Dr. Chris Tucker:
Welcome to the Arthroscopy Journal podcast. I'm Dr. Chris Tucker from the Walter Reed National Military Medical Center and the podcast founding editor. Today, we're discussing patellar instability and medial patellofemoral reconstruction techniques. I'm joined today by Dr. Miho Tanaka from Massachusetts General Hospital. Dr. Tanaka is an associate professor at Harvard Medical School, the director of Women's Sports Medicine at Mass General, an editor for the Journal of Women's Sports Medicine, and an avid educator and world-recognized expert, especially in this field of patellofemoral surgery. Dr. Tanaka was the lead author on the infographic titled “Medial Patellofemoral Reconstruction Techniques for Patellar Instability,” just published in the June 2023 issue of the Arthroscopy Journal. Miho, congrats on all your work, and welcome to our podcast.
Dr. Miho Tanaka:
Thanks so much for having me.
Dr. Chris Tucker:
You've built quite a resume when it comes to researching and educating others on the patellofemoral joint and patella instability. Could you just share with us the backstory on your interest in this field and just how you became so passionate about this aspect of orthopedics?
Dr. Miho Tanaka:
Yeah, so I think I originally got involved with research on the patellofemoral joint when I was working as a resident at Hopkins under Andy Cosgarea. And he had just kind of started developing this dynamic CT and so I was able to get on some projects with him and I started to realize that there are more questions than answers in this area. And I think that really kind of started my interest. And I would say that John Fulkerson also has played a huge role in my career in that early in when I was in practice, he started talking about the MQTFL and that really drove a lot of my interest in the anatomy and the biomechanics of the ligament. And so I think the two of them have really contributed to a lot of the work that I've ended up doing to date.
Dr. Chris Tucker:
Sure, those are some great patellofemoral experts to really start under and have as mentors, so that's always interesting to see how people get their start.
Dr. Miho Tanaka:
Yeah.
Dr. Chris Tucker:
So let's kick off big picture. Could you just review for us the normal anatomy and function of the patellofemoral joint as well as what happens when there's an injury that leads to symptomatic pathologic instability?
Dr. Miho Tanaka:
Sure. So I think what we now know is that patella stability is multifactorial. So there are the osteochondral restraints, the alignment, the dynamic restraints such as the muscles, and then the static restraints, which is really what we focus on in terms of surgery. And any abnormality or disruption of any of these can lead to patellar instability. And I think that's what makes it a little bit complicated because it's not always one thing that we're treating that leads to the outcome of instability.
But generally what happens is that with a dislocation events, the medial restraints will become disrupted and when those become insufficient, then patients will have continued instability events, which is, A, bad for the cartilage and B, bad for function because you need to be able to stabilize your knee during cutting and pivoting events.
Dr. Chris Tucker:
Sure. So as you and your infographic nicely explain, what we're now calling this medial patellofemoral complex is that term used to describe those soft tissue stabilizers of the patella within that patellofemoral joint. And like you said, when it's injured, that structure can be surgically repaired or reconstructed. Before we get into really the specifics of your infographic on these techniques and those pearls and pitfalls that you're going to hopefully share with us, hoping you could just speak to the clinical workup that you find most useful when you're evaluating these patients.
Dr. Miho Tanaka:
Yeah, absolutely. So I think the history is really important in terms of, I always want to know how old were they when they had their first dislocation? So not what just happened recently, but when did this happen first, and how did it happen? I'm interested in how much force and how much trauma was placed on the knee that caused it to dislocate, asking about contralateral symptoms, asking about family history. All of these things will start to give me a sense of whether there might be a little bit more than just the soft tissue that we might be needing to think about.
Same thing on the exam, we're looking at alignment. So I'm having them stand, I'm seeing if they have femoral anteversion with the squinting patella. I'll do a single-leg stance and squat, seeing how well they're rehabbed essentially or optimized from a dynamic stabilization perspective. And of course, for the stability exam, it's not just about the translation. So using the patella quadrants to see how far they move both medial and laterally, but also whether they have apprehension because you can have patients who are lax who aren't actually functionally unstable. So I think the apprehension test is really important.
