This week’s Orthopaedic Crossfire® debate was part of the 32nd Annual Current Concepts in Joint Replacement® (CCJR) – Winter meeting, which took place in Orlando this past December. This week’s topic is “MOM Hip Resurfacing: An Option for Right Patient & Surgeon.” For the proposition is Koen De Smet, M.D., Anca Medical Centre, Ghent, Belgium. Opposing is Michael J. Dunbar, M.D., F.R.C.S.(C), Ph.D., Dalhousie University, Halifax, Nova Scotia, Canada. Moderating is Thomas S. Thornhill, M.D., Harvard Medical School, Boston, Massachusetts.
Dr. De Smet: Metal-on-metal hip resurfacing is still an option for the right patient and surgeon.
For the people who may not know me, I’ve been a hip surgeon for 20 years and done more than 8, 000 hip joints, 800 revisions and more than 4, 000 resurfacings. I like to do crazy things — not just revisions, but of course, a lot of resurfacing.
I’ve done all types of resurfacing, so I can talk about most of them. The use of resurfacing has decreased. In the UK it has gone down from 11% to 1%. The reason, I think, is because of bad prostheses and bad surgery.
So, why is metal-on-metal resurfacing still a good option?
We have excellent data. If you look to the Australian Hip Registry, the Birmingham had 13 years, 92% survival, which is a very good thing in young people. In the UK the National Joint Registry data showed a 9% revision rate at 10 years and that’s the same for all cases in hip replacement and resurfacing.
So, what broke everything? It was ASR. With a lot of revisions it was recalled. Too small coverage angle of the cup and a too small margin for error with edge loading, that’s what we saw in small sizes with ASR, possibly in all sizes.
But there are very good results. If I look to my own less than 50-year-old patients, 600 patients, I get practically 99% survival in males, and in females, 97%.
But you need experience. You need training. Resurfacing only can be done when you are doing 200 hips a year and when you’re doing 25-50 resurfacings a year. Otherwise, you shouldn’t be doing it. The Australian Hip Registry just showed that if you do less than 25 cases, you have 3 times more risk to get revision.
Why resurfacing? Because we’ve got a normal gait and normal activity. And there are more and more papers showing this and, for me, the most objective paper was from Justin Cobb that shows that only with resurfacing do you get a normal faster walking, and a normal stride length when you walk faster.
You also get decreasing wear over time with metal-on-metal resurfacing. Wear disappears with time. And wear is not activity related.
Why resurfacing? Because you’re not only conservative to the femur, but also the acetabulum if you do it well. If you see how much bone we have on the tear drop, I don’t think you can say you are destroying the bone. Revision of resurfacing is not a drama, it’s not a catastrophe.
We showed if you have a good surgical technique, if you have a good follow-up, you get better results also in the revisions. And last, mortality of the patient is less with resurfacing, and that we have seen out of the registries. If you look to the UK National Joint Registry, with 400, 000 people, the deaths are less when you do resurfacing.
So in conclusion, I would like to say that, we have registry data to support resurfacing. I think surgical experience is one of the most important factors and we have an excellent 10-year survivorship in the younger patients.
Dr. Dunbar: Let’s look at data. The Joint Replacement Registry in the United Kingdom showed that it probably wasn’t the best bet to take young patients and switch them all over to resurfacing. The Australian Registry drilled down a little bit further on this where they looked at risk factors. It turns out that women do particularly poorly and this is relevant because we have to figure out who are the right patients. The data largely informs us to probably avoid this on women and in AVN. Which is interesting because it was one of the diagnoses that was proposed specifically for the procedure, but it has a terrible outcome with resurfacing, followed by developmental dysplasia.
Older patients do worse. And there is a stratification, but there’s an age hook over 75, so this is certainly not an operation for an older patient. And head size matters. Patients under 50, particularly from the Australian Registry, did poorly and this may be somewhat confounding with the female/male issues that females would tend to have smaller head sizes.
So, risk factors for revision after resurfacing would be females, smaller femoral heads, older patients, AVN, DDH, and certain implant designs, which means that you’re left with a young, big male with osteoarthritis, whose name is Joe, and he wants his surgery tomorrow.
