Della Valle v Callaghan: Dual Mobility Obviates the Need for Constrained Liners in Revision THA

This week’s Orthopaedic Crossfire® debate was part of the 16th Annual Current Concepts in Joint Replacement® (CCJR) – Spring meeting, which took place in Las Vegas this past May. This week’s topic is “Dual Mobility Obviates the Need for Constrained Liners in Revision THA.” For the proposition is Craig J. Della Valle, M.D. Rush University Medical Center, Chicago, Illinois. John J. Callaghan, M.D. University of Iowa, Iowa City, Iowa, is opposing. Moderating is Thomas P. Sculco, M.D., Hospital for Special Surgery, New York, New York.

Dr. Della Valle: Dislocation, like it or not, is the number one reason for revision of a total hip in the United States and is also probably the most common complication after revision total hip replacement. Constrained liners have been used very heavily in the past to solve or prevent these kinds of events from occurring. That being said, I think a lot of the issues that we’ve seen have been changed, to a certain extent, by large femoral heads and I think they’ve really become the mainstay for preventing and treating instability.

This has really been facilitated by cross-linked polyethylene. Several studies have basically shown that there doesn’t seem to be a meaningful increase in wear with larger head sizes.

Two randomized control trials—one that I was involved in with Garbuz showed that when you compare a 32mm head or a 28mm head to a 36mm or larger head, there’s a decreased risk of dislocation with larger heads. And I think that large heads in general have really decreased the use of constrained liners.

Big heads don’t always work, however. There is a great article by Mike Ries that basically showed even when large heads were used, if you have situations such as deficient abductors, you need a constrained liner in that situation because a large head just doesn’t seem to work.

Constrained liners are obviously a very tantalizing solution and can be very effective. You can either engage into a compatible shell or you can cement into a well-fixed shell, and John Callaghan has done some beautiful work showing a very high rate of success, a 94% success rate at four years, with only one liner failing at the cemented interface…and that’s with a constrained liner that was cemented in place.

I think, however, that a lot of those cases predated the routine use of large femoral heads. I think a lot of the problems that John reported on, in contemporary practice would probably be solved simply with a large head and I don’t think they were the same level of complexity that we use constrained liners for today.

It’s also imperative to understand that different constrained liners work differently. The Tripolar Constrained (Stryker) has, in my mind, the best track record. When you compare that to some of the ring-locking ones, like the DePuy Constrained liner that I reported on when I went for my fellowship, we had a much higher rate with the ring-lock designs. Again, many of these problems in the past probably would be successfully treated with large heads today.

So one of the problems with constrained liners is increased stresses at the bone implant interface. In one case when I was a chief resident we did a structural allograft, very complicated deficient abductors, used a constrained liner like I should have. Then the patient came in at their six-week visit and had torn their fresh cup right out of the acetabulum.

In addition, constrained liners decrease range of motion, for most of the designs. There are unique designs out there that I think may have skirted that problem but they create higher stresses on the polyethylene. They can often require thin polyethylene and some of them aren’t cross-linked. They may increase the risk of late loosening, and usually require open reduction if they fail.

I think John and I will certainly agree that whether you use a constrained liner or a dual mobility bearing, constrained liners do not compensate for component malposition. I think you really need to optimize the position of components and all other factors in the reconstruction to wind up with something that’s successful.

We really looked at dual mobility as an alternative to constrained liners. There’s a lot of European literature that supports their use for both treatment and prevention of instability.

While dual mobility does have its own problems, including intraprosthetic dislocation, wear and concerns about high torque at the bearing surface, it also solves some pretty difficult problems. Patients who are completely abductor deficient and even in the most challenging situations, we found these bearings were successful.

In a clinical series we have 43 constrained liners versus 31 dual mobilities. It is a non-randomized series, but the indications were similar. Basically we looked for abductor deficiency, revisions for instability, or any inadequate stability at the time of revision with a larger head. We found recurrent instability 23% versus 13% with dual mobility and two of those were early cases where we cemented that liner into place and it mechanically failed. We looked at repeat revision for instability…it was 26% versus 6.5% for dual mobility. The constrained liners did have a longer follow-up. Yet, three of our dual mobilities that we used in the series were for treatment of constrained liners. Based on this, dual mobility has really become our go-to instead of a constrained liner.

I think my take-home points are if you’re dealing with patients with complex situations, you absolutely need to optimize all other factors, including component position and soft tissue balance. I think large femoral heads should be your first option to optimize stability. Really I think you should keep in mind that constrained liners, while useful—and I still think they have a role—have several serious disadvantages you need to think about. And at least in our experience, we’ve had dual mobility emerge as a really good alternative and at least at short-term follow-up are showing a lower risk of failure.

