more of that in neurosurgeons and more neurosurgeons are looking to educate themselves on the topic.

- Here listed are the disclosures for both of the surgeons involved today, first is Dr. Koski's disclosures, and then followed by mine. And we're going to jump straight into it. Rather than waste time with any real introduction we have a lot of material to cover and I thought most surgeons would really rather get right to it. Talk to us a little bit about deformity, recognizing deformity, and patient's symptoms in relation to this.

- Well, anytime we see a patient in the spinal clinic, we see patients with back pain or leg pain or other issues. Deformity can factor in, in a lot of those, those problems. And you really have to be looking for it to recognize it, often times you can say a patient with back pain and an MRI that shows degenerative disease, but really assessing the global picture of the patient is really what deformity is all about. So looking for things like scoliosis and kyphosis, and trying to factor in how those patient's symptoms can relate to that overall alignment problem, and that really helps to build a treatment plan that works best for those patients.

- I'm gonna ask you early on, because this is a question frequently on my mind, and I don't want to forget about it as we get further, when a patient comes in complaining of back pain, how do you know the pain is more related to a sagittal imbalance or a deformity versus a set arthropathy degenerative disc disease or any of the other multitudes of things that can cause back pain?

- Well, there's no real simple answer to that. Unfortunately we all know that back pain is very common and a difficult thing to diagnose and treat oftentimes. Certain, you know, symptoms such as back pain that's really a fatiguing type back pain, a low back pain across the lumbosacral region that gets worse throughout the course of the day, oftentimes tends to be characteristic for a sagittal imbalance. And that's about the easiest one to pick up. You know, it's very difficult when a patient has a degenerative scoliosis and back pain thinking, is it that the facets, or the discs, or the alignment. And that really is something that you have to talk to your patients about. It comes down to a lot of counseling and a lot of careful evaluation on the part of the surgeon. The best part about spinal deformity is when you're coming up with solutions for these, if you really think you need to correct the deformity and you end up doing a long segment construct, you take care of facet pain, disc pain, and alignment pain, all in one. So you actually have patients that are pretty happy in the end that they've unfortunately just lost a lot of motion segments to get there.

- So do you think it's a possibility that when you correct somebody's imbalance and you treat all those other problems, part of their pain may be coming from these other pain generators, but it's really hard to know.

- It's very hard to know. I think it's always a multi-factorial system and you try and identify what's the biggest drivers of their pain and make sure you include those in your treatment plan.

- So let's talk a little bit about the different types of deformities and what you're looking at when you look at a deformity patient.

- So when I'm looking at a deformity patients, and what you see listed on the slide there are really the two big types of deformity, which is scoliosis and kyphosis. In most adult patients. We end up seeing a kyphosis scoliosis combining the two as being a very common occurrence, particularly in the degenerative spinal deformity patients, you oftentimes will see some adolescents, idiopathic that have progressed in adulthood, where we call it an adult idiopathic curvature that oftentimes can be relatively well-balanced. But most of the time when we're dealing with these adult degenerative patients seeking treatment, they end up with a combination of those and looking for those is really key. And the way to do that is both clinically and with radiographs. And you see here at 36 inch x-ray that unfortunately I don't have flipped to the appropriate way. We usually like to look at it left side on the left and my PowerPoint flipped it back when I was reformatting some pictures. But looking at that from an AP and a lateral view is really key trying to assess the overall balance, both coronally and sagittally. And when you see I listed there, the sagital, the SVA stands for sagittal vertical access, and that's usually a C7 plumb line, which we'll talk about a little later.

- Let's talk about initial evaluation, which you sort of touched on with x-rays, assessing these patients and then planning.

- Well, when you look at correcting a deformity, so this is taking into consideration that we've already gone through a preoperative workup and decided the patient needs surgery. Then we're talking about planning for a correction and really identifying the deformity. And what type of deformity is with those 36, 36 inch x-rays is key, and then getting dynamic films. Those are very useful when you're planning a correction, really they're attempting to find out how mobile the spine really is and the most useful in the adult patients in my practice are the supine and a supine side, bending views, looking for coronal correction of those scoliotic curvatures. We also will do supine lateral x-rays over, a bolster called the hyperextension bolster x-ray, which can help you identify if a kyphosis is mobile. There are other types of x-rays such as push prone and traction films that are generally more useful on the flexible adolescent patients and less so in the older adults. But then as we identify what we need to treat, we assess the patient's overall balance and we start planning our operation and really it all begins in the preoperative setting, a successful outcome.

