Transcript

- So let's talk about some of our options for changing alignment and gaining angles. Why don't you go through the Smith-Pete Osteotomies, and talk a little bit about this.

- Certainly, so this is an example of the Smith-Petersen Osteotomy or Ponte Osteotomy. People use them interchangeably. Technically, the Smith-Petersen was described in ankylosing spondylitis in a fused spine, and Ponte was in a mobile spine, but people tend to use the two terms interchangeably. So this is simply a posterior facet osteotomy. You can see in the picture here, spinous processes have been partially removed. The inferior aspect of the lamina has been removed, extending out through that facet joint, and removing all of that facet material. Then with segmental instrumentation, you can simply compress on those, enclose those osteotomies, getting a small correction, maybe five, maximum of 10 degrees at each level to correct that. You can see that x-ray here. A significant thoracic kyphosis is segmentally realigned over a long construct, kind of in a harmonious correction, and that works quite well in many cases.

- When you do these cases, do you leave a certain length of rod at the top, in case you have to add on to something you've done, or not necessarily?

- People have described that. I don't necessarily do that. If I have one side where the rod is a little long, in the past I would have bent it up and tried to cut it, or do things. Now I'm a little more likely to leave a little bit of a length of rod in that setting, just in case you can do that. But I don't intentionally do that regularly. If I left a little bit too much, I just have a lower threshold to leave it, at this point.

- You haven't really talked about it throughout the talk, but at this point when we start to talk about osteotomies, do you wanna mention something about monitoring?

- Absolutely. Every single one of my spinal deformity cases gets multimodality monitoring. So that's somatosensory evoked potentials, and we tend to do transcranial motor evoked potentials, and we also have free-run EMG hooked up on our lumbar roots. I think that's crucial. When we talk about realigning the spine, there is a risk of neurologic injury, and an early warning with some evoked potentials, really can save you if you can reverse a corrective maneuver and try and save somebody's function.

- Why don't you take us through the next slides and walk us through this procedure?

- Sure, so this is a 3-D representation. One of my previous fellows, Fetty Nasser, put these together nicely for us. So, these are SPO or Ponte osteotomy is a segmental resection, you can see the components listed there. So, interspinous ligaments, the inferior aspect of the lamina, the facets, and the ligamentum flavum are all released to mobilize the spine segmentally. And you can see that we do that with a drill or a punch. And you can see here, that 3-D model again, where you see the inter raft of the lamina has been cut, and it angles up, and they call it a Chevron osteotomy, because it angles up through those facets. And really the key is to get that superior aspect of the superior facet from the level below. The tip of that needs to come up. Here's a little magnified picture, and you can see there's no bone remaining in that foramen. And when you look here, the tip of that superior facet is really the key. Oftentimes, when you drill through here, or you punch through here, you leave a little remnant of that. You don't wanna leave that bone in there. If you do, and you compress this down, you're leaving, essentially, a free-floating piece of bone in your neural foramen, and you can end up with a radiculopathy.

- So, how often do you see neuromonitoring changes when you're doing osteotomies?

- Fortunately, not very often. We have an algorithm in place to deal with them. And sometimes we end up seeing a false positive, which is stressful, but better than a true positive. It's very rare, quite honestly. Throughout the case, you sometimes will see some potentials drifting down, and the key is to pay attention to that. If the patient's getting sweaty and electrodes are falling off, or things like that, to address those. And particularly before I do the correction maneuver, I wanna make sure I have got a good baseline set of potentials before I do my correction, and during, and then after to make sure they're stable. And we continue to monitor through the remainder of the case to make sure they haven't drifted down or changed. Just because you do your correction doesn't mean that you're out of the woods, or five minutes later, they're stable. We monitor all the way 'til the end, and then we get a wake up test at the end.

- Now, looking at this x-ray you have on this slide, it looks like we're advancing beyond Smith-Pete's, and going into the PSO area.

