Should patient age thresholds dictate fixation strategy in total hip arthroplasty?

Listen to Andrew Duckworth and Benjamin Bloch discuss the paper 'Should patient age thresholds dictate fixation strategy in total hip arthroplasty?' published in the February 2022 issue of The Bone & Joint Journal.

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Transcript

[00:00:00] Welcome everyone to our BJJ podcast for the month of February. I am Andrew Duckworth and a warm welcome to your team here at the Bone and Joint Journal. As always we would like to start by thanking all of you for your continued comments and support as well as a big thanks to our many authors and colleagues

who've taken part so far. We hope you are continuing to enjoy our podcasts and all our knowledge translation work delivered from your team here at the journal. We focus on papers each month published in the BJJ as well as our special edition podcast series, that's included our insights from the US along with the special editor series with our invaluable specialty editors here at the journal, both of which we're continuing into this year.

So today I have the pleasure of being joined by Mr Ben Bloch who is Consultant Orthopedic Surgeon at Nottingham Elective Orthopaedic Services, to discuss his study entitled 'Should patient age thresholds dictate fixation strategy in total hip arthroplasty?', which has been published in the February edition of the BJJ.

Welcome Ben and a big thank you for taking the time to join us today. Thank you very much, Andrew and thanks for the invite. So Ben, the aim of your study was to examine the long-term outcomes of total hip replacement procedures with different fixation techniques in different age groups[00:01:00] with the aim to sort of determine whether cemented fixation results in superior outcomes in terms of implant survival.

So Ben if you could just give a brief introduction to the paper and maybe some background to what we know about in the literature or readily about the overall survivorship of total hip replacement. So yes, thank you. So generally, as we all know, hip replacements is associated with reliable outcomes and generally excellent survivorship and excellent patient satisfaction.

And in fact, The Lancet determined it the operation of the century. We know there have been some historical issues with some implant types, particularly for example, large head metal on metal bearings and some hip resurfacings. And we know from registries that there are increased revision rates in younger age groups.

But as we've noticed, certainly in Nottingham, there's an increasing revision burden with things like infection and periprosthetic fracture less with implant loosening, probably associated with better polyethylene over the years. But in general you can get excellent long-term outcomes with both cemented and cementless constructs and using particularly contemporary metal-on-poly, [00:02:00] ceramic-on-poly and ceramic-on-ceramic bearings.

So we set out really to see whether there was any difference in fixation in our tertiary referral centre with a fairly large number of patients. That's a very nice overview Ben of where we are in terms of literature. But before we move on to the study that you've, you've mentioned there, can you give our listeners some details about the idea, which you mentioned very nicely in the introduction, about the idea of the cementless paradox and how this relates or maybe contradicts the GIRFT initiative and its recommendations with regards to fixation strategy.

The cementless paradox was really introduced by Henrik Malchau and his group in 2013. And looking at various joint registries around the world, they all really report increasing uses of cementless hip arthoplasty often despite the very same registry data suggesting that cemented hip arthroplasty is associated with the lower rate of revision.

So your paradox is that you know, your registry is showing one thing, but surgeons are doing something else. Now the GIRFT Report, 'Getting it Right First Time' report came out in 2015. And, and parts [00:03:00] of it examined trusts' usage of different types of implants. And in fact, came out with a recommendation that we should increase the use of cement components, both because of reduced revision rates in the NJR, but also because of a possible cost reduction and cost effectiveness is obviously something that is as important as outcomes.

And it noted that in general, a cemented hip arthroplasty was expected to have a 95% survivorship at 10 years, but that younger surgeons tended to be using more cementless hip arthoplasty and that was likely to be a reflection of what they observed in training and possibly the effect of overseas fellowships.

Certainly not only the US but Australia is using a lot more of cementless arthroplasty than cemented and parts of Europe as well. So if you go overseas to do your hip fellowship, you're much more likely to see cementless arthroplasty than cemented arthroplasty. And there's a best practice tariff as a result of all that to incentivize cemented fixation, which was later modified to include hybrid fixation as [00:04:00] well.