And then of course there are the other things that kind of speak to the acuity of the problem, looking for effusion and checking the other ligaments, but those are kind of the main things that I look at on the physical exam side. For imaging, I always get weightbearing X-rays. For the axial views, I get the merchant view, so at 30 degrees instead of the sunrise view, which merchant view kind of shows it a little less inflection and so allows us to see more of the trochlea where it really matters in terms of stability. And I always get both sides that allows me to kind of compare both knees.
The ones that go on to surgery, of course, in addition to the MRI, the ones that go on surgery always get in my practice a dynamic CT as well as standing long leg alignment views to see everything from the hips down to the ankles. So that's kind of my general workup for patients who are having surgery.
Dr. Chris Tucker:
Yeah, that sounds really thorough. One interesting pearl that I had picked up in my training when Dr. John Fagan had come and he would always spend time with the fellows was he would explain to us that patients often have a lot of this apprehension with their patellofemoral exam and he would examine them prone with their leg off the side of the bed and their quad kind of relaxed by on the bed and get a patellofemoral exam with them prone with really no quad tone. I don't know if you've ever done that or seen that or have any kind of thoughts on that technique he taught us.
Dr. Miho Tanaka:
I haven't. I think that's a great idea. I might try it next time in my office. I think having the quadriceps relaxed is a really important part of the examination. I usually do this supine and extension and I do kind of everything else first. And a lot of times I'm just starting out with a little bit of a wobble just to get them to relax. I'm not really trying to push them way out. So I think as long as you're getting some sort of exam with a quadriceps relaxed, that's the goal. But I think turning them prone really sounds like a nice option and a way to do that.
Dr. Chris Tucker:
For those of us who had the fortune to work with Dr. Fagan, he was probably most known for his Prone Lachman for the ACL exam, which requires a fair amount of practice, but he was really an innovator and really interesting to learn from. So yeah, the prone knee exam was kind of a hallmark of working with him, something you had never seen and then you learn from him and it was quite interesting and unique to have that-
Dr. Miho Tanaka:
Yeah, that's amazing.
Dr. Chris Tucker:
Experience. So given the appropriate workups now done and you find that your patient has this patellar instability, what are you using as kind of your currently acceptable indications for medial patellofemoral complex reconstruction?
Dr. Miho Tanaka:
Yeah, so I think recurrent instability or recurrent lateral patellar instability so this is not for pain and you want to make sure you rule out medial instability as well, I do think that there are indications for the first-time dislocator, especially if they have an osteochondral fragment or something that needs to be addressed. I think historically we were treating these with maybe an MPFL or MPFC repair, but we now know that even in the first-time dislocators, the repair itself when you're addressing the osteochondral fracture doesn't necessarily hold up well, especially in the setting of malalignment. So I've really moved towards reconstruction in these settings as well.
And then the last indication I would say is the first-time dislocators who's high-risk. This is still an area of development. I would say my one kind of main indication for these patients are when they're bilateral. So they have high-risk factors, they have alta dysplasia, high TTTG, and they've had one on the other side and they knew that that went on to needing surgery. I think those patients are usually the ones that don't want to wait for a second dislocation and they'll usually end up having this done early on.
Dr. Chris Tucker:
Hmm. So in that high-risk category, do you use age or gender or specific sport activity at all in your decision-making?
Dr. Miho Tanaka:
Yeah, so there are a couple studies that have detailed this and I think the most commonly cited ones or the one that Shital Parikh did, which was out of Cincinnati and that was a retrospective one looking at dysplasia, skeletal immaturity, and patella alta. And then I think Liza Arnd also did one that was prospective also using MRI measurements and really found pretty much a similar finding with alta trochlea dysplasia and skeletal immaturity and maybe one other factor.
But those three things are really the key. And I think if you have all three of them, your chances of having a second dislocation based on that data is somewhere around 70 to 80%. So that's a discussion that I have with the family. But you have a 12-year-old female athlete who has a first-time patella dislocation and usually the parents are not going to be on board with a surgery after first-time patella dislocation. So it's more of just patient education. At least giving them the information that this might not be something that just is going to go away with physical therapy so that they don't find themselves in a situation where they're surprised by this.
