I think the talk on pedicle screw fixation actually segues pretty nicely into this talk in regards to posterior lumbar interbody fusion, the PLIF, and the transforaminal lumbar interbody fusion, TLIF. I'd like to thank Pat and Praveen for inviting me to give this presentation. Can I ask, how many people have done PLIFs here, resident-wise? Quite a few. I'm actually surprised. I thought TLIFs would be pretty popular. How many have done TLIFs? So, definitely more. So, I think now these are very standard procedures. Here are my disclosures, which don't have any bearing on this talk. So, why interbody fusion? Well, it preserves load-bearing capacity. It facilitates compressive loading on bone. It can restore disc height. Definitely restores sagittal alignment. Combined with pedicle screw placement, it stabilizes all three columns of the spine. And biomechanically, it's definitely superior to posterior lumbar fusion. It's definitely more rigid, particularly with pedicle screw fixation. So, there are multiple options for interbody fusion now. Anterior lumbar interbody fusion, I think everybody's familiar with. Originally attributed to Southwick. The PLIF, originally described by Cloward back in 1945, so 70 years ago, and modified by Lin in the early 1970s, which made it become more popular. It was an easier method of doing it than Cloward's original technique. Transforaminal lumbar interbody fusion, TLIF, was really popularized by Harms. It was, in my opinion, a modification of the PLIF. Again, made it easier to do, I think, technically, and thus its popularity. You know, for lateral lumbar interbody fusion, I don't know anybody exactly. I think Louis Pimenta is probably the one who's promoted it the most, so I'm going to attribute it to him. I really couldn't tell with axial lift, and I'm not entirely sure if people still do them. So, we're going to really focus on the PLIF and the TLIF. So, I always like looking back in history, I think. And this is one of Cloward's original articles on PLIF, and it was published in 1953, Journal of Neurosurgery. Cloward, you know, popular for the ACDF, too. We use, typically, the Smith-Robinson technique, but Cloward had an ACDF technique as well. And I didn't know he lived in Hawaii, but he did, so great place to live. And this is his original diagram, and as you can see here, he advocated definitely a partial laminectomy, basically a complete facetectomy, and retracted a dural sac to allow the view of the posterior disc space here, and this is where the autograft was implanted. You can see him doing the discectomy here with retraction. This is how he did the interbody fusion. So, he harvests his cancellous bone from the other crest, and oxytocin cuts it to take three basic plugs in the wing of the iliac spine there, and then he just impacted it into the disc space. So this is 1945. I don't think we're much different now when we're doing PLIFs in general. But it really was not popular, and the reason why is, if you look at Cloward's original technique, he's doing complete facetectomies without any sort of fixation, so there was a risk of spondylolisthesis with that, so you're creating pars effects, essentially. And so, Lin's technique was a modification. This was published in Neurosurgery back in 1972. It was not actually doing much of a facetectomy, so it was less surgery, and in a way, it retracted nerve roots and dural sacs more, but without doing the facetectomy, there was less of a risk of a listhesis. So, it actually became more popular. Otherwise, it's very similar to Cloward's technique if you look at it. So, you know, often PLIFs these days are combined with pedicular fixation and postural fusion, so you get a circumferential fusion, anterior and posterior, through a single incision. And ideally or optimally, it's limited to the L3 to S1 levels, and again, it has to do with the amount of retraction of the dural sac. And one of the criticisms of this technique is the amount of dural retraction resulted in radiculitis from nerve root stretching or potentially even a nerve root injury, spinal fluid leaks at the axilla of the nerve root were purportedly fairly common with this procedure, and so it really wasn't recommended above L3. TLIF, very similar to PLIF, allows circumferential fusion, but the advantage of PLIF, and this is a purported advantage, is less or minimal thecal sac and nerve root retraction, which I think is true. You can perform it at upper lumbar levels, even thoracic levels. There are studies doing thoracic lateral interbody fusion, basically a TLIF version in the thoracic spine, just because you don't have to retract the dural sac very much. Less scarring, less bleeding. It's a unilateral approach, so probably less bleeding in the epidural space. I think it's faster, typically. You're only putting one implant in rather than two or three. Disadvantages over PLIF. I think you get less of a discectomy. Honestly, from one side, you're bleak. I don't think you do as good a job. And it is one cage placement. Some people would argue two cages are more stable. So what are the indications? I think this is out of a review article that was published a number of years ago. And I think acceptable indications, high-grade spondys, degenerative