Lee v. Padgett: Ceramic-Ceramic Bearings in Patients <60 Assures Longevity

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.