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 “Ceramic on Ceramic THA in Patients <60: A New Standard.” For the proposition is Stephen B. Murphy, M.D., Tufts University, Boston, Massachusetts. William J. Maloney III, M.D., Stanford Hospital & Clinics, Stanford, California is opposing. Moderating is Jay R. Lieberman, M.D., Keck Medical Center of USC, Los Angeles, California.
Dr. Murphy: So my job is to argue in favor of ceramic-ceramic total hip arthroplasty in patients under the age of 60 years.
To begin I’d like to review our 18 years of experience with ceramic-ceramic bearings. We have previously published in patients under 50, starting in 1997 and then uncemented in 1999, 307 hips in total with 262 having a minimum of two-year follow-up with an average age of 42; more males than females. This study was initially part of a prospective IDE study with the FDA. The acetabular cup design utilized was flush-mounted with an 18-degree taper. Seventeen percent of these patients had previous surgery and a number of them were relatively complex. Surgical techniques all were posterior capsular preserving whether it be transgluteal, trochanteric slide, or more recently through the superior hip approach.
In terms of component positioning before 2001 I did them all freehand. From 2001 to 2008 we used traditional navigation and from 2008 to now we’ve used smart mechanical navigation. Our survivorship at 14 years is 97% for these patients and that’s survivorship with any reason for revision.
What about < 60, instead of < 50? We recalculated a similar series of our patients over a similar time course starting in 1999; 243, average age 46. Follow-up average 8.1 years out to 15. Again, a preponderance of men and 17% bilateral. Six patients revised. We had a couple of fractures with high energy trauma and one atraumatic liner fracture in the presence of a trochanteric non-union. Three components did not osseointegrate. The 11 year survivorship was 97.8% with revision for any reason. In terms of dislocations, there weren’t any. No revisions for infection. And no cases of osteolysis.
This is similar to a previously published study (Hsu JE, et al, Semin Arthroplasty 2011) where they showed equally high survivorship for alumina ceramic-ceramic bearings.
Why is it that we don’t really recognize the superiority of these bearings? Is it cost? Is it the squeaking? Registry dislocation? Well, cost I don’t think is a significant issue. Many of the available polyethylene bearings with porous coatings are actually more expensive than the implants that I use. In terms of squeaking, that’s clearly related to a particular design utilizing an elevated rim. What about registry data? Well, in Australia in particular, a lot of the latter components were used and that would explain the higher failure rate in Australia. If you could filter out just for the flush-mounted, 18-degree taper liners, I think it would show clear superiority.
What about dislocation? Well, I think dislocation is a function of soft tissue preservation and component positioning. There weren’t any dislocations in this series.
What about concerns for polyethylene? Well, my concerns are that polyethylene changes all the time. There are a million products out there. The products that were used 10 years ago are not the same ones that are used now. There are no long-term studies of any of the current ones that people use with high frequency. Certainly there are mechanical problems with decreased tensile stress, strength, edge loading leading to fracture; sub-surface oxidation; and reports of osteolysis.
I think another big, big problem right now is liner dissociation. There will be a number of studies coming out in the next year about this and this really relates to the mechanical integrity of the plastics, so not only can it break, but it can dislodge from the metal shell. And in terms of some of the newer ones, certainly there are concerns about in vitro wear and, again, I just point out that we don’t have any long-term follow-up on these components.
So in summary, I would say that I hope that these polyethylene bearings turn out to be good bearings. I think that removing cobalt chromium and polyethylene from the total hip construct is really the best thing for long-term outcomes. But I know based on clinical outcomes at more than a decade that alumina ceramic-ceramic bearings have excellent results.
Dr. Maloney: The question is: ‘Is this a standard?’ Well, a standard is something established by authority, custom or general consent. And it’s clearly not true for ceramic- ceramic total hip replacement. There’s a better question. ‘Is there any indication for a ceramic-ceramic total hip replacement in 2015?’
Well, why the interest in ceramic-ceramic? First, the low wear rates. Clearly it does have a low wear rate. But is that relevant in today’s bearing surface? I think the answer is probably not.
You cannot tell a difference in wear of ceramic versus cobalt chrome femoral heads on highly cross-linked polyethylene. Highly cross-linked polyethylene is very difficult to make wear under any condition. In fact, we did a study looking at the wear of conventional versus highly cross-linked polyethylene with retrieved femoral heads. We took retrieved heads from revision surgery with various degrees of roughness, and on conventional polyethylene there was direct correlation between the surface roughness and wear. Taking clinically relevant rough heads, it was even difficult to make the highly cross-linked polyethylene wear at 5 million cycles. Very low wear despite the rough femoral heads.
What about the negatives related to ceramic- ceramic? Well, Steve did a good job of telling you about the negatives and I think they are real. First, there’s cost. If you’ll look at the cost, it’s substantially more at most institutions and it’s simply not cost effective. They are more expensive and we’d have to have a substantial reduction in revision to justify that cost. The risk of complication data in the United States, from all payers, looking at metal and plastic and ceramic, ceramic-ceramic does not produce a substantial reduction in revision. When we looked at the revision rate for metal- plastic and ceramic- ceramic for several thousand hips in the United States, there was no significant difference. They were essentially identical.
In the Australian registry data, metal- highly cross-linked polyethylene is the most reliable bearing, which includes ceramic- ceramic. When reviewing femoral head sizes less than or equal to 28mm, adjusted for age, which is a surrogate for activity; and gender, a surrogate for bone quality, metal- highly cross-linked polyethylene is the most reliable bearing surface. Further, for larger heads, those greater than 28mm, again metal-highly cross-linked polyethylene is the most reliable bearing surface.
