Hello, my name is David Parker from Sydney, Australia, and this talk is about common complications of osteotomy and how to avoid them. These are my disclosures. So in this talk, I will briefly talk about general complications of surgery, and then we'll focus on the perioperative complications that can occur with osteotomy, and then longer term complications. So with regards to general surgical complications, anaesthetic complications are possible, but rare. DVT is relatively common, as we'll discuss later, pulmonary embolism is rare. Infection, certainly deep infection should be quite rare, and also regional pain syndromes are possible, but rare, and compartment syndrome is theoretically possible, but should be exceedingly rare and certainly is not something I've experienced with an elective osteotomy. More specific complications, neurovascular injury, non-union, fracture, correction, failure, issues with the alignment loss, implant failure, and also potentially compromising near placements in the future are all of the things that we will cover in this talk. If we look at the literature around osteotomy, and we have to remember that this reflects a lot of the earlier experience with osteotomy, and a lot of this literature is relatively old, and it reflects some of the learning curve with osteotomy, but complication rates have been reported up to 55% with opening wedge HTO, 34% with closing wedge HTO, and as high as 70% in some of the literature with distal femoral osteotomy. Certainly not my experience, but it can be, and it also depends on how you define complications, as we'll discuss later, and there's differing complications depending on the technique used and the fixation used. Another study looking at opening wedge HTO complications with an overall rate of 15%, fractures with 4.5%, infection 3.5%, and non-union 1.5%. So it does have a low serious complication rate, but a relatively high overall minor complication rate. This is our own personal database, which goes over about 20 years, so again, it presents some of the evolution of the technique, and we had an overall incidence of 21%. The main one was hardware-related, which refers to hardware being symptomatic enough to need removal. Infection was 14%, but this is mostly superficial infection. DVT was 16%, and pulmonary embolism was reported to be 4%, which seems relatively high. Delayed union was 2%, and in my experience, the overall incidence that we see of non-union is around about 1%, which is comparable with the literature. Another study looking at distal femoral osteotomy with 16 studies included, with a mean follow-up of 78 months, an overall rate of about 9.1%. A lot of this was hardware removal, and some of this was conversion to total knee replacement. So not specifically necessarily early complications, but some of the longer-term complications as well. They saw a 3.8% delayed union and 3.2% non-union. And again, I think with more modern techniques, the non-union rate should be closer to 1%, and there wasn't any difference between the lateral opening or medial closing wedge. Now if we look specifically at certain complications, neurovascular injury is obviously a very concerning complication, but it's quite uncommon. It depends a bit on the approach that you're taking in terms of what is actually at risk. Vascular complications are reported to be 0.7% to 1.7%. In my experience, they should be exceedingly rare and well under 1%. It's more commonly the anterior tibial artery, which is usually the level of the osteotomy with an HTO. And be aware that there is an aberrant branch of the popliteal artery, which can run in front of the popliteal tendon, which is said to occur in about 2% of patients. Neurological complications, compranial nerve injury can occur most commonly in the setting of a lateral closing wedge osteotomy, again, should be very preventable with careful surgical technique. If we're trying to avoid neurovascular injury, particularly the vascular injury, then we need to get a subpariosteal exposure around the entire length of the osteotomy. We can see here that the subpariosteal exposure with the blunt retractors anterior and posteriorly. It's important that you look on the fluoro when you're taking a picture as to where the retractor is located and making sure that it's actually located where you're doing your osteotomy. And there are certain types of sores such as this one here that has a much smaller excursion than the traditional oscillating sore. So these can also be a little bit safer and a smaller zone of action and therefore much kinder to the soft tissues. But again, the most important thing here is having your exposure and knowing where your instruments are protecting the neurovascular bundle posteriorly. If we move on now to fractures, fractures can be hinge fractures and also intraarticular fractures. And they all relate to the location and the completeness of your osteotomy, as we'll discuss, and all are avoidable. So it's very important to preserve the hinge. When we do an osteotomy, we're just putting fixation from one side, usually the medial side. So the hinge is your lateral fixation, your lateral stability. If you lose the hinge, it can create multi-planar instability, which can lead to loss of correction and a non-union. So if we look at the hinge fracture, as you see here, it can lead to failure of the osteotomy. It can lead to a non-union. It can lead to well-established non-union with implant failure. It can lead to loss of correction. Takeuchi described different types of fractures related to the hinge. A type one fracture, which goes into the proximal tibiofibular joint, which is thought to have better stability. A type two fracture going below the tibiofibular joint is more unstable than a type