Thank you. This talk is a nice bridge from what Tyler just spoke about. These are my disclosures. Just a quick cartoon depicting the general posterior osteotomy techniques. This is from an article that was published a few years ago on ankylosing spondylitis. We use the term Smith-Peterson osteotomy pretty cavalier, but if you look at the original Smith-Peterson osteotomy, the original description of it was an anterior column lengthening and posterior column shortening procedure at the same time. You get a pretty big correction similar to what you would achieve from a pedicle subtraction osteotomy when you have that anterior column lengthening. When you do what we colloquially refer to as a Smith-Peterson osteotomy today, it really is a polysegmental wedge osteotomy where you remove the posterior facet joints on both sides with midline lamina. These are the ponte osteotomies that you see. This type of correction achieves about 5 to 10 degrees per level, whereas this type of correction achieves around 30 degrees. This type of correction, as Tyler mentioned, is only achievable when you have some degree of flexibility in the spine. If you have a fixed sagittal plane deformity from ankylosing spondylitis or from a flat back syndrome, someone who's had a previous fusion and was fused into kyphosis, you're going to want to use a heavier duty osteotomy, whereas if you have some degree of flexibility that relies on, see how this disc space becomes short in the posterior aspect and is stretched to its limit in the anterior aspect, you need to have some degree of flexibility to your disc space in order to take advantage of these polysegmental wedge osteotomies. We're going to move on to a case just to illustrate these principles a little bit. This is an interesting case. A 59-year-old woman who had a previous T2 to iliac fusion that was done in California sometime and she moved to Baltimore and developed a pseudarthrosis at L2-3. She was treated by one of my former partners, and as a result of the treatment, she had at the time, what he wanted to do was a focal treatment at L2-3 where she had the pseudarthrosis and so a D-lift was performed at that level and because she was so solidly fused distally, the hardware distal to that was removed. While she initially did well from that treatment and had recovery of her symptoms, she started to develop progressive kyphosis and then presented to the ER with cauda equina syndrome. You can see over here, she's significantly imbalanced. This is where they did the D-lift and she still has her old hardware up from L2-3. From T2 down to L1 or L2 and then there's this L2-3 D-lift. Looking at the pelvic parameters, you can see that she's compensating a great deal with her pelvic tilt and you can see that she's got a significant mismatch. She's very, very kyphotic. The important point, which you don't appreciate until you see this on CT, is the fact that she had a very bad sacral fracture and that was part of the reason why she was so bent forward and kyphotic and the reason for her cauda equina was due to this as well. A pretty substantial problem. Basically, in order to address the sacral fracture, we plan to do instrumentation down to the pelvis. In order to address her sagittal balance, I decided to do a PSO at L1. This was the result. You can see that we got a good correction of her sagittal alignment. The plumb line goes down. Normally, she's standing straight and is doing tremendously better. You can see she's got some reconstitution of the lumbar lordosis. This is two years later. She's really doing a lot better. This is a CT scan from two years later showing that that sacral fracture has really amazingly healed and a very impressive ability for this woman to fuse. I think she has this natural predisposition to fuse. It's surprising to me that she developed this pseudarthrosis. When you go to the original CT over here, while I was intending to do a PSO, what really ended up happening was during the process of doing the PSO, she really ended up having an inadvertent SPO, one of the old-fashioned SPOs where you have that anterior column lengthening. You can see that this is a disruption of the anterior column right here. In the middle of doing the PSO, the spine suddenly snapped. I noticed immediately that the correction was achieved instantaneously. It was actually the easiest PSO I've ever done because of that phenomenon. Fortunately, that's the whole reason why we have the temporary rods. The temporary rod salvaged that patient. This was L1. That could have easily resulted in a permanent deficit. Yes? Correct. That was going to lead on to the next thing, which is a video. This was supposed to be a book chapter from Alfredo Quinonez. Remember that video, Atlas, but somehow I don't think that ever amounted to anything. This is just depicting getting your instrumentation in. You can see that this is a patient who had a pretty focal kyphosis. We have a lot of patients with osteomyelitis discus at University of Maryland. This is someone who has healed osteomyelitis discus who healed into a state of kyphosis. What you want to start out with is a central decompression, especially in an area where there has been previous infection or previous surgery. It's very important to remove all of the scar tissue and to get fresh dura or to get as close to fresh dura as you can because the dura ends up becoming somewhat redundant during the osteotomy closure. If you have a whole bunch of scar sitting on top of that dura, it's going to become even more of a problem than the standard buckling itself. As you can see, this is the application of a temporary rod. I put the temporary rod on after I've started the removal of the pedicles on both sides. Once you start going into vertebral body work, before you start proceeding to the vertebral body work, you want to put on a temporary rod. It's a good idea if you have someone with ankylosing spondylitis who might be somewhat brittle like the lady that we just discussed. It's important to have probably more than just one fixation point above and below the osteotomy construct. You can see we're retracting the thecal sac over here and drilling the rest of the vertebral body and pedicle over here. It's just a sequential process of going from side to side and applying hemostatic agents. Thrombin gel foam can go in on this side. You let that clot off a little bit and then you work on the other side. You can see despite the presence of this temporary rod, you still have a lot of room to work. It's not like you can't do your surgery with a temporary rod in place. A temporary rod is not a big hindrance to doing this. This is depicting further lateral dissection, exposing the nerve roots on either side. Really trying to get a very thorough decompression such that you can see both nerve roots in their entirety on both sides. Such that by the time you close the osteotomy, you have nothing that's impinging upon those nerve roots. The other thing is that you're going to get a lot less buckling if you remove bone centrally above and below the osteotomy site. It's very important to do a good central decompression prior to the closure of the osteotomy and to have good fresh planes between the dura and the ligamentum flabum such that when you do the closure, the dura will essentially slide and not be stuck to the surrounding bony anatomy. This is a central decancellation of the pedicle. Once you drill away the center of the pedicle, then you can easily bite off the cortical margin of the pedicle. It's just sequential drilling. You can see that there's not much blood coming out on this side because we packed that off. You just sequentially go from side to side and pack off with thrombin gel form or flow seal. That way you can help minimize your blood loss during this process. Once you've done a satisfactory removal of some of the components of the vertebral body, it's at this point where you slide in this osteotome underneath the thecal sac in order to cut away the bone from the posterior margin of the vertebral body. At this point as well, it's important to make sure that you also have had satisfactory clearance underneath the dura. That was inserted with the assurance that the dura was detached from the PLL and that there was mobility. Using the mallet, we'll just break through across and then into the osteotomy cavity. Now we're going to put the contralateral rod on. That's the final contralateral rod to help us compress across it. You can see that once you get that contralateral rod on, then you can sequentially compress across the osteotomy site. The osteotomy will start to close. It's at this point where you want to check your signals, making sure you have free-running EMGs and making sure that as the osteotomy is being closed that you're not creating a new deficit is important. Similar to what Tyler was saying, you want to do it gradually from side to side. You don't want to do one big sweep on one side all of a sudden. You can see we got a good correction of that deformity. That's pretty much it. That's a video of a case that is a good example of how you go about dealing with a fixed sagittal plane deformity. That patient had a post-infectious fixed sagittal plane deformity. If you have a fixed deformity, a PSO is the way to go for a good correction. If it's a flexible deformity, and fortunately most deformities do have some degree of flexibility to it, I think Smith-Peterson osteotomies or polysegmental wedge osteotomies can be achieved at multiple levels. You can get 5 to 10 degrees per level. Any questions?

posterior osteotomy

Smith-Peterson osteotomy

polysegmental wedge osteotomy

pedicle subtraction osteotomy

surgical technique