Here's what I see when I'm in in my academic practices. Sometimes people do laterals and they do the posterior percutaneous fixation and they're not paying attention to the sagittal balance and that's a very big problem because then what you end up doing is fusing people into a flat back. The concepts of when to utilize these kinds of techniques and when not to is very important and I'm not sure that a lot of people get that just yet. So there's been some work through this International Spine Study Group, the MIS arm, to try to look at some of these kinds of issues, to try to give us some guidance and maybe an algorithm on how to select patients appropriately for when to consider minimally invasive surgery. You saw my disclosures earlier. Basically the issues are this. Here this is a reason why we would think about doing less surgery for adult spinal deformity. Justin showed you some pictures of open deformity surgery in his practice. I find that curious since he was a Fessler fellow how that ended up being that big and wide open, but it is what it is. And the pseudarthrosis rates can be problematic. Complication rates are high. This has been reported in a number of different articles. This is our article from some six years ago looking at some of the cases that we did with open PSO and here's all the complications that we found in the literature as well as some of the things that we've experienced. Durotomies, coagulopathies, cardiac issues, neurological deficits, infections, altered mental status from being under anesthesia for so long, urinary tract infections, hematomas, DBT, PEMI, etc. So there's a number of things where we could potentially have an impact on complications. Schwab looked at an article in European Spine Journal, risk factors for these major perioperative complications. Justin and I were both co-authors on this, but basically what ended up happening is here's the issues that were found not to have a significant impact on complications. The demographics of the patient, their vital signs, their ASA score, their cardiac disease, common comorbidities. These were not the major issues that correlated with the complications. What was the major issue that correlated complications was the number of stages of surgery you had and the type of surgical approach you had. So these are surgeon controlled parameters. They are not patient reliant parameters and so it's more procedure related than patient related, these kinds of complications. So what I can tell you is that if we're not having too much problem with the BMI, the age, the sex, and the ASA score, and those do have a role, but they didn't have as major a role as the procedure related risks. The number of stages of surgery and what kind of surgery that you did. So for these kinds of reasons people started trying to do some of this stuff MIS to try to control these surgeon control parameters. And in degenerative spine disease what happens is there is a measurable impact if you do it MIS versus if you do it open. So in degenerative disease for single-level surgery, the hospital stay, the EBL, those are pretty much lower in MIS cases for TLIF for example. Most of the patients who are candidates for an open TLIF and for an MIS TLIF are pretty much the same patients. The issue is does this hold true for MIS and open deformity surgery? And the answer is no. Patients who you can treat with open deformity surgery sometimes cannot be treated with MIS deformity surgery. I think that's a key take-home message. There are some people who shouldn't have this kind of MIS type stuff if they have certain parameters and if you do it for them you're gonna probably predict failure and re-operation. So just looking at the DGEN literature and Jason Chang was one of our residents who last year helped me look at some of our MIS TLIFs at UCSF and what we found was length of stay is shorter. Because the length of stay is shorter the overall global cost of hospitalization is smaller compared to open TLIFs and the long-term outcomes are similar and they had less EBL, less transfusions. So does this hold true for MIS? And here's all the questions you have to ask yourself. Can you decompress these patients? Can you place hardware? Can you correct sagittal balance? Will you match the LLPI within 10 degrees? And these two questions are not asked by a lot of people who do these MIS surgeries. Is it going to take a long time to do and are you going to get a pseudoarthrosis? This is a problem that I've had where if I didn't do an inner body at every level I ended up getting pseudos because you have an incision that's really small, you got just about this much view of the facet joint trying to pack some bone in there and a 65-year-old is not reliably getting a fusion. So in 2010 was probably the first time that you saw a number of publications on this kind of topic and it was a neurosurgery focus in 2010 where a number of MIS articles and Neil Anand had one and if you look at his article here's the problems that he had at that time. He had dysesthesia from the lateral approach, he had quadriceps palsy from the lateral approach, from the lateral approach a hematoma near the kidney from moving the kidney around, there was one remote hemorrhage in the brain, screw prominence, screw fractures, a number of issues with doing these kinds of cases MIS. And this is the article from Tormenti and these guys, he's with Adam Cantor and David Aconqua at U-PIT and they do a lot of lateral approaches in patients who have deformity. And what happens when you have deformity is not only is your spine rotated around, but your abdominal contents are rotated around too. So as a spine gets rotated, the bowel gets rotated. As a spine gets rotated, the iliac vessels are rotated. So you come in on your routine lateral approach and I know there's a lateral talk here by Sancer later today I think, but as