I'm going to step in here a bit for Dr. Lesniak and do a quick review of considerations of meniscal transplantation in the setting of frank meniscal deficiency. Is there a role for this with ACL reconstruction? And then we'll have Volker and Alex come in and take on even more complex discussions of tibial slope and varus alignment insufficiency. Bryson presents this case from his practice in Pittsburgh, 17-year-old female soccer player. Not your primary ACL situation, but a situation of revision ACLs, has had a hamstring graft at age 13, unfortunately failed, subsequently revised with a patellar tendon autograft, but at that setting a quote-unquote partial medial meniscectomy, and then a year later failure and revision partial medial meniscectomy. So you can imagine what's coming here, which is this patient has had two years of issue-free return to soccer, unfortunately now presents with a recurrent injury of a pop and swelling in the knee, and is now referred for revision ACL reconstruction. And while that often becomes the focus, the revision ACL, you have to grapple with the fact that there's been all of this treatment and resection of the medial meniscus. So for sake of time, exam fairly typical, minimal hyperextension, but a positive Lachman and a positive pivot shift. Imaging findings here, plane films, to be honest, pertinent to this ACL, reasonably positioned tunnels, perhaps some widening, tibial slope of 8 degrees that Volker will chat about how much is too much, and some early Fairbank changes on the medial side, but otherwise well-preserved joint spaces. Here the alignment is in neutral, so we'll take that issue out of the equation, but this is kind of in some ways the most pertinent findings for this portion of the talk, as you can see on the sagittal and coronal MRIs here, there's effectively subtotal medial meniscectomy and significant medial meniscus deficiency with some early chondral changes. And this then begs the question of if we're addressing this now with yet a revision and re-revision ACL reconstruction, is there a role for addressing this functional medial meniscus deficiency? There is a CT scan that's obtained in this circumstance, and this is not uncommon, particularly with two revision ACLs, to look at tunnel position. You can see here that there is some tunnel widening in Bryson's case of 13 millimeters, but otherwise reasonable tunnel position. So now what? And this comes to the question of the role of the medial meniscus, the consequences of meniscectomy, and the outcomes of ACL and meniscus transplant, and what can we hang our hat on in the literature? Well, to step back, all of us are familiar with this great work from Russ Warren and Amos and Shoemaker and others, again, recognizing that in particular, the posterior horn of the medial meniscus functions as a secondary stabilizer of anterior tibial translation, and in particular, in the setting of ACL deficiency. If you look at this study from Dr. Fu and the group out of Pittsburgh, when you look at the biomechanical interdependence of the ACL graft and the medial meniscus, you can see in the ACL deficient knee that compression forces double between 30 to 90 degrees, and those forces are restored with ACL reconstruction. In the setting of medial meniscectomy, you see increased graft forces for all flexion angles with the exception of terminal extension, and those forces increase anywhere between 33 to 50 percent in these biomechanical models. So there's no question that lack of the posterior horn does increase the stress on your ACL graft. This is a study that Volker did, that I had a privilege of working with him and Andy Perlon at HSS, looking at the effect of meniscus deficiency and really looking at both the role of the medial meniscus and the lateral meniscus. As was mentioned, the medial meniscus plays a critical role with anterior translation, and in particular, correlating with our physical exams, the Lachman and the drawer. On the other hand, the lateral meniscus is important as well, and in this study, it appeared that lateral meniscus deficiency had more of an impact on the pivot shift, which makes some sense in terms of the critical shift of the lateral compartment. So in some level, both menisci are important. The challenge is that there's a big leap between biomechanical studies and real life, and so as Bryson points out, what do we have to hang our hat on in terms of clinical outcomes? And if you look at clinical studies, these are what we have. Tim Spalding out of the UK looked at meniscal integrity as a predictor of ACL reconstruction, and no surprise, when there was meniscal deficiency in the medial side, the hazard ratio of graft failure after ACL reconstruction was 4.5 hazard ratio, lateral meniscus 3.5 fold. So there's no question that meniscal deficiency has an impact on your survivorship curve, if you look at the Kaplan-Meier survival analysis from Tim's work. If you look at this study, again, from David Dejour and the group out of France, looking at tibial slope and medial meniscus deficiency, both of these factors did affect longevity of an ACL reconstruction, and in particular, increased static and dynamic anterior tibial translation was noted. Stefano Zaffagnini looked at meniscal allograft transplantation combined with ACL reconstruction, and again, this is a clinical series, small numbers, but when you looked at PROs compared to pre-op levels, they improved, they just never achieved pre-injury levels. So there's no question there's a glass ceiling effect to having significant prior meniscal surgery and meniscal deficiency. 85% did return to sport, but 37% only to the same level of sport. So this is, again, modest clinical outcomes, but at least demonstrating some role and consideration for meniscus transplantation. This study out of Russia and from Brian Cole's group, where they looked at prospective clinical and radiographic outcomes after ACL reconstruction and meniscus transplantation at five-year follow-up, when you look at their series, PROs improved, knee stability improved, survivorship at 10 years was 45%, at five years, 84%. Again, the challenge here, however, is that much of this was clinical outcomes and radiographic outcomes in terms of meniscal allograft, in terms of extrusion and survivorship of the compartment really remains to be determined. So what's Bryson's summary here, which I think is very fair in 2022? The indications to consider meniscal allograft transplantation for ACL reconstruction is based on a paucity of clinical data, but what we have is a setting of neutral alignment, a preserved joint space with less than grade two or three chondral changes, reasonable expectations not returned to elite sport, but returned to reasonable activity level in the setting of what's otherwise a well-performed ACL reconstruction or revision. When should you probably not consider meniscal allograft transplantation in this setting? If you already have changes that are grade three or more, if there's significant correlation with elevated age as a surrogate of arthritis, BMI being relative with some studies indicating greater than 35 or 40, the presence of autoimmune arthropathies, smoker, or unreasonable expectations for return to elite sport. Meniscal allograft transplantation won't correct those factors or get you back to elite competition. So in summary, meniscal deficiency in the setting of ACL revision or re-revision should not be ignored. This laxity can be identified early post-operatively, and it's clear that it is an increased risk for graft failure and graft strain in the setting of ACL reconstruction. Addressing concomitant pathology, for example, tibial slope or enteralateral insufficiency is an important consideration, but you must temper the expectations of your patients that a meniscal transplantation is not the solution to all problems in these needs. So back to Bryson's case, I'm showing how he managed this patient. There was a subtotal prior medial meniscectomy with meniscal deficiency as seen here. There is some early medial femoral chondral changes, but as mentioned per his algorithm, these were less than grade 3 changes in tonus grade. These were semi-anatomic tunnels, meaning that they were viewed as half right and half wrong on the femoral side. I think in this case, Bryson appropriately made the decision that there's one chance to get this right, so he chose to stage this and to graft these tunnels, particularly given the enlargement on the tibial side. This provided an opportunity to treat the meniscus with transplantation at that setting, so he performed a medial meniscus allograft transplantation, well done here. This provided then the opportunity to allow for the tunnels to heal and graft to incorporate, and also then to perform a staged revision ACL reconstruction with quad tendon autograft. This gave them a second look at the healing between the capsule and the meniscus transplant. You can see this is incorporating well. Tunnels had healed, which allowed him to then perform this anatomic quad tendon revision. And again, appropriately, Bryson shared with me that the update and follow-up on this patient is that they're doing well, but they're certainly not returning back to soccer and elite sport, which fits with our expectations of achieving a stable knee and hopefully preserving the joint. So thank you.

meniscal transplantation

meniscal deficiency

ACL reconstruction

functional medial meniscus deficiency

biomechanical interdependence