- So just to touch on a few things you mentioned, if somebody has a relatively mobile deformity and you see good movement on your bending x-rays or with the bolster, is that change how you do the operation?

- It will change my plan for the operation, most definitely. I will talk to them about how much bony release or osteotomies I need. And each time I have to add an osteotomy that adds a little time and a little blood loss to the operation. And quite honestly, the more mobile a deformity, I start looking at what options exist from a minimally invasive standpoint and what can, where can I maybe spare a little bit of time and blood loss? So the more mobile a deformity, the easier it is to correct. It doesn't necessarily affect my overall fusion level selection though.

- What about if, if we're talking about whether to do anterior releases versus a purely posterior procedure, is the mobility of the spine effect whether you go anteriorly, whether you're doing soft anterior releases, or are you doing more and more things from a posterior approach now a days?

- I'm generally a posterior or posterior approach surgeon. Everybody does things a little bit differently, but in my practice, I find that even a fairly stiff spine with some posterior facet release or small osteotomies and good pedicle screw fixation, we can mobilize the spine enough to get it where we need it to go. And I don't generally do formal anterior releases. I almost never do a true formal anterior release. On rare occasion, I'll add a minimally-invasive trans soas technique, trying to really increase the disc height for a pyramidal distraction almost and use that, but not usually for a true anterior release procedure.

- Well, why don't we touch on other surgeons? What would be an indication that another surgeon who, who enjoys doing anterior like, or believes they get a better correction. What are their indications for an anterior versus a posterior, if they tend to do a little bit more anterior work?

- It all depends on the surgeon's comfort level and, and what you're looking to achieve. There's nothing wrong with doing an anterior release and getting a good correction that way. Quite honestly, an anterior release affords an opportunity for good interbody fusion at each level, and probably reduces your overall pseudoarthrosis rates. So there are some, some added advantages of doing that. Really in the past, that was the way things were commonly done, but the morbidity of the traditional anterior approach was such that it started driving surgeons more towards an all posterior approach and towards doing larger scale osteotomies with minimally invasive anterior techniques coming in. I think we're seeing a little bit of migration back towards that anterior posterior techniques, but it's done in a little bit different way today.

- So when I look at this x-ray, obviously we see a pre and post-op film, and then we don't have all the films in this particular instance, but clearly there's gotta be some new instruments techniques that we have available to us that make this easier to do than it was done 15 years ago, you utilize newer technology to achieve this, or do you continue to do it in the traditional fashion?

- I absolutely try and stay on the cutting edge of technology. I tend to be not exactly the most early adopter in some niche, new techniques, but I tend to try and stay as technologically advanced in terms of materials and techniques we use. This is a patient here that had a fairly rigid, fairly rotated scoliotic curvature, but in this operation and you see that's my intraoperative X-ray as a patient, I did just this past week. You can see a fairly good correction with an all posterior technique. No anterior releases, simple posterior, facet releases and good pedicle screw fixation, but more and more, we're getting more tools inter operatively to help us translate the spine. So many device companies now have given us the ability to do a good translation type technique, which we'll talk about a little later, which really is helpful in these lumbar curvatures to bring that back towards the midline. And you can do almost a combination translation D rotation, which can be a really powerful maneuver to get good correction and restoration of alignment.

- Are you incorporating navigation into your deformity cases at all?

