Reliable outcomes and survivorship of primary total knee arthroplasty for osteonecrosis of the knee

Listen to Mr Andrew Duckworth interview Dr Matt Abdel about his paper "Reliable outcomes and survivorship of primary total knee arthroplasty for osteonecrosis of the knee", published in the November 2019 issue of The Bone and Joint Journal.

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[00:00:00] Welcome everyone to this month's BJJ Podcast. I imagined a quiz and a warm welcome to our podcast for the month of November, from The Bone & Joint Journal. It is now a year since our very first podcast and from all the team we would like to thank our readers and listeners for the comments and support we've received so far for our series, as well as to our many authors and guests in who have taken part so far. 

In the past year, we've covered a range of topics and heard from a range of authors from across the globe. We've spoken to guests all the way from the US to India, including a fascinating dialogue between Ian Murray and Dr. Scott Rodeo on cell therapies and orthopedic surgery. As well as a really excellent discussion between Sam Patton and Professor Ajay Puri from Mumbai about his paper on Neoadjuvant denosumab and giant cell tumours.

Through this, along with a series of podcasts that accompany our supplements for the American Hip and Knee Society closed meetings, we do hope these are improving the accessibility and visibility of the studies we publish for both of you as our readers, as well as for our many authors.

So moving onto this month study, as you know, the next 15 to 20 minutes or so [00:01:00] we'll cover a range of topics and aspects of the chosen work emphasizing the important points of how the study has been designed, as well as the key findings from the data and how these potentially fit into each of your day-to-day practices. We also hope to give you a behind the scenes insight into how the authors have developed the study and give them an opportunity to put forward the key findings of their work. 

So today I have the absolute pleasure of being joined by one of my editorial board colleagues here at the BJJ, Dr. Matt Abdel, who joins us from the world renowned Mayo clinic in Rochester USA to discuss his study, entitled Reliable outcomes and survivorship of primary total knee arthroplasty for osteonecrosis of the knee, which will be published in the November edition of the BJJ. Welcome Matt and a big thank you for taking the time to join us today.

Well, Andrew, thank you for the warm welcome and thank you to the journal for allowing us the opportunity to do this podcast on our article. It's exciting and I do think these podcasts provide a large amounts of information accessibility to the leadership and actually the larger orthopedic audience.

Thanks very much, Matt. That's really, really good to hear. So if we [00:02:00] move straight onto your paper, Matt, as you nicely describe knee osteonecrosis develops from a disruptive *inaudible*  causing periarticular bone and cartilage loss, which in the advanced stages may lead to joint degeneration and destruction. And you state that total knee replacement or arthroplasty for this condition has traditionally been associated with likely suboptimal results. So with this in mind, can you give us a brief background to the paper and in particular, what we know from the current literature about the role of TKA for this condition?

Now you've highlighted some of the main points nicely, andrew. We know that knee osteonecrosis in both primary and secondary situations can lead to degenerative joint disease, and this can be profound for patients. They can have debilitating pain, inability to emulate an exponential increase in their degeneration.

Typically, total knee arthroplasty has been associated with core results and those are results in regards to survivorship, high rates based septic loosening or clinical outcomes and a higher rate of complications, namely periprosthetic joint [00:03:00] infection and manipulation or anesthesia. And we asked in our study with contemporary knee arthoplasty, including the adjuvate use of metaphyseal fixations, such as cones, or even some proximal diaphyseal engaging, cemented stems, would the results be better in three main areas. That is survivorship primarily free of aseptic loosening, free of any revision and free of any reoperation, clinical outcomes, namely Knee Society scores, because that's what we capture the Mayo clinic total joint registry longitudinally since the inception really of the registry, and how were the radiologic results. And that was kind of the impetus to study that we move forward with. 

That's great, Matt. And I think that's a nice way to explain  the sort of potential holes in literature and how this study was going to add to it and the primary aims of it. So if we move on to the study itself, this was obviously a retrospective review of all patients who underwent a primary TKA for knee osteonecrosis at your [00:04:00] institution over a 10 year period. That was from 2004 to 2014. You initially identified 173 knee replacements and 161 patients for primary or secondary  knee osteonecrosis. And that comprised just over 1% amazingly of the primary TKA or institution over this time period of the study. So with that in mind, it's a large volume center Matt, could you just give us like a brief overview of the routine assessment you've alluded to already, the follow-up assessment of these type of patients in your institution? 

Yeah, you've highlighted some of the big points. Just to reiterate this is a small patient population. This is 1% of all primary total knee arthroplasties done at the Mayo clinic. And this is total knee arthoplasty. We've independently published on unicompartmental knee arthroplasty for osteonecrosis. So this is truly primary total knee arthroplasty for osteonecrosis, with two thirds of these patients were primary osteonecrosis and about one third were secondary ostenecrosis, mostly steroid induced versus idiopathic. 

