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Proper implant selection can quiet ceramic hips
Nine surgeons with 11 years and 1,100 ceramic-hip experience have never heard a squeak.
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A squeaking ceramic hip is not a cause for concern if you choose your implants wisely. This issue is primarily an implant-related phenomenon and not bearing-related.
The real question is: Why after 30 years of using ceramic hips and after two 7-year long IDE studies did this squeaking phenomenon only after FDA clearance of the bearings? Also, why, after FDA clearance was there suddenly an epidemic of squeaking in New York and Philadelphia in particular? Finally, why was this assumed to be universal to ceramic-ceramic bearings, when it fact, we now have data that demonstrates that this problem is clearly related to the use of specific implant combinations.
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The first time that I heard a squeaking hip, I was in Berlin in March 2003 during a presentation by Ian Clarke, PhD. That squeaking hip had an elevated metal rim around the ceramic liner and clearly demonstrated metal-on-metal impingement and metalosis at the time of revision. Watching the video, it was clear that the squeaking occurred in the mid-range of motion and not in extension/external rotation, where the metal-metal impingement was occurring. I thought that it was reasonable to conclude that metalosis affected the ceramic bearing and likely had a causal role in generating the squeaking. I believe that this particular prosthetic design, with the elevated metal rim, was withdrawn from use shortly thereafter.
We were looking at the issue of impingement at the same time, from 2002 to 2003. We caused impingement experimentally 5 million times with a titanium-ceramic articulation and found that little happens after 5 million cycles. The conclusion there was titanium on ceramic impingement is relatively benign and that metal-on-metal impingement was not.
Not enough experience
Going forward, I was in New York when the Lenox Hill group presented their paper on squeaking hips in the fall of 2006. At that point, I had been performing ceramic-on-ceramic hip arthroplasty for more than 9 years and I had never heard a patient with a squeak. They were showing videos with squeaking after just a couple of years and the obvious question in my mind was, what were they using and what were they doing? I think that they did not have enough experience at that time to put into perspective what was happening and to recognize it as an implant-specific problem. Unfortunately, they went on to present their assumption that squeaking was an under-reported phenomenon of ceramic-on-ceramic articulations in general, which it is not.
We started an investigational review board study to look at the clinical results of all of the ceramic hips that we had implanted over an 11-year period and revisions of ceramic hips over a 5-year period. Overall we had five revisions of ceramic hips in patients who had complained to articulation noise preoperatively. All five hips had metal-metal impingement and metalosis — all also had an elevated metal rim.
We looked at the incidence of squeaking in primary hips as a function of different designs and we broke them into two groups: flush mounted and recessed liners. We then broke the recessed liner group into two different types: recessed liners with conventional titanium alloy stems and recessed liners with stems made out of a beta titanium alloy, TMZF, which is comprised of titanium, molybdenum, zirconium and iron. We found that the incidence of squeaking was statistically significantly higher in the recessed liner/TMZF group (Accolade stem with Trident cup, Stryker Orthopedics) than the recessed liner/conventional titanium stem (Omnifit or Securefit with Trident cup, Stryker Orthopaedics) and that both were significantly higher than flush-mounted liners (Wright Medical, Johnson and Johnson, Biomet).
Device-specific
What is more interesting is the severity and frequency of the squeaking. We have seven surgeons who have used the Accolade/Trident implant combination, and all seven have heard squeaking in their office. We have nine surgeons with more than 10.5 years experience with 1,100 hips with flush-mounted liners and none of those surgeons had ever heard a squeak in their office with the exception of one bearing and liner that had mismatched diameters.
Why does the Accolade-Trident implant combination cause squeaking? Could it be the neck geometry or the taper geometry? Could it be that the HA doesn’t adhere well and it comes off? Could it be that the metal debris has some sort of different quality? Could the metal adhere more to the bearing or abrade the bearing more?
Because of these questions, we studied the joint fluid of a squeaking Accolade-Trident hip and found the presence of metals from both the cup (aluminum) and the stem (molybdenum). Could oxides of the TMZF metal impingement be affecting the bearing? It is possible that molybdenum oxides, zirconium oxides or ferrous oxides (rust) play a role in adhesion, abrasion or lubrication disruption, or that impingement of the TMZF neck against the titanium cup rim is more adverse?
There is no question that regardless of the mechanism, squeaking ceramic hips are clearly associated with this particular implant combination and that further joint-fluid analysis and experimenting with TMZF particles in joint fluid in the laboratory circumstance would be prudent.
I would like to thank the co-authors of this research: Timo M. Ecker, MD; Claire Robbins, PT, DPT, MS, GCS; Geoff Van Flandern, MD; Daniel Ward, MD; Douglas Patch, MD; and Benjamin Bierbaum, MD.
For more information:
- Stephen B. Murphy, MD, can be reached at Center for Computer Assisted & Reconstructive Surgery, New England Baptist Hospital, 125 Parker Hill Ave., Suite 545, Boston, MA 02120; 617-232-3040. He has indicated he is a consultant to and has intellectual property rights related to Wright Medical Technology.
Reference:
- Murphy SB. The squeaking hip: A cause for concern — opposes. Paper #23. Presented at the 24th Annual Current Concepts in Joint Replacement, Winter 2007 meeting. Dec. 12-15, 2007. Orlando.