Proper implant selection can quiet ceramic hips
Link
http://www.orthosupersite.com/view.asp?rID=27494
Nine surgeons with 11 years and 1,100 ceramic-hip experience have never heard a
squeak.
By Stephen B. Murphy, MD
ORTHOPEDICS TODAY
April 2008
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.
Stephen B. Murphy
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this particular prosthetic design, with the elevated metal rim, was withdrawn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.