- We certainly are. So, when we think about the instantaneous axis of rotation, we use that with the Smith-Petersen osteotomies, manipulating the intrinsic axis of rotation. In a pedicle subtraction, we can create our own. That is useful in a patient that has a fixed imbalance, where they don't move. We can do a pretty significant focal correction at one single level. Now, this is a very useful technique. We use it quite often, but it is a more morbid technique, in that it takes longer, it has more blood loss, and it's technically more difficult, and carries with it, a higher neurologic risk. And if I can run through that procedure briefly, you can see here's a artist illustration we had done, showing the pedicle subtraction osteotomy here, which is a reverse wedging of that vertebral body. Now that's done with a laminectomy, a complete facetectomy. So the facets are gone and the pedicle is gone, in its entirety. The key is, you need two nerve roots exiting through one vertebral superforamen. If you leave a little remnant of bone, you can get some traction, and you get some root problems. So we resect the vertebral body using a wedge resection, the lateral wall. And I have these listed in the order that I actually do this procedure. I do everything posteriorly first. I take the pedicle down. I do my vertebral body work and my lateral wall. And then the last thing I do is take the posterior vertebral body wall down. The reason for that is the epidural veins there will start bleeding when you take that down, and they don't stop until you close the osteotomy. So you don't wanna do that until the very last thing, and you're ready to close. I make sure everybody's ready with our fixation. We are ready to close that osteotomy, announce in our operating room, we're gonna take that down. Tell anesthesia it's gonna bleed for a few minutes. Take it down and then close the osteotomy right away.

- What degree of correction do you seem to get with the PSO?

- Generally, 25 to 30 degrees is common. Some people will do more of an eggshell de-cancellation. We tend to do a real custom cut osteotomy. We try and actually template our osteotomy with some angle templates. We have to either 25, or 30, or on occasion you can get 35 degrees if you take that disc above. But that's generally how much correction I get. Now a very focally kyphotic vertebral body can give you a lot of correction because you can bring it past neutral to lordotic, but generally 25 to 30 is a good estimate.

- Why don't you show what you're, discuss what you're showing here in this slide?

- So, here you can see again, that artist's illustration of what's going to be resected. So the pedicle taking out here, apexing at that vertebral body, one of the keys is, that you're going to leave that anterior cortex. You're gonna bend it down all the way to it, but you leave that anterior cortex, and that's your axis of rotation. It's gonna pivot right at that point. If you cut all the way through here, this can gap open in the front, and it becomes a little bit of a messier closure. So you wanna correct it on that. And you can see here, an inter-operative x-ray, showing a 35-millimeter gap between those bones. And you can see here, you can just see this single line here where there's just a millimeter gap of closure. And that really significantly changes that lordosis. You even get an estimate of how the rods are really kyphotic here, those temporary rods. And they're back to lordotic on this image here.

- One thing we didn't talk about was what levels you do this in the spine.

- So you can do this at many levels in the spine. The most common are L2 and L3. Generally, because they're a little easier to do. The roots are a little less sensitive than the lower lumbar spine. And it's easy to get good fixation above and below, but this can be done at any level, really. People will do it at C7, in patients with chest deformities. And the thoracic spine, we've published a paper where it seems to be a little less effective in things such as vertebral column resection. Tends to be a little more un-useful. In the thoracic spine, due to some of the local anatomy, but it can be done throughout the spine. Obviously at core levels, there's a higher level of risk and you need to take appropriate precautions.

- One thing we didn't mention as well, is what tools are you using to make these cuts? Are you using osteotomes?

- I use a combination of things. I tend to use the drill for lots of things. So I like to use a drill. We have some specialized osteotomes. We use pituitary rongeurs, curettes, we do a variety of things trying to de-cancellate and save as much of that cancellous bone. It's a very useful source of autograft. So we take all that bone graft we can. But it's a combination of tools, and everybody has their own little technique. And if anybody's interested in going through that, I recommend you, there are many courses, and sometimes really live surgeries. I'm gonna show a video here of a live surgery where you can see that done, and practice on a cadaver first. And you can see.

- Okay, so why don't you walk us through this video?

