Lachiewicz v. Callaghan: Dual Mobility Cup: Emergent Standard for Recurrent Dislocation

This week’s Orthopaedic Crossfire® debate was part of the 18th Annual Current Concepts in Joint Replacement® (CCJR®), Spring meeting, which took place in Las Vegas. This week’s topic is “Dual Mobility Cup: Emergent Standard for Recurrent Dislocation.” For 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. Daniel J. Berry, M.D., Mayo Clinic, Rochester, Minnesota is moderating.

Moderator Berry: This debate—Dual Mobility Cup: Emergent Standard for Recurrent Dislocation—is not about utilizing a dual mobility cup in the standard primary situation but rather as a means of treating recurrent dislocation. Paul Lachiewicz speaks in the affirmative.

Dr. Lachiewicz: Thank you Dan. We have seen in history that certain techniques and protheses have become obsolete. And John, constrained liners are obsolete now.

Dual mobility components have a long history of use in Europe. It is, in my opinion, the preferred alternative to constrained liners.

The presumed biomechanics are due to the dual articulation. These give you greater range of motion and greater jump distance. There is some data from Mayo that shows that tri-polars do have a greater range of motion.

In terms of wear, if you allow the inner bearing to move, at least in one laboratory study with one type of highly cross-linked polyethylene, it is very acceptable.

There are numerous European designs for both cemented and cementless. In the U.S. we have limited selection.

What are the indications? The number one indication is for recurrent dislocation, and it is, again, the preferred alternative to constrained liners.

In a literature study we did several years ago where we looked at mostly European studies, we found 90-100% success rates in cases of recurrent dislocation (JAAOS 2012).

The Swedish Registry, at 2-years, found a 99% success rate for dual mobility; at 4 years it was slightly lower.

A study from Great Britain (Vaskutty et al., Bone and Joint J 2012) also reported that dual mobility was very successful for a variety of revisions. Looking at 10 studies, the dislocation rate is about 3%.

I have used dual mobility to revise failed constrained liners in 2 cases, and with 1 success at 2 years and another at 4 years.

Rob Trousdale, as he showed in a recent study, successfully salvaged a failed constrained liner with a large dual mobility (Hip Society 2016).

Dual mobilities outperform constrained liners in the Rush series that was presented in the society several years ago (Plummer et al., Hip Society 2014).

Not everything is 100% successful. There are mechanisms that fail with dual mobility components. They can pop out at the large bearing. They can pop out through the small bearing—which is a real problem.

We have seen 1 case of early acute disassociation … it was not our own case…done by another surgeon. What was unusual about this case was that it was a skirted femoral head and we think that impinged … I think that’s something that we need a little more data on, but I’m recommending against using any type of skirted neck if you’re doing dual mobility. You do have to revise these cases.

Chronic intra-prosthetic dislocation…they’ve had a lot of experience in Europe … this is generally due to late wear of conventional polyethylene which can then lead to impingement and polyethylene fracture. We have not yet seen that in the U.S. and most of the dual mobilities are highly cross-linked poly.

I think there are advantages to dual mobility. Its #1 indication is revision of recurrent dislocation. Will they always work when the abductors are deficient? There is some debate about that. Poly wear and intra-prosthetic dislocation are rare phenomena. We certainly need more data.

Moderator Berry: Dual mobility, emergent standard for recurrent dislocation…John Callaghan in the opposition.

Dr. Callaghan: Thank you Dan. It’s good to see Paul not quite as passionate as the last time he and I did this debate. I’m going to take the opposition to this.

At least in the United States I think dual mobility is kind of the new kid on the block.

Everybody says dual mobility just cannot dislocate. Well, all I have to have you do is talk to some of the folks in the ER who are taking care of Paul’s patients.

So, are we always trying to find a better solution to prevent and treat dislocation, especially in revision surgery? Absolutely. Dislocation following revisions are somewhere up around 6 to 20%. There’s no question we need something. Now maybe a dual mobility will do it, but there are some situations where I just don’t think it’s enough.

There are plenty of options to prevent instability following revision. But we are really debating just two: dual mobility and constrained liners.

There’s no question that constrained is by far the best thing for stability … but, it also has the most risk. I’ll be the first to admit that too.

When you look at bearing technology—the concave surface should be soft and the convex surface should be hard and that’s why polyethylene liners and metal heads work so well. I’m still concerned long-term about impingement … but also the wear issues. We don’t know anything about that with dual mobility.

We know that big heads are not enough. Beaule et al. (JBJS-Am 2002) had one study, a primary study, where he showed around a 9% failure rate. And when your abductors are off there is just no question that you need more than a large head. However, I am not convinced that there is enough data out there indicating that dual mobility is going to take care of this.

