These are my disclosures. I haven't managed to pick up any other deals during the lunch break. And again, a lot of these principles are in the handout, the paper that I passed around a copy of earlier. So you can go back and read through it at your leisure and there's actually more details even in this review and you can learn more about these parameters and how you apply them to planning your cases. So the first case, and it goes along, they go in order in your handout. The first case is a 70-year-old woman and she came in to me, or she initially presented not to me, to someone else. And she had severe back and leg pain when she stood and progressive difficulty with upright posture. And over the last several months had progressed from a cane, actually this is how she presented to me, I'm sorry, cane to a walker to a wheelchair. So when she came in to me she was sitting in a wheelchair. She had diffuse lower extremity weakness, in part due to deconditioning, didn't have any bowel or bladder symptoms. And she'd had a number of surgeries in the past as you'll see from the x-rays when we start going through them. She'd had an L45 T-lift five years ago for back and leg pain. Someone had worked on her neck as well, did a corpectomy, and then had an L12 T-lift ten months before she came to me. And ever since she had that L12 T-lift something just didn't quite go right and she hasn't done well since then. She's not a healthy patient. She has significant osteoporosis, coronary artery disease. She's had an MI. She has a pacemaker. She has a stent. You name it. And this is how she looked after, I had some x-rays from before she presented to me. And this was how she looked after the outside surgeon had done an L45 T-lift. And you can clearly see that it had frank pseudoarthrosis at that level. And that's the x-rays that were following a subsequent T-lift when she broke down at the upper level. But you can see that after her L45 T-lift she subsequently developed L12 stenosis and compression fractures. And you're seeing the signs of her osteoporosis. And they thought it would be a good idea to maybe do an L12 T-lift and leave some floating segments in between. And they for some reason got a CT after their L12 T-lift. You can see there's cement they used to support the screws, which is I think an off-label use. And it's dribbling down in the canal as well behind the vertebral body. And this is how she presented to me. It didn't quite hold together, as you can see. The screws are pulling out and it's collapsing down. But that's not the point of the case. The point of the case is for you to then be able to do the measurements. Because when she comes in, you'd certainly want to get full-length x-rays on her to see the whole picture. You can see all the work that's been done in her alignment. You can see her CT myelogram. She has pretty bad stenosis at this level. And this vertebral body is pretty much collapsed down and decimated. So it should be the first sheet is how do you draw a coronal alignment? So just take, if you would, the first page on your handout and just draw how you would assess the coronal alignment on the AP x-ray. Obviously you can't measure unless you have a ruler and you have no scale. But it's just more or less drawing the lines so you can get comfortable knowing where you draw them. They get harder than this, don't worry. So the way you measure it is you draw a C7 plumb line. So you find the center of the C7 vertebral body. And you just draw a line straight down from there. You draw a line, the central sacral vertical line, which is down the center of the sacrum. And the offset of those two lines is the coronal alignment. And when you hang these x-rays, the full-length x-rays, the AP, the left should be on the left and the right should be on the right. That's just a standard way of hanging these x-rays. And in figures and manuscripts, that's the way they should be displayed as well. And if you display them that way, if the C7 plumb line is offset to the left side, then it's a negative value. And if it's offset to the right side, it's a positive value. So in this case, the coronal alignment is a minus 2.1 centimeters. How about from the sagittal alignment, the C7SVA, how would you measure that? And would you consider her significantly coronally malaligned there, a minus 2 centimeters? Do you think that's significant? Probably not. I mean, any offset is abnormal, but patients generally can tolerate a couple centimeters either way. And then as you get beyond that, up to four, then people start getting symptomatic from it. Okay, so the C7SVA, okay. So in a similar way, you find the center of the C7 vertebral body, drop a straight plumb line down, and then look for the posterior superior corner of S1 and measure that distance from that corner to the C7 plumb line. And again, typically for these kinds of films, we hang it so that the patient is facing toward the right. And if the C7 plumb line is to the right side of the posterior superior corner of S1, then it's a positive value. If it's behind it, it's a negative value. So in this case, it's a plus 2.8 centimeters. Does that make sense to everyone, how you'd measure that? And what about 2.8 centimeters? Do you think that's, is that normal or is that abnormal? Yeah, it's probably not too bad. So she's compensating, but that's not the whole picture, as you can probably guess. So if you go on to the next page, let's start looking at the pelvic parameters to see what's going on there. So the first thing we do when we want to measure our pelvic incidence is we draw a line along the sacral end plate and then draw a perpendicular to that line and then also draw a line down to the