- Sure, so this is a video that my mentor, Steve Aandra, provided me with. This is actually Steve Aandra and Larry Lenke, two legends in the field, that we're performing this osteotomy together at a live surgery course. And you can see they're doing a pedicle subtraction. They've taken down the majority of it. They've done the majority of the work. They're removing some of the lateral vertebral body wall here. The head is up here. The feet would be down here. The nerve root is here. You see the dura, obviously. You see screw fixation in place. And I really wanted to show the anterior cortex. You can see it actually crack right there, and you can see as this is pushed into lordosis, the significant change of alignment you can get. And you see that dura and nerve root disappear beneath that very wide gap. You can see it here, there are the nerve roots, you watch it crack right there, and you can watch that significant amount of lordosis you focally can get, as that wedge closes down. And you can see there, their pre- and post-operative x-rays, getting both coronal and sagittal correction in that procedure.

- That's certainly an impressive video. Let's get back to the other point. So now we're gonna do a little trigonometry, I hear.

- It is, so, this is something that, again, Steve Aandra came up with. This was our trigonometric formula for sagittal correction. And really, the point of this is, if you take the patient's plumb line, which you want to be here, and their spine is really here, you can actually calculate the angle that's needed to move them back to this. Now we published this several years ago, and you can see this was our formula here, that you could calculate that, and we use, you take the inverse tangent to calculate this angle. And then, you then could apply that angle to the spine and get that same amount of correction. Now, fortunately, on a PAX machine today, I don't need to actually measure the lengths of the line and do trigonometry, which was back in plain x-ray data. Now I can actually draw my line, if I can go back, I can draw this line here. I can draw this line here. And it simply calculates a Cobb angle for me, and it tells me in about five seconds what my angle of correction is. Now, this is not the be-all, end-all of treatment. This will tell you if you correct it right here, but you can correct it in a variety of positions. It will differ, how much correction you need, and then factoring in that pelvic incidence and pelvic tilt is really the key. If you add that in to this correction, then you can get a pretty good overall realignment.

- Let's move on here. I want you to discuss this as well, this example.

- Sure, so here's an example of how I would plan a correction using those. Now, I do two things. So if you look at their C7 plumb line that I've drawn here. And then I draw their pelvic tilt or their pelvic parameter. So I draw the posterior to the anterior portion of the sacral endplate. I draw my line to calculate my pelvic incidence. I draw my vertical line to calculate my pelvic tilt, which you can see is very high in this patient. And then I calculate, if I take those, if I want the spine to move from here to here, and I'm going to do an osteotomy here, that angle, which data, equals 35 degrees. So I need 35 degrees to move this patient from here to here. That again, doesn't factor in their pelvic tilt. So if you look at this patient, she had no lumbar lordosis, a pelvic incidence of 58 degrees, a pelvic tilt of 35 degrees, and this angle was 35. So, I take 35 degrees, plus my pelvic tilt minus 20. That gives me 50 degrees of total correction to bring this patient from here to here, and get her standing upright with a neutralized pelvic incidence. I actually double-check my numbers every time. So if I look at this 58-degree pelvic incidence and a lumbar lordosis of zero, well, I'm supposed to be within nine degrees, if I give her 50 degrees of lordosis, that actually normalizes that parameter as well. And with that, I'm comfortable that that amount of correction can get her back. Now it's not easy to get 50 degrees of correction, but that's the goal of the operation.

- So the value I'm seeing when we were discussing pelvic incidence early in this case is, if you didn't account for that pelvic incidence, you may under-correct this, going straight off the other numbers, is that correct?

- Absolutely. If I gave her a 35-degree correction, thinking I'm gonna correct her C7 plumb line, I would correct her C7 plumb line, but she'd still stand forward because she'd let a little bit of that pelvic tilt relax. She'd still be imbalanced, and she wouldn't probably have as good an outcome, as if I can get her all the way back.

- I want you to back up, and both pass those lines again, and start over. I wanna hear this one more time, 'cause I think I need to hear it once more to understand it.

