“Cup position is critical, ” says Wayne Paprosky. “And if the abductors are deficient then I’m not sure there is an advantage to constrained liners.” “Really?” says John Callaghan; “There are good results with large heads in revision surgery. And if you need something very large you can go to the dual mobility rather than jumping straight to a constrained liner.”
This week’s Orthopaedic Crossfire® debate was part of a landmark event, the first Brazilian CCJR meeting. The event, which took place in September 2014, was held in Iguassu Falls. This week’s Orthopaedic Crossfire® debate is “Use of Constrained Liners in Revision THA: More Problems Than They Solve.” For the proposition is Wayne G. Paprosky, M.D. from Midwest Orthopaedics at Rush in Chicago. Against the proposition is John Callaghan, M.D. of the University of Iowa. Moderating is Daniel J. Berry, M.D. of the Mayo Clinic.
Dr. Paprosky: “One of the main reasons for re-revisions is dislocation. People think about instability, revision, constrained liners and it became almost an automatic reaction. But contemporary studies show increased risk of failure and they require open reduction; they are also associated with decreased range of motion (ROM). If you’re retaining the cup make sure that it’s in the right position…use a CT scan if you have to. And you must evaluate whether the abductors are intact.”
“We can do big heads because we have highly crosslinked polyethylene (XCLP). Head size has long been known to influence the risk of dislocation; big heads and impingement are more for primaries. In these revisions, it’s the jump distance that makes the difference…but jump distance is still dependent on cup position. You lose this advantage if the cup isn’t in the correct position. If the cup is not in the right position get the biggest head you can.”
“What if you can’t get a big head? The tripolar construct, as we have shown at our institution, is a very good method. You should find the biggest poly before you go to the dual mobility; you can get a lot of mileage out of a 48mm poly. Then you can put a tripolar construct into it and you don’t have to jump right to this dual mobility concept.”
“Several studies show that we have good results using the large head in revision surgery. However, if you’re stuck and you need something bigger (the 48mm is still not stable) then you can go to the dual mobility for this indication rather than jumping straight to a constrained liner. I cement this construct into a highly porous shell.”
“What about constrained liners? John Callaghan has shown a high success rate with one failure at the cement-liner interface. But constrained liners are not all created equal, and there are studies showing a high degree of dislocation. Most of the cases I deal with that are unstable are Type 3B sockets and there is a higher rate of loosening in these cases. You increase the stress at the bone-implant interface, but you don’t need a constrained liner. Go with a big head and if it does dislocate later, once the ingrowth occurs, you can always go to a constrained liner. Many studies show loosening for these very difficult problems.”
“We did a direct comparison between the dual mobility (43) and constrained liners (36) in high risk patients. We had 10 constrained failures, 3 dual mobility failures to redislocation. Two were because of cementation of a smooth surface into a shell.”
“Constrained liners can solve some difficult situations, especially with the deficient abductors. But you have to weigh that against the potential for cup loosening. In conclusion, instability in revision—like primaries—is multifactorial. And we believe the large dual mobilities are better, especially in patients with severe bone loss. I believe the advantage is uncertain in abductor deficiency…and no matter what you do you must have the cup in the correct position.”
Dr. Callaghan: “In revision surgery the dislocation rate is up to 20%; in revisions for dislocations—even in Wayne’s own practice—they’ve only been able to get to 85% success.”
“There is no question that with increasing stability you only use what you need. But what’s available is not always working. Large heads seemed like a good idea, but wear simulators reveal some concerns. But the issue is the high failure rate that we’re starting to see now that is related to trunionosis with larger heads. And is the big head really enough anyway?”
“Lachiewicz has a study with older patients in a primary setting where he didn’t decrease his dislocation rate. Beaule had 9% recurrent dislocations with larger heads. And the real data that Wayne mentioned is that if you have an absent abductor then the large heads don’t work. Ries showed 33% dislocations using large heads in those situations. And as Wayne said you should really check the abductors. Often we see metal-metal with no trochanter and we get in there and it seems that all you can do is use a constrained liner.”
