Managing revision risk and dislocation: the role of enabling technology and surgical approach

Listen to Andrew Duckworth, Dominic Meek, Ed Davies & George Haidukewych discuss the management of revision risk and dislocation in hip replacement.

This episode is kindly sponsored by Smith & Nephew.

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Transcript

[00:00:00] Welcome everyone to episode one of our Smith & Nephew sponsored special edition podcast series. I'm Andrew Duckworth and a warm welcome back to you all from your team here at The Bone & Joint Journal. As you may know, this special edition series is focusing on hip hip replacement surgery, including what the current issues are, what the emerging technologies that may help this, these issues, and what the future may hold for this area.

In this episode, we will be looking at the ongoing challenge of dislocation risk in hip replacement surgery. Now while dislocation rates have been decreasing over time, they still present a significant complication and risk to our patients. We will thus explore how a combination of surgical approaches along with enabling technology can play an important role in reducing this complication.

We'll also take a dive into how using advanced materials and leveraging innovation planning and execution tools can potentially enhance surgical outcomes. And additionally, we'll discuss how some modern technologies offer a comprehensive solution that addresses the surgical journey from pre-op planning.

To implant selection and finally precise execution. So for today's podcast, I have the pleasure of being joined by two guest surgeons and a colleague here from the [00:01:00] BJJ. Firstly, I'd like to welcome Professor Ed Davis, who is a consultant orthopaedic surgeon based in the Royal Orthopedic Hospital at Birmingham.

Ed, great to have you with us. Hi. Thanks very much for having me. Looking forward to it. Secondly, I'd also like to welcome Dr. George Haidukewych, who is an orthopedic surgeon based at Orlando Health. George, thank you so much for taking the time to join us today. Great to be here. My pleasure. And finally, I'd like to welcome my editorial board colleague here at the Journal, our specialty editor for hip Professor Dominic Meek, who is based in Glasgow.

Dominic, great to have you back with us. Great to be here. Thanks very much. So to kick off team, I thought we would take a look at where we are at with dislocation after total H hip arthroplasty. So Ed, if I could maybe start with yourself. For our listeners, can you tell us why dislocation remains a concern following hip replacement surgery and what the key current causes are?

Well, I think the, the first thing to say is none of us have ever had a dislocation, so of course we haven't. So we're always talking about somebody else, aren't we? Somebody else's dislocation? And we hope to goodness that when the phone rings and there's a dislocated hip, the first thing that the fellow or the registrar says is that it's somebody else's, not your hip.

So [00:02:00] dislocation is clearly still a problem. We did some recent work from, from our NJR and dislocation if you choose a decent bearing, certainly with XLP in the last 10 years or so, the dislocation the need for revision, the second highest course is dislocation. Next to periprosthetic fracture. I think if you look across lots of different registries, you see that it sits in second or third place for the, for the reason of dis for major revision, major revision surgery.

So I think it, it is still causing a problem. I, I think the other issue when we just look at revision for dislocation is that hides actually what's happening to patients.

We know that a patient who has one dislocation has a 50% chance of gonna get a second dislocation. And even if they might not end up to revision, we know there's a significant psychological burden. Having a dislocated hip is an incredibly traumatic event for any patient. What are the rates? Well, the rates of dislocation are definitely coming down with simple things like increasing head size with the use of new bearings.

[00:03:00] It's difficult to know what the number actually sits on. I think most, most people would say it's around about 1%. I mean, you can see other studies where it drifts up a little bit and some that it drifts down to maybe 0.7, but, but I think 1% is a realistic number now for. For dislocation rates. So I think it is a problem.

It's, it's one of those issues that I think the psyche of the surgeon tries to ignore and we try to downplay, but, but patients still rate it as a very traumatic event, which, which they'd like to avoid. And I think therefore, as surgeons, were obliged to try and reduce that rate as low as we can possibly get it.

Absolutely. And just just before I, I move on from that, in terms of, you know, the causes of dislocation, do you think that's sort of changed over the years? Do you think we have, because that rate has dropped, has the causes changed over that time period? Do you feel? I. I mean, I, I think we, we've certainly increased our head sizes and I think that's [00:04:00] had a very major effect on the rates of dislocation, I think as stem designs change, they also increased offsets, and we know that offset is, is very good at.

Resisting dislocation or reducing your instance of dislocation. We know that neck geometry also helps. So I, I think as we've changed head size and geometry of, of femoral components of change, that's probably brought the risk down. We published and others have on the use of elevated rim liners that, that, that seems to reduce.