- Certainly, I'm gonna clear those off of there. So I take that patient, I generally measure the lumbar lordosis to start off with. I draw a C7 plumb line, and I measure the distance here to see how imbalanced they are. That's really for my dictation, to give me an idea of how much it is. And she is somewhere 15 plus centimeters imbalance, so grossly malaligned. I then draw my pelvic parameter. So I start with drawing a line over the S1 endplate. I pick the midpoint, and I draw a line to the midpoint of the femoral heads. And I draw a line that, also, is perpendicular to that S1 endplate. This angle here, is the fixed parameter of pelvic incidence. If I take, and draw a vertical line, this angle here, so this is, this line to the vertical is the pelvic tilt, that position-dependent parameter. And in this patient, that pelvic tilt was 35 degrees. Which, if I think normal's 15, and I wanna get them within 20, that means I'm adding 15 degrees to my overall correction. I then draw where I want them to be. And in this case, this line didn't even pass through her spine. So I actually drew separate lines to calculate an angle drawn, if I'm doing an L3 PSO, and I do that angle from here to here, I can bring that patient's spine from here to here. Then if I just add that in, it gets me to where I need to be. Does that make sense?

- I think it does. I'm gonna have to think about it for a few more days.

- It seems daunting, actually. And I take residents and fellows to my clinic, and I make them draw it out. And, within five patients, they measure it like it's nothing. Doing it a few times, it's hard to listen to, and the first time I heard it, I said, "Oh, I don't know about this." But if you draw it out a few times, it really becomes second nature very quickly, and it's very effective.

- So we mentioned this a little bit earlier, talking about degrees of correction. Here, we talked about an ALIF, with the correction you can get with that, versus a PSO. This is obviously, this is the same patient you showed earlier, isn't it?

- It is. So I, an effort to get 50 degrees of correction through a fixed spine, that was a fairly daunting task. But in this patient, she was fused down to L5. So her L5-S1 disc was still mobile. Now it was collapsed, and that's why she was leaning so far forward, over time. She had this flat back deformity from her old Harrington construct, but then she degenerated L5-S1. I knew if I could mobilize that by going anteriorly first, I could get a pretty significant correction with this stage one ALIF. And I actually got 20 degrees with that. So that takes my 50 degree correction and places it into a 30 degree correction, which I then can do with one pedicle subtraction. And I like to do those in a staged procedure, just for this reason, I can get her up, I can get an x-ray and measure how much I need, and then I can template a 30-degree correction. And lo and behold, they actually balance out really well after that operation. So, 50 degrees seems like a lot in a fixed spine, but breaking it into two smaller pieces like this, becomes quite doable.

- Let me ask, how are you getting 20 degrees of correction with an ALIF when the cages are only eight or 12 degree options?

- That's true. Those eight or 12 degree cages, depends on how you put them in a little bit, because they're always sort of molded to fit that endplate a little bit, and that L5 endplate is never quite, just flat. So you can get more than that by putting that cage and leaving it right at the anterior edge. But honestly, in this setting, I will take those cages, and much to the manufacturer's reps chagrin, I will shave down the back of that a little bit to make sure I'm getting even a little bit more. And in doing so, oftentimes, I will use the cages that I can secure with either some screw fixation in the front, because I wanna get them up, and not have it slip in between stages, but sometimes I only put screws going into one of the vertebral bodies, which essentially keeps it from spinning out, but doesn't provide any real fixation, so I can compress down posteriorly and get a little bit more.

- And this is a CT scan of the same patient?

- That's a CT scan and that same patient. You can see the ALIF, we have a significant restoration of height there, you can see S1 screws, which I navigated in there to get that optimum trajectory. And you can see that pedicle subtraction osteotomy. Now you can see her staples here and her JP drains in places. This is her immediate postoperative film. And it's very nice in patients with old Harrington fusion masses. You can see this enormous amount of fusion bone that is coming bone on bone right there. It actually looks fused already, which we know it's not. A thing to be careful with in a pedicle subtraction is these discs right here, can lead to rod breakage if you get toggle on those discs. If I don't have a fusion mass that I can put bone on bone, and I'm fairly confident we'll fuse early, I generally will fill those in either with a TLIFs, or even a second stage to try and prevent a late rod failure, which unfortunately, is more common than we'd like.

- Would a trancellous approach be another option here?

- Certainly, it certainly is. It can be a little difficult when you have a long segment fusion, if you're trying to get down to L4/5, but at the other levels, it's quite useful.

- So let's talk about this hybrid construct that you're starting to mention.