Dr. Chris Tucker:
Mm-hmm. So as your infographic describes, there's obviously various approaches to either surgical repair or more commonly and likely more favored reconstruction. In summary, could you just run through the commonly used surgical techniques and then maybe the potential advantages and disadvantages of each?
Dr. Miho Tanaka:
Sure. So the MPFL is probably the most commonly utilized and there's the most data on this. Of course, one of the most catastrophic complications of an MPFL reconstruction is a patella fracture. And so that is partially why some of us have kind of moved away from that. The MQTFL is a little bit newer, and of course, John Fulkerson initially described that, and we've kind of had several iterations of this, but really the focus is or the point is that the fixation is on the quadriceps tendon, so there's no drilling into the patella and there's no risk of patella fracture with this.
And we've moved this fixation point down to be anatomics. So really now we put this, even though we call it an MQTFL, it's not way up on the quad. It's really right at that junction between the quad and the patella. Downside is that there's not as much long-term data on this, although John Fulkerson and I recently presented a series of I think over 130 of these showing that short-term-wise, there are very few complications, but of course there's more to come with long-term data.
And then with the double bundle, of course, there are plenty of small series that show that this does pretty well. You're actually not bypassing the issue of the patella fracture risk because you're still putting a hole into the patella. So I think that's one downside. Biomechanically speaking, some of the studies have shown that having two bundles maybe does a little bit better than one, but I think real comparative studies don't really exist there.
My one sort of, I wouldn't say concern, but I think area that still needs to be studied with the double-bundle is that we've shown that there are specific fibers of the medial patellofemoral complex, and that if you cross those fibers from the femoral side to the extensor side, that they don't behave as normally in terms of length changes.
And so I don't think that we've really figured out a way to attach something to the patella and to the quadriceps tendon and have a single tunnel on the femur. And so it seems like clinically they do well, but we just don't have a lot of answers in terms of how to set the tension on those and make sure that they're biomechanically behaving equally.
Dr. Chris Tucker:
Mm-hmm. Now you've described the anatomy of the medial patellofemoral complex being fairly predictable and most of us are familiar with the crucial nature of getting that femoral insertion exactly right. And working on the isometry of that side, I was hoping you could just outline some of your elements that are critical to success of reconstructing this anatomy. In your infographic, you mentioned several things like that femoral tunnel placement, the tension on the graft, things like that. Could you just talk to us about your pearls for success and maybe some of the significant pitfalls to avoid?
Dr. Miho Tanaka:
Yeah, sure. So on the femoral side, obviously this is kind of the most important part to make sure that it is anatomic because this is what determines how the graft functions. And so I use kind of three ways to check this before I actually drill the tunnel in that location. So the first thing is anatomy. So I'm feeling for the adductor tendon, I'm feeling for the medial epicondyle, and that you always want to be posterior to the medial epicondyle.
I think the gastroc tubercle is always the most palpable in these patients because everything else tends to be a little bit dysplastic, especially when they have trochlea dysplasia. But that's less sighted, I would say. But that's a pretty good guide. John Fulkerson always talks about, well, if you can't find the adductor tubercle, you can just make a bigger incision, find the adductor tendon, and then follow that down. So I do think that that's one option as well.
And in general, we're looking for the point described by Fujino, and most studies have shown that the midpoint of the NPFC insertion on the femur is one centimeter distal to the adductor tubercle. So once I find that, I'll put the pin there and then I'll check this on fluoroscopy. And on fluoro, of course, there's lots of different ways to check this and Schottle's point is the most commonly cited. I will say that there are certain things to know about Schottle's point, one, Cory Edgar has shown that you can't have any rotation on the fluoro, otherwise, those points are going to be off. We've also shown that you need at least four centimeters of the distal femur visible in order for that sort of posterior cortical line to be accurate.
But I'd also say that there are several other studies, including ours that have shown that that point is a little bit more posterior to the posterior cortical line than he's shown. So there's a little bit of discrepancy in the literature and it depends on which study you read. Regardless of which one that you want to aim for, I think it's really important to note that where you're putting your pin is different from where the graft is going to be because once the pin is in, you're going to ream around it and then put a screw behind the graft in most cases.
