“Keith has been stung by metal-on-metal, ” says Fares Haddad. “Pick the right patients and things often go quite well.” “Hold up, ” counters Keith Berend. “There is a lot we don’t know…and here in the U.S. we hardly have a chance to assess metal-on-metal because the lay media is always interrupting us with ‘alerts.’”
This week’s Orthopaedic Crossfire® debate is, “Metal-Metal Hip Arthroplasty: Going, Going, Gone.” For the proposition was Keith Berend, M.D. from Mount Carmel New Albany Surgical Hospital in Ohio. Against the proposition was Fares S. Haddad, M.B., F.R.C.S. of Princess Grace Hospital in London; moderating was Thomas S. Thornhill, M.D. of Harvard Medical School.
Dr. Berend: “My mission is to attest in the affirmative that metal-on-metal [MOM] is going, going, gone. Look at the data…less than 10-year survivorship. What Fares will fail to understand is that in North America we’re bombarded with the data of science—and the data of The New York Times.”
“Second generation: 94% greater than 10 years with an average 12-year follow up. If we compare this with metal or ceramic on polyethylene the survivorship in most studies at an average of 12 years is going to be in the 97-98 percentile range.”
“Again…we’re trying to collect data, take care of patients…and we’re faced with The New York Times. An article claims that as hip implants surge, the dangers are studied. It says that metal hip replacements are on a trajectory to become the biggest, most costly medical implant problem since a company recalled a heart device in 2007.”
“Back to the data. There’s a second generation…a mix of implant designs…we’re trying to improve on each design…less than 10 years. Well, there’s The New York Times again. ‘Concerns over Metal-on-Metal Hip Implants.’ So again, as we’re trying to ferret through the data we’re overcome by the lay media.”
“The data: We’ve improved again…less than 10 years, four-year follow up, 94% survivorship. There’s a problem—each generation of improvement we’re getting worse. Ah, another warning: New York Times, March 2010. A doctor who was consulted to give his opinion on this article said it’s way too late…we’ve already done this and it has a high failure rate, requiring costly and painful replacement procedures.”
“Back to the data: greater than 10-year results with the second generation—92% at an average of 10-year follow up. We’re getting worse. But let’s focus more closely on the data. Oh, well, we can’t—because the UK government has issued a medical device alert along with an action plan. The problem is that we don’t know what’s going on with these devices…they’re not all created equal. There are multiple variables: metallurgy, geometry, design, fixation, is it with a femoral component, is it resurfacing?”
“A new term comes up every six months to describe what we’re seeing. One is, ‘ALVAL (aseptic lymphocyte-dominated vasculitis associated lesion). After six years we still don’t know what this is. We need to stick with what works. We must opt for fewer variables, fewer issues, and a more reliable solution…which may mean going back to what we knew from John Charnley. Thank you.”
Mr. Haddad: “I feel guilty because I think we got Keith into this game. In 2004, Keith came to the UK and we got him into metal-on-metal. What you’ve just heard is a talk from someone who’s been stung by metal-on-metal because it’s been a large part of their practice.”
“If you’re surrounded by pseudotumors, or you’re seeing lumps in your clinic where you didn’t see them before, or if your colleagues are abandoning this technology—this is upsetting. But you must stop and break it down. Not all MOM is one.”
“Large head MOM was perhaps embraced too soon. The larger the head, the greater the trouble. This is where we in the UK have seen the biggest source of trouble in terms of bony destruction and soft tissue damage. And it doesn’t necessarily link into wear. It seems to be more friction and trunion issues.”
“But there are other areas, and some of the papers in relation to 28mm, standard, understood MOM hip replacements. Minimum five year results, better radiographic and survival results than ceramic-on-poly…one study: onto 10 years, 99% survivorship; another study: onto 10 years, 98.6% survivorship. A randomized controlled trial that showed no difference from ceramic-on-poly at 10 years. There are many such studies.”
“Early results from hip resurfacing in expert hands were spectacular…they continue to be very good in expert hands with appropriately selected patients. And size matters. If you have heads 50mm and above these implants do well if you insert them correctly. Many of the failures are surgical…they are not the fault of the technology.”
“We’ve done a comparative study that is now out to almost 10 years looking at resurfacing replacement. These were mostly above 46mm [head size]—they weren’t all above 50mm, so there are some that would be regarded as high risk above them. We found that there were some aspects of the resurfacings that were better, especially in relation to endurance and jumping ability.”
“Looking at our standard scores, we didn’t see any differences; but once you looked at functional tasks, you see that the BHRs [Birmingham Hip Resurfacing] behaved much closer to normal hips than the THRs [total hip replacements], which had much higher scores. In sports or heavy manual work, they outperformed standard total hips significantly.”
“We must not throw away everything we’ve learned. So can we use metal-on-metal in 2012? Yes…but with some caution.”