We have to counter Joe’s arguments when he comes in because he is also reading the popular press literature and he comes in with the same argument, which is why should we do this on the select patient?
Well, we’re told it’s a less invasive procedure. I don’t think so. These are large, young males, as I’ve just said by definition, with big muscles. These are difficult exposures. You have to get access to an acetabulum with the femoral head still in place. They’re not minimally invasive. And there’s implications associated with tissue oxygenation at the femoral head that may lead to neck fractures, and also narrowing.
The other issue that we talk about is while this is a good procedure to do in a young patient because if it fails, you’ve preserved the femoral canal and you can change this over to a total hip replacement. No foul. Just move on. Is that the fact? Well, it’s not actually.
If you look again from the Australian Registry on a sub-paper looking at 400 cases that were converted from resurfacing to total hip, you see a significantly worse revision rate for a patient who’s converted from a resurfacing to a total hip replacement. They are not on the primary total hip revision curve. They’re in a distinct curve. They do not do as well, so this argument does not hold up in large series data.
From our group in Montreal…Pascale and Martin Levine…we found that there was no significant functional gait outcome difference between resurfacing and total hip replacement. And it’s not a surprise when you think about it because the ratio of the head and neck is at a disadvantage in resurfacing, as compared to a total hip replacement. And subsequently they may have better functional outcomes and certainly have better range of motion with the total hip replacement, than a resurfacing.
And finally, the elephant in the room, is metal ions. And I think this is really the issue in my mind. We reported back in 2008 that the metal ions were up. They didn’t go away after two years and they were way up in some patients. As a group, most of us stopped doing the procedure. Sure enough, we come along and find out that the pseudotumors could be related to specific implants, etc. Well, it turns out that in other series from other groups in other parts of the world, looking at implants that are proposed to be favorable, you can still see the same problem. So when you image these patients, almost one-third of them had evidence of a pseudotumor at five years. Controversial, but there’s evidence that there’s something going on.
In conclusion, I would suggest to you that resurfacing is more invasive. It has worse outcomes. It produces metal ions and pseudotumors that are worrisome to you and the patient. It’s difficult to revise and does not put you back onto a primary curve. And it doesn’t provide better functional outcome. You get all this for a premium price and my conclusion has to be that there is no right patient for patient resurfacing.
Moderator Thornhill: Michael, can I convince you to do a resurfacing on somebody, and if so, who?
Dr. Dunbar: You could convince me for a patient that had a high offset neck, who’s young, arthritic, who’s informed about ion levels. I think that’s part of my argument is that we need to be really careful when presenting to the audience because you shouldn’t feel like you’re inferior or you’re doing something wrong if you’re not doing this procedure. We need to be very careful in terms of generalizability.
Moderator Thornhill: Koen, let’s say we don’t do any women, don’t do any people with osteonecrosis because of the biology of the head, don’t do it in older patients, don’t do it in someone whose cup size will be less than 50. Do you agree with all that? Or any exceptions?
Dr. De Smet: Well, I agree with that if you start with resurfacing and that’s what we were saying from the beginning on.
Moderator Thornhill: Michael, let’s say you’re somebody who says, “I like this, I think I agree with Koen. I want to start doing this.” What is the obligation that you need to just—not just with this, but other procedures—to tell your patients your experience?
Dr. Dunbar: It’s a really complicated question and it’s one thing to switch from regular poly to cross-linked poly because it doesn’t change your technique. This is a radical departure. I don’t know the answer to that, Tom, it’s a great question. Does it need to go in the informed consent that I’m at the beginning of my learning curve for this procedure? Pilots would sort this out. They wouldn’t let you get on the line unless you’ve checked out your simulator ride on a new aircraft, right? You wouldn’t be allowed to expose the passengers to that. So, this is where we’re behind in surgery where we need to have better mentorship, better simulation and better qualifications and say you’re not ready to do that. You should go to places, see the experts, see the volume, get mentored, get proctored, have someone stand by your side when you do it the first time.
Moderator Thornhill: I want to thank both of our speakers for a very good debate.
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