- This hybrid construct is an extended pedicle subtraction. Really, that is simply, you can see a regular pedicle subtraction here and you can see an extended one here. Extended, in my terminology, just means we're taking the disc above, usually putting a little bit of a pivot point. It tends to work a little better in the thoracic spine where you can get a little more of a correction with that extended pedicle subtraction. But it's just a variation on the theme of the same osteotomy. We're showing a little bit of an advancement. So, if you think about the pedicle subtraction as taking down the pedicles and taking a wedge out of the vertebral body, extended pedicle subtraction takes the disc above, a vertebral column resection takes the disc below as well. It's very much like a lateral extracavitary or transpedicular corpectomy, except it's done with shortening the spine in mind for deformity correction. So I've got a few slides here that will show us how we do that. If you look here, I've started on this 3-D model with a Smith-Petersen style osteotomy above my level, done a laminectomy, removed the facets below, removed the transverse processes and the pedicles. You need to remove the ribs, and particularly the rib head, where it articulates with that vertebral body, bilaterally. And we'll switch to the lateral view, crucial in the thoracic spine, because you cannot tolerate any accidental subluxation. So you need to hold the spine in place. And we've removed the vertebral body and the discs, with the posterior vertebral body wall being the last thing, again, because those epidural vessels will start to bleed once you get into that space. You remove that. And then generally we place a cage, which generally is 50% of the height of the space you created. And you want it to be relatively anterior, and you don't want it to be very big, because you want it to simply block the anterior collapsing, and allow the posterior compression to continue. We oftentimes will place rods through a domino connector, and then correct here, where you can see that cage then becomes structural in that interbody space. You can see an AP view, and a lateral view of what the finished product looks like.

- How much correction do you get with a vertebral body resection?

- So, people oftentimes quote numbers of pedicle subtraction getting 25 to 30 degrees, and a VCR getting up to 40 to 50 degrees. Quite honestly, in my mind, it's variable. It depends on how much kyphosis you have. Most of the time, you aren't putting that spine into lordosis with the VCR, as you're getting it back to neutral, to maybe slightly lordotic. So if things are highly, focally kyphotic, being 40 or 50 degrees kyphotic, you can get them back to pretty neutral. The problem when you go past neutral and into lordosis, is you start to gap that anterior space, and that interbody you placed in there starts to get a little bit loose. It's really dependent, in my mind, on how much you get. I don't, in my practice, think there's any set number to say, I can always get X degrees with this osteotomy.

- So Tyler, let's talk about translating the spine, and why don't you walk us through this video?

- Certainly, so translation maneuvers are really useful in adult deformity, and particularly adult degenerative deformity, where we're trying to bring the spine over to the rod with good screw fixation. And, this video here is gonna show a little bit about how we go about doing that. And you can use reduction screws, which was traditionally the way we would do this, but now most companies have a variety of these extenders, where you can essentially turn screws into reduction screws. And I don't know if it shows very well, but the screw heads are way over here in the rod. I've got fixed at the bottom and I've got this hook holder attaching it to a screw at the top, loosely, and then generally, or gently, and sequentially, you can begin translating that spine over. And if you use model axial screws, as I have here, that rotation, you can do a couple of translation and de-rotation maneuver here as well. And you can see that I've got my resident here, holding on to the rod, keeping that in position, and then we're gonna bring that spine over. Now, this only works if you have strong fixation and you've, essentially, loosened up your spine with osteotomies beforehand. So, all of the osteotomies have been cut. The sets have all been released. Interspinous ligament has been released. And then each time you can turn that down just a little bit more, a little bit more, and you can see I'm applying a little bit of pressure upwards, trying to get a a couple de-rotation and translation as well. Now, this is an adult patient with, I'm not trying to do a chest wall compression, so I'm not doing a huge formal de-rotation maneuver, but I'm getting a little bit of that de-rotation and standing those screws up. The fact that those screws are model axial, and that they don't pivot in that lateral plane, that force is applied to that screw and around that vertebral body. And this is just a short video here, where pretty easily and quickly translated down. Sometimes it takes longer than that. Sometimes I do a little bit, let it sort of settle in, let the viscoelasticity of the properties kick in and let it relax a little bit more and a little bit more. That can be done over a few minutes, like you see here, or that can be done over a much longer period of time, if we're trying to slowly pull the spine into position. That's a very effective way of bringing that spine back towards that midline.