So that graft is actually going to be, however, whatever your radius is anterior to that point. So I always try to cheat posterior to where I want the graft to be or where I think the midpoint is going to be. And I think that's really important as you're starting to think about where to put the pin and if anything, you should be posterior. I wouldn't accept anything anterior to the ideal point.
Once I've done both of those things, the last thing I check is the length changes of the graft. So I do the patella or extensor side first, the quad side first, so that's already fixed there. I take the graft, I loop it around the pin, and I take the knee through range of motion and I want to see less than five millimeters of length change throughout range of motion, even less. I like to see probably three or less or so.
And so once all three of those things are good, then I know that I like that position and not until then will I actually draw that tunnel. For setting the length, there's a lot of discussion in terms of the best way to do this. I have found that the most reproducible way is to bring the knee to about 60 degrees of knee flexion. At that point, there's really no dysplasia, and so the patella has only one place to go in the trochlea, and at that point, if you take the slack off of it and set the length, which is a term that Jack Farr says, that will kind of reproducibly allow the patella to engage in the trochlea and still have two quadrants of translation in extension, have less than a quadrant around 30 degrees of knee flexion and will still kind of slack in as you go into flexion.
Some of these other methods of doing this, allowing a quarter quadrant or half quadrant or something like that in 30 degrees of knee flexion, I think is really challenging. I think that it's really, really hard to feel that and to try to adjust a tension on this ligament during the procedure. And so I think that just removing the slack and having this in a little bit of deep reflection for me has been an easy way to minimize any risk of over-tightening.
Dr. Chris Tucker:
Yeah, those are absolutely valuable pearls. I agree with you. I kind of do a similar technique where I like to just have the knee flexed about 60 degrees, set the length, and then you don't have to worry about over-tightening because you know if that's the maximum length it's going to need for the knee motion, you don't have to worry about over-tightening. Just a follow-up question though, on setting that length, mostly you're just driving an MPFL, but if you're doing the MQTFL, obviously you can't fix it on the quad side, usually fix it on the femur side and then loop it through. Are you passing a suture from your pin through that path to set that, or are you just fixing it on the femur side, flexing the needle of 60, and then looping it through and tying it to itself like John Fulkerson showed us how to do?
Dr. Miho Tanaka:
Yeah, actually I have a new technique for the MQTFL that's probably coming out in Arthroscopy Techniques this month or next month or something like that where-
Dr. Chris Tucker:
Okay. So a sneak preview here.
Dr. Miho Tanaka:
Yes, that's right. I do the extensor side first, just because I think to adopt this, a lot of us do the extensor side first, and so I didn't like to change the way I do this, and I really like having the graft available to loop it around the femoral side, which is what we just discussed. So I do that side first. I loop it through the quad, I sew the loops together, I sew the graft together using a fiber loop, and then I take one end of that stitch and I put it through the patella periosteum at that corner, super medial corner there, and then I do everything else the same way that I do with an MPFL.
Dr. Chris Tucker:
Gotcha. Okay, great. Yeah, look forward to seeing that one come out.
Dr. Miho Tanaka:
Yeah.
Dr. Chris Tucker:
A few other quick questions about the specifics of your preferred technique. Talking about graft options, what's your preference and why? And does it vary at all based on certain patient characteristics or history or anything else?
Dr. Miho Tanaka:
Yeah, no, I think if you're talking about allograft versus autographs, I generally use allograft unless the patient has some real desire not to do that. In terms of what type, I prefer something... I generally use semi-T. At my institution, those have been on backorder for three years or something like that. And so you can also cut down a Tib-Ant or a tibialis or something like that.
The graft size that I pick on the paper, it usually says 7.5, ends up being about a 5.5, which is what I use. So if it's bigger than that, I'll cut it down to that. And for length, especially because for the MQTFL, you have to create that loop, I usually try to get something around 270 or so. In terms of autograph versus allograft, really no difference has been shown in terms of recurrence rates or re-instability rates, and it's kind of mixed in terms of who does better, but I would say there are more studies showing that patients actually do better with allo than with auto, which is promising.