you come in on your routine lateral approach, structures that you don't expect to be in the way of your surgery are suddenly in the way of your surgery. And so this is how they ended up with a bowel perforation. Didn't even know about it during the case and figured it out later when the patient became quite ill. So we have to watch for how are these abdominal structures going to be rotated in the field because the normal anatomy is no longer normal in a deformity case with a lot of rotation. This is an article from Uribe's group in Tampa and basically what they saw is that they were very good at correcting the chronal curve, they were not good at correcting the sagittal plane. So this is not the curve that you want to focus on. What you want to focus on is the SVA that I talked to you about this morning, trying to get that back to normal, matching the LL to the PI. Because in those times people who did a lot of this kind of surgery didn't understand that, what they ended up doing is one-third of the patients in their series did not have sagittal balance restored. So the coronal correction is not that important as the sagittal correction. So we've got to keep these things in mind. Not everybody who has one of these coronal curves is a good candidate to have it fixed through a lateral approach with the posterior percutaneous fixation. Another thing that happened in this kind of a case is over time some of these screws fractured and it depends on how well you're going to get a fusion. If you don't get a fusion, the hardware is going to give. Mike Wang and I looked at our series of about two dozen patients back then in 2010 and we had a very high pseudo rate every time we did not do an inner body fusion and we did posterior percutaneous fixation. So this business of trying to put a tube down and a 70 year old rough up the facet, Pax Miliac autographed in the facet, didn't work out for us real well. We had a number of patients who had pseudos and loosened screws and so we needed to figure out is there an algorithm of when you should consider doing these kinds of surgeries for deformity patients and so we came up with this and was just published actually this month in Neurosurge Focus and there's a number of articles in this month's Neurosurge Focus from some very well-established deformity groups and I would urge you to look at it. It's free online of course you can pull it up pretty much here in the room if you want. This is one of the articles of when to do MIS deformity surgery. So basically if you have an SVA of less than six centimeters and you have a pelvic tilt of less than 25 you have essentially a moderate deformity and even if your SVA is more than six centimeters they lie down it corrects nicely and you have a flexible curve again with the pelvic tilt to less than 25 again a moderate deformity. If you have such a mild deformity that you don't have any LLPI mismatch, you don't have any lateral slippage, you don't have a big coronal cob angle, you certainly could decompress that patient through a tube not even have to put any hardware in a lot of cases or if they have a bit of a listhesis you can do a single level fusion. So you can do a fairly small surgery with a low SVA, normal pelvic tilt, a really really good LLPI match, no listhesis, no coronal cob problem, small surgery maybe even without hardware be just fine. What about if they have a pelvic tilt of less than 25 but they have LLPI mismatch up to 30 degrees and if they have that problem you can basically end up doing what you see a lot of being done nowadays lateral approaches with percutaneous screw fixation. However they have a very high SVA, a very rigid curve with a massively big pelvic tilt of like 30 degrees and LLPI mismatch of 40 and 50 degrees with the thoracic hyper kyphosis. These are cases that are going to predict failure if you do them with MIS. You're not going to be able to achieve those kinds of parameters. Those cases should be done open in the way that Justin was shown pictures because you're just not going to get from here to there especially if they got old hardware in there and you have to go dig it out. These are the ones basically that we need to focus on for the majority of patients who are candidates for this kind of surgery. The apex of lumbar curve is going to be included in the instrumentation. The LLPI mismatch is somewhere between 10 and 30 degrees. They may have a grade one or two listhesis either lateral or anterior listhesis. Their pelvic tilt is relatively small at less than 25. They have a coronal cob angle of more than 20. These folks do pretty well if you do a lateral and percutaneous fixation. This is the group that we need to focus on. These are the kinds of cases that will be done well using this kind of approach because there's a ceiling effect or a limit to how much you can get away with with MIS. And Mike Wang had a very nice paper and again this month's Neurosurge Focus where he looked at what is a ceiling effect? How much can I do and where can I stop? And basically found those parameters I just talked to you about to be the limits. That if you start having really bad SVA, high SVA of like seven centimeters, eight centimeters and you have an LLPI mismatch more than 30, then those cases were not getting done real well with MIS. So don't try to do those with MIS. So this is the kind of case you don't want to do with MIS. It's a patient who has a lateral listhesis and an anterior listhesis. I didn't show you the coronal here but has already got hardware in here, PJKed over the top. We're not going to be able to get this SVA corrected MIS and get this hardware out MIS. We're gonna have to open this case and we ended up doing a VCR for this patient. But these are the kinds of cases that predict failure with MIS. Can you do iliac fixation MIS? Yeah you can put in all your lumbar pedicle screws. You can