And, our follow-up [00:05:00] routine is we see people, we call them at two and five weeks to get on the phone. We see them at three months, one year, two year, five years, and every five years thereafter. And so their capture is robust. And when we're seeing these patients at follow up, we're obtaining clinical outcome scores, radiographs and of course having their clinical follow-ups. So we have a large amount of information and a great capture for these patients. 

Yeah. That's amazing, Matt. And I think in terms of  the fact that you're seeing them, not just, you know, sending out outcomes scores or whatever, you're actually seeing those timepoints is amazing. And in terms of for this study itself, what was your follow-up like and retention like for the patients? 

Yeah. So, you know, there were some people that were lost to follow-up secondary to death. There were some patients that had early rerevisions or reoperations, less than two years, but greater than 90% of the patients had greater than two years of [00:06:00] follow-up and were living greater than two years. So that's kind of my cutoff as follow-up so excellent follow-up in this cohort. 

Yeah, definitely. I completely agree. And in terms of, if we move on to , I suppose the technique and the indication itself, what were those over the study period, I suppose, what would also be important to discuss with the implants and the protocol used during the study period?

That's a great question, Andrew. So, we treat these patients from regards to indications, just like any other knee arthroplasty patient. They have to have failed conservative management, debilitating daily pain that is impacting their activities of daily living. And so that's very important to us. I will make a side note that most of these diagnoses were made on radiographs on advanced imaging. That's something that often comes up when we discuss this paper. And once patients have truly failed conservative management, we then proceeded with total knee arthroplasty. 

Our routine at the Mayo clinic during this time period and continues to this date is [00:07:00] a primary posterior stabilized total knee arthroplasty that's cemented which 88% of patients in this series received. So the vast majority. Our workflow is traditionally, and as you might anticipate in North America to resurface that patella, so the large number of patients in a series had their patella resurfaced. And then the nuance part of this was whether or not fixation was utilized with the cemented stem and that was utilized on a case by case basis, the decision made by the operative surgeon. And I can tell you, my personal workflow is not to use a tourniquet on these cases, evaluate the bone, see if the cancellous bone is bleeding. If it is, and I feel like I've got robust bone quality in addition to the quantity, I may not use a stem. If there's any concern at all, it comes into my mind, I will utilize short stem, usually something that's anywhere from 50 to a hundred millimeters.

Okay. Okay. That's really, that's brilliant, Matt. I think that's very clear in terms of the indications of the patients you've included. Just briefly going back to that point, [00:08:00] just to clarify, not many of these patients had MRIs, is that right? It wasn't routine for them all to have them?

Yeah. So it was very rare in fact. It was the diagnosis made on radiographs. And I think we can't forget that the series span a large time span, including a span in which MRI, even CT was not commonly utilized in practice. And so we've utilized it since our indication was degenerative joint disease, secondary to osteonecrosis, we still made most of the diagnosis for knee arthoplasty based on radiographs. 

Absolutely. That makes total sense. So if we go onto just before we get onto the result, I suppose one of the, it's always just good for our listeners, just to briefly lay out the analysis you performed, which I suppose is really related to the regression analysis. Can you just talk about that briefly, Matt? 

Yeah, we used a two-way analysis, the first one was a Kaplan-Meier survivorship. And really you could use a Kaplan-Meier survivorship curve, or we could utilize a competing risk with a competing risk being death. So many of these patients [00:09:00] survived and so we didn't feel that it would be beneficial to have a competing risk analysis so we utilized Kaplan-Meier survivorship curve. Looking at survivorship free from aseptic loostening, survivorship free from any revision and survivorship free from any reoperation. 

Then we did a Cox regression analysis. And that was helpful for us to look at hazard ratios and look at possible factors that might indicate failure. And we'll talk about that in the results section, but those were the two main analyses we utilize in the series. 

That's great Matt, a really nice summary. So if we move on to the results then, so just reiterate to our listeners and we're repeating ourselves a bit here, but 156 patients of which are 167 had TKAs in the analysis. The mean follow-up from surgery was six years. The range was two to 12 so very good. And again, the main outcomes that you mentioned earlier, survivorship free from aseptic loosening in revision, or reoperation. The second being complications and then finally it was clinical and radiological outcomes. So if you can just detail the findings, I suppose, probably the key one really in relation to [00:10:00] survivorship on what those analyses show when looking for risk factors for failure. 

Yeah. That's very well summarized as always Andrew. So I think like you said, we had three main buckets, survivorship, clinical outcomes and radiologic outcomes. And the key one to the surge of the audience who we were talking to today is survivorship free of aseptic loosening. And this is traditionally the outcome they had done for another series. And we looked at survivorship free of aseptic losing at 10 years. So this is not short term follow-up, this is a decade. And, that's when I kind of, in my mind, consider that beginning to be long-term followup. And that survivorship free of aseptic loosening at 10 years was remarkable, so 97%.  So, I mean, those are numbers that compete with the most routine run of the mill osteoarthritis with excellent implants, excellent surgeons.