head of the femurs. And that's our angle for the pelvic incidence and our angle is there and it's about 54 degrees. Is that, would you say that that's a normal pelvic incidence? How about right there on the front? Does that seem like a normal pelvic incidence? Close to normal? What's normal for pelvic incidence? Yeah, well actually, it's a trick question because there really isn't so much of a normal pelvic incidence. It's sort of just what it is. So there really isn't. It's a trick question. Sorry guys. But there really isn't a normal necessarily. Certainly people who have a high pelvic incidence, they're probably going to be more prone to developing a flat back because they're going to need more lordosis. They might even be more prone to developing a spondylolisthesis or a lytic spondylolisthesis just because of the sheer stress. So in that sense, you could say a high pelvic incidence may set them up for a little bit higher risk of pathology down the road, but there really isn't a normal pelvic incidence. What about the pelvic tilt? How would you draw the pelvic tilt here? Yeah, it's pretty. It's actually, once you've got this drawn on your screen or on your sheet, on the packs, all you have to do is just draw a vertical reference line from the head of the femur straight up and there's your pelvic tilt right there. So it's really kind of a zigzag and that gives you both of your measurements. And since the pelvic incidence is equal to the pelvic tilt plus the sacral slope, if you measure two of them, you know the third one. Yeah, it's nice. Thanks for sharing your patience with me. I knew you could do well. Especially the cement that's in the canal, it was a very nice touch. So then sacral slope, sacral slope you can draw on there too. It's simply, all you need is a horizontal reference line to the sacral end plate and there's your sacral slope. So once you get used to drawing that, I usually draw out my pelvic incidence first because then all you have to do, as someone mentioned, is put a vertical reference line and there's your pelvic tilt and a horizontal reference line and there's your sacral slope. This can take all of 30 seconds to measure on a PAX in clinic. And in her case, so would you say that pelvic tilt is normal? I'll go back to you. What do you think? 39 degrees? No. Yeah, exactly. This is elevated. This you would typically want less than 20. And so this is an individual who, although she's keeping her C7SVA normal, she's only plus 2.8 centimeters, she's retroverting her pelvis fairly significantly to be able to stand up. And I can tell you, she wasn't able to stand up very long. She was primarily in a wheelchair. And so in this case, as you would expect, the pelvic incidence is equal to the sum of the pelvic tilt and the sacral slope, as you would expect. And so you can then measure the pelvic incidence and lumbar lordosis mismatch. So that's the next sheet. Looks nice, doesn't it, Charlie? That's nice. And so we've already measured out our pelvic incidence. We know that's 54 degrees. And when I measure lumbar lordosis, I usually go to the inferior end plate of T12. There are some people who will measure from the superior end plate of L1. I don't think that typically matters as much because there usually isn't much of a difference between the inferior 12 end plate and the superior L1 end plate. But I do think it's important when you're measuring your lumbar lordosis, make sure that you measure it from the S1 end plate because a lot of your lumbar lordosis is occurring at those lower levels. And if you just do like an L1 to L5 to measure your lumbar lordosis, you're missing all of it at L5, S1, which is a big part of your lumbar lordosis. So I draw a line from inferior end plate of T12, line along the sacral end plate. And in the old-fashioned way is to draw perpendiculars, but with a PAC system, you don't really need to do that. You can just draw the end plates and it will give you the angle. So in this case, the lumbar lordosis is about 8 degrees. So that's a mismatch of, if we do the math, of 46 degrees. Does that seem like a normal mismatch? Winston, what do you think? Yes, 46 degrees? Does someone else want to give it a try? It was abnormal, yeah. What's normal? Within about 10. Yeah, okay, sorry, I didn't hear. So she's got a significant mismatch between her lumbar lordosis and her pelvic incidence. So the way I managed this was to basically take her apart. I removed her screws. I did an L2-3 SPO, an L5-S1 SPO. I took her down to the ilium and I took her up to T10. And as of now, she's holding together nicely. I just saw her back, actually. She's out three years now, a little over three years. I saw her back a couple weeks ago and is still doing exceptionally well. She's complaining she has some neck pain now, which is a good sign that she's no longer focused on her back. Okay, now the second case. We're going to go through three of them here real quick, some repetition. This is a 54-year-old woman, comes in with back and leg pain when she stands, difficulty standing upright, and she quickly fatigues whenever she's up on her feet or walking. No motor weakness, no bowel or bladder symptoms. She's had some lumbar laminectomies. As pointed out in one of the earlier talks, anytime you see a lumbar spine that has like zero degrees or almost zero degrees of lordosis, it looks that flat, there's probably going to be something wrong. So if we go to the sheet and draw out the chronal alignment, the lines for that, you can see if we drop the C7 plumb line in her case and the central sacral vertical line, you can see that she's pretty chronally balanced. And again, it's off to the left side, or let me see, she's