- I think navigation is a really big advance in the spine surgery world. It's not that we haven't had stealth navigation or other forms of navigation around for many years, but it wasn't very technologically useful. It was cumbersome in the past. Newer techniques and newer abilities to get better intraoperative imaging and easier registration has really made that useful. There are some people that are using it for every screw they place in. I tend to be a free hand screw placer, but I use it in any revision setting. I use it for my sacral screws because I like to really optimize the screws to get tripe cortical type fixation, which I'm not good enough on a freehand to reliably get that every time. So I, I like to use that to augment things and in cases, such as this, any pedicle that is really difficult and I need to have it. I have a low threshold to use the navigation. I think, I think it makes it safer and more accessible.

- Let's talk about the sort of key concepts with spinal balance. What do you consider to be the most important or criteria or key that you're looking for in achieving success with surgery?

- Well, when we talk about spinal balance and that really is the key when it comes to deformity, we're not trying to make spines straight, we're trying to make them stable, and balanced. And when we look at spinal balance, the sagittal plane has proven to be the most important factor when we talk about outcomes in terms of the literature. And then when you just see your own patients, anecdotally, the patients that you get back to balanced are always happier than somebody that's left imbalanced. So really analyzing what their imbalance is preoperatively and how much you need to correct to get them back into a normal range of balance is really key, both coronally and sagittally, but sagittal plane and not pelvic parameters are really a key factor in the analysis.

- Okay, so let me ask you, how is it that we see 80 year old patients in clinic who have horrible sagittal imbalance, multilevel degeneration, disc facet disease, but they come in with foraminal stenosis, a significant L5 radiculopathy, but really describe no back pain?

- That's a great question. And we certainly all see those patients, you know, oftentimes when patients have severe radicular pain, that tends to be quite disabling for them. And oftentimes they don't notice any spinal imbalance or back pain because they don't get around and up enough to really notice that. And I have had patients where I've done a decompression and the patients do well from a leg pain standpoint only to come back later, beginning to complain of some imbalance. That being said, you see patients that are grossly malaligned that really don't have any complaints. And it really comes down to how well they can compensate for that imbalance.

- And how do they compensate for the imbalance?

- General compensatory mechanisms tend to be a pelvic retroversion, so they rotate their pelvis. They bend their knees and they really move any area of their spine that they still can. So if they've got a lumbar flat back deformity, oftentimes you'll see a thoracic hypho kyphosis where they're trying to stand up with everything they can. And if they, as long as using those compensatory mechanisms, they can actually get to pretty neutral, they tend to tolerate that fairly well. When they are compensating, maximally and still imbalanced. Those are the patients that are the most disabled.

- If I do a L four five T lift on somebody with severe lumbar radiculopathy, who's got a coronal defect, a sagittal imbalance, they're 82 years old, and they get relief, have I done that patient a disservice?

- [Doctor Koski] I wouldn't think so at all. The key in those patients is to factor the deformity into your treatment plan and you treat what's bothering them the most. You counsel them that they might see some progression if you're near an apex over curvature, but I certainly wouldn't do a big operation, if I thought a small operation could really take care of the problem without causing a significant long-term problem for the patient. And oftentimes in those older patients, simply decompressing infusing the symptomatic segment can be key. That being said, I oftentimes will attempt to maximize the local correction of balance I can, I can get at that level to make sure I don't set them up for an even worse imbalance afterward.

- So if you see somebody with a great one to two spondylolisthesis at 5'1 like this patient here, are you going to check full lengths X-rays?

- Well, I'm, I'm definitely in the camp of people that believe in long segment X-ray. So yes, I would in this case. Most spondylolisthesis, particularly in L5-S1 where you're not talking about more degenerative, but more isthmic spondylolisthesis. You generally see a focal kyphosis with that spondylolisthesis and assessing their overall balance becomes key in treating that. Not that I'm implying, you need to do a long segment of correction on every patient with a spondylolisthesis, but you need to know whether you need to correct that focal kyphosis or not. And in doing so, you really can set them up for a long-term good outcome, or if you fuse them in kyphosis, they most certainly are going to come back for a revision operation at some point.

- So, would you want a anterior approach here to get a more lordotic restoration at 5'1? Or would you do this through a posterior approach?