And I think we see the results of that now with the 2021 NGR report showing for the first time that hybrid fixation has overtaken cementless fixation but all cemented fixation, does continue to fall. And I think the growth in hybrid fixation is really at the expense of cementless and cemented fixation with cementless fixation peaking in about 2012 and hybrid fixation growing significantly since then.

Yeah, I think that's a really nice overview Ben of how there really continues to be a, maybe an absudity of debate about, about the mode of implant fixation, which I think is where your paper comes in nicely. So if we move on to the, how it was designed, it was a retrospective analysis of prospectively collected data that was conducted on all patients who underwent a primary, total hip replacement in your institution

in just over a 16-year period from the 1st of April, 2003 to September, 2019. You identified patients from your local database and then link data obtained from the NGR. So Ben with regards to the study design, firstly, what were the criteria for the patients included or excluded? And why was that the case?

Yeah. So the inclusion criteria were really [00:05:00] all primary hip arthroplasty performance here in Nottingham University Hospitals. We did exclude resurfacing. I think that's a different procedure, has got different indications and a different patient population. So it wasn't really generalizable. And there was a few options of the bearing options like large diameter metal-on-metal,

fortunately, not too many here, a smaller diameter metal-on-metal and ceramic-on-metal. And also a few dual mobility procedures, which we really excluded either because of small numbers or because the bearing surface option had now been withdrawn. And there were a very few reverse hybrids and only about seven or eight of those

so we excluded those as well. So can you then give us a brief overview of the primary procedures you performed and how the baseline demographics of those compared in terms of your cemented hybrid and cementless? Sure. So I think it's important to note that in our series, the cemented group was generally older and the cementless group was generally younger.

And most of the surgeons here in Nottingham don't have necessarily have a one construct fits all approach.[00:06:00] And we'll we'll do both cemented or cementless and generally choosing cemented for poorer bone quality. The cemented patients were generally a bit frailer having a higher ASA grade, but also tended to have the lowest BMI.

Yeah, very reflective of people's general practice of those various construct types. So, and then in terms of the outcome, what was the primary outcome measure for this study? And how did you sort of determine it? The primary outcome was just revision for any cause. The advantage of revision for any cause is it's very easy to measure and you can cross check with the NGR data.

But it's a very crude endpoint. Yeah, absolutely. Absolutely. And in terms of the secondary analysis you performed, you looked at sort of age cutoffs. Why did you, why did you look at those and why were those cutoffs chosen? So the first cutoff we chose was the age of over 70 and that's the original best practice tariff and GIRFT recommendations for cemented fixation.

So we just looked at that as that was an easy correlation. The NGR then reports age [00:07:00] ranges either less than 55. 55 to 64, 65 to 74 and then greater than 75. So at age 75 seemed to be a logical cutoff to use. And then we looked at age over 80 because these would seem the least likely patients to have their implant revised, and likely to have the poorest bone quality.

So that was the group where one would expect to see the greatest difference between constructs. Yeah, absolutely. Yeah. That makes, that makes complete sense. So if we, if we move on to the results of the paper, the study group included just over 10,000 total hip replacements from a prospectively collected database.

And that included 1,699 cemented replacements, 5,882 hybrids and just over 2,600 cementless. And of these, 179 were revised and this included 47 cemented, 93 hybrid and 39 cementless. So in terms of your primary outcome measure, Ben, what did you sort of find in terms of the overall implant survival and how the three groups compared?

So I think the first thing to say is that all three groups did pretty well. [00:08:00] Near survivorship was 97% in the cemented group, 97.6% in the hybrid group and 97.9% of the cementless group. That does open up a little bit by 15 years with 95% in the cemented group versus 97.4% in the hybrid group, but still pretty good at 15 years.

We found that the cemented group had the worst survivorship, but this was not statistically significant. Interestingly then when we look at the reasons for revision you do start to see some differences. So there's a difference between an aseptic loosening between cemented and cementless cups. So we had, I think, 16 cemented cups, that were revised for aseptic loosening, which is almost 1% of all cemented cups that went in. Look at the cementless cups in both the hybrid and the cementless groups and its about 0.05% of the cementless cups are revised asceptic loosening, so there is a significant difference there. Yeah. If you look at the numbers revised for instability, it's about the same percentage in all [00:09:00] groups. But again, the cementless cups had a different revision profile rather than the socket revision about half of them could be dealt with, with a liner exchange rather than the full revision.