put in your iliac fixation. You can do all of it MIS if you want to. What cases need to have iliac fixation? What are the characteristics of your operative plan that are going to tell you that you need to have iliac fixation? Let's have a volunteer. Indications for iliac fixation. All right how many of you at your home institution do iliac fixation? Okay when do you do it? You got person in the back, way back there. Long being longer than what to S1? Into the lower thoracic. Okay I would say L2 or more to S1. Okay that's one. What are there what that's one good reason why you should do iliac fixation. What's another? Yes you have pseudoarthrosis loosened S1 screws. Absolutely. What is the purpose of the iliac fixation? So you want to get your L5 S1 to heal without loosing your S1 screws. Is the SI joint going to fuse if you put in iliac fixation? What happens two years after you put in an iliac screw to that iliac screw? Is that going to be a good solid fixation in two years from now? No it's not because you're not fusing across the SI joint. We don't put bone graft across that joint. It's massive. It's really big. So what ends up happening two years after your iliac fixation is if you go back and you do a CT scan or an x-ray a lot of times you can see haloing and loosening around that iliac screw. That iliac screw is there as a temporary stabilizer. It's there to temporarily stabilize your S1 screws, give some structural rigidity so you can achieve a solid L5 S1 fusion. That's the purpose of it. And when do you need it? Constructs bigger than L2 to S1 is the primary time you need it. Cases where you don't have good S1 fixation. High grade listhesis cases. Cases where you can't even grab the sacrum because it's destroyed or fractured. Those are the primary reasons why you need to do iliac fixation. So it's important to keep in mind the indications before you just do the surgery. So I think a lot of what happens that I see our residents doing and sometimes people come to the courses, they're so fixated on the techniques that they're not thinking about the indications for the techniques. So you've got to take a step back and think when do I need this? I have an armamentarium. It doesn't apply to all the patients. So just because you have a hammer doesn't mean you're going to want to hit every nail with it. So some nails don't need a hammer. And so you've got to figure out when to do it. But you can do iliac fixation in two different ways now. Most commonly it's done is you put a sacral, excuse me, an iliac screw or you can put an S2AI screw. And these are the different trajectories for each and you can place both of these MIS. And so an iliac screw typically from the PSIS is one centimeter superior and a centimeter deep to the PSIS. And then it has that trajectory here in the blue. And basically we'll go over the greater sciatic notch. Now what happens when you penetrate the greater sciatic notch? What are you going to hit? It's a mumbling but someone speak up a little bit louder. Sciatic nerve, okay. What else are you going to hit? That's right, superior gluteal artery. And if you hit that what ends up happening is that vessel, if you cut it, will retract up in the pelvis and keep bleeding. So Zia I think had a case where he had to have IR going to embolize that vessel because he couldn't get it. So we don't want to be in the notch. We want to get this thick bone right above the notch. So you want to get close but not in. So this again is the entry point for the S2AI screw. That's going to cross the SI joint and it's going to end up going over the greater sciatic notch. But those are the issues that you've got to think about. You can do it MIS as well. So one thing that I see at our place is that people don't like to push the gear shift. So they take a mallet and they start hitting it. You lose all your feel if you use the mallet. But some people have thick pelvis and that's what you end up having to do. But you got to be careful. An AP view is also a nice way to make sure that you miss it. So this is placing at MIS. Basically if you think about doing it MIS and you look at a pedicle MIS, a pedicle, if you do an end-on shot, looks like a circle and this looks like an oval. And so long as you're within the oval you can put your Jamshidi there with the operator outlet view and you can do this MIS as well. And Mike and I published a paper of looking at that in a couple dozen patients. And I'll show you a video basically of doing this kind of surgery and someone who qualifies for it. So it's a 64 year old with back pain, leg pain. Here's his preoperative imaging. He's got bad stenosis, multiple levels. You can see he's got a relatively flat back. We measured his coronal cob angle at 22 degrees. His SVA is a little bit high at 8 centimeters. He's a bit of a thin guy though. His lumbar lordosis is 28. His pelvic incidence is 68. So he needs about 30-40 degrees of correction. So this is a bit more than you can get with the average MIS surgery by itself. So I ended up starting with an A-lift with some hyperlordotic grafts in the front. And then I put him prone and I did the posterior part with T-lifts. I wanted to get an inner body at every level if I could because when I don't get an inner body at every level I was having pseudoarthrosis. So basically I make a skin incision here. I leave all the fascia intact. And it is an option of course to make multiple stab incisions. You could do that too and it looks like the train tracks ran up and down somebody's back. But if I have a single midline skin I leave the fascia intact. It usually to me is easier to deal with. So now I'm going to be dilating to put down my tubular retractor and do the T- lifts. So we dilate the paraspinal muscle. The spinous processes are here. This is sacrum down here and this is going to be the L1 area up here. So putting the the expandable