Lee v. Padgett: Ceramic-Ceramic Bearings in Patients <60 Assures Longevity
OTW Staff • Tue, December 26th, 2017
This week’s Orthopaedic Crossfire® debate was part of the 33rd Annual Current Concepts in Joint Replacement® (CCJR®), Winter meeting, which took place in Orlando. This week’s topic is “Ceramic-Ceramic Bearings in Patients <60 Assures Longevity.” For is Gwo-Chin Lee, M.D., University of Pennsylvania, Philadelphia, Pennsylvania. Opposing is Douglas E. Padgett, M.D., Hospital for Special Surgery, New York, New York. Moderating is Thomas S. Thornhill, M.D., Harvard Medical School, Boston, Massachusetts.
Dr. Lee: I must confess I routinely use polyethylene for my total hip arthroplasties. There is no doubt that these are forgiving surfaces and reliable and certainly good enough for most patients undergoing total hip arthroplasties, but I don’t think it’s good enough for all patients.
We all know that younger patients are undergoing total hip arthroplasties. Patients tend to be more active. And our implants are being asked to carry the burden of survivorship beyond 20 years into 30 and maybe 40 years.
The problem is not fixation, it remains wear and osteolysis. Coupled with the fact that most of us are trying to guard against dislocation by using larger heads, this compounds the problem and it’s topical to this matter.
The American Joint Replacement Registry (AJRR) 2014 Annual Report has a breakdown of the heads implanted in 2012-2014. In 2014, nearly 50% of the total hip arthroplasties were implanted with head sizes greater than 32mm. And the problem is that the science behind highly crosslinked polyethylene in terms of excellent wear rates is documented most on 28mm and 32mm ball heads. So, when you extrapolate this, the larger ball heads and even younger active patients, and you look at the osteolysis threshold traditionally described as 0.1mm per year, a study by Selvarajah et al. (Bone Joint J 2015) shows that 2D wear and 3D wear exceeds this threshold. That’s concerning.
Others have also observed that, particularly, in first generation highly crosslinked polyethylene. Wear is observable, so it’s not like the surface doesn’t wear, and the question remains whether the surface is going to last 30, 40, or 50 years.
If you don’t believe in linear wear rate in highly crosslinked polyethylene, perhaps volumetric wear rate should concern you. A study by Lachiewicz et al. (Clin Orthop Relat Res 2016) shows that if you use a 36mm ball head, the volumetric wear rate, as expected, is double that of 28mm and 32mm ball heads.
And at 10-14 years, small osteolytic lesions are starting to become visible. The significance is unknown, but certainly concerning.
We all know that ceramic-on-ceramic has the best wear rates in-vivo and in-vitro. Most importantly because of its properties—its wear rate and fracture rate actually improve with head size so it’s naturally well-suited for the use of large heads, if you like to use large heads.
The literature is actually well populated with studies showing that very young patients do well and experience very low failure rates with very high activity levels. We have institutionally observed this even in patients under the age of 21, with very high, high activity levels and low fracture rates and low squeaking rates. And this is clinically relevant durability…these patients remain highly functioning even at 15 years follow-up, with excellent survivorship and very low complications.
The problem is that if you look at it on a relatively short-term basis—5, 10, maybe even 15 years—registry data and comparative studies have not necessarily shown significant clinical differences or survivorship differences at 10 years. But if you start to extrapolate, it’s important to note that ceramic-on-ceramic bearings fail differently compared to conventional bearings. Loosening is actually more rare in ceramic-on-ceramic couples as compared to conventional bearings and polyethylene bearings.
Even when you use a 28mm ball head for polyethylene compared to ceramic-on-ceramic, wear rates at 10-14 years are significantly lower with ceramic-on-ceramic implants. And in meta-analysis if you look at revision risk and actual wear osteolysis, ceramic-on-ceramic always wins (Hu D, et al. J Orthop Surg Res 2015.
So why not ceramics for everybody? It’s less forgiving. Potential squeaking. Risk of fracture and risk of cost prevent wide adoption.
Head fractures have been eliminated with improved materials. Understanding proper taper handling; not mismatching tapers. Liner fractures remain at a relatively low rate. Problems are largely related to intra-operative events, surgical technique and poor instrumentation.
