This week’s Orthopaedic Crossfire® debate was part of the 17th Annual Current Concepts in Joint Replacement® (CCJR®), Spring meeting, which took place in Las Vegas. This week’s topic is “Dual Mobility Obviates the Need for Constrained Liners in Revision THA.” For the proposition is Paul F. Lachiewicz, M.D., Duke University Medical Center, Durham, North Carolina. Opposing is John J. Callaghan, M.D., University of Iowa, Iowa City, Iowa. Moderating is Andrew J. Shimmin, M.B., F.R.A.C.S., Melbourne Orthopaedic Group, Melbourne, Australia.
Dr. Lachiewicz: So, I’m going to try to convince you ladies and gentlemen that my esteemed opponent is stuck in the 1990s and his device is on the dust heap of history.
Dual mobility components have a long history of designs and use in Europe. It’s only now that we’re catching up. It’s an alternative to large heads and it’s certainly the better alternative to a constrained liner. So, it provides for two articulations. There probably is a third articulation when the neck contacts the polyethylene liner. It certainly gives you a better jump distance and range of motion.
Data from Michael Mont shows that if you allow the bearings to move, after 2.5 million cycles there is very low wear. Obviously if you restrict the bearings, you can have very high wear.
Now my colleague, John, will tell you that the Europeans are using less and we’re using more. That’s not the truth. The Europeans are using them quite frequently.
What are the indications for doing dual mobility revisions? I think, obviously, recurrent dislocation, revision of metal-metal resurfacings, total hips, hemi-arthroplasties. I use them for two-stage re-implantation for infections. Certainly, alternative constraint in younger patients. I’ve even used it for failure of constrained devices.
The operative technique is fairly simple. You ream the acetabulum. You do a trial reduction. You place the femoral head into the polyethylene using a press clamp. It is slightly more difficult with ceramic than metal. You impact this construct thoroughly onto the femoral stem taper and then reduce the polyethylene into the shell.
I have used a dual mobility acetabulum twice for failure of constrained liners and at two-year follow-up no further dislocations. The results of revision for recurrent dislocation, at least, when we first looked at them four years ago, had a success rate of 90-100% at short-term follow-up.
The Swedish Registry has a larger series. The two-year non-dislocation rate is 99%. It does drop at four years. Generally, these are in patients who’ve had multiple revisions. Many of these were for infection.
The experience in the United Kingdom reflects that of mine. A report in The Bone and Joint Journal several years ago (Vaskutty, et al., 2012) reported only a 2% early dislocation rate. Now all of these were with abductor deficiencies and their literature review showed a 3% re-dislocation rate.
The results of our series at Duke Orthopaedics have been very favorable. No dislocations in the short term. We’re calling these patients back now for a longer follow-up.
There is some evidence, although it’s weak, that dual mobility outperformed constrained liners in the group from Rush that presented at The Hip Society a year and half ago. When they looked at their constrained liners they had a 23% failure rate as opposed to 8% with dual mobility.
Dual mobility components can fail. I’ve had the large polyethylene ball come out from the metal shell. This can be reduced. You rarely see dislocation or disassociation of the metal head from polyethylene.
I do believe that dual mobility devices obviate the need for constrained components in the vast majority of patients. I think it’s an alternative to constrained liners in most patients.
Now will they work routinely when the abductors are deficient? I showed you several cases where they did work, but will they work all the time? That remains to be seen.
Polyethylene and intra-prosthetic dislocation are rare, but possible phenomena. We certainly need more data and longer follow-up on these components.
Dr. Callaghan: I’m glad that Paul at least ended with the right comment about how it’s too early to tell, at least in the United States. I’m going to take the opposite side that we still need constrained liners in revision surgery.
At least in the United States dual mobility seems the relatively new kid on the block. First I’m going to go over some of the problems, or potential problems, with dual mobility.
The first one is in the ER. When the ER doctor sees the patient they don’t even know if it’s a dislocation. They’ve said they’ve heard about these intra-prosthetic dislocations and they see this stem which is off-centered and they start yanking it around. That’s one of the first things that you have to watch out for if you’re doing these.
So, do we need to try find better solutions in revision surgery? No question about it.
Dislocation rates following revision surgery occur somewhere between 6% and 20% after revising for dislocation. And if you look at the early data back in the 1990s there was a 39% failure of operations for patients who had dislocated after a revision. But I would remind you that I’m using the same data that Paul showed you and even with contemporary treatments the Rush group still had a 14% recurrent dislocation rate after the surgery.
So we haven’t taken care of this problem with all the things that we have, so I’d be very cautious to say that one specific implant or one specific type can take care of the problem.
There obviously are all sorts of ways of preventing instability and, as I’ve said before, you need all of those options in your armamentarium. We’re talking about dual mobility, constrained liners, large fixed heads. There’s no question that if you go from large head to non-constrained tripolar or dual mobility to constrained you increase stability, but as Paul would probably tell you, you increase the risk.