- Excellent. If you see any neuromonitoring changes, do you stop? Do you release some of what you've done?

- Absolutely. So in my paradigm, if I see changes in that, I essentially, I'll stop what I'm doing, immediately have anesthesia check the blood pressure. I generally release what I did a little bit, so reverse the last thing we've done, and then see. We obviously have a whole algorithm we go through, but generally you'd release what you've just done and make sure things aren't buckling in, and re-explore.

- Okay. So let's talk about some coronal correction here.

- So another corrective maneuver we use, and this is that same patient. After we translate this spine over, I've got my set screws in, but not really tightened. I've loosened them after the patient's come over, and I'm doing a little bit of insitu contouring. So, even if you're using a fairly rigid rod, which I was using a cobalt chromium rod, in this case, it still tends to bend a little bit as you're doing that translation. And this maneuver is really taking that bend out. The key, this video is showing that, how many segments I do that over, whether it's compression distraction, whether it's a translation, or whether it's coronal bending, you wanna do things over multiple segments, again and again. You get a little bit at each. If you try and just really crank it over at one segment, you end up pulling out a screw or ploughing a screw. So doing a little bit at each time, using both rods in this instance, you can see that's fine, where before it looked fairly rotated, and what was started out with a pretty good scoliosis, is actually pretty well neutralized in the end of that video.

- Let's go through some case examples.

- Sure, I've got a few cases. And some of the principles we talked about earlier, such as identify the deformity. Here's a case that I've shown several times at some meetings. This is a patient that came to me 58 years old, and having multiple falls. She was treated with a laminaplasty for spinal stenosis, and this is her post MRI. See, she doesn't have any stenosis, but was falling and nobody was really looking at why. And so they thought her MRI was improved, and thought she just was a failure of myelopathy patient, essentially. Well, if you look at how lordotic her spine is here, you can imagine when, before her laminaplasty, she had a lot of ligament and lamina that was buckling into that spinal cord. You could see how it would cause stenosis. But, when I go in to see her in the room, she's sitting in the chair. And the first thing I do, I have her stand up. And lo and behold, this is what she looks like when she stands up. So we sent her down for a 36-inch x-ray, and when I Photoshopped them together, this is her best effort at standing. She has a huge sweeping thoracic kyphosis. And her circle hyperlordosis is really compensatory. Just her trying to get back towards a neutral position. So a cervical MRI, the pathology was found to be here, where just getting a simple inexpensive x-ray, you can see the pathology really lies here. Now, this isn't easy to fix. I did a very large operation over several segments to get her standing up. But after that, with a lot of work and a lot of screws, she gets back to a neutral alignment. And one thing do wanna say about this case is, this is not normal. That patient is not normal after this, but at least she can stand up. She can see where she's going. And that's generally a more functional position. Although, I wouldn't want anybody fused from their upper cervical spine down to their pelvis, unless they really needed it.

- I certainly don't wanna get too bogged down, but what kind of postoperative course does a patient like that have?

- Well, that was done over a few segments. I actually, if you look at that film here, I corrected that. And some of those thoracic VCRs, and the extended PSL I showed you, that's that extended PSO. That's a regular PSO. So I did multiple osteotomies in addition to multiple Smith-Petersen osteotomies. And I got her back actually quite nicely neutral, stopping in her mid-lumbar spine, which she promptly fractured through that, not promptly, but within six months, she was breaking that down and ploughing those screws, even though her alignment was quite good. So this was an extension later. So I was hoping to save this motion at the bottom, but I wasn't able to, and within six months I had to revise it. So, that construct I did over two days, the initial, and then this was a third day. So that's three days worth of surgery for her to get there. It's broken up into a few segments, but still a fairly lengthy recovery. And getting that much bone to heal is a real challenge.

- Let's move on.