For posterior approach certainly reduces your risk of, of revision, of all causes and dislocation. So I think, yeah, we, we have made advances and then more recently with the interest in dual mobility. Which has clearly been around in parts of Europe for a very, very long time. But the rest of the world has certainly become more interested in that, be because of its effect on reducing dislocation rates.

Yeah, no, absolutely. And that sort of leads me on to yourself, George. I wanted to touch on something that Ed just mentioned there, but you know, [00:05:00] looking at dislocation rates and the various surgical pro approaches, obviously there's been quite a lot of this that's developed over the past few years, particularly the idea of the DAA and things like that.

Where, where are we at with that and what are your thoughts on it? You mean, you mean dislocation rates comparing the two approaches? Yeah, absolutely. Yeah. Yeah. I think that the bigger series there are series that show no difference. There are also series that show that the DA dislocation rate averages out at about one half of 1% compared to, as Ed said, about 1% for the posterolateral approach, and the direct lateral is even lower.

It's about 0.2. If you look at the comparative series from the Rothman group perhaps has the best comparative study on this because it's the same surgeons choosing approaches. You know, guys that are experienced high volume surgeons and that's what they found about one in 200 for the DA, one in 100 for the posterolateral, and one in about 350 for the direct lateral.

So approach still does matter. I, I think everybody believes that at this point that approach can influence your [00:06:00] dislocation rate. The interesting thing is that if you look at the series on DA, which is growing in volume as far as we could really get analysis of dislocation rates when they're that low, they mo most of them are posterior, which is fascinating.

Mm-hmm. You would think that more of them would dislocate anteriorly because of all the releases, but more than half dislocate out the back. And that's I'm sure when we get to the patient specific modeling, how that could be extremely helpful to figure out why that's happening. Yeah. Absolutely.

Absolutely. George and, and Dominic, before we move on to that, 'cause that's what we're gonna be talking about next, what George just mentioned, but it'd be good to hear your sort of take on this thing from, you know, from a journal perspective and sort of you know, our registry perspective. What are your thoughts on how that, that dis dislocation rate has changed over the years and also about the approaches.

Well, I think if you, if you start with the surgical approaches, it's just one factor of many factors and sometimes it's difficult to tease that out. Registry data obviously has selection bias. I think one of the things particularly is that we do know the high [00:07:00] volume institutes and surgeons that are associated with lower dislocation rates.

It was interesting Ed pointed out about his paper on from the NGR. Posterior lip was important in a posterior approach, but didn't actually have an influence in other approaches. And that was where all revisions, not just in dislocations, perhaps impingement and loosening or whatever. And quality of life is obviously something that particularly does affect dislocation, but I think age is another thing in.

You have to look at the demographics of the patients you're operating on. Older patients have a higher instance of dislocation, so you have to be careful. You're comparing like for like with IT and the NGR data. And it's not really a substitute just doing the surgical approach for preoperative planning and anticipating, for instance, age and spinopelvic.

Changes in the movement and how the, a stiff spine, a flexible spine, may change over the, the, the decades. But yes, it's, it's it's complicated. The anterior approach. Also, there's different varieties of anterior approach. Some [00:08:00] will do releases posteriorly, so. In fact, you are still releasing the, the top of the femur.

So and you're comparing a supine patient with a lateral patient and the pelvic relationship to the, the spine may be different as well in those cases. So lots of factors that are difficult. You're using radiographic assessment often for inclination, inverse, and in the anterior approach, which you don't use in posterior approaches.

But there again, we're now using navigation and robotics. So it's an ongoing field and we don't know all the answers yet. Absolutely Dominic. And that, that sort of leads us on nicely into talking about like the role of technology, which you've sort of mooted already. But maybe George, if I could come to you back to yourself, you know, looking at the role of technology in total hip arthroplasty, can you sort of give us an overview and a, a bit of a concept of the concept of personalised hip replacement surgery and how this may, may help with with us moving forward.

Yeah, I think the key takeaway is that there is no safe zone for everybody on earth, right? There's no number that will [00:09:00] work and ensure everybody an optimally placed component. To avoid impingement, wear, et cetera, dislocation. So the big question then is if there is no safe zone for everyone, how on earth do you define that safe zone for a particular patient?

What is the formula? And this is where technology helps. If you do advanced, whether you use a CT or 2D planning. You input the position of the pelvis. In other words, we get sitting and standing views of the lumbosacral spine and we know the pelvic tilt and we know whether it's mobile or not. The purpose of that is to catch the outliers, the people that are either tilted way back or way forward where you need to do something to change the version of your cup regardless of approach.

But the older recommendations would tell you, okay, if your pelvis is tilted forward, add a little anteversion. If it's tilted backward, take a little anteversion off. But they never told you what number. What does that mean? Take a little anteversion off. Five degrees, two degrees. And how do you do that? How [00:10:00] with your naked eye, can you move a stick from 41 to 44?