scoliosis, I don't think these are common indications, typically, for TLIFs or PLIFs. This relative indication is probably the more common indication for a PLIF, TLIF, low-grade spondys, recurrent disc herniations, DGN disease. These contraindications, I think, are relative these days. I routinely do this operation with people who've had scarring or infection cases, conjoined nerve roots. That's a challenge. So I definitely think that's a contraindication. But everything else here, severe disc space collapse, I really don't think is a contraindication anymore, particularly with the current instrumentation techniques, which are modifications of the original TLIF approach. So biomechanically, is there a difference in stability between a PLIF and TLIF? There's been multiple studies looking at this. Just one of the more recent ones published in the Journal of Neurosurgery by the Stanford Group. They took 14 cadaveric specimens, seven of which they did essentially a single-level TLIF at L4-5, consisting of a right-sided fascitectomy, whereas compared with a PLIF, again L4-5 with partial fascitectomies, all of these were combined with pedicle screw fixation. So this is the testing. This is pretty standard, you know, 6 degrees of motion, axial rotation left-right, flexion extension, lateral bending left-right. So these are the results. So when you look at it, this is L4-5, and the asterisk means statistically significant versus intact. So whether it's PLIF, which is a black bar, and two gradations of TLIF, so this is a posteriorly implanted cage and an anteriorly implanted cage, they all were statistically more stable than the normal specimen essentially, but not different amongst themselves. So only here, this is the pound sign, where the PLIF was more stable, so lateral bending, than TLIF. So this is looking at axial rotation. So better than the intact specimen, but not any different between TLIF and PLIF. So when you look at this, they're significantly more rigid. It's not surprising against an intact specimen, whether it's PLIF or TLIF. The PLIF by absolute numbers was more stable than TLIF, but only statistically significant in lateral bending. Now what does that mean? Is that a clinically relevant finding? So when you look at the literature, it's sort of surprising. PLIF has been around a long time. TLIF, probably popular for a decade or so, but there's no really direct comparisons except this one study I found. And it was a retrospective comparative study, but really no other direct clinical comparative studies. And published in the European Spine Journal in 2008, and they spelled PLIF wrong. And they go back and forth on doing that. PELF, I don't know, but they're definitely talking about PLIF. So, you know, it was retrospective. They actually had a fair number of patients, 176 patients, underwent single-level interbody fusion for grade 1 or 2 D-Gen spondy disease. And the groups are fairly comparable, actually. Not statistically significantly different on demographic levels. And just L4-5, L5-S1. When you're looking at mean follow-up, I think it was very reasonable. 29 months total for the whole group. And very similar between groups to 29.5 versus 29.6. They looked at two outcome variables when it came to clinical outcomes. One was the pain index, which was just the BAS score, 0 or 10. And very similar preoperative baselines. And very similar, actually, almost exactly the same improvement between groups. Japanese Orthopedic Association score for back pain was very similar in terms of the degree of improvement. So no difference between groups. And this is a radiographic comparison. This is the improvement in spondylolisthesis rate. So this is like 30 versus 7.3. So actually fairly good improvement between the both types of procedures. So in terms of sagittal alignment improvement, very similar. Reduction rate, this is just a percentage. And again, the PILF here, I don't know, but they see PILF in other places. The disc height restoration actually was much better. So they averaged about 5 millimeters of increased disc height with either procedure. So really no difference radiographically. They actually CT'd everybody. Everybody got a CT, and the criteria for fusion was continuity of trabecular bone across disc space. And they had the same fusion rates, 100% in both groups. Complications, this was really what was surprising to me. The PILF, everybody says it has more risks, more complications because of the amount of nerve retraction, but they really didn't have any statistically significant difference. So three in the total, and three radiculitis, two radiculitis in the T-LIFT group. And the one other complication in each group was instrumentation malposition when the pedicle screws were medial in either case. So very similar. So in conclusion, both procedures had improved outcomes. There was no difference radiographically or clinically for both procedures. So I just want to talk about technique a little. And this slide summarizes everything. So the PILF, more midline, straighted, T-LIFT, vasotechomy, oblique cage. And this right diagram just shows it to you. And so this is, again, from that review paper. And you can see with typically the PILF, at least most people do a fairly good