We then secondary looked at 10 years survivorship free of any revision. Now that's important because any revision of course includes periprosthetic joint infection, for [00:11:00] instance, because you have implant removal and that was 93%. And, as I alluded to, there is the usual one or 2% of infection that occur. And that's why that rates a little lower than a free of aseptic loosening. And then we looked at survivorship free of any reoperation, which I personally think is important cause any reoperation includes anytime you open up the knee, but you may not exchange implants, i.e. wound dehiscence, stitch abcesses, things of this nature. And that was 82% so lower, but we can't forget that most of those reoperations are quite minor. And the take home here is that the survivorship free of aseptic loosening at 10 years was 97%. 

Which is, like you say, it's remarkably comparable to just routine joint arthoplasty as you say. So, with regards to the complication profile in these patients did you find anything different there or anything untowards? 

You know, I think Andrew, the thing that popped out to me to just kind of go directly if someone's listening to this that are going to be taking care of a patient, is they had a higher [00:12:00] than expected manipulation under anesthesia rate. That was the main complication that came out with this. And what I define a complication is something that wasn't a reoperation revision or boosting above. And so that rate was almost four to 5%. And so it's important to be cognizant about surgical technique, component positioning, implant design, but most importantly, be cognizant in how you counsel your patients and how you post-operatively manage these patients. So this is a subset of patients that I'll see more frequently to ensure that their motion is on track. 

Yeah, that's interesting. And is that because you think it's related to the primary condition, I suppose, or are these patients slightly younger or is there anything particularly you feel from either from the data or from your practice about that, why that is?

I think it's threefold. I think one in general, this is a younger patient population. We know that's a higher risk for a manipulation under anesthesia. Number two, I do think there's something with the pathologic process and the pathogenesis of osteonecrosis that impacts the [00:13:00] synovial membrane. In addition to this *inaudible*  that arrive in the knee that may contribute to it. And I think finally, a lot of these patients are so debilitated that the pairing the musculature becomes quite contracted, that it just takes a little more time to loosen up the soft tissue envelope, if I may say it that way, surrounding the knee, after the arthoplasty is done.

Yeah. That makes sense. That really makes sense. That's interesting. And just before we actually move on from onto the sort of clinical and relapse outcomes, was there any factors you did find in terms of the increased risk of revision. 

It was interesting, but we went through an extensive analysis using the Cox regression analysis and did not find any real significant factors that predicted failure. And that's probably because it's rather homogeneous population of individuals that develop this very nuanced and quite unique pathologic process of primary, secondary osteonecrosis. 

That's interesting. [00:14:00] That's interesting. 

So I think Andrew, I think, you know, what happens is that the process of osteonecrosis overpowers any other factor that we were unable to see other factors as contributing to failure. 

Yeah. Overwhelms everything else you mean? 

Yeah. 

Just to clarify though you didn't find a difference between primary versus secondary though did you either, that was part of the analysis.

That's correct. That's a great question. So we did look at that. Now you have to keep in mind that two thirds of the patients were primary one-third were secondary osteonecrosis and within the secondary osteonecrosis, there were a variety of etiologies that contributed to that, but you're right in regards to survivorship, we found no difference at all, between those patients who had a need for primary versus those had a total knee for secondary osteonecrosis. 

That's interesting. Well, we can obviously come on to that in a bit when we discuss why that is and how that compares to literature. But before we move on to that, I suppose, what did you find in terms of, I suppose, the clinical outcomes and the Knee Society scores and the radiological outcomes from that.

[00:15:00] Yeah, for Knee Society scores we found that patients went from a median of 57 preoperative to 91 postoperative both in themselves, impressive numbers, very low pre-op and very high in the nineties post-op and that's their most recent followup and that was statistically significant. I would also say that's clinically significant jumped like that, that's nearly 40 points. And at most recent followup, we had no radiographic evidence of loosening at any patient that have yet to be revised. So there were no impending failures. Based upon radiographic criteria of impending loosening.

Yeah. So that's interesting. So that's great Matt, if we sort of move on to the implications of the work Matt. The strengths are, I think that without question, it's a large contemporary study of cemented TKA for osteonecrosis. It's from a very high volume center. And as we've already discussed the outcomes and the follow-up are excellent. And the retention is really, I think, remarkable. What do you feel are the key findings of the work, I suppose, in the [00:16:00] context of any potential limitations of the data?