- Another case you can see here. So this is a patient that, we saw this MRI earlier, that was having intermittent L4/5 radiculopathy. So her MRI was fairly unimpressive as to why she was having all this radicular pain. But if you looked at a standing x-ray, even a lumbar one, you could see that significant hyperlordosis in her lumbar spine. And she was simply closing down her foramen due to postural mechanisms. And what she had was a cervical thoracic junctional kyphosis. And what she was trying to do was balance her head out over her sacrum and pelvis, as we all do, and leaning back on her lumbar spine to do so, and closing down those foramen. Now, treating her cervical thoracic kyphosis seems like a bold way to deal with back and leg pain, but it neutralized her parameters, and she actually had all of those symptoms go away. This is a one out of several in the series we have with patients just like this, that present with back-related, low back related symptoms, and have a cervical thoracic junctional problem. So, this is my example of identifying the deformity. So really looking globally at the patient and finding out what the real driver of their symptoms are, and then treating where appropriate.

- This is starting to get a little like the RED compression for chronic fatigue syndrome.

- It is a little bit, it is a little bit outside the box. Here's another patient actually, where you can see, that had drop head syndrome. And she had neck pathology and neck problems. And this is her best effort at standing. But you can see she's really hyperlordotic and had a lot of low back pain. She had a little thoracic kyphosis too. And just to show you I don't treat every part of the deformity. I simply treated her drop head syndrome here with neutralization. And this is, these plumb lines you see here are something we've done some research on, is a cranial center of mass as a plumb line. And if you notice, that falls right where it should, right over the sacrum of the pelvis. And the C7 plumb line always goes neutral until you correct the two, and then they come back to right where they should be. So I wanted to talk a little bit about a couple, I talked about assessing the flexibility, a couple more cases where you can see this patient here, that had a prior fusion, had a pseudo, they removed instrumentation, and we see a significant grade four, mid-lumbar spondylolisthesis with a severe sagittal plane imbalance. Now, assessing the flexibility, whether it's supine x-rays, or I find CTs quite useful when I'm looking at things such as this, where it can be a little bit hard to see, or the patient doesn't tolerate a bolstered film, you can see this reduces, really to a grade two slip with simple supine positioning. I know if it's that mobile, that what seems a very daunting task to me, in this x-ray, with some simple posterior facet releases, I can get this to move even more, and you can take that patient and realign them, not needing pedicle subtraction osteotomies, not needing anterior releases, simply releasing and using that mobility that the patient showed you in their preoperative film to get them back in balance. And this is one of my happiest patients that I have.

- I don't wanna get too bogged down, but along the ways, lots of deformity surgeons are talking about having to remove their iliac bolts or only doing unilateral rather than bilateral. What is your experience with that then?

- There are a lot of controversies with iliac fixation. Most people that do long segment constructs would agree it's necessary, and certainly helps your fusion rate and your success rate of your surgeries. There are so many ways to place sacral, pelvic fixation. Now with S2 alar-iliac is a common technique. When I place iliac screws, I pay a lot of attention to placing them really very deep into the pelvis. And when I palpate over the top of the iliac crest, and I want to feel nothing but a ridge with maybe just the slightest of bumps, where that screw is. So I really pay a lot of attention to driving it down there. And I personally have not had to remove any of them due to pain. That doesn't mean I won't at some point, but the historical data of 20 to 25% removal rates, I do not think holds true with the newer placement techniques, and really, with implants that have smaller heads and are easier to connect up to the rods.

- So you're making sure that you take out a piece of the PSIS, so that that iliac head can fit all the way down in line with it rather than being drilled.

- I do. My technique is to leave just a very caudal aspect of bone at that PSIS, as it starts to fall off. And there's that little area right below the PSIS that falls off. I leave a little ridge of bone there, and then I take my wedge of the bone out. So there's bone on either side of my screw and it's protected in. I really think that helps in terms of pain.

- One other topic that we didn't really broach on, which I think is important, is anterior column biomechanical strength, either some sort of ALIF raft in these long constructs. There's certainly a lot of biomechanical data showing how much increased strength you create by doing some sort of anterior interbody fixation at the bottom one or two levels. Do you believe in that?

- I do believe in that. So, historically in deformity operations, pseudoarthrosis has been a problem. So, and the L5-S1 segment tends to be the most difficult to get fused. So, any construct that extends down to the sacrum of the pelvis that is really above L2 to S1, I generally am adding iliac fixation and an interbody support. So, if their L5-S1 disc is terribly degenerative, and there's really no motion there at all, I might not do so, but in any other instance, I'm trying to add some type of interbody support, whether that's via an ALIF, or TLIF, I decide based on what I think is necessary in that patient. But I think that helps your fusion rate, and helps build a really solid foundation to build that long construct off of. I don't want to belabor the--

- We move on to the last case.