laminectomy. It's a lot of nerve retraction, look at this. It's a ton of nerve retraction to get the cage in. And it's cage is easy, it's not autograft typically. And you want to do a good discectomy here. And initially, these were threaded cylindrical cages that were just screwed in. And in my training, we did these. And I recall retracting the drill sack like crazy because you had to go beyond midline, actually, because you wanted to be safe. You don't want to catch a drone and screw it in. And so a lot of retraction. This is pretty classic. But nowadays, with different cage technology, you're really probably talking about a peak cage that's bulleted, self-distracting cages that are implanted. But these were the variety of cages that have been used for PILFs. This is probably what's done these days if you're going to do a PILF. T-LIFT, very similar. Really, the only difference is this facetectomy here. And I just wanted to show here. Initially, there were these rounded cages or rounded pieces of bone that were placed obliquely and then pushed aside. A lot of effort, a lot of work. I've done this before. It's much more work than, say, using an oblique cage, which is actually probably what the standard is right now. So you get more disc-based distraction anteriorly, and you can compress and get more segmental lordosis. So there are a lot of options. But there's a lot of evolving technology that makes this technique, I think, simpler, and you get better outcomes. So I just have a video, and hopefully it'll run. I think video is always kind of helpful. So this is a patient we did. Grade 1 spondee, a good grade 1. And he's got high-grade stenosis associated with it. So this is a T-LIFT example. It's very versatile. With high-grade stenosis that this patient has, I would typically do a laminectomy with that. So you can see it's very high-grade there. So combined with the laminectomy, it's actually a very straightforward procedure. And actually doing the facetectomy makes the decompression a lot easier, particularly on the side of the facetectomy. Now the screws are put. I mean, this is pretty standard. You're putting your pedicle screws in. And then for orientation purposes, this is cranial, caudal, this is right, left. And we're doing a right-sided T-LIFT. So just remove the spinous process there, essentially. And I don't know if this projects well. So basically a laminectomy has been mostly done. So at L4-5, it's the L4 PARs we're going to remove. And so all you do is essentially a laminectomy, make a transverse cut through the PARs interticularis with the drill. We use an osteotome as well. It's fairly quick. So this is the PARs right here. So remember, this is cranial, caudal, right side. We're just cutting through the PARs here. And that disarticulates this inferior articulating facet. So the inferior facet of L4 can be removed fairly easily. You can actually save it as an autograph bone. So it's not a very long video, but you'll see. So the transverse cut is made. Now it's a mobile segment. That's the inferior facet being removed. And I think this is pretty standard. So it's a big knobby joint. A good autograph. And this is a naked facet right here. So that's the superior facet of L5. You have to be careful if you drill too inferior. You'll drill into the L5 pedicle. Once you do that, this is just showing the laminectomy. This is pretty standard here. It's not too long of a video. So then we do a complete discectomy. This is an important part of a T-lift. You shouldn't just put a rotate shaver in a couple times and impact your cage. How you do your discectomy is going to be very important in terms of outcomes. The better the discectomy you do, the better the end plate preparation. I think it's going to make a huge difference in terms of your outcome. So that's just ligamentum and laterally. We're not going to have to retract at all. So here's a traversing nerve root right here, L5. There's a lateral edge of the thecal sac. Look how much room we have laterally. This is pretty standard for a T-lift. L5S1 is even more capacious. It's not retracting at all. So hardly any retraction is required here. So just standard discectomy now. This is a fairly big disc. It's a rotate shaver that goes in and breaks up the disc a little so you can make your discectomy a little easier. It's not much longer in the video. You can see the segment is pretty mobile now. You can distract pretty easily. Taking time with your discectomy is very important. So once it's in, we're going to impact your trial in. Typically, they start at 8mm. Pretty standard 8mm trial. Notice we're not using pedicle screws to distract or displace at all. That tends to kyphosis spine. Sometimes you need to do it, but try not to. One important factor is you want to maintain your segmental lordosis here. So that's just a trial going in. This is an expandable cage, so that's just a threaded expansion. You can see it definitely improved discite restoration. So just preoperative. I think with the T-Lift in, disc space distraction, it's more segmentally lordotic there. I want to briefly talk about the pitfalls of T-Lifts. One of them, and this is a criticism that T-Lift has, is because the entry into the disc space is narrow, a lot of