tubular retractor there, what I'm basically doing is docking this on the facet joint. How many of you do MIST lifts at your institution? You know I'm interested to see that lateral approaches are being done more than MIST lifts in a lot of institutions. From what I can see of your audience polling, interesting to me since MIST lift has been around for a bit longer. So I'm getting the muscle off the facet joint. I put down the tubular retractor. So as you can see there's not a lot of bleeding going on here. And then by expanding it a little bit now I have access to do my decompression through the tube and I have access to do my T-lift through the tube. So I chose which side to do the T-lift based on where the foraminal stenosis was. So at this level the foraminal stenosis was more on the right. You'll see I'll put another tube in on the left. This because of the level above the foraminal stenosis is more on the left. So we were able to do simultaneous T-lifts, the fellow and I, and this is John was my fellow that year. Here we're taking off the facet joint or I'm taking off the facet joint. John's about to take off his facet joint. He likes to use a drill. So I save all the local autograft. People ask me sometimes where do I get my bone graft. I don't make a separate incision on the pelvis. Through this midline skin incision if I take an Army Navy and I lift up the iliac crest is right there and I can harvest a whole bunch of it. And so I usually do that. So here's the A-lifts from before. This is the T-lift here. I take a lot of time to make sure I get that disc out and I scrape those end plates. Because you can do a T-lift and take out like a third of the disc and squeeze the cage in and get a pseudo or you can take your time and get all the disc out and then make sure you get it full of bone and have a much higher chance of effusion. And so for me I don't want to have a pseudo. So this is why I ended up doing that. Now I've already cannulated screws looking through the tube and putting in pedicle markers. You saw that there. I don't put the screws in while I'm doing the T-lift because the heads getting in the way. And this is a little bone funnel and you'll just see how much bone I start putting down this funnel to get into the T-lift. And so I pack that funnel full of crest. You see John doing the same thing. He's getting the disc space shaver in there and he's going to clean out that disc. Now I put in my cage. My cage is full of bone graft. Meanwhile the other side is pretty much ready to go now too. So here we have the T-lift here. We're doing a T-lift in here too. Here's a cage going in on the other side. Again this is for a class 2 type deformity in that algorithm I was showing you. Now we're going to do some pedicle screw fixation. This guy had hard bone and the little awl was bouncing off of it so I do use a little drill. And I have a cannulated gear shift. You could just do it with a with a jam sheeting needle and putting a K wire down the jam sheeting needle if you want to. That's another way of doing it. All kinds of variations on this theme. But so here I have a cannulated gear shift and I put my K wire down the center of it. Here you see all these percutaneous screws on that side through the fascia. There's a couple over here. Now I can tap over it and put the put the screw down over the top. Notice again not a lot of bleeding going on here. What's the number one issue of this is like how much fluoro you get and how much time you take. And as you get better at it you figure out ways like with the cannulated gear shift to use less fluoro. So you don't get cataracts later. There's a certain number of shots of fluoro you're going to take before you get a cataract. This is tapping over the K wire. Notice that I bounce the K wire up and down. Why? Because if you tap you don't have the K wire bouncing up and down. You can grab the K wire and push it out the front. What lives there? The iliac. So that makes for a bad day. Mike Wang had a case report where he didn't have the K wire and the tap perfectly coaxial. And so the K wire is at an angle to the to the tap and as he tapped it sheared off the tip of the K wire and left it in the material body. So all kinds of things can happen if you don't pay attention. So you got to pay attention by bouncing it up and down. I call that the K wire dance. I make sure that the K wire is not getting bound up and it's not going to get sheared off. And then putting the screw in over the wire. So now that the hardware is in, take basically a lordotic rod and we can put it in there. And we can by doing a rod placement and derotation. And then I use these extended tab screws. But basically you can dial the screws down and it will correct the spine to the rod. So put the lordotic rod in. That's also something that with a little practice gets much quicker. A lot of it was because I had two A lifts and those two T lifts. But the rod did get some. The rod gets me the derotation. Now we put in our set screws and essentially do the correction. So you basically get the idea there. I'm not going to take up all your time with the video. But I think the takeaway points here is that PI is a fixed parameter. The pelvic tilt is a temporary compensating mechanism. You must have the same goal whether you do it open or MIS. If you're not going to achieve this don't do it MIS. You got to be in that class 2 of deformity. You want to match that PI within 10 degrees of lumbar lordosis and get your SVA corrected within 5 centimeters. So I think this is helpful for class 1 and 2 mild to moderate deformities to do at MIS. You must restore sagittal balance. It's not great for cases that currently need a three-column osteotomy to really get the correction. Thanks very much.

sagittal balance

minimally invasive surgery

patient selection

spinal deformities

iliac fixation

surgical technique