Constrained liners have gotten a bad reputation and I’m the first to admit that. Some of that is because of where the capturing mechanism is. Some capture between the head and the polyethylene, which I don’t think has worked out as well. The literature shows somewhere between 9-29% failure in those types of cases at 31-month follow-up. The one we have the most experience with, though, really has been the tri-polar design where you have a bi-polar inner bearing and then an outer bearing between the socket and the constraining ring. These have totally different outcomes in the literature than the other type.

We did a study years ago that showed most of the motion doesn’t even involve constraint because you get the motion on that inner bearing and it’s really only that last 10% where you have the outer bearing motion.

We had the opportunity to look these up both in revision in general and in dislocation cases, and there is 93% and 96% success, respectively (JBJS-Am 2004 and J Arthroplasty 2003). That’s out to 10 years.

You do get some loosening but it’s very acceptable especially with the designs that were used at that period–somewhere around 5%.

A typical case: 80-year old person, poor abductors, big shell and we put in a constrained liner which lasted until that patient’s death 8 to 10 years later. We’re not asking all these to last for 20-30 years. You can cement the liners into the shell. We’ve discussed that with 94% success at 4 years. That’s in those cases where you’re doing it in a shell that can be saved because the shell is in good position. And we still do this. We’re now up to 15-year follow-up with a 9.7% failure rate.

There is some data that dual mobilities don’t work that well. The French are using less dual mobility than we are – and they were the ones that developed it. What I would tell you is I’m liberal in the use of a constrained liner, but I do have exceptions with spine pathology today and complex acetabular revisions.

So, Paul, I think you ought to keep constrained liners in your armamentarium and not quite give up on it.

Moderator Berry: Paul, do you have any quick rebuttal, or should we just go right into the questions?

Dr. Lachiewicz: I remember getting up at the American Academy of Orthopaedic Surgeons a few years ago, John, and you showed your great results with the constrained liners, but they were shaking the femoral components loose, they were shaking the acetabular components loose. If you add up all those failures … I remember one of your papers, it was close to 30%. All didn’t dislocate, but they shook the acetabular loose. We don’t see that … and I don’t think the French have seen the dual mobility loosen the acetabular component. I think there’s a little more safety on the implant fixation with dual mobility.

Moderator Berry: Paul, in the previous session I heard you expounding on your concerns about taper corrosion with metal heads, and yet, now, in this session, you’re advocating use of an implant, that at least in North America, typically is a modular dual mobility implant that’s got a metal liner, typically made out of cobalt-chrome put into a titanium shell, thereby creating an interface which, at least in theory, could be a risk just as you described on the femoral head. Do you think that’s a potential theoretical concern?

Dr. Lachiewicz: The one report of elevated metal levels came from Philadelphia. The problem was those were all the high trunnion failure components and that was 4% and they used chrome-cobalt head. I think most of us are using ceramic heads with this dual mobility.

Moderator Berry: John, you want to comment on the corrosion question?

Dr. Callaghan: Exactly, but you know, Westrich just had an article in J Arthroplasty where he showed some changes on the backside to damage in that interface. You’re right, Paul, there’s not a ton of reports out there but, we don’t have that long of a follow-up on this stuff. That’s what really concerns me.

Moderator Berry: Paul, in your practice when you’re revising somebody for instability, how often are you using a large diameter head or getting the cup position right? How often are you yanking out a cup and going to a dual mobility implant?

Dr. Lachiewicz: I have done one constrained liner in the past year. She had so many risk factors. In that patient I slipped a constrained liner into a well-fixed socket rather than ripping that out. I’ve done some—which John mentioned—the head liner exchanges for people who have late subluxations with standard polyethylene. They come to see me at 20 years, they feel their hip slipping out. I will do a large ceramic head and cross-linked poly in those.

Moderator Berry: And not everybody with recurrent dislocation gets dual mobility implant, but it is a powerful tool and a selected group of patients. Is that fair to say?

Dr. Lachiewicz: Absolutely.

Moderator Berry: John, how about your practice? Who gets a dual mobility implant when they’re being treated for instability and who gets a constrained implant?

Dr. Callaghan: The older the patient with more abductor deficiency—for me is going toward constrained rather than dual mobility.

Dr. Lachiewicz: Dan, I also want to tell the audience that dual mobility will not save you if your acetabular component is grossly malpositioned.

Moderator Berry: That’s a good point. I think that does deserve emphasis. If you’ve got a failed dual mobility implant that is due to recurrent dislocation, what are you probably going to put in next? John? Quick answer.

Dr. Callaghan: Constrained for sure.

Dr. Lachiewicz: I’ve done repeat dual mobility with a larger component and changed the position.

Moderator Berry: Ladies and gentlemen, please join me in thanking both Paul and John for an excellent debate.

Please visit www.CCJR.com to register for the 2018 CCJR Winter Meeting, – December 12 – 15 in Orlando.