I think one of the thoughts behind this, which really hasn't been shown, but a lot of us in the patellofemoral world talk about is ligamentous laxity is always a concern for these patients, and I didn't mention that during my exam, but that's also something important to check for. And does it really make sense to take someone who's loose and then take a tendon from them that's also probably a little bit loose to replace a tendon that's a ligament that's loose? So for all of those reasons, I tend to use allograft in these cases.
Dr. Chris Tucker:
Sure, yeah, great thought process. How about your experience with various fixation methods? Do you think it really matters and what are you currently using and why?
Dr. Miho Tanaka:
Yeah, so for the anterior side, I've moved to the MQTFL, and on the femoral side, there are lots of different options. If you look at, I think it was Aaron Krych's paper out of Mayo, they did a nice systematic review comparing bone tunnels versus cortical fixation on the patella side and showed no difference with that. On the femoral side, we actually we have a paper hopefully coming out soon that shows a similar thing that bone tunnels versus cortical fixations don't seem to show much difference, although there's a lot less of those that are just anchor fixation there.
I do bone tunnels, I use an expanding anchor, and I do think that matters. Andreas Gomoll actually published a study several years ago showing that with the interference screw, if you're kind of screwing it in, you can overtighten the graft during that process. A button is an option as well, but I don't like anything where you can't undo it. And so the benefit of potentially an expanding anchor is that I can put it in, see if I like it. If I don't like it, I can just unhook it, reset the length, and then whenever I think I'm happy with how everything is moving, then I can deploy it. But I think that in terms of the literature, all of those are good options and there's really no right answer with those.
Dr. Chris Tucker:
Sure. Great. Okay. We talked about a little bit already, but with respect to alignment, could you just speak to your thoughts on the rotational alignment of the extensor mechanism, how you're evaluating this clinically and radiographically? I know you already kind of mentioned that a little bit. But then really when are you adding a tibial tubo osteotomy to your medial-sided soft tissue reconstruction?
Dr. Miho Tanaka:
Yeah, that's a great question. There's so many ways to do it. And so I've tried to streamline this and I usually use TTTG as an indicator of everything else that's going on around the knee, whether it's valgus or rotation. It really is kind of the distance between the tuberosity and the trochlea and it's not just about how lateralized is the tuberosity. You can have external rotation of the tibia or femoral anteversion. Any of those things can kind of change that distance.
So that's kind of the first thing that I look at. And I do that on CT in full extension, and 20 is my approximate cutoff. But of course, if someone is short or tall, that could change. And if it's high, then I'm starting to look at, well, where is that coming from? Is it the eversion? Is it tibial external rotation? Is it the fact that the trochlea is so dysplastic that the groove is actually medialized and that increases the distance?
So what I do next kind of depends on where it comes from, but in terms of that sort of cutoff, we also showed in our study looking at length changes that if it's greater than 20, that's when you start to see abnormalities there. That doesn't mean that I would correct everybody who's like 21 millimeters with no other risk factors, but I do think that it kind of gives you a sense that there may be other things going on that you might want to think about fixing.
Dr. Chris Tucker:
How about the coronal plane alignment, especially valgus obviously for lateral instability? When are you looking at that on your standing alignment films? When are you looking at doing something about it?
Dr. Miho Tanaka:
Yeah, it's honestly pretty unusual for me to do a valgus correcting osteotomy. A lot of these patients, they come in and they have unilateral instability and bilateral valgus. And I talk with them and sometimes their TTTG is not that high, so they have not as great of forces playing that role in their instability. We talk a little bit about it, especially if I see a weightbearing axis that's in the center of the lateral compartment or over from there. But my experience has been that even in these patients who generally if they have that much valgus, they're not high-level athletes for the most part. They don't really like the idea of that correction because they feel fine on the other side. So it's kind of a discussion that I have with them. That's kind of where I start to think about it. But in all my experiences, having that discussion with the patient, almost all of them really don't want that fixed. So my experience there is fairly limited.