- I would factor that in with the patient, whether it's male or female, their age, whether I want to do an anterior approach, but I also would look at that overall balance. If this patient was well-balanced with this listhesis I would likely do that posteriorly, try and get a little correction, and really decompress and stabilize as the goal. If the patient was grossly malaligned in my hand, I'm a little better with an anterior approach to lift that height and improve that lordosis. So I would, I would vary that technique based on what their balance was. That would be my main driving factor in how I plan that.

- Well if this patient's main symptom was foraminal stenosis in an L5 radiculopathy, but they were sagitally imbalanced to the point where an A lift you didn't think was enough. Would you recommend a bigger operation with multiple levels involved for something like an L five radiculopathy and a little bit of back pain in this situation? Or just stick to the level you're trying to treat?

- I might extend it by level, if I thought I could correct their overall alignment. The problem is when we do fusions on these patients that are malaligned, they do okay when they're not fused, when you use them in that segment, you then change the dynamics of the adjacent segment. And when they're malaligned, you have a bigger impact it seems. And those are the patients that tend to either fracture their sacrum or loosen their sacral screws, or have an adjacent segment degeneration early and end up going for revision operation. It's always easier if that caudal segment is well lordosed than to fix, even with an adjacent segment problem than if they're flat at that L5 S1 segment that really makes it challenging to try and correct that in a later surgery.

- Let's talk about regional sagittal balance. How do you look at this differently than say what we were just looking at?

- Well, regional balance in my mind is thinking a little more globally than, than just that simple local. I have a spondylolisthesis, factoring in how much lumbar lordosis they have and how much thoracic kyphosis. If you look at those and you don't necessarily have to calculate every variable, but looking how those relationships both clinically with the patient simply standing and walking in your office and radiographically is, is really helpful to try and understand what is going on and what you have to treat.

- Let's talk a little bit about the spinal sagittal balance and the plum line. How important is this in what you do on a daily basis?

- This is very important to what I do on a daily basis. It's one of the most important things, quite honestly. When we talk about spinal sagittal balance, the real gold standard has been the C7 plumb line, which is essentially a line dropped from the center of the C7 vertebral body. And it's measured based on the posterior superior aspect of the sacrum. If you're in positive balance, that means you're in front of the sacrum negative balance means you're behind. With normal, really being anywhere from four to five centimeters in front of the sacrum can be the upper limit of normal in most cases.

- Is that normal variable change as you get older?

- It tends to, we have done a study looking at older adults versus younger adults in a 20 to 40 and a 60 to 80 year age range and normal asymptomatic adults tend to be a little more sagely imbalanced, but really still fall within that four centimeters. I think our young patients fell just behind their sacrum or the posterior superior aspect of S1 so slightly negative. Our older patients were 1.5 centimeters positive, so slightly positive, but still within what we would consider a range of.

- So are you a little better off being a little negative at a young age? So you're not too imbalanced as you get older?

- I don't know if that's true. I think the more negative patients are, the more they load their tacet. You get different types of disease, but, but unfortunately there's no best position that we know of yet.

- Let's go through a couple of studies that sort of support the things that we're discussing today. Why don't you talk about this study that Glassman did?

- Sure, Steve Glassman and the spinal deformity study group did a couple of studies, We'll talk about here briefly. Looking at does sagittal alignment matter? And I took, what's called the adult deformity outcomes database, which is a multicenter database, many centers, including ours, put patients into. And they looked at these near 300 patients and looked at all of their different factors they could find on their x-rays and tried to correlate them with their outcomes measures.

- And obviously the most important outcome we discussed earlier hasn't changed.

- No, it was definitely sagittal balance. In all the factors you see there, pain scores, function scores, self-image scores and social function, all with sagittal balance was the most important.

- I guess we've discussed a little bit, age seems to have a role as well.

- Age, patients, you know, when we talk about disability scores, older patients tend to score a little worse than the younger patients, but even when they factored in the age of the sagittal balance, it was the most significant factor in here. And that's what we see described in that table there.

- All right, well let's and then the followup study.

- The followup study was, again, looking at that same database, looking at a large group of patients, really looking at that C7 plum line and trying to look at the balance and then how it specifically relates to those outcome scores.

- And the outcomes were as expected.

