In this part of the ANNA toolkit, we're going to be focusing on outside-in femoral tunnel drilling for ACL reconstruction. My name's Adnan Saifner, orthopedic surgeon from Scottsdale, Arizona, and I'd also like to acknowledge the contributions from my co-authors, Benjamin Fréchet and Bertrand-Sanricote from Lyon, France. This slide summarises the main benefits of outside-in femoral tunnel drilling and why you should consider using it in your practice. We're going to consider each of these points in more detail throughout the presentation. However, one of the main advantages of outside-in femoral tunnel drilling is that it avoids the need for knee hyperflexion. Other advantages include that it's anatomically unconstrained, it allows for new divergent tunnel trajectory in revision ACL, providing more opportunity for single-stage revision, and it also allows us to avoid tunnel collision in multi-ligament reconstructions and also in the setting of lateral extra-articular tenodesis. Antromedial portal drilling of the femoral tunnel is common. However, it requires knee hyperflexion to avoid injury to the common peroneal nerve. If you drill your tunnel using an AM portal in 90 degrees of flexion or less, there's a high chance of injury, therefore hyperflexion's required. However, the disadvantage of that is that it reduces visualisation and increases the risk of iatrogenic injury to the meniscus and cartilage. Obviously, decreasing visualisation also means that there's an increased chance of tunnel malposition. If you are able to avoid hyperflexion by using outside-in drilling, you have improved visualisation, you reduce the risk of iatrogenic injury, and you can also free up your assistant to perform other tasks. This slide demonstrates the typical anatomy of an outside-in drill guide. Obviously, there's many different variations, but they all have key features. The first is an intra-articular targeting area. This particular one uses a hook that hooks around the condyle, but other examples include the use of a footprint guide or a point-to-point guide. Other features to highlight are an area for angle adjustment, which allows accurate positioning and placement of the guide individualised to each patient. There's a locking mechanism that holds the drill sleeve in place. This is an important feature because it allows us to remove the drill guide while keeping the drill sleeve in place. Because we're using outside-in drilling, once the drill is fully deployed and we want to retro-drill to create our socket or tunnel, we need to remove the guide to be able to do that. In that situation, once the drill sleeve is positioned, it's malleted into bone to hold it into position, the locking mechanism is undone, and the drill guide is removed from the joint. This clinical photograph shows the lateral aspect of a left knee. The outside-in guide is sided, and therefore this is a left-sided guide placed in the left knee. You can see that the guide is placed intra-articularly through an anterolateral portal, and the drill sleeve has been inserted through a small percutaneous incision on the lateral cortex. This is anteromedial portal viewing in the same patient. Because we don't need to hyperflex the knee, we have a good view of the notch. This is a footprint guide, so I've placed this in a mid-AM bundle position. The outer diameter of this guide is 9mm, so I need to ensure, because my graft is 10mm, that I leave a posterior margin of at least 1mm to avoid tunnel blowout. Once drill guide positioning is confirmed, a 2.4mm pin is drilled. This is done from an outside-in trajectory through the drill sleeve. It's not necessary to do this step, you can go straight to the drill, however I prefer to place a 2.4mm pin first, because in hard bone, the larger drill size can be diverted, and a pin is less likely to be diverted. Furthermore, it gives the opportunity to fine-tune it if you're not perfectly happy with the position. Once the 2.4mm pin is in place, the drill guide is removed, and the step sleeve is malleted into bone to hold it into position. Having malleted that sleeve into bone, the 2.4mm pin is switched over for the drill. Here you can see that I'm going to deploy the blade in this drill, which is then going to be used to retro-drill and create a socket. It's important that when you first start drilling to create the socket, that you do so with that deployed blade off bone. If you start with it on bone, it can break off. You drill back to determine the size of the tunnel or socket that you want, typically 15-20mm. Once it's drilled, you undeploy the blade and remove the drill, and then you can retrieve a passing suture. Once the passing suture is removed, a shaver can be inserted to remove bony debris and soft tissue to allow easy graft passage. This is the outside view of the same patient. You can see that drill sleeve has been malleted into bone and is stable. The drill is being placed into the knee. Once it's in the knee, we deploy that blade, in this case, to drill a diameter of 10mm. There's a little rubber grommet there, which is brought down to the drill guide, and that way, when we drill back, we can measure precisely the depth of the socket or tunnel that's created. Bony debris can collect in the notch, and therefore, to aid visualization, you can either use outflow or place a shaver into the notch to remove debris. Once you've finished drilling your socket, you undeploy the blade and pull that drill out, and then place a shuttling suture of your choice, which is used to shuttle the graft. Once that's retrieved you proceed with ACL reconstruction in a standard manner. In this video I'm going to demonstrate a different type of targeting of a tunnel position intra-articulately, but still using the same concept of outside-in drilling. In this situation you can see that my probe is retracting a partly torn ACL. The AM bundle is still intact, the PL bundle is torn. You can see my repair sutures in that ACL stump. Obviously I can't use a footprint guide here because I wouldn't be able to place it in the correct location due to the intact AM bundle fibers, so I'm using a point-to-point guide. I've placed that directly up against the intact AM bundle fibers to identify the correct position for the PL bundle. I'm drilling my outside-in guide pin. I'm going to mallet in a step sleeve externally. I'll then reverse the pin having placed a passing suture in there which will allow me to retrieve my repair sutures from intra-articulately to externally where I'm going to fix the sutures either tying them over a button or fixing them with an interference screw type anchor. You can see on the right hand side the before and after pictures. Above you can see the torn PL bundle. Below you can see the repaired ACL repair rather with an internal brace suture. In this slide I want to introduce the concept that outside-in drilling is anatomically unconstrained compared to other drilling techniques. For example, if