times people will distract out the pedicle screws to open up the disc space so you can do your discectomy and get a reasonably sized cage in. A lot of people try to go big, so we're in Texas, but that's true nationwide, a lot of people like to put a big cage in. I think the problem with doing that is you can't compress enough. A lot of times you end up with kyphosis, so you may even start out lordotic and then you end up neutral or even kyphotic and there's a number of papers looking at that. Or if you don't distract, you put an undersized cage in which subsides and limits your discite restoration and how much discite you get. So that's a pitfall of a T-Lift case and it's definitely a criticism. So this is an example of that. You start off 15 degrees of lordosis and you end up with 6 after your posterior base interbody. That's not uncommon. So I think one way to prevent that is try not to distract off your pedicle screws, and I think that's feasible in a lot of cases. Use intradiscal distraction. Osteotome is my favorite instrument when it comes to these T-Lifts. Sequential distraction immobilizes the disc space and once you do that, whether you use an expandable cage or not, which I think is also important, you can maintain your segmental lordosis or improve upon it. I have multiple examples of this. This is a patient's back, bilateral leg pain, L5 radiculopathy. He has a good grade, I would call that grade 2 spondy. L5 S1, complete disc space collapse. Here's an example. Intraoperatively, this is an MIS procedure, so you can see the 2. I'm just going in with the osteotome. Osteotome, once you get it in there, this is a distracting osteotome. You can distract the disc space. If you've done a fascitectomy, it loosens things up. Then you can just use paddle distractors, do your discectomy, and here's the cage going in. This is an older case of mine, so I didn't have expandable cages. Expandable cages weren't very common, but you can see here you've still got the slippage, but using the reduction capability of the screw extenders, you can reduce it completely. Then you're left with good disc cut restoration and you reduce the spondylolisthesis. This is him a year out. You can see the bridging bone. Clinically, he did fine. I'll give you a bigger example of this. This is a patient who had a pre-existing fusion when she was younger. She's 33. Her real problem is here at 5'1". This is a good grade 3, borderline grade 4 spondy. You can see the lumosacral angle here. You can address this with a T-lip. That's what I did here. You can see the spondy. She's got a grade 3 here. I'm using a curved osseotome because it's hard to tell here, but you're basically almost horizontal with this osseotome trying to get in. I put L4 LX screws and L5 S1 screws in. Here's the video. You use an osseotome on either end of the spine. You want to loosen it up, so I'm not going to show all that. The osseotome goes in and the segment is fairly mobile now. Then you put a paddle distractor in and you sequentially distract this. You're getting distraction. You're pretty ventral here. Remember, the vessels are going to be in front of the thigh body. Then you can start to reduce. This is a reduction set screw. You're reducing it back and you're improving the lumosacral angle here. That's decent, but you have the other side. I've already reduced off one side. This is a distracting osseotome that goes in because I'm trying to get a cage in. This ends up being a 6mm cage that goes in. Not that high, but enough to get a cage in. Then you can distract off the other end. You end up with this as a final. It's mostly reduced now and you've improved the lumosacral angle quite a bit. Here's a CT. It looks like a pretty good reduction there. Here's the pre. You can see the lumosacral angle. You can see it's almost robotic here. Her sacral balance has improved. It wasn't horrible to begin with, but it's much better. I want to talk about expandable cages. Besides the osseotome use, these are very helpful too. If the disk space is narrow, you don't want to pound a disk space in. You undersize the expandable cage and it expands into the area. You can compress beyond it. Just an example. This went in unexpanded and I'm expanding it. You can see it expands to the end plates. This is segmentally lordotic with disk height restoration. She started mildly kyphotic here. With TLIF, we're getting disk height restoration and segmental lordosis. Just another example. 5'1 becomes always an issue. This is not horrible, but it's collapsed. Same type of deal. You get 5'1 and wedges open like crazy. This is either a 10 or 15 degree lordotic cage that goes in. You expand to the area. It contacts the end plates and you get segmental lordosis. Here's a pre and a post. A lot of disk height restoration and segmental lordosis. In summary, both TLIF and PLIF are clinically very comparable in terms of outcomes. I'm a TLIF person so I'm biased. I think it's typically less type intensive. Definitely less dural sac and nerve root traction. I showed you that video. It really can be performed at any level in a lumbar spine. That's it. Happy to answer any questions. Thank you.

PLIF

TLIF

interbody fusion

spine stabilization

surgery techniques

study outcomes