- Yes, the more imbalanced, the more, the more disabled those patients were.

- We haven't talked about this quite as much yet, but the lumbar kyphosis is also starting to play a little bit more of a role.

- It does, and you can see on one of the slides coming up here that the more, the lower the overall kyphosis, the more disabled the patients were. So patients should have their maximum kyphosis and their mid thoracic spine. And you can see that depicted here where their Oswestry Disability Index, if their maximum kyphosis was in their upper thoracic spine was the lowest. And it went up as that became lower and lower in the spine. So the more kyphotic they are in the lower manner actually tends to matter in terms of their outcome.

- So obviously this paints a picture regarding evolution?

- So not only an evolution of our standing posture, you can see there, but really I put this in here as it's somewhat an evolution of thought in spinal balance.

- So now we're going to start to challenge the neurosurgeons. This is a little out of our area. Let's talk about pelvic incidents. And so that's become a hotter topic in the past few years.

- It certainly has. And that's when I talk about the evolution of thought, it's really the pelvis that's become key. And when you think about the pelvis, it's the bottom of the spine. So John Dubasai had described it as the pelvic vertebra, and it really impacts how much lumbar lordosis you need. And pelvic incidence is a key parameter there. And that's something we measure simply by drawing a line over the top of the sacrum. So this S1 end plate, you take the midpoint of that line and drop perpendicular. So it's related to that, that perpendicular to the midpoint of S1 and that line drawn to the midpoint of the femoral heads. If they're perfectly aligning, you have a great x-ray you pick simply the midpoint. If you have two femoral heads, which you usually do, you draw a line from the midpoint of each and take the center of that line. That pelvic incidence is a parameter that doesn't change throughout your lifetime. So that's a fixed static parameter. That's how you're built, whether you're standing up, lying down, upside down, it doesn't matter. Your pelvic incidence should be the same. Now that those two parameters that make up your pelvic incidence, and there's a geometric proof that proves that, but I'm not going to go through that today, but the pelvic tilt and the sacral slope are two position dependent parameters that make up that value. So your pelvic tilt tends to be the key that we use nowadays to try and predict O alignment, is simply taking that same point at the midpoint of the S1, to that same head midpoint of the femoral head, and then it's drawn to a vertical. So you can imagine as your pelvis rotates around, that vertical line doesn't change. So this angle changes with position and similarly, the sacral slope is that angle across the S1 end plate to the horizontal line. And you can see here how the pelvic unit rotates around those femoral heads. And so by rotating your pelvis one way or the other, as you see here, you can verticalize your sacrum. That's called a retroverting your pelvis in an effort to stand up, or you can have a very horizontalized pelvis with that needs a lot of lumbar lordosis to stand up. And that really is key that this pelvis can rotate around those femoral heads. And that's the whole point of that compensatory parameter I discussed earlier. You can see a depiction here from the spinal deformity study group radiographic manual, that's out there, which is an excellent reference. You can see somebody with a relatively low pelvic incidence. It needs a small amount of lumbar lordosis, medium, and somebody with a high pelvic incidence needs a lot of lumbar lordosis to stand up in balance. And generally we think that their pelvic incidence should be equal to your lumbar lordosis plus or minus nine degrees. You can use 10 degrees, 'cause that's a little more of a round number, but you should be within 10 degrees of those two parameters. And if that's the case, then your pelvic incidents and your lumbar lordosis tends to balance out. And that sets you up for success. You can see here a depiction of a compensated pelvis. So somebody that stands up neutrally with a pelvic incidence that matches a lumbar lordosis, where their legs can be straight and they stand up straight versus here. Somebody that has a lumbar hyperlordosis, they're retroverting their pelvis. So their sacrum is becoming more verticalized. Their knees are bent, and that's the classic compensatory posture we see in patients that are sagitally malaligned.

- So let me ask you a little bit about this. Are you measuring this angle in all the patients you see in clinic?

- I generally do measure it in most patients I see in clinic. Now if I see somebody with a herniated disc, am I measuring the pelvic incidence? No, I'm generally not. If I have a patient that I'm thinking about doing a fusion or somebody I'm certainly worried about their overall spinal alignment, I do definitely calculate their pelvic incidence. I calculate their pelvic tilt, I measure their lumbar lordosis and their C7 .