I mean, I don't know if I could do that. So not only is it difficult to hit the number, but you need to define it. And in my practice. We do that in every patient. We get sitting and standing views of the of the pelvis. We look at the tilt and we use in some patients 3D imaging to do an impingement analysis.

So I can essentially trial before I even open the patient. I know that, for example, with a size 54 cup, a 36 plus zero head, a high offset size five stem, I will have an impingement free arc of motion if I put the cup in 40 22. So my target, my sizing is everything is available to me. Then all I have to do is execute that in the OR.

Mm-hmm. And I know I'll have an impingement free arc of motion. And not, not only that, but it'll tell me the effect on offset and leg lengths. Basically the operation is done in your brain. Before you get in there, all you have to do is execute it. And then how do you execute it? Well, with navigation, it gives you the number.

Say it's 42 17, you can hit that number. [00:11:00] So that's why technology, at least in my hands, has really transformed the accuracy of my hip replacements. And George, before we move on anecdotally, have you found that has actually changed your outcomes as well? Is that, have you felt that that confidence when you're actually doing the hip replacement that you're just, you know, it is in the right place?

Yes. Yes. And you know, so far, so good. Obviously I'm keeping an eye on my own dislocations, infections, what have you. Any, any other problems? And so far, so good. I haven't seen It'll take probably thousands of patients to show a difference in outcomes, because if you're looking at a dislocation rate of one to 200, the power needed to show a difference.

It's gonna take a while, but if you look at the data from the posterior approach on navigated hips. Data from Vigdorchik, data from the Australian registry, from, from the UK as well. That it does make a difference. It definitely does lower dislocation rate if you navigate, which to me conceptually means if you have a target and you hit that target, that should logically translate into better outcomes over time.

But you'll need a huge amount of patients to prove that. [00:12:00] Yeah. Does that make sense? Absolutely. I think that's a really good point, you make, George. And actually something we'll maybe come on to towards the end in terms of trying to show that difference, like you discussed. Ed, if I could maybe come to yourself there and maybe delve a bit more into this area and maybe for our listeners, highlight some of the, you know, the material, how material and implant design advances are helping with this as well, and reducing that risk of dislocation, some of which you've mentioned already.

Yeah, I mean, I think that the materials that we're using in hip replacement now with the bearing surfaces, all it's key to it give us that confidence that we can start increasing our head size, which, which we know makes the biggest difference. So I, I mean, I think we're seeing a very obvious shift around the world as to what bearings we're using and.

We we're settling really now that if, if you want to choose the best bearing, it's either ceramic on highly crosslinked polyethylene, or it's ceramisised metal on highly crosslinked polyethylene. And the wear rates from those bearings are phenomenally low, almost unmeasurable. So that's now given us the confidence that we can start to go to the thinner [00:13:00] polys.

Moving towards the thinner polys increases our head size. In the US and Australia, they've, they, they've kind of gone up quicker than I think we have in the UK. We've still remained quite conservative in the UK on our head sizes, and I must admit it took me a while to go from 32 to 36 and much more than 36.

I'm still a little bit cautious, and that's mainly because the tape, the concern around taper problems, but I'm sure we will go up. So we know that a 36 head has a lower dislocation rate than, than certainly than the 28 or a 30. 32, so 36 if, if you can, I think really helps. But, but I mean, I, I think.

It's not just, it's not just frank dislocation that we want to avoid. It's component optimisation for the feeling and the PROMs that we're striving for as well. And I, I'm a big believer that that, that there's not a spectrum of a hip that's in joint and that's dislocated. A a and not just subluxed, [00:14:00] it's that instability that may be leading to some of those that dissatisfaction in some patient groups.

And, and malorientation of the components. And, and we haven't talked about leg length offset changes that obviously affect functional recovery as well, which these type of technologies also help us balance the hip. And as George says, I, I love this, this philosophy that you do pre-op trialing. All your trialing of your hip replacement is done before you walk in the operating room.

Instead of getting that situation where you are swapping out high offset from standard offset, you're putting a plus four on, and then you're back to a minus three. And then you've already put your cup in and then you need a lateralised liner. So instead of doing all that intraoperatively, you can do it all beforehand.

And, and which, which has gotta be better for the patient, but I think also is better for the surgeon. Yeah. In, in removing that cognitive load, just when everything's happening that you are trying to then work out distances, [00:15:00] angles and, and trying to judge. So I love this concept of, of preoperative trialing and planning to, to optimise, to optimise your hip replacement.