Squeaking hips have also been reduced with the removal of certain implant designs from the market and revision for squeaking is quite low. But it’s also important to remember that crosslinked polyethylene can also break. Polyethylene bearings can also make noise. All mechanical devices can make noise.
If you want to do total hip arthroplasty in the young patient with polyethylene, there is literature supporting that, but only if you use 28mm heads. I think we need to make patient-specific choices that are clinically sound but most importantly economically responsible. Highly crosslinked polyethylene may be winning the battle at this point, but I think that in the long term you may lose the war.
In summary, recognition that there is a role and place for ceramic-on-ceramic articulation in total hip arthroplasty should exist and modern ceramic-on-ceramic hip arthroplasty should be the standard in young, active patients considering total hip arthroplasty.
Dr. Padgett: The long-term success in total hip arthroplasty really resides in two things. Number one, avoid short-term problems such as instability and infection. Number two, ensure long-term fixation and address concerns about bearing wear and osteolysis.
I’d like to take you back in time to eight years ago—this is the venue—it’s the HSS alumni meeting—and at that time I was challenged to defend the possibility of the use of metal- or ceramic-on-polyethylene. The number one public enemy at that time was osteolysis. The question at the time was what was the optimal bearing in the young patient.
My opponents were two—one of my partners Ed Su who made a very recent case for metal-on-metal at the time, looking at hydrodynamic fluid film lubrication, essentially becoming an almost wear-less type of articulation. Improved manufacturing was suggested, including a better understanding of radial clearance. More problematic on the metal-metal side though was my concerns about metal ion release and the potential secondary affects and organ tumor induction—hypersensitivity—again the timeframe is 2008.
My opponent on the ceramic side was none other than my mentor, Chit Ranawat. Chit gave a very reasoned approach to the use of alumina-on- alumina with very low wear rates. And again, the advantages were due to wetability, low friction, and scratch resistance.
In 2008, the arguments about ceramic were the following: noise—approximately 20% in almost all series and they fell into two types: clickers and squeakers. The clickers were due to micro-separation and it was a common phenomenon. Squeakers? Again, an article from the front page of The New York Times, “That Must Be Bob. I Hear His New Hip Squeaking” and I was quoted as saying “There is something amiss here.”
More specific and more concerning events dealt with fractures. An early series reported approximately 1 in 1,000. Causes were attributed to large grain size; ceramic impurities; and trunnion mismatches. There were some improvements in decreasing grain size, reducing impurities, and reducing fracture rates—which were estimated to be about 1 in 25,000—but still not zero.
From our retrieval lab we looked at the effect of marginal impingement, chipping in several instances. We were concerned about metal transfer onto the surface as a result of this impingement.
And finally we looked at ceramic mal-seating. While none were associated with any squeaking we were concerned about the long-term consequences of this.
I was left at this point to defend the role of crosslinked polyethylene with three studies at 3 and 5 years (Digas, Dorr and Martel), looking at a 50-60% reduction in wear rates. And that was the basis of my argument.
Well, the year now is 2016. Donald Trump is the president. The Cubs won the World Series. And quite frankly, let me give you an update…metal-on-metal total hip is dead. Hip resurfacing on life support. I think we can stop that.
What about ceramic-on-ceramic in 2016? There’s a slow, but steady, decrease in its use in Europe. The issues with ceramic-on-ceramic…we’ve got more data; newer data and the latest—345 Delta-Delta ceramic hips with a mean follow-up of 5.3 years, looking specifically at clinical outcomes, noise and fracture rates from Bill Hamilton’s group (J Arthroplasty 2015). Three fractured ceramic liners and a 7.5% reported incidence of ceramic squeaking.
A large series (Hamadouche et al., Clin Orthop Relat Res, 2016), looked at over 2,000 revisions of both metal-polyethylene and ceramic-on-ceramic. The mean time to revision on the ceramic-ceramic cohort was approximately three years. And the reasons for revision are exactly the same—ceramic breakage, squeaking, and implant mal-seating.
Despite the newer generation of ceramics, increased awareness of the importance of implant positioning, fractures and squeaking still occur.