Dr. Callaghan: I’m going to talk about the use of constrained liners and how dual mobility may not be the way to go. The dual mobility is the new kid on the block and Craig Della Valle is not a young guy any more, but he’s about 20 years younger than me. There is no question…I think we all have some interest in this device.

We’re always trying to find better solutions for dislocation. There’s no question about it. Dislocation rates are from 6% to 20% following revision surgery. Revision for dislocation, even in Craig’s group, is still only 85% successful.

I think all of us would use the increase in stability only as needed and I think Craig really articulated this well. You have to also realize that in bearing surface technologies the concave surface should be soft and the convex surface should be hard. This is why polyethylene liners in metal heads have worked so well. And that’s one of the concerns with dual mobility. In addition, you can’t use screws in the non-modular shell and you have to use modularity in the screwed shells. We don’t know what the effects of that are going to be.

Why have constrained liners gotten a bad rap? There’s all types of constrained liners. It’s really the tri-polar type of design that’s had the best track record. All our experience has been with the constrained insert…the tri-polar type of insert. At 10-year follow-up we reported a 93% success in preventing dislocation in complex cases. And the failures that did occur were in the younger patient, <45 years, and I would agree, the younger patient is where we should think about using the dual mobility cup. You can get osteolysis, but it was very low in our series.

We have cemented constrained liners into well-fixed shells with a lot of success. We’re just doing our 10-year follow-up of these and there’s been no change in the success rate, 94% at 4 years. Nowadays, they actually have a way of doing that where you don’t have to prepare the liner.

So do we have failures, absolutely, and goes to what Craig said. You’ve got to make sure you don’t cement that liner proud. You can’t put it into a malaligned shell. You can’t use it in a real tough reconstruction where you’ve put bone graft.

How about dual mobility at Tom Sculco’s institution? They’re not working out quite as well—10% revision rate at two years; 13% revised if it was treatment for dislocation. I was just recently in France and it’s interesting that the French who developed the prostheses are doing less dual mobilities and we’re starting to do more.

So if you’re in a sand trap, you first have to get out; constrained liners get you out of the sand trap. We still are liberal with the use of constrained liners; we use dual mobilities in patients with spine pathology and in complex cases in young patients. And Dr. Della Valle would sleep a lot better if he would use more of these, I think. I’m afraid he’s going too much the other way.

Moderator Sculco: Craig, let’s go to you first. John brought up, and it seemed like the 23% incidence of dislocation in your constrained liner series seems very, very high…

Dr. Della Valle: That’s because we’re using them when you need them and that’s what really led us to dual mobility. You take these patients who are abductor deficient, or multi dislocators…that’s why we’ve looked for a change because we’ve looked at our results and said, ‘Hey, most of our failures are these constrained liners.” Interestingly, we’ve done analyses and looked at our dislocations overall. We found that the constrained liners were actually protective because without the constrained liners they should even have a higher dislocation rate. But none the less, 23% failure rate. You look at that and say, ‘I need to look at something different.’ So if you use this mechanical construct with constraint in it and the patients who are abductor deficient, I think that over time they’re going to fail.

Moderator Sculco: I reported on this and our incidence was similar to John’s. Is there anything different in that series? Granted there are serious cases…in my series some of them had polio. Was there anything else that you could point to in terms of that dislocation rate being so high?

Dr. Della Valle: Again, I think there were severe cases where they had deficient abductors and those types of things, and once you get two, three years post-operatively we started to see the constrained liners break. The ring breaks, dislocates, pulls out, or something like that happens over time.

Moderator Sculco: John, let’s go back to you now. You’re constrained liner experience has been pretty good. Have you seen mechanical problems like Craig is mentioning? Those rings, the metal rings do break, and that can lead to instability of those tri-polars. In general, you’ve had pretty good results. Is that still your experience?

Dr. Callaghan: Our experience is still pretty good and I want to give Craig some credit in that they have a very complex practice there at Rush and you have to take that into account. I am more concerned about constraint in the younger patient. All of our failures in that earlier study were in patients under age 45. So I think that patient is the one that I would experiment with dual mobility for sure. I still think older patients are better off going right to a constrained liner.

Dr. Della Valle: I have two quick questions. The series you reported in 2004, a lot of those cases, do you think those are cases now that you would have solved with just a big head? Do you think they were not as complicated?

Dr. Callaghan: Very good point. A lot of those could have been solved with a big head. We have one series just for treatment of dislocation and I should go back and look at those as we look at the 20-year results to see which ones may not have required a constrained liner because abductor deficiencies were not as big a problem back in that time. Abductor deficiency has been a new problem related, I think, a lot to metal-on-metal, at least in my own practice.

Moderator Sculco: I’d like to thank the speakers who’ve done a wonderful job here.

Please visit www.CCJR.com to register for the 2016 CCJR Spring Meeting, May 22 – 25 in Las Vegas.