And you could argue that that's a potentially lesser procedure. Yes, it's still another operation, but it's potentially less morbidity than taking out a well-fixed socket and revising the socket. Again, another advantage of a cementless socket is this allows you to do a liner exchange for a dare type procedure.

And the final thing to say is we saw a definite increase in stem revisions for periprosthetic fracture, with cementless stems compared to cemented stems and that's a well-known factor in the literature. And I suppose one of the things that I would say, and we will maybe come on to weaknesses of the study a bit later.

But one of the things that is that you could say is that we don't have data on any fixation of periprosthetic fractures. We only have revision data. Absolutely. But before we move on to the sort of secondary outcome measures related to that, I noticed as well with your mean time to revision[00:10:00] you know, it was about 4.5 years in this mentor group and two to 2.5 in the hybrid and

cementless, how, how do you sort of interpret those numbers? What was your thinking behind that? Yes, that's interesting. I did wonder whether there is possibly the option of people considering a, for example, let's look at a dislocation, a more conservative option such as revising a liner to a constrained liner and going in there slightly earlier than you might do, if it was a cemented socket and you had to revise the socket. It is possible that, that the, the difference in implant fixation would have an effect in terms of the time to revision in that you might look at a dislocatng hip with a cementless socket and the well aligned components, and think you could go for a more conservative option of revising to a constrained liner earlier than you might do

if it was a well-fixed cemented socket. But our study did not really look at the differences in time for those revisioning options. Absolutely Ben, I think I agree that was one thing I thought, but, also [00:11:00] there was obviously enough real revisions to maybe delve into that in to too much development

thankfully. And what about in terms of your secondary outcome measures when you looked at sort of patients over age of 70 and then your other age cutoffs, what did you see then? So I think the first thing to say is there is no significant difference in revision rates from a statistical point of view at any time at any age group that, even in patients over 80, we found that an all-cemented construct had the highest revision rate compared to hybrid and cementless. Was that surprising to you? Was that what you were expecting to see? Did you think when you looked at the overall analysis to begin with? It was slightly surprising. I thought that slightly surprising that the cemented had the lowest implant survivorship at 10 years.

I didn't think one construct would be better than another, but I thought they would all be fairly evident. No, absolutely. So if we move on to the, sort of the implications of the study Ben, you know, the strengths of it are without question in terms of the size of the study and the analysis performed, and it has shown I think quite clearly that while all fixation devices for [00:12:00] total replacement perform well at long-term follow-up cemented fixation is associated with the lowest implant survival in all age groups, including more elderly patients, although this was 

obviously not significant as you've very nicely highlighted. So Ben what do you feel are the key take home messages of the study, I suppose, sort of caveating and considering any potential limitations of the data. So the first thing to say is that all implants perform well, but certainly in our unit an all-cemented fixation had the lowest implant survivorship.

And so we would suggest that surgeons should carefully monitor their own outcomes and make sure they are getting the best results they can. I think the other thing to say is that there isn't much evidence out there that switching the implant choice or fixation philosophy of a poorly performing surgeon will improve their outcomes aside from perhaps removing an implant

such as a large diameter metal-on-metal bearing. Certainly here the, senior surgeon on this paper, probably the highest volume hip surgeon, really does have a truly mixed fixation philosophy. And I'm not sure that one philosophy fits everyone. And certainly in my own practice, I [00:13:00] use a variety of philosophies depending on bone quality, age, activity levels, and so on.

And so a nuanced and individualized approach to accommodate those variables is probably a sensible solution. We certainly found that cemented sockets seem to be a bit of a problem with loosening. And there is also the, again, coming back to the limitation of using revision as your endpoint, there are quite a lot that I think have certainly have loosened lines around them, but may not be revised particularly if they're loosening in elderly patients.