Yeah, my key finding take home, and what I say is when you go back to your practice and you see the next patient with primary, secondary osteonecrosis who has joint degeneration, that's failed conservative management, you should not be hesitant to proceed with total knee arthoplasty. If they fail conservative management, radiograph showed joint degeneration. In contemporary series with contemporary implant hands of high volume surgeons, these patients do extremely well, have significant improvements in clinical outcomes and have 10 years survivors free of aseptic loosening. It competes with any other routine osteoarthritis. So I do not think that this is a contraindication for total knee arthroplasty. Second thing, I think, you know, traditionally surgeons have been apprehensive about proceeding with total knee arthoplasty in the subset of patients concerned about aseptic loosening. 

The second thing I always say, and I learned from this paper in looking at the data, writing [00:17:00] the paper, editing the paper is that if you think you need agiment fixation with a cemented stem, proceed with that. In contemporary implant design, it is minimal incremental time, there's minimal bone that you have to remove. And it does give us the protection, if there's poor bone quality for long-term implant fixation. 

Finally, my kind of third take home from this is be cognizant about manipulation under anesthesia and the limited motion that these patients may have postoperatively. And so if you use any new Agilent treatments, if you want to follow these patients closer, if you want to have a lower threshold for manipulation under anesthesia, just be cognizant about it and you should set the expectation preoperatively that this is one of the most common complications after the procedure in this subset of patients.

Fantastic. That is a really clear three messages,  from the data - very much supported by it as well. But if we just move on to, I suppose, [00:18:00] just briefly about limitation, could it be argued that obviously the Mayo clinic is a very high volume center, a lot of expertise there, could that potentially be perceived as a limitation of it in terms of, does it have to be high volume surgeons or high experienced surgeons that are doing this do you think?

 I don't think so, but we all are aware of the data on volume and complication profiles. So I think that's unrelated to this particular topic, but more related to knee arthoplasty in a bigger perspective. So clearly if there's any concern or you're uncomfortable with having to increment to use additional fixation, then maybe the patients should be referred. I think, you know, in this series, it spanned a time period that included a number of surgeons from the Mayo clinic and so that in itself almost takes care, even though it's from a high volume institution with the majority of surgeons being high volume, we do have a number of surgeons that participated in the series. So it mitigates that with a [00:19:00] heterogeneous number of surgeons who participate and take care of these patients. 

Sure. No, that makes sense. And I suppose as well, what you're sort of saying is that the condition itself doesn't preclude people from doing it as long as their volume is reasonable, is that correct?

Yeah, absolutely. 

So in terms of looking at the previous literature then, how do you feel that your results fit into that Matt? Particularly with, I suppose, we've alluded to already, in terms of implant design, and as we've already said, comparing it to routine TKA for osteoarthritis. 

Well, this series seems to indicate it better than historical series. There are a couple of more recent series that have shown contemporary results, have done much better in patients with knee osteonecrosis. But this is I think the largest that I'm aware of, unless anything's changed recently with this length of followup and this completeness of followup showing with contemporary implant designs, contemporary surgical techniques, and contemporary perioperative management to these patients, [00:20:00] the results compete with knee osteoarthritis, and it does seem to be better in regards to survivorship free of the numerous and points I noted before, better in regards to clinical outcomes. And, you know, to date, knock on wood, our radiographic evidence of loosening is zero in those who aren't revised so great results in regards to the radiographic parameters. So we are moving in the right direction compared to historical series. 

Absolutely. And if we just briefly go back to what we alluded to before, how does your study compare in terms of the previous data? What we discussed earlier about the indication for it, whether it's primary or secondary osteonecrosis, because there is a slight difference there isn't there

yeah. You know, previous series had shown a difference between primary and secondary osteonecrosis. And I thought that would be the same for a variety of reasons that if it was a primary osteonecrosis, there was more of a pathologic process. If it was secondary, it might be temporal related to the external environmental [00:21:00] factor, that for instance corticosteroids that might have been used for A, B or C other pathology, 

And in this series throughout the entire analysis, we found absolutely no difference whether it was primary, secondary, and the cause of secondary. So in my mind, in contemporary practice, I lumped them together when I'm treating them. And I look for the same indications. You fail conservative management and you have radiographic evidence of joint degeneration in my mind, regardless of primary, secondary, I treat you the same. You have the same potential outcomes in regards to the parameters we've discussed. 

That's brilliant. That's great.

Well, Matt, I think that's actually all we have time for - we're running out of time there. But thank you so much for joining us, Matt and congratulations on an excellent study that is without doubt a real invaluable addition to the literature in this area. So thanks for joining us, Matt. 

Yeah. Thank you very much, Andrew greatly appreciate it.

Not at all. And to our listeners, we do hope you've enjoyed joining us and we encourage you to share your thoughts and comments through Twitter, Facebook, and a like, and feel free to post a tweet about anything we've discussed here today. And thanks again for joining us.