“Why have they gotten a bad rap? There are different kinds of constrained liners. Some capture between the head and polyethylene—those are bad. But the tripolar ones that capture in the distant site have been effective. Lombardi showed a high failure rate early-on with those captured at the head in the poly. The long-term failure rates when you get to the constrained liner where there is an inner bearing and an outer bearing constrained at the outer liner are much better. Our data show that most of the motion occurs at inner bearing, so it doesn’t go to the capturing ring.”
“Over 10 years we have looked critically at the distant capturing mechanism; we had 93% success. But we wouldn’t use this in a 45 year old patient. We did have a bit of acetabular and femoral loosening, but these are complex cases; we didn’t see much osteolysis. We had failures, but they were somewhat technique related and they go back to Wayne’s point. If you cement a liner into a shell you can’t cement it in a proud fashion or it will come out. If you malposition it then the patient may dislocate.”
“In spine fusion patients we’ve seen a higher rate of recurrence in those cases recently. In the U.S. a lot more people are getting these big spine fusions. And this is Wayne’s biggest point: you put this on a big construct and you are at some risk of it ripping out.”
“I use dual mobility, but this was a bit alarming—Mathias Bostrom recently gave me this data: a 10% re-revision rate at two years at Hospital for Special Surgery and a 13% re-revision rate if treating for dislocation. So dual mobility cannot take care of everything. We still use this liberally in older patients, but I’m concerned about the spine pathology issue.”
Moderator Berry: “Would you agree that with the advent of large diameter heads and dual mobility implants that the use of and indications for constrained implants have gone down?”
Dr. Callaghan: “It should go down, but I’m not sure if it has.”
Moderator Berry: “Wayne?”
Dr. Paprosky: “I’ve seen a decline.”
Moderator Berry: “What are the indications for constrained implants?”
Dr. Paprosky: “My main indication is when I go in to do a poly liner exchange on a female with a well fixed component and a small diameter cup. Or, revision for trunionosis or something along those lines. Or I just have to go to a skirted ball and I don’t have stability…that’s when I go to a constrained liner.
Moderator Berry: “So Wayne, you’d use it in situations where the abductor is deficient or when you just can’t reestablish sufficient stability in surgery to feel comfortable that anything else will work?”
Dr. Paprosky: “Yes, and most of the time these cups are small and I can’t even get to a 36mm head.”
Moderator Berry: “John?”
Dr. Callaghan: “Same indications except in elderly patients I’m a bit more liberal. And if I’ve gotten into a revision situation with my acetabular construct and I know that the screws are the way I want them and I’m not concerned about ripping out the shell, then I’ll use them in older patients.”
Moderator Berry: “Both of you have said that you’re worried about using constraint if you have a fresh cup in—particularly in a revision—and you have a tenuous situation in terms of bone fixation. And you both say that you’re more liberal about constraint if you’ve already got a bone ingrown cup or a cup with a lot of fixation. Do you like to emphasize that, John?”
Dr. Callaghan: “Yes, and I give Wayne great credit for bringing that up.”
Dr. Paprosky: “The big issue is when the abductors are not there. You are going to destroy some constructs if you liberally put a constrained liner in, especially a type three socket.”
Moderator Berry: “All constrained implants will eventually impinge intra-articularly, so what do you do in surgery to minimize that?”
Dr. Callaghan: “I use a posterolateral approach with extended osteotomy; I want to protect the backside more. I still use an extended lip and I’m more concerned about impingement up the front than I am about anterior instability. We put our cups in a bit more vertical now with tantalum and such and then we can realign the liner…but you must ensure that you do that realignment a bit more horizontal than that verticality.”
Moderator Berry: “If you cheat to have a cup that’s flat and anteverted then you’ll increase the risk of posterior impingement.”
Dr. Callaghan: “I don’t think you can totally do it with a constrained cup. I take patients through a ROM, but that Stryker liner only gives you about 80-90 degrees of motion.”
Dr. Paprosky: “These things—because of abductor deficiency, trunionosis, and metal issues—they are flopping into external rotation. The failures that I’ve been seeing—the posterior aspect of the acetabulum, the ring are destroyed and there’s more metallosis from the rings. And this is a huge problem because there’s no way to control multidirectional instability.”
Moderator Berry: “Thank you, gentlemen.”
Please visit www.CCJR.com to register for the 2015 CCJR Spring Meeting, May 17 – 20 in Las Vegas.