If metal-on-metal and ceramic-on-ceramic are out, what’s my alternative for the young patient?
Crosslinked polyethylene with the latest updated data (Bragdon et al., 2016). Thirteen year follow-up, 264 hips, a mix of both 32mm and 36mm, as well as some ceramic heads, and the wear rates of 0.002mm/year—that’s a lot of zeroes—increased wear rate with larger heads at 0.035mm/year and no reported incidences of osteolysis.
This has led me to conclude that ceramics are extremely sensitive to implant position.
Despite the newer implants that are out there, we still have an incidence of fracture, squeaking and impingement. With crosslinked polyethylene the wear rates are almost zero, there’s no observable osteolysis. Larger heads have not compromised performance. And, I’d say, that the current use of ceramic-on-polyethylene mitigates the trunnion issue. And the use of crosslinked polyethylene gets the advantage of a ceramic head without the concerns of a ceramic-ceramic bearing.
So I’d like to conclude that plastics are the future and the future is now.
Moderator Thornhill: That’s great. Dr. Lee, you said that squeaking rate was very low and Doug said it was 7.5%. That’s high. Can you reconcile that difference of opinion?
Dr. Lee: Yeah, I think it depends on how you ask the question and what you truly define as squeaking. I think if you poll all your total hip patients --conventional bearings versus ceramic-on-ceramic hips—and ask whether their hips make noise, a large proportion of them will say that their hips make noises that are inaudible to anybody else.
If you define true squeaking as somebody that walks down the hallway and you can hear squeaking, that incidence is probably less than 7.5%. If you basically poll for whether their articulation makes noise clicking or snapping, that incidence may be higher.
Moderator Thornhill: So you’re saying that much of that is insignificant squeaking.
Dr. Lee: Correct.
Dr. Padgett: We looked at our original alumina-alumina series that we published and squeaking incidence was about 9%. Chit reported noises of any incidences as high as almost 20%. I would agree that almost all articulations can generate some noise, although I’ve never actually observed any ceramic- or metal-on-polyethylene squeaking. If you’re one of those patients that has squeaking you are not happy.
Moderator Thornhill: What is the cost differential between…I know it varies from institution to institution…but what is the cost differential?
Dr. Lee: It varies. At our institution a ceramic-on-ceramic hip is about $1,000 more compared to a conventional bearing hip replacement.
Moderator Thornhill: There’s always been concern about ceramic debris in terms of its bio-reactivity. If you have a fracture or some chipping, does ceramic debris concern you?
Dr. Lee: Ceramic debris does concern me if it fractures. That’s why there’s a specific way to revise a broken ceramic. With a broken ceramic liner or head you have to do a wide exposure, complete debridement, make sure as much of the debris is out and you want to put a ceramic ball head back in because they’re more scratch resistant and harder. You don’t want to use a metal ball head since they could be scratched up.
Moderator Thornhill: Doug, your wonderful biomechanics expert, Tim Wright, has talked about crosslinked polyethylenes in the loaded areas leeching out some of the antioxidants in the weight bearing areas and their crosslinking goes down, right? Is that a long-term problem?
Dr. Padgett: I don’t think we know the answer to that. I can tell you that the data that we’ve got now is 13-15 year data and it looks very impressive. I would be somewhat cautious about the introduction of second and third generations to solve a theoretical problem as it relates to oxidation of the polymer.
Moderator Thornhill: I’d like to thank the speakers. They both did a great job and stayed on time and on top of it.
Please visit www.CCJR.com to register for the 2018 CCJR Spring Meeting, – May 20 – 23 in Las Vegas.
Senior Editor: Jay D. Mabrey, M.D., whose 35 year career in orthopedics included residency at Duke University Medical Center, service in the United States Army Medical Corps, Fellowship at the Hospital for Special Surgery and a long, distinguished career at Baylor University Medical Center where, in addition to his overall leadership at that institution, developed the Joint Wellness Program that helped patients get up after surgery more quickly, developed the first virtual reality surgical simulator for knee arthroscopy and chaired the FDA Orthopaedic Device Panel, is Orthopedics This Week’s newest contributing writer and editor.