The, the other thing that. That I don't think has become clear with technology is that we tend to lump technology as in the navigational robotics all into one term. Yeah. But we, we know that navigation for hips is incredibly precise, and that's been shown for well over a decade. But, but of course we need to know where we're going.

There's no point in having a technology that's incredibly precise if you ask it to take you in the wrong direction. Yeah. And, and that's where I, I think we're, we're starting to understand that and separate the technology so you have your planning so you know exactly where you want to go, and then you, and then you execute that with something like navigation that takes you to that position.

[00:16:00] And, and I think that that would be a key point that I'd want to get over to our listeners is, is when we judge these type of technologies, we separate those two things out. So what's our target? And then what are we using to get us to that target? And, and I think what George is talking about, which is in the uk we've had the modeler system that, that takes us through the sort of range of motions for, for, for quite a while now.

And then we can execute that with navigation. But at the end of the day, you need to know where you want to go. And I think these technologies help tell us that. That's a really good point, ed, isn't it? I, I like how you break that down in terms of that there's the navigation, but actually, like you say, and as George has talked about, personalising that place to go with for each patient is a really important, important concept.

And Dominic, maybe we come to yourself with this with regard, you know, we've just alluded to it a bit already, you know, what are your thoughts on this? First of all, and actually what, why is the data on this in terms of, is this actually giving us a [00:17:00] tangible, a tangible benefit? I mean, I think as George pointed out, the, the, the trouble with the big numbers trying that have to be involved to actually show this, it is difficult because we've got a very successful operation.

Yeah. I mean, Ed's point about navigation versus robotic delivery is very valid. There's quite a few papers coming through showing that show through lower complication rates in navigation only. Compared to robotics. Now that may be particularly regarding infection, extra people in the room, extra contamination of the wounds et cetera.

But it certainly is knowing where to put it and delivering it. There is some evidence for that. The trouble with looking at PROMs is a lot of the PROMs traditionally used have ceiling effect. And, and you're more gonna have to look at the ones that are. Specifically may be designed for looking at impingement as opposed to dislocation.

And there may be range of movement types, sort of issues with that. But the moment you don't tend to do that and dislocation is so low from dual mobility, large heads, et cetera, et cetera, that statistically just show the reduction is difficult when you've got so [00:18:00] many intrinsic bias factors in, in registry data, for instance.

But I, I think the overall direction is you get a sense that there is. An improvement with using, knowing regarding where to plan, where to go for, and then knowing how to guide yourself to that position. Yeah, absolutely. Dominic. And may just before we move on, I'll just come back to yourself 'cause it's the point you made at the beginning, Ed.

And, and I think it's, you know, we could probably go down a bit of a rabbit hole with this in terms of how we look at outcomes for all of orthopaedics, really more than anything. But the dislocation rate is low. But when it does happen in that patient, it has a devastating, potentially devastating effect on their quality of, of life.

And I think that's a really important point, isn't it? But we, we are looking at fine marginal gains here, but it's maybe something where an RCT can't really pick up that the, the impact on the patient, the cost to the health service if they do run into this complication. It's, it's quite stark, isn't it? It, it's absolutely.

And all complications don't, don't, aren't counted the same. And, and I think we're doing some, [00:19:00] there's some good work going on about trying to look at that in PROMs and what patients rate as the most important act you know, outcomes, but also the complications that patients rate as the most disastrous.

Yeah. And, and you know what worries me is you meet these patients who've had recurrent dislocations and they, they've kind of lived their life in fear. That that you know, and, and just because they haven't dislocated again and they only had a single dislocation, that that might be just because they are so paranoid about what they do in life that it's completely destroyed their life.

'cause they're just worried about that hip coming out again. Yeah. So it, it is tricky. You are right. One, one of the issues, which is a lovely issue to have in hip replacement. That our outcomes are so good. So we are looking for marginal gain, aren't we? Which is why, as you've heard the numbers, we need to show a difference, a large, but, but I, I think we, at the end of the day, what's it about?

It's about the patients and complications that have very [00:20:00] significant effect on patients. We should probably rank more significantly. Absolutely. Yeah. No, I think that's a very good point, Ed. And so maybe just to sort of wrap us up, I was gonna ask the same question to all three of you. Maybe I'll start with you yourself, George, you know, where, what are your overall thoughts on the future direction in this area?

You know, in terms of optimising the surgical planning attempt, eat that personalised surgery concept, and, and, you know, how, how can we, where are we gonna go forward with this to ultimately show, you know, reducing that revision risk and enhancing patient satisfaction. Well, I'll take the second question first.