It was brought up earlier that the concave surface should be the soft surface and the convex surface should be the hard surface. That’s true of all bearings. Why it’s going to be any different with this, I can’t really see it.
In the non-modular component you can’t use screws. In the modular one, you can use screws, but remember that’s another area of modularity and they’ve already shown corrosion in these modular-type components used with dual mobility.
We know that big heads aren’t enough. Paul’s shown that in primary situations, but the big thing—and Paul brought it up—that when abductors are off, big heads are definitely not enough and when abductors are off there may not even be a good solution.
So why have constrained liners gotten a bad rap? Well, they’re all different, number one. The ones that captured between the liner and the head have not done as well. You can see somewhere between 9-29% failure rates at early follow-ups.
We’ve been more interested in the tripolar liner. We showed that the inner bearing is where most of that motion occurs—somewhere between 70-90% in our study. When we’ve looked at these out to minimum of 10 years—we’re at 20 years now—we had 93% success. There’s no question that we had some revisions for femoral loosening and acetabular loosening, I’ll give you that.
We also cement liners into well-fixed shells. There are some liners with grooves in them that you don’t even have to worry about preparing that surface. Once again in many of these revisions, especially when we are using trabecular metal-type components, we have to cement the liner into the shell.
You shouldn’t put them in when you have a big reconstruction and I would agree with that. I actually use a dual mobility in those cases initially because I can pop it into a constrained liner later with the component that I use.
So if you’re in the sand trap, you first have to get out and this kind of gets you out of the sand trap. Dual mobility…there’s some data that shows high re-revision rates even at two years of follow-up. I’m still very liberal with the use of constrained liners in the elderly. My recent exceptions are spine pathology cases and also cases with complex acetabular revisions where there is concern for fixation. In these cases I use dual mobility.
Moderator Shimmin: I’m going to start with Paul. You publish a lot about the adverse effects of rapid introduction of new technology. I know you’ve been asked to take this role, but I think it’s great that you’ve been asked to do it.
Dr. Lachiewicz: I am critical of new technology, but I’ll be one of the first to adopt something if there’s a problem I think needs fixing. Such as trabecular metal for acetabular revisions. I certainly wouldn’t jump on the direct anterior approach. I think the constrained liners are essentially an impingement device. If you get away with it, that’s great. But what I’ve seen…I respect John’s work, but when you truly dissect out the result of Dick Johnson’s constrained liners, there’s 10% femoral failures; 10% acetabular. Yeah, they don’t dislocate, but they will pull everything else apart. I think there was a group from Hospital for Special Surgery that figured out seven different ways, John, that your component could fail. So if somebody’s got to think of seven different ways to fail, that device seems to be trouble to me.
Dr. Callaghan: They’ve figured out a few ways for dual mobility to fail too, as I showed you there.
Dr. Lachiewicz: That’s true.
Dr. Callaghan: There’s no question that you want to use as little constraint as you need to. But I’ve got to tell you, in the elderly patient you’re going to rarely have this type of problem. Our failures in those series actually were in younger patients. In addition if you’re in between on things, especially in this area of revising for dislocation, or even just revision in general, I’m going to go on the side of having a little more than a little less. Though I will give it to you, and especially with the component that I use for constraint, that I do have the ability to put in a dual mobility. What I like about that ability is that I can come back into that same system and all I have to do is pop out that dual mobility liner and pop in the constrained liner to deal with the problem.
Moderator Shimmin: We’ve talked about the abductors and the relevance of them being present or not. Do you routinely image your abductors with ultrasound or are you just prepared to take what you find? Do you do some imaging pre-operatively? In a revision scenario?
Dr. Callaghan: I do it especially in the metal-on-metal ones.
Moderator Shimmin: Oh, you do? Imaging just to study abductors in an instability scenario?
Dr. Lachiewicz: I don’t routinely do that. I’ll use the MARS [metal artifact reduction software] MRI in patients with the metal-metal problem or trunnion problem just to confirm the diagnosis.
Dr. Callaghan: But Andrew, I think you have to examine the patient and make sure pre-operatively that you don’t have a problem. Especially if in your ORs, you don’t have all those devices because you can get caught short as you know.
Moderator Shimmin: I think we can summarize here by saying that these gentlemen have talked about two technologies to deal with sometimes a very difficult problem. I think there are clear pros and cons of each. They both have a place and hopefully this has helped clarify how these implants can be used. Thank you very much.
Please visit www.CCJR.com to register for the 2017 CCJR Winter Meeting, – December 13 – 16 in Orlando.
Senior Editor: Jay D. Mabrey, M.D., whose 35 year career in orthopedics included residency at Duke University Medical Center, service in the United States Army Medical Corps, Fellowship at the Hospital for Special Surgery and a long, distinguished career at Baylor University Medical Center where, in addition to his overall leadership at that institution, developed the Joint Wellness Program that helped patients get up after surgery more quickly, developed the first virtual reality surgical simulator for knee arthroscopy and chaired the FDA Orthopaedic Device Panel, is Orthopedics This Week’s newest contributing writer and editor.