Dr. Chris Tucker:
Sure. Okay. So slightly outside the scope of this infographic, but related, can we just speak briefly on the topic of trochlea dysplasia and how that plays into your evaluation and management of these patients, i.e. your thoughts on trochleoplasties or how much are you thinking about that and does a traumatic versus a chronic recurrent atraumatic dislocator factor in?
Dr. Miho Tanaka:
Yeah, so you were talking about in terms of whether or if I would add a trochleoplasty onto these patients. Yeah, absolutely. So that is probably the question of the day, and there's a lot of discussion on this. We know that almost everybody has trochlea dysplasia in people who have dislocations, but not all of them, or hardly any of them actually need a trochleoplasty. And it's a little bit confusing, I think the limitation right now is that when we assess the trochlea on 2D, we don't really have a great sense of what that looks like, and oftentimes it looks convex, even though it really isn't.
And I think John Fulkerson has done a lot of work with the 3D to really kind of help improve our understanding of that. I myself am very reliant on the dynamic CT, and the reason for that is when you see a patient go into active extension, so this is basically the radiographic version of a J sign, we're able to see the path of the patella. And in the ones that need a trochleoplasty, in my opinion, you can see that there is this prominence of the trochlea that's literally pushing the patella out of the way.
That combined with seeing a TTTG, that's usually abnormally high, something like around 30 or so that even with a TTO, you wouldn't be able to get them in line, those are the ones that, in my opinion, need a trochleoplasty very, very uncommon even in my practice.
Dr. Chris Tucker:
Yeah, that's insightful and I agree, probably one of the most popular topics discussion at this point when you're going to a patellofemoral session.
Dr. Miho Tanaka:
Yes.
Dr. Chris Tucker:
So just what is the most currently available data on outcomes? What's it telling us about reasonable expectations for patella stabilizing surgery with respect to things like recurrence rates, returning to sports, and just general complications? I.e., how are you currently counseling your patients?
Dr. Miho Tanaka:
Yeah, so I think the data overall is pretty good. With recurrence rates generally under about 10% for these procedures and return is for somewhere around 70 to 80%. Overall pretty good. If you look at some of the smaller series, even after a TTO, they have pretty high rates of return to sport, and I think there was one looking specifically at football that was low 90s or something like that.
But recurrences is always a possibility. I think that degenerative changes after just having had the dislocation, even if you get it fixed, that's a discussion that I have with my patients. And then in terms of rates of complication, I think they've come down from, originally we were looking at 20-something percent risk of complications, and I think over time we're seeing maybe less of those as people are becoming a little bit more used to performing this procedure.
But of course, the risk of patella fracture is real. The risk of re-dislocation is real. The risk of continued or developing arthritis similar to the ACL literature where it's not just fixing it is not going to undo the fact that you've had some dislocations in the past. And so those are kinds of the things that I talk about. But in terms of return to sport for patients who do undergo this, I think this is a very reliable procedure.
Dr. Chris Tucker:
All right. Well, Miho, you've provided us a really fantastic summary of patella instability and its surgical management. Did you have any other closing remarks you wanted to share with us before we wrap up?
Dr. Miho Tanaka:
I think the only thing I would just add is that this is a rapidly evolving area. And so what we talk about today will be very different than maybe the next time I get invited back onto here. And so I think it's exciting and we'll see what comes next in this field.
Dr. Chris Tucker:
Well, you're always welcome. I look forward to more studies coming out from you and a chance to have you back on again with some updates in the not-too-distant future.
Dr. Miho Tanaka:
Thank you so much, Chris.
Dr. Chris Tucker:
Well Miho, once again, congrats on all your work. Thanks for sharing your time and your thoughts with us today. Dr. Tanaka's infographic titled Medial Patellofemoral Reconstruction Techniques for Patella Instability is published in the June 2023 issue of the Arthroscopy Journal, which is available online at www.arthroscopyjournal.org. This concludes this edition of the Arthroscopy Journal podcast. The views expressed in this podcast do not necessarily represent the views of the Arthroscopy Association or the Arthroscopy Journal. Thank you for listening. Please join us again next time.
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