And if you’re going to use ceramic- ceramic, it’s probably better to use a larger femoral head because they do a little bit better than the smaller femoral heads. With the larger heads you do have a few more options. Breakage is probably no longer a significant issue. Certainly, I think delta ceramic is significantly better. The fracture rate with delta ceramic is quite low. There have been a couple of reported fractures, but I don’t think that’s the main issue going forward. It’s not going to be zero.
What about the squeaking? Well, for those patients who squeak, they’re fairly upset. I saw a nurse in the clinic who had bilateral ceramic- ceramic total hip replacements. Both were squeaking. One fractured and she was worried the second one was going to fracture because of the squeaking. When you have it, it’s not a trivial issue. And there are various types of squeaking. Some are like an old door hinge. Others “chirp”. Some squeak like a cat. Most people tolerate the squeaking fine, but for some patients it’s obviously a problem and occasionally you need to revise for squeaking.
I think in summary, ceramic- ceramic hip replacement is clearly not a new standard and any use is based on the long-term theoretical advantage which is yet to be proven.
Moderator Lieberman: Steve, so who in your practice gets a ceramic- ceramic hip?
Dr. Murphy: I use alumina ceramic bearings on people well into their 60s and sometimes in their early 70s. I think Bill makes a good point that the results of some highly cross-linked polyethylenes have been okay, but the long-term results are always shorter than what ceramic-ceramic has and the polyethylene’s are changing all the time. So when you advocate for a highly cross-linked polyethylene, you’re using in vitro studies instead of long-term clinical results to justify it and I think there is a big difference, as we all know, when you actually operate on patients and look at them in the long term.
Moderator Lieberman: So you use ceramic- ceramic on a 70-year-old?
Dr. Murphy: Yeah, and I think they’re proven.
Moderator Lieberman: So how about the head sizes, Steve, you want to briefly comment on that?
Dr. Murphy: With alumina ceramic, there are 28mm, 32mm, 36mm and with delta-delta the sizes are 28mm and 36mm. I use 28mm bearings with some frequency in dysplasia patients. Again, I think in that clinical study there were no dislocations. Hip joint stability is a function of surgical technique, soft tissue preservation and component alignment, and if using bearing diameter to back that up, that’s fine, but you shouldn’t need it.
Moderator Lieberman: I think that the data would clearly show that the larger the head the more stable the hip. Bill, what are your feelings about ceramic heads against highly cross-linked polyethylene?
Dr. Maloney: I think clinically they’re indistinguishable. I think the data would suggest that’s the case in multiple registries. We’re doing it more currently on a gut reaction over concerns with taper corrosion. In our own study at our own institution we’ve yet to identify a significant taper corrosion case.
Moderator Lieberman: Steve made a very good point about concerns about the biomechanics of highly cross-linked polyethylene and looking at things like vitamin E to reduce in vivo oxidation. Can you give the audience some perspective on where you think we are with that and what the future will hold?
Dr. Maloney: I think it’s going to be impossible to prove that any new released polyethylene, highly cross-linked polyethylene, or enhanced polyethylene would be better than the one I’ve been using since late 1998. I’ve yet to see a case of lysis on my own practice—we follow those patients under 50. If you’re looking at 10+ year data with no lysis, it’s hard to prove anything’s better. We have not seen a fracture in those as well, so I don’t think it’s a real issue.
Moderator Lieberman: Steve, you’re a real advocate for ceramic- ceramic. Are there any patients for whom you wouldn’t use a ceramic liner because you were concerned about stability or any other issue?
Dr. Murphy: There aren’t young patients that I would not use a ceramic-ceramic bearing in because of a technical issue unless it were somebody with polio or something I really felt that it was a small cup that needed a big bearing. I haven’t been in that situation in the past decade. But I might consider something else in a circumstance like that. That would be about it and I have a lot of confidence in those bearings, obviously, and they’ve been around for a long time so there are no secrets. I do have concerns about the polyethylene disassociation problems that we’re seeing now and the fractures and the fact that I think those will become more commonly recognized in the near future. Whereas when I use ceramic-ceramic bearings, I know exactly what I’m going to get. They’re not going to disassociate. They wouldn’t fracture typically unless someone fell from a height and it saves them from some other injury. No osteolysis. I just think they’re incredibly, incredibly reliable bearings.
Moderator Lieberman: What about concerns about the chip fractures, or even people just having some difficulty with smaller incisions when impacting a ceramic component and getting a good fit?
Dr. Murphy: Well, the 18-degree taper components are really easy to put in. You put them in by hand you just let them go in themselves and you just help them. If you try to force one in at the wrong angle it will get stuck, so you just don’t do that. The delta ones that are a 10-degree taper are a little bit trickier, but you need to use the same technique to put it in. They go in quite well and you can tell when they’re seated. It’s not a big deal.
Moderator Lieberman: Bill, finally how about any concerns about elevated lip liners? Or lateralized liners with the new highly cross-linked polyethylene?
Dr. Maloney: We don’t use lateralized liners in general. Occasionally we use elevated lip liners. Again, it goes back to what Steve said. If a surgery is done well, it’s not an issue.
Moderator Lieberman: Well, gentlemen, thank you for a very envisioned discussion. Excellent presentations.
Please visit www.CCJR.com to register for the 2016 CCJR Spring Meeting, May 22 – 25 in Las Vegas.