to the right side, so it's plus 1.8 centimeters. So she's fairly chronally aligned. How about her C7SVA? An SVA is sagittal vertical axis, if you don't know what that stands for, that's another name for that. And so we drop that C7 plumb line again from the center of C7. We find that back top edge of S1, and that distance in her case is plus 13 centimeters. So she's off, positively sagittally imbalanced. How about her pelvic incidence? And I think the femoral head is here, and then I think there's one right next to it. So they're almost superimposed, depending on how you look at it. And so for pelvic incidence, again, we find that sacral end plate, draw a perpendicular to it, and draw a line down to the center of the femoral head, and that's the angle. It's 64 degrees in her case. And then how about pelvic tilt? We just draw a vertical line straight up from the femoral heads, a vertical reference, and that gives us an angle of 34 degrees. So is that normal? Probably a little bit high for her. It would reflect some pelvic compensation. And then the sacral slope, just draw in our horizontal reference line, and that's 30 degrees. And that adds up to 64 degrees for pelvic incidence, so 30 and 34 degrees. And her mismatch, if you measure that out, we've got her pelvic incidence already of 64, and the lumbar lordosis is 30 degrees, and she has a mismatch of 34 degrees. And when we talk about osteotomies, we can start getting an idea of what kinds of osteotomies you may think she needs, depending on her stiffness and on how many degrees you might need to try to restore her match between her pelvic incidence and lumbar lordosis. Okay, and so for the last case, it's a 64-year-old man with back pain, difficulty standing upright. He fatigues when he walks any distance. No weakness, no bowel or bladder symptoms. He had an L5-S1 MIS-T lift that was done elsewhere. And you can see his AP and his lateral full-length imaging studies, AP and lateral lumbars. So the next is to draw the lines for coronal alignment, and that again is the C7 plumb line and the central sacral vertical line, and that distance is minus 0.9 centimeters, so fairly coronally aligned. How about the C7 SVA, the sagittal alignment? Sometimes it's hard to see. You can change the screen parameters on your PACs, and you can see the C7 a little bit better. We drop the C7 plumb line, look for the posterior superior corner of S1, and measure that distance, and it's plus 18.5 centimeters. And how about the pelvic incidence? This is a nice one where you can see the femoral heads are almost superimposed here, so this is nice. So we draw our line on the sacral end plate, perpendicular to that, and then the line down to the femoral head, 58 degrees. And pelvic tilt, it's just a vertical line straight up from the femoral heads. In this case, it's 14 degrees. Is that a normal value, or is that kind of low? Normal, exactly. It's within normal range. And then sacral slope, just draw the horizontal reference line, 44 degrees, and they sum up to the pelvic incidence. And in the mismatch here, in this case, we've already done our pelvic incidence, that was 58 degrees, and you can measure out the lumbar lordosis, again, remember going from the superior end of the sacral end plate, superior end plate, and that is 35 degrees, and so he has a mismatch of about 23 degrees, so he has a mild mismatch between his lumbar lordosis and his pelvic incidence. And just as a quick plug, there is software that can help in planning surgery, and this is SurgyMap software, I have no stake in this or any conflicts of interest. I work with some people who do own this software, Virginie LaFage and Frank Schwab at NYU, and they have contact information there if you were to be interested. It's freeware, you can get it online for free, and it's pretty powerful software to play around with, where you can take the image and tell it what you want to do. You can draw out the pelvic parameters, just showing the femoral heads here, and finding the centers of them, and so it'll draw the pelvic parameters for you, and then you can tell it what you want to do, what you want to correct. Say you want to do a PSO at this location here, you can draw out where you want to do your PSO, and what the software does is it'll make all of the adjustments for you, and then it will, in real time, update what the pelvic parameters and what the alignment parameters would be predicted to be after the surgery, if you did that surgery. So it can be very nice to help plan, you know, would a PSO in this location, what would it do to my pelvic tilt, what would it do to my global alignment? And they've gotten quite sophisticated with this software, and it actually does a pretty good job at predicting what it's going to be like in the end. Nothing's ever going to be perfect, but it can help give you an idea, is it okay if I did an SPO here, would that give me enough realignment? And so this is, again, you can simulate your planning, showing the person before sagittal malalignment, and then you simulate an osteotomy, a PSO at the L3 level there, and then the actual case turned out fairly similar to what was simulated based on the surgery map. And so that's just free software that's available out there. If you're interested, I can give you the contact information and you can download it. Okay, so now you're all experts in pelvic parameters, so hopefully you'll start using them when you're looking at x-rays in the clinic, and it starts giving you some information about is there more going on, because people can compensate for a significant sagittal spinal pelvic malalignment.

pseudoarthrosis

stenosis

SurgiMap

pelvic parameters

spinal alignment