three is a fracture into the joint, which obviously has implications for the health of the joint, particularly if it's not recognized and not reduced. So why does the hinge fracture? Well, it can be a malposition of the hinge point. Most commonly, it's an incomplete osteotomy, and this is most commonly going to be posteriorly where it can be harder to access. Insufficient release of the medial collateral ligament can also be an issue. If it's very tight and you have to put excess force to try and open, then that can lead to an inadvertent fracture. And of course, poor technique. If you take your osteotomy too far, you will directly disrupt the hinge. If you use a wedge that can distract it rather than spread it, that can be an issue as well. The ideal hinge point is at the level of the proximal tibiofibular joint, usually about 10 millimeters from the lateral cortex. So close enough that that lateral cortex and the lateral bone can plastically deform, but not disrupting it. And it should be about 15 millimeters below the articular surface. It obviously varies depending on the size of the patient, but it's important that it's closer to the lateral cortex than it is to the joint line. Otherwise, it will tend to fracture up into the joint. This is a study looking at 111 patients with 22 fractures, and they defined the region in relation to the proximal tibiofibular joint, both in the horizontal plane and in the vertical plane. And what they found was that the type 1, which is in the region of the proximal tibiofibular joint, didn't have any sequelae. The type 2 in this zone B here, as you can see here, both led to a non-union. And the type 3 also led to a non-union. And the majority of patients without fractures was when the hinge was in this blue zone here in the zone WL. So this is the area that we should be aiming for the hinge to be. And the relative risk of an unstable fracture when it was in this zone was a quarter of the other areas. So there are ways we can try and avoid this other than doing the osteotomy in the right place and at the right depth. This system creates a pivot hole at the most lateral side of the osteotomy to create a stress riser to release some of those stresses in that area. And also you can use a hinge pin, which protects that lateral hinge. When we tested this in the cadaver lab, even with massive opening, it seemed to protect the lateral hinge very well. So this is another technique that you can use, but it does not substitute for the other principles of creating the correct osteotomy to the correct depth in the correct location. If we look at how you can create an incomplete osteotomy, it usually is in that red zone posteriorly. It can also be related to incomplete release of the medial collateral ligament, putting too much tension on the medial side as you're trying to open. And also when you open the osteotomy, it's better to spread it rather than inserting these wedge devices, as you can see on the right hand side here. And this is what they used to use to split wood open. And what it tends to do is it does spread it open, but it also distracts it and can also lead to a distraction on the lateral side and the force and banging it in can also pull that lateral side apart. So I would caution against using this sort of device and it's better to use spreading osteotomes or a laminar spreader and just a very gentle, gradual opening. If you do create an unstable hinge, it's not a disaster necessarily. It's best to avoid it. But if you do create one, the most important thing is to recognize it and fix it as you can see here. And then there usually isn't a problem. If you move on to intra-articular fracture, as you see here, it's generally due to an incomplete osteotomy, usually posterior. So this osteotomy has only gone to that point. So the distance to the joint is that much. The distance to the lateral cortex is that much. So naturally it will go through the path of least resistance and fracture into the joint. So this osteotomy should have been directed more to the proximal tibia-fibula joint and gone further across the tibia. So again, completely avoidable. If it occurs, it's important to recognize it, reduce the osteotomy. Usually you can put a lag screw across that, check your reduction on the fluoro or with the arthroscope or both, then complete the osteotomy beyond that point and reopen it. So again, it's a situation that is usually salvageable if you recognize it, but again, best avoided. Union failure is generally pretty uncommon. Delayed union has been reported up to 8.5% and non-union up to 5.4%. In our experience, it's usually about a 1% risk, which is usually what we quote to patient, but there's obviously, again, avoidable. It's much higher risk if you fracture the hinge, if the implant fails, usually due to the non-union and smoking significantly increases the risk such that I would not do this operation on someone who smokes. Failure of alignment is another possible complication. This can be over or under correction. This usually relates to your preoperative planning and you can see here that if you do the correct planning, then you can usually avoid this over or under correction. The intraoperative technique is obviously important as we discussed before to achieve the appropriate correction and you can do secondary checks during the procedure. You can use an alignment rod with the fluoro to check that the weight bearing axis is passing where you would like it to be. This obviously has potential errors with rotation, but it's better than not checking it. Navigation is something I've used for many years and this can be very accurate in determining the final alignment you've achieved and of course, PSI can allow us to plan things so we know before the procedure