But flip that round and cemented stems, I think certainly confer advantages. They do well. They certainly offer you advantages in the conservative cement and cement type revision procedure as well. So I think we just simply suggest that implant choice and fixation philosophy is fairly complicated

and surgeons should be aware of their own and their own unit results and act if their results are of concern, but if their results are good and they're practicing in a sensible and a cost-effective environment, then we feel our review should support surgeons doing what works in [00:14:00] their own hands.

No, absolutely Ben and I think that's a very nicely put, I think it's always our nature, so just to find, trying to find the one philosophy or the one way of doing things, but I think you discussed very nicely in the end of the paper about how there probably isn't one philosophy that suits all, and you've got to adapt to the patient and to your practice as well.

In terms of just what we touched very briefly on, your findings, your thoughts basically, in terms of the findings in relation to the causes of resistance between the groups, is that what you sort of expected and is that sort of consistent with the literature? Yeah, so I think that is 

 fairly consistent with the literature. So we've been here before, but a cementless socket allows for liner exchanges, which a cemented socket obviously doesn't. We did see significantly lower revision rates for aseptic loosening of the cup with a cementless cup, but a slightly higher revision rate for stem, aseptic

loosening with a cementless stem and definitely a higher revision rate for stem periprosthetic fracture rates with a cement stem. There are the implant design options that can mitigate that. So for example, Josh Lam's paper in [00:15:00] the BJJ in 2019. Michael Morlock's one from the German registry earlier last year show that adding a calcar collar can be protective against aseptic loosening and periprosthetic fracture fixation.

And the German registry paper is really quite interesting because one of the analyses it does look at the same implant with and without a collar. Same implant with a collar has got a significantly lower revision rate, both for periprosthetic fractures and for all collars. And the revision of that collared stem is the same as the best cement at the stem in that German registry.

So there does seem to be some implant factors that can improve the performance of cementless prosthesis. That's really interesting. That's a really interesting paper as well, and sort of Ben to maybe finish off, you know, we've maybe touched on it at the beginning but what is your take on the data and the literature that suggests, you know, one of the potential driving for using cemented prostheses is the reported lower costs.

Do you think that really bears out in reality and in practice day-to-day or, or do you think there's multiple factors to that as well? So there [00:16:00] are multiple factors to that. Implant cost is fairly complex. It's driven by volume and by local procurement contracts. And, and those can be affected by other procurement contracts as well

for example, if your knee prosthesis comes from the same supplier. But clearly a polyethylene cemented cup is cheaper than a cementless cup, which has got a metal backed cup, a liner, and possibly one or two screws. Cementless stems are generally equivalent to a cemented stem and cement and a mixing system and the restrictor and a pressurizer.

So we don't certainly in our own unit, there is very little difference between the cost of a hybrid construct and the cementless construct, clearly an all-cemented construct is going to be cheaper possibly by about 2 to 300 pounds. I think it's also important, not just to look at the cost of the procedure, but also cost effectiveness.

And there are some studies out there looking at cost-effectiveness of different constructs. There's one from Pennington in the BMJ in 2013, which showed that hybrid was the most [00:17:00] cost effective option in all age groups, except women over the age of 80. And there was one from the BJJ in 2015, which really showed no evidence that any one.

fIxation philosophy was more cost-effective than another in any age group. There are people who argued that cementless hips allow for the potential increase in productivity because it's time taken for the sector between 18 to 24 minutes, depending on what study you read. But I think it's also fair to say that in the NHS, this is rarely an issue.

We generally don't have as many cases on the list as for example, high-volume Australian or US surgical centres. And even the GIRFT report noted that high volume cementless units seem to have issues with productivity. So that may not be the best arguments in the UK practice. No, absolutely Ben. I think that's a really nice point to finish on.

A really nice overview I think of a balanced argument of the findings for your paper. So I'm afraid that's all we have time for today. It was really great talking to you Ben. Thank you so much for taking the time to join us and congratulations again on an excellent study that has [00:18:00] without doubt added to the literature considerably in the area.

It was great to have you with us. Thank you very much. To our listeners, we do hope you've enjoyed joining us, and we encourage you to share your thoughts and comments through social media and the like. Feel free to tweet or post about anything we have discussed here today. And thanks again for joining us

everyone. Take care.