- Sure, I'm just gonna show this. This is the one I showed earlier with this 45 year old with kyphoscoliosis. Looking here, you can see that's a real common thing people will see, that degenerative kyphoscoliosis saggitally, slightly imbalanced, and having a lot of pain. With simple posterior facet releases, even in an adult degenerative curve that's fairly stiff, not needing new pedicle subtractions, you can really mobilize that curve. Now, this isn't straight. This is meant to show what the goal of the operation is. She's balanced saggitally, she's balanced coronally, she's stabilized. And that is really the goal. It's not the most straight spine you've ever seen. And I really don't care about how straight it gets. I care about it being balanced, it being less painful, and structurally building a construct that I think is going to last.

- I like your white board here. You wanna walk us through that?

- Sure, this is my example of a preoperative planning. So we have a whiteboard in our operating rooms, and this is exactly what my room looks like each day, when I'm doing one of these big cases. Now this is a patient that was getting a, it looks like a T4 to S1 and ileum, with a asymmetric pedicle subtraction osteotomy, a couple of Smith-Petersen osteotomies. You can see I've got Rs on here for where I want reduction screws. So I have a lot going on in this plan, and that really helps to think through it in that level of detail. It helps our residents and fellows stay on track. They help in the planning process. So it's a good teaching tool. It helps our O.R. staff and anesthesia staff stay on task and know where we are in a procedure, where we're likely to have blood loss and not. So I've got my goals of correction, and it looks like I drew that up just for this, but I do that every day we're doing a big operation and assessing what the patient needs. And when I have my goals on the board, I can really tell them in surgery with some x-rays, "Did I accomplish those goals?" And if I didn't, I reevaluate and see, is there's something more I need to do? That doesn't make it perfect, it doesn't make it easy to execute that plan, but at least I know where I'm going and at least where I want to be in the end. And I find that to be really helpful during these complex operations.

- Are those screw measurements preoperatively planned screw measurements, or what you've decided intraoperatively?

- Those are preoperatively planned, usually. Now I know a lot of people don't do that, and we use it as much for a teaching tool as it is a screw placement tool. And those are a rough guide. So, you can see some of those are 45 and 50 screws. I tend to try and place as big a screw as I can. Now, granted, there are some surgeons that really place really large screws through some pretty small pedicles. I try and fill the pedicle. So if it says 50 or 45 on there, I'm trying to upsize it by a little bit and trying to get a 55 screw in a lot of those levels. But it's really a guide to tell us, if it says I should have a 65 by 45 screw in, and I'm measuring a floor at 30, my trajectory's off, or there's something wrong with my screw. So I reevaluate and see, and that really is a guide to help us place screws. And it's a guide to help our nurses and our vendors, really, stay on task to know if I have a whole board full of 65 by fifties, they know they better get up to the storeroom and pull down some more 65 by fifties to make sure we have enough for the case.

- I have to thank you for this. This has been incredibly informative. And I feel like there's a lot of information that you've brought to the table that a lot of neurosurgeons really don't think about. So, even if this may not be a part of somebody's practice, I think just hearing these information sessions are incredibly helpful. And attending meetings and understanding other things that may be going on with their patients.

- I appreciate the opportunity. I really think spinal deformity is something that we all are going to see more and more of. And the more we pay attention to it, the more you recognize it. And it doesn't mean you need to be treating patients T4 to the ilium all of the time, but recognizing what's deformity and what symptom drivers are, it makes us all better surgeons. And the last thing we wanna do is create deformity, which oftentimes, half of what I do tends to be revision operations of things that tend to be slightly malaligned after an operation. And, nobody wants to have their patients undergoing revision surgeries. So, paying attention to that and knowing what is, and is not the appropriate alignment, I think helps everybody understand things more. And I certainly don't know everything about this topic, and I'm always learning more and more, but the more you pay attention to it, I think the better off we all are.

- Thanks so much. This is concludes another session, the AANS operative grand rounds, and we look forward to the next one, have a good night.

- Thank you.

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