the exact amount of the gap opening we need to achieve to get the right alignment and then once we put our plate and screws on, if all the screws line up with the holes, it's highly likely that the correction will be accurate. And then of course, it's important to do postoperative imaging just to confirm that you did achieve the right alignment, which is good for feedback to correct things again in the future. Tibial slope, the medial opening wedge height of the osteotomy has a tendency to increase the tibial slope, whereas the lateral opening wedge has a tendency to decrease the tibial slope. And again, this relates to your point of view as I'll explain. If you look at this osteotomy where we're coming from medial opening wedge, it's a tendency to come from more anteromedial, which will tend to open it up anteromedially. If we come from the lateral side, you tend to come for directly lateral and then you're closing it down and often the fibula will impede the closing posteriorly so you can get a reduced slope. And if you look at here on this diagram here, depending on the direction you're coming from with your osteotomy, if you're coming from anteromedial, it will tend to significantly increase the slope. If you're coming from the lateral side, you tend to decrease the slope. Again, it's important to be aware of the implications of how you do your procedures to how this can affect the slope. And this is a very clever study that was done some time ago to look at the geometry of the tibia and it's essentially a triangle. So if this is the medial side, this is the most medial part of your medial opening wedge. And when you're looking at it clinically and you look in the region of the tibial tubicle, that's about half of the way or slightly more across the tibia. So the gap will be much smaller at the front of your osteotomy than it is at the back. And as a general rule, when you're doing a medial opening edge high tibial osteotomy to maintain your slope, the posterior gap should be about twice the height of the anterior gap. And again, if we're doing it with preoperative planning with PSI, you can get very accurate measurements that you can check intraoperatively for the gap posteriorly and anteriorly that you need to have to achieve the desired slope. Patella height can be affected by tibial osteotomy, it can be affected by the surgical technique, by the amount of correction. And to some extent, the postoperative rehab, if people don't move and getting their knees moving early, then you can get in for patella scarring that can cause tibial bar heart. So this is what it looks like preoperatively. If we do a lateral closing wedge, in theory, this can cause a mild degree of patella ulcer and an opening wedge will bring the tubercle distally and can create patella bar heart. But realistically, the overall effect in the majority of osteotomies is relatively small because the tibial tubercle is quite lateral. So by the time you get to the region of the tibial tubercle, it's less than half the original opening. So for example, a 10 millimeter opening posteriorly will probably equate to about a three millimeter distalization. So that's not a big effect, but it's most significant in large opening wedge osteotomies. And if you're concerned, then you can do a procedure like this with a reverse biplanar to keep the tubercle with the proximal fragment. It doesn't need to be done very commonly, but it's a good option to be aware of. If we look at longer term failure and conversion to total knee replacement, the Finnish national registry had 89% at five years, 73% at 10 years, and then quite a lot of failure in the years after that. So almost 50% failure after 17 years. And this is our own data. This is some of this is historical. And we had almost 100% survival at five years, and then it decreased about 80% at 10 years. When we analyze those failures, then we do know, and this has been shown in other studies that if you have much better patient selection, your survival rate should be above 90% at 10 years. Planar replacement after HTO-DFO can be more technically demanding, both with the surgical approach and also the balancing because the anatomy has been altered. And there's some equivocal reports. Most of the reports actually show no difference to a primary knee, and that's reflected also in the registries in terms of survival, but there are some reports describing increased difficulties with balancing, alignment, and other things. And it's generally a more difficult conversion after a lateral closing wedge. You see this one, how the anatomy has been quite distorted. This surgery is still achievable, but more difficult. Whereas if you have an opening wedge, the anatomy is much more normal and it's usually an easier procedure to do. So in summary, it's important to select patients well. It's important to plan your procedure well. You need to deliver it accurately, which can be with PSI or careful preoperative planning or navigation. Don't break the hinge. Whether you're doing any type of osteotomy, you are reliant on the integrity of the bone on the other side from your osteotomy to give stability on that side. Remember, the osteotomy should end closer to the lateral cortex than to the joint. Use of other devices like the hinge pin can also help protect against this. Be aware of the direction of your osteotomy and making sure you have a complete osteotomy to avoid creating a fracture. Be aware of the medial ligament. And be aware of the way you're opening the osteotomy and do it very carefully and gradually. And then use rigid fixation. I'd like to thank you for your attention. I look forward to seeing you at the course.

osteotomy surgery

complications

neurovascular injury

implant failure

total knee replacement