- So tell me how the pelvic incidence number changes what you did before we were measuring this, meaning you had the plum line before, you had how much out of their balance they were. How does this incident number effect what you do to fix the problem?

- Well, it, it certainly factors in, you know, in the past many years ago, before my time in practice, but in my early training, patients with spinal deformities got corrected and straightened and some did better than others. And people started to figure out really that sagittal balance and the C7 plum line really played a big role, but even then some patients still do better than others. When you start to factor in the pelvic tilt, you start to fuse patients. And again, when you fuse somebody, they tolerate imbalance a lot less than if they're unfused because you take some more compensation away. So a fused patient that is in balance that doesn't have to compensate, meaning you lined up their lumbar lordosis, their pelvic pelvic incidence, and factored in their pelvic tilt. Those patients don't have to compensate. They can stand up much easier than the patient that you left a little bit forward and still have to spend some energy trying to pull themselves back up.

- I'm gonna back up just to this picture again. So if you're seeing the retroverted pelvis in compensation is the value, the number you're getting, help you identify that they're compensating so that you need a better correction to deal with this, is that what's happening?

- It does, absolutely. I generally take their pelvic tilt, which a normal pelvic tilt. Now that's the one that's referenced to the vertical line. So it's position dependent. Normal, we think is around 12 to 15 degrees. So most of the time in a correction, it's very common to see patients with pelvic tilts in the 30 and even 40 degrees, meaning they're really, retroverting their pelvis trying to stand up. I'm factoring in an amount of lordosis to get that down under 20 degrees when I'm calculating things. And generally that works quite well in getting patients to stand up. And when you factor that in, we tend to do a better job of achieving our goals of spinal alignment.

- So let's talk about the techniques we have, how are we going to fix all these issues?

- Well, so when we think about our crushing techniques, really most of the time we're manipulating the spine around this instantaneous access of rotation, we all take the, the IAR for granted. We know that things move around, but really thinking about how you're doing that and where the spine rotates helps you plan a correction. And usually in these operations, we're trying to restore lordosis in adults. And that's usually a shortening of the posterior column. We certainly can lengthen the anterior column, but it carries with it a little more neurologic risk and it's harder to do. And this instantaneous axis of rotation you see is usually in the posterior third of the vertebral body. So if you compress posteriorly, you add lordosis, which is usually a part of our goals.

- So in, in thinking about the IAR, does that sometimes tend to make, you want to go more anteriorly or laterally as opposed to posteriorly?

- Sometimes, and in certain cases, such as patients that need a lot of lumbar lordosis that are, have hypo lordosis at their L four, five and L five S one levels, I certainly will employ an anterior approach in those patients trying to lift that up. Generally though, when we talk about correction of deformities, we're trying to shorten the posterior column and not lengthen the anterior column. Particularly if we're dealing with cord levels since the spinal cord doesn't tolerate the anterior lengthening very well. So oftentimes we're trying to get the majority by a posterior shortening, which tends to be a little safer neurologically.

- So when I look at this X-ray you have here, I was a little bit surprised. I see that a L three and L four are nicely lined up, but it seemed like there's a, is this just the view that I'm seeing? It seems like force very tilted on five, or is that just what the X-ray appearance that I'm seeing?

- Well, no, that's, so this is not my, my case. This is borrowed from Washington University in St. Louis, where they in the past had done a lot of anterior approaches. So this is what would be considered a Blinky five adolescent idiopathic curvature where, has a thoraco lumbar primary curve, these other curves are compensatory and simply stabilizing and treating this and taking a 53 down to a 32 degree curvature with some anterior surgery, really saves some fusion levels in a young patient and gets a pretty nice overall alignment, which hopefully serves that patient well for decades of their life. And that's really the key when you're talking about a young patient is saving some of those fusion levels. Where in an older adult, we might not want to keep that same amount of tilt down at the bottom if they have degenerative disc disease, at those levels.

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