you use an anteromedial portal drilling technique, your portal position and degree of knee hyperflexion, which are not easily modifiable without compromising other aspects of your surgery, dictate the position at which that guide wire is going to exit the lateral cortex. In contrast, if you use an outside-in technique, you can see in the illustration on the left that you can insert your guide wire anywhere in that green area and still achieve an anatomic position intra-articulately. Obviously, you need to be mindful of avoiding iatrogenic injury to the lateral collateral ligament and posterolateral corner and articular cartilage and avoiding tunnel blowout, but bearing in mind all of those considerations, there is a wide area of that lateral condyle that you can use as an entry point. This becomes extremely useful in the revision ACL setting where we are often dealing with tunnel overlap and widening. Using this technique allows a divergent tunnel, a new divergent tunnel, which still allows you to have excellent fixation even if there is overlap at the aperture, and I'm going to show how that works in a moment. The clinical photograph there shows three different guide wire positions, which demonstrates this principle of divergent tunnels. All of those are directed at the anatomical mid-AM bundle footprint position intra-articulately, so you can see there's a wide range of options on that lateral condyle with an outside-in technique, which is anatomically unconstrained. Here is an example of the use of the anatomically unconstrained nature of outside-in drilling to deal with tunnel malposition in revision ACL reconstruction. In image A, you can see a malpositioned femoral tunnel. It's in a mid-bundle position rather than our preferred mid-AM bundle position. In image B, you can see an outside-in femoral guide hooked over the back of the condyle to allow for anatomical mid-AM bundle positioning as confirmed by placement of the guide wire in image C. In image D, you can see that we have our guide wire in that new position, but we have also placed a guide wire in the original AM portal drill tunnel to demonstrate that these tunnels are completely divergent. This is also well illustrated in the clinical photograph, which again demonstrates that there is a great degree of divergence between the primary inside-out AM portal drill femoral tunnel and the new revision outside-in femoral tunnel. Image F shows the graft in position. In the next slide, we'll see a video of this procedure. So we see again that that femoral tunnel is malpositioned. It's a mid-bundle position rather than a mid-AM bundle position. Here's our new tunnel trajectory and the new tunnel drill guide wires being placed in both the original and revision tunnels to demonstrate that divergence. Which we also see here on the external view. So here's the tibial tunnel being drilled. And then suture retrieval through the new outside-in femoral tunnel. You can see that there is some overlap of the apertures of the two tunnels, but here's our BTB press-fit graft being pulled into the knee from the femoral side to the tibial side. And we'll see in the post-operative CT images that there's no concern whatsoever about fixation of this graft, even though there is some overlap of the apertures of the tunnels. And that's because the tunnels are completely divergent and there's excellent press-fit fixation. We're going to look at the post-op CT in more detail on the next slide. Here we see that post-operative CT in detail. We've got various sections to consider. The previous failed non-anatomic AM portal drilled femoral tunnel is demonstrated in red. The new mid-AM bundle femoral tunnel is depicted in blue. You can see that there is some overlap of the two tunnels at the intra-articular footprint. That's what we saw at arthroscopy and we see it here on the post-operative CT. But what we also see is that we have our press-fit BTB bone block in situ and there's absolutely no concerns about that press-fit fixation because the tunnels are completely divergent. So this is a really good use of outside-in drilling and it can avoid the use of two-stage surgery to deal with many different configurations of tunnel widening and malposition at the time of ACL reconstruction. Another very important benefit with post-operative CT is that it takes advantage of the anatomically unconstrained nature of outside-in drilling is the avoidance of tunnel collision in multi-ligament reconstruction and also in the setting of a concomitant lateral extra-articular procedure. This study from Jay Kuratel really serves nicely to highlight this problem. In this study they drilled an AM portal guide wire and they demonstrated that tunnel collision occurs predominantly at the lateral cortex in approximately 70 percent of examples that they studied. So as we already mentioned it's very difficult to change the trajectory of an AM portal drilled tunnel and so tunnel collision in the setting of a modified LMAIR or ALL reconstruction is a major concern. One of the recent strategies to deal with this has been to use cortical fixation with a suture anchor and avoid placement of an interference type screw-in anchor. Although that does perhaps reduce the possibility we can see from the images below that the tunnel collision is typically occurring at the cortex. So that's maybe not the best strategy however using an outside-in drilled tunnel allows us the opportunity to place our outside-in guide wire from many other locations in the condyle and completely avoid the risk of tunnel collision. On the top row you will see an example of an ALL reconstruction. You can see that that femoral position of the ALL graft is in a proximal posterior position to the lateral epicondyle similar to the position for a modified LMAIR from the perspective that there is a risk of tunnel collision when you drill from an AM portal for an ACL femoral tunnel. Therefore a tunnel collision is a consideration with both modified LMAIR and ALL reconstruction. In the post-operative CT below you can see the ALL socket encircled in red and you can see that we've used an outside-in technique to drill our femoral tunnel. So we've completely avoided tunnel collision by avoiding an AM portal drill technique and using the anatomically unconstrained nature of outside-in drilling. Of course there are other strategies for avoiding tunnel collision. Our preferred strategy is actually to use a single tunnel for both the ALL and ACL procedures which you can see demonstrated here. That still requires outside-in drilling and we have a specific presentation on ALL reconstruction elsewhere in this toolkit which you can refer to for more information. Thank you for your interest in this presentation. If you have further questions please feel free to email me.

outside-in femoral tunnel drilling

ACL reconstruction

revision ACL surgeries

Dr. Adnan Saifner

multi-ligament reconstructions

revision surgeries

clinical effectiveness