We're going to discuss miscalculated allograft transplantation today and looking at some of the technical consideration, pearls, and pitfalls. This operation can certainly be a fairly challenging and technical one, and having done this for over 20 years, I'm going to share with you some of my observations of making things a little bit smoother for you. I think one of the most important things to consider initially is even before you start the surgery is make sure you have adequate preoperative evaluation of the knee joint, including the ligament stability, the alignment, and the status of the articular cartilage. And extremely important, on the day of surgery, you must confirm that the tissue has been delivered, that is the correct sided meniscus, right or left, medial or lateral, and it is for the appropriate patient. The first part of the surgery is always the arthroscopy, and at that time you have the opportunity obviously to reevaluate the knee joint, and if necessary, bail out because something has developed that you didn't previously recognize. Once you decide that you're going to proceed with the procedure, the first thing we'll do is to trim the meniscus rim back, and you want to try to leave some remaining rim of tissue, maybe one to two millimeters, so that leaves the hoop configuration. If you take too much of that meniscus, or unfortunately if someone has taken all of it out before, it can actually enhance the ability of the meniscus to extrude, which is not ultimately a desirable configuration for it. You want to also make sure that both on the anterior and posterior horns you have adequate resection, especially so that you don't create any type of ramp on the posterior aspect, and you may need to do a modified notchplasty, either medially or laterally, to allow for visualization of that posterior attachment point, as well as for passage of the meniscus tissue. You must have visualization of alignment of the anterior and posterior horn attachments. You must make sure that's in the appropriate geometric pattern, otherwise you will compromise the function of that meniscus. And overall, while we always want to try to do things as much arthroscopically assisted as possible, you don't want to compromise exposure here if it means compromising your result. The next step we'll look at is tibial bone preparation. If you're using the bone plug technique, the appropriate angle for the bone tunnels is very important, both for the anterior and posterior bone plugs. And it's very important to remember that anatomically, the anterior horn of the medial meniscus does not actually sit on top of the tibial plateau, it actually sits across the anterior portion of it. So if you just place that meniscus anterior horn wherever it sits, it may not be in the best anatomic position. If you're utilizing the bone bridge technique, you must create the initial marker between the anterior and posterior horn at the correct angle. This is so key in the bone bridge technique because that sets the whole alignment of where your meniscus will be and make sure that's an anatomical position. When creating that marking divot for the placement of the guide using the bone bridge technique, you must make sure you're four millimeters in depth, going all the way from anterior and posterior, so therefore taking into consideration that tibial slope. If you're out of balance there, your tunnel is going to go more high or low anterior or posterior, which will adversely affect the placement of that meniscus. Again on the bone bridge technique, you want to try to maintain that posterior cortex of the tibia. Once we have the tibial bone prepared, we'll then look at preparing the meniscus allograft. I think whether you're using the bone plug technique or bone bridge technique, you always want to remember accuracy is important. The preparation of the bone must be very accurate and therefore that old carpentry principle of measuring twice and cutting once applies because if you destroy or ruin that tissue, you're out of luck. On the bone plug technique, you want to make those plugs as robust as possible to avoid them fracturing when you place them into that little tunnel that you created or when you pull really hard on there, making sure that suture does not necessarily pull through the bone. On the bone bridge technique, there's measuring blocks that you'll utilize that will correspond to that initial tunnel that you make in the slotting of the anterior to posterior cortex of the tibia, and you'll have a ruler also to make these measurements of correct sizing. Most of the time on the bone bridge technique, you'll be about 10 millimeters in depth by eight millimeters in width. So you want to make sure that you have as much bone as possible in both techniques and that they're going to fit appropriately where they need to. The next consideration is placement of that meniscus allograft. Again, if you're using the bone plug technique, the anatomical placement is key. I've seen too many people that will place that posterior horn very nicely, reduce the meniscus into position, and kind of accept wherever that anterior horn lies and fixate it there. That is inappropriate and will lead to failure of that meniscus allograft. You must place both bone plugs in an anatomical position. When doing the bone bridge technique, your placement is essentially guided by the trough that you've already created. What I like to do with this to reduce that meniscus into position is use two pull-through sutures as opposed to one. I find that this gives me a little bit better control of that meniscus and a little bit less stress on that bone bridge to avoid fracture. You can actually use both sutures on two pull-through suture technique on the bone plug technique as well. Again, being certain of the corresponding anatomical position of the meniscus and the knee. Once that meniscus is placed, though, we want to cycle it through a range of motion, make sure it's moving nicely, and make sure the joint is not being captured in it. This is just an example of these two pull-through sutures placed on this meniscus. I tend to use purple for posterior and that kind of keeps it nice and clean without any confusion using a non-dyed vicral suture on the more anterior plug. Once the meniscus is in place, then we need to secure it. In the bone plug technique, you can secure the bone plugs by tying it down over a button or an endo button type of fixation, or just tying it down over the bone itself. It's very important, however, to make sure that anterior horn is firmly fixed and anatomical. In the bone bridge technique, you can either be stabilized as a press fit or using an interference screw or rotator cuff anchor. I prefer using a rotator cuff anchor because it's a little bit smaller and still gives us my interference fit. Then I utilize those sutures that actually close the anterior capsule over that very anterior horn of the meniscus, giving us a little bit more fixation and a little bit more source of blood supply anteriorly. The meniscus is then stabilized by a combination of using all inside technique, inside out technique and outside in technique or direct visualization on the anterior portion. You may require to use both the horizontal and vertical sutures to kind of get that meniscus sitting in the right position, especially on the periphery as it matches up to the synovial tissue. One of the downfalls of the meniscus allograft is we can size it very nicely, anterior posterior or medial laterally, but we don't know the exact depth of the meniscus we're getting, which may alter and be different from one person to another. One thing that I found is very important is not to over constrain the meniscus with too many sutures or tie down the sutures too tightly to the periphery, which can pull that meniscus out and actually cause extrusion before the meniscus is even in place and healed. And again, making sure that anterior horn is very well fixated. This is just an example of fixating that bone bridge. You can see the bone slot here in the in the trough. And here's our rotator cuff suture anchor with the sutures coming out. This was a little bit bigger incision, this was also doing a part of the restoration procedure. But when we close this, we utilize the sutures to close and approximate this tissue over the anterior aspect of that meniscus. Once the meniscus is sewed into place, we'll use an arthroscope and probe to make sure the meniscus is stable. And we can also visualize it as we place the new knee through a range of motion to make sure the meniscus is stable and not subluxating or impinging on the joint. At this point, it's very important to correct any concerns. And don't assume that, well, it'll be adequate and it'll work itself out. It's very important to make sure everything is as smooth and secure as possible at this point, because chances are it'll only get worse. And that's our discussion for today. I think the things that we want to think about the most here are good planning, know where you're going with this meniscus, be aware of the anatomy, and make sure that you take your time in preparing the bed for the meniscus, preparing the meniscus allograft itself, and making sure you have good anatomical and secure fixation. Thank you.

allograft transplantation

preoperative evaluation

meniscus rim trimming

secure fixation

anatomy knowledge