You know, we're gonna need tens of thousands of patients. Hmm. But yeah, one thing Dominic touched on it, that a lot of the studies published are from high volume surgeons, from big institutions, that they show low dislocation rates. But if you look at the Medicare claims data across the US was a patient, 65 and older, hundreds of thousands of patients was published in JBJS a few years ago.

Dislocation rate was 3.3%. [00:21:00] So I think it's a lot higher in the so-called real world than in studies published comparative studies comparing approaches from high volume places like Mayo and HSS and what have you. So I think the number out there is bigger. So. It'll take registry data on a large scale to show a difference in our interventions because it, as mentioned, is a very forgiving operation in general, and the complication rate's low.

But where I think it's gonna go moving forward is the cost of all this technology will decrease like any other, electronic technology we use. And I think a lot of it'll be automated. You know, we'll see the patient, we'll get the x-rays and, and some patients will tell you, you need a CT on this one because this is unusual anatomy.

Mm-hmm. It'll be selective. So not everybody will need 3D imaging, but a lot will, and this will be automated. AI will make a plan for you, do an impingement analysis in a, in a matter of minutes. They'll spit back your sizes, your offset, your leg length, what have you, and then I think that'll be coupled with.

A robotics [00:22:00] light, some sort of handheld robotics, so you're not bringing in this giant Volkswagen into the operating room to try to get a reamer in a patient. But it'll be something you hold that functions in a robotic fashion to guide your ream and maybe even your neck cut. Mm-hmm. And that'll interface with that plan.

Yeah, and it'll show you that you hit the plan. And then what I'd love to see is that data then is stored, and those PROMs are collected over the years. So you can circle back to see did you execute the plan? Did you hit the target, and did the patient dislocate or have any problems with the hip? So we'll get our feedback loop through that data set, and I think 10 years from now, we'll all be retired, but that's when we'll know.

Conceptually, there's no logic that defies that. If you define an impingement free arc of motion to optimise hip mechanics and you hit that target, that hip has to be better in the long haul compared to when you didn't do that. Right. Yeah. But we'll need a huge studies to prove that. No, I think that's really nice to put George and Ed, I maybe come to [00:23:00] yourself next and then I'll finish up with Dominic.

What, what are your thoughts on that and sort of adding to what George has already said? Yeah, I, I, I think the optimising component orientation, we're going to learn a lot more about we, we've got some good systems that George talked about that looks at modeling activities of daily living and taking the hit through the virtual range of motion.

That's gonna be key. But how we build in extra layers to that, which is, you know, how a soft tissue, how the bone interacts, how the muscle force specters all bring in are accounted for. So I think some really clever stuff we'll see coming with that and building on that. So we, we've got our plan for that individual, our personalised plan, and then like George says, what we really need.

Is a really simple and fairly cheap way of executing that in the operating room to make sure that we've optimised that plan. We, we've executed that plan. And, and I think we'll see that quite quickly. I think we need handheld. Reamers that are controlled, but you know, we can just bring it [00:24:00] into the, into the field of vision and it, it starts and stops and turns off when we're not in the right place without a big arm.

I think we'll see that certainly for the DAA group. I, I think having some robotic execution of neck cut would be phenomenal. And, and I think we'll see that coming. So I, I think it's exciting times. I, I think. The key for us moving forward with how we judge these technologies. And as I've said earlier, I'm really keen that, that we understand that there's a plan and there's an execution technology rather than lumping them all into one.

No, absolutely. Ed, that's a really good point you made about that. And Dominic, just to finish off your thoughts on this and you know. Like, you know how, how we're gonna show it. Sure. And I think Ed and George have really very nicely summarised it all up. I mean, I think AI and deep learning will have a role in analysing the databases and looking at how to maybe even future proof some of the data they're coming up with.

And that the planning is for a patient at that [00:25:00] age group. With a certain amount of hip spine movement. I think if it'd be great if we could try and predict what they're gonna be like in 10, 15, 20 years as well. And if you could do that, you can maybe stop that impingement occurring with time. So lots of interesting research I think will come from the AI analysis of the data as the these databases grow.

Yeah, absolutely Dominic. Well, I'm afraid that that's all we have time for today. So thank you so much for taking the time to join us and, and I really appreciate all of your insights and discussion. It was great to have you all with us. To our listeners we hope you've enjoyed our special edition podcast that we hope has provided a deeper understanding of the causes of dislocation and revision, revision risk after total hip arthroplasty, as well as providing some insights into the role of technology, materials planning, all in improving the surgical outcomes for our patients, and recognising that personalised surgery could really play a key role in optimising our patient outcomes moving forward.

Feel free to be in touch with us about anything we've discussed here today, and thanks again for joining us. Take care, everyone.