Moderator Thornhill: “Fares, you said that large heads might be more challenging maybe because of the friction, the sweep distance, etc.—yet you then said that in a resurfacing if it’s above 50mm it does well. Is it the trunion that’s the biggest part in the conventional hip?”
Mr. Haddad: “If you’re looking at MOM hip resurfacing, the bigger the head size the better the data. If you turn it around and look at big head metal-on-metal, the bigger the head the worse the data. That seems to be because we’re transferring a force across the trunion. In cases where the failure in resurfacing is a wear-related issue, in the large head MOM it seems to be more of a corrosion issue.”
Moderator Thornhill: “Keith, the reactivity that we’re seeing, is it a toxicity, an immune reaction or is it a nonspecific granulomatous response that we see at the joint?”
Dr. Berend: “We don’t know. If you look at the descriptions from back with Willard and others in 2005, we thought it was hypersensitivity; we studied this in the ‘70s with McKee-Farrars and showed that it’s not related to metal allergy. It may be an ion level in the local tissues; it may be a tissue necrosis, it may be a hypersensitivity…or a combination of all those factors.”
Moderator Thornhill: “Fares, is there any role for using MOM now in anything other than a resurfacing?”
Mr. Haddad: “If you’re in a practice that’s already been using small head MOM, you don’t necessarily need to stop. But don’t introduce it. There are too many unknowns.”
Moderator Thornhill: “So it’s just a matter of what box you open to put it in.”
Mr. Haddad: “If you’ve got a 99-100% survivorship with a 28mm head MOM there isn’t any reason to pull that out right now.”
Moderator Thornhill: “Keith, what percent of all the MOM hips we’re doing is the burden of the problem?”
Dr. Berend: “It depends on the implant design…it’s going to dictate the early, mid- or long-term failure mode. So if we’re talking about pseudotumor, ALVAL, it’s probably 1% or less…but there are a lot of them put in. It’s a catastrophic failure if you lose your abductors. If you look at big head total hip, and even some resurfacing design related factors, early failure is more related to failure of ingrowth of the cup.”
Moderator Thornhill: “So if you use a MOM and you don’t put it in too vertical and you don’t have edge loading and it’s a large person, and it’s only 1% of the problem, you’re probably OK?”
Dr. Berend: “Yes…in a male.”
Moderator Thornhill: “How many are you doing now?”
Dr. Berend: “Zero…other than selected resurfacings.”
Moderator Thornhill: “Who are you doing those on? People you don’t like?”
Dr. Berend: “A good implant design with a proven track record; in patients less than 40, and only in men.”
Moderator Thornhill: “And if they had a well functioning one on the other side?”
Dr. Berend: “Yes. But if it’s a female patient I would counsel them about our data which suggests that MOM is catastrophic in women.”
Moderator Thornhill: “Does the metallurgy differ by manufacturer…that would increase the risk of leaching of metal ions?”
Mr. Haddad: “I think it does. Those implants that have the metallurgy right have done better, both at 28mm and at the resurfacing level. I think we’re also going to see a differential at the large head failure rates because those implants that have the metallurgy and the radii clearance wrong will have a much higher shorter/medium term failure rate with large head MOM.”
Moderator Thornhill: “You implied or I inferred that the MOM was a high activity hip.”
Mr. Haddad: “We believe that our resurfacing patients are more active than our total hip patients. It may be that patients who have that procedure believe they can do more just because they’ve had that procedure.”
Moderator Thornhill: “In the U.S. patients often come to you. Do people in the UK do the same thing?”
Mr. Haddad: “We went through this same thing and our study was a prospective randomized study that ended up with two side limbs because we couldn’t actually randomize all the patients because that was the year in the late 1990s when patients chose to have resurfacing. We have to have a much stronger conversation than before, ‘You’re dysplastic, female, 35, etc.’”
Moderator Thornhill: “What percent of your practice is MOM?”
Mr. Haddad: “The only MOM I’ve even done has been resurfacing and that’s about 15% of my practice.”
Moderator Thornhill: “How many people in the audience still do MOM implants? OK, that’s about 70. So Keith, if it’s 1% of the cases where this occurs, is this the media that’s frightening us over 1%?”
Dr. Berend: “It’s a combination of the lay press, the barristers…but us seeing the clinical results and outcomes of decisions that we’ve made without knowing the end result. When I say 1% that’s worldwide. And the attrition rate of patients dying before they would have this complication isn’t zero. So it’s going to occur. The biggest concern I have, regardless of design, is, ‘Is there a latency period?’ Let’s say the results of MOM, small head diameter are good at 10 years…are we going to see this phenomenon at 15 and beyond? And we’ve selected out young patients who are going to live that long and then the percentage is going to go up.”
Moderator Thornhill: “Thank you both.”
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