| Thomas P. Gross, MD
13 years experience. Over 3000 cases.
For more information:
www.grossortho.com
A recent Article in the Lancet medical journal has
criticized hip resurfacing arthroplasty (HRA) as less
durable than cemented 28mm total hip replacement (THR). I
take exception to the inappropriate conclusion that the
authors drew from this highly flawed study.
However, there are two conclusions that can be drawn from
this study. Surgeons, who are inexperienced in hip
resurfacing, have more revisions in the short term with
resurfacing than if they stick with standard hip
replacement. Women have a higher failure rate than men with
hip resurfacing. Both of these are old news.
Hip resurfacing has several distinct advantages over stemmed
small bearing total hip replacement. The resurfaced hip most
closely resembles the natural hip. Biomechanically the hip
is stable, most of the bone is preserved and stresses are
transferred more naturally to the remaining bone. Near
normal function can be achieved, even by impact athletes.
Thigh pain (3-5% of stemmed THR) does not occur in
resurfacing. Dislocation is rare (<0.5%), and revision for
recurrent instability is extremely rare (0.03%).
The problem is not with resurfacing. The first problem is
that two poorly designed hip resurfacing implant systems
were released into the marketplace. The second problem is
that too many surgeons have dabbled in resurfacing and never
achieved enough experience with this difficult operation to
get over the learning curve. It is worth emphasizing that
the average surgeon volume for resurfacing in the Lancet
study was 3.7 cases / year. The results of inexperienced
hip-resurfacing surgeons are nicely captured in the Lancet
article.
Therefore, the first challenge is to develop more specialist
surgeons who can match the current results of numerous high
performing hip resurfacing surgeons. The second challenge is
to elucidate the underlying reasons why women have more
failures with resurfacing and find ways to improve the
outcome in women.
My conclusions from this study, the other available data and
my personal experience with hip resurfacing are:
• Most orthopedic surgeons are not qualified to perform hip
resurfacing.
• Very high failure rates are achieved by surgeons who
perform an average of only 40 resurfacings / in 7 years (4.6
cases/year).
• Cemented 28mm total hip replacement has an unacceptably
high failure rate in young patients.
• Hip resurfacing done by specialists in hip resurfacing has
a high success rate in young patients.
• All young patients requiring a hip replacement should be
referred to specialist hip resurfacing surgeons. Young
patients’ risk of failure is higher if they have a 28mm
cemented THA or if they have a HRA by a surgeon who is
inexperienced in this operation.
• If you are a patient who wants a hip resurfacing, choose a
surgeon who can demonstrate (in writing) a personal high
success rate with this operation.
A recent article analyzing and comparing failure rates of
various hip replacement types has recently been published in
the Lancet Medical Journal. It finds that the revision rate
for hip resurfacing among hundreds of surgeons in England
and Wales is higher than the revision rates for cemented 28
mm cemented total hip replacements. Therefore, they suggest
that hip resurfacing should be abandoned. They focus
particularly on 5 -year survivorship data; the failure rates
reported were:
• Resurfacing, all patients: 5.2%
• Resurfacing in men: 3.5%
• Resurfacing in women: 8%
• Cemented 28 mm M/P THR: 2.8%
I am concerned with the revision rate reported among this
cohort of 698 English and Welsh surgeons trying to perform
hip resurfacing. My personal experience is completely
different than what these British surgeons can achieve.
I have now performed 3000 hip resurfacings since 1999. This
is more than 10% of the entire British experience reported
on in this Lancet article. I have practiced very limited
patient selection. About 2/3 of my patients are men and 70%
have osteoarthritis. I do not avoid patients with smaller
implant sizes. I have maintained follow-up on 92% of my
patients. I keep track of causes for revision as well as
complications. My 5-year failure rates are as follows:
• Resurfacing, all patients: 2.8%
• Resurfacing in men: 1.9%
• Resurfacing in women: 5.2%
• Uncemented Resurfacing: 1.9%
• Uncemented resurfacing in men: 0.9%
• Uncemented resurfacing in women: 5.1%
How can we explain this significant difference?
Should I accept the conclusions of AJ Smith et al from the
British Joint Registry Data published in the Lancet and
discontinue hip resurfacing?
I think we can safely conclude one thing from the Lancet
article:
Many British surgeons are NOT qualified to perform hip
resurfacing and should abandon this procedure.
The problem is, that previous registry studies have shown
that young patients have much higher 10-year failure rates
with cemented THR. In fact, this same Lancet article quotes
a Finnish registry study showing a 28% failure rate at 10
years for cemented THR.
Although the Lancet article confirms that most surgeons
cannot perform hip resurfacing well, several high volume hip
resurfacing surgeons have demonstrated far lower failure
rates than 5% at five years or 28% at 10 years: McMinn,
Treacy, Amstutz, DeSmet, and myself, for example.
This indicates that young patients should not receive
cemented 28mm THR, they should not receive resurfacing from
inexperienced resurfacing surgeons, they should rather be
referred to specialists in hip resurfacing who CAN achieve
high success rates with hip resurfacing.
Although large registry studies are one valuable source of
information for surgeons, it would be foolish to use only
registry data to make all of our decisions. There are many
shortcomings of registry data:
1. Only revisions are counted as failures.
2. Complications are not reported.
3. Function is not assessed.
4. Bone preservation is not considered.
5. Patient activity level and restrictions are not
evaluated.
6. The effect of surgeon skill is disregarded.
7. Overall effect on the patient’s life is not measured.
Before addressing these issues, I have two other major
concerns with this study:
First is their low rate of follow-up. The methods section
states the analysis is based on 82% of THR’s undertaken.
What happened to the other 18%? This is supposed to be a
national joint registry? My data is based on 92% rate of
follow-up and I don’t have the benefit of a national
registry. This fact alone casts great doubt over the entire
study.
Second is their choice of implant inclusion. They did
appropriately remove the DePuy ASR implant from analysis
(recalled by DePuy in the US 2010). But the Zimmer Durom was
another failed implant, which was removed from the US market
in 2008 because of a high failure rate. Why was this implant
not removed from this analysis?
Now we will critique the other shortcomings of registry
studies listed above:
1. Because registry studies only count revisions as
failures, it is not known which group studied has more
unrevised but failed implants. If a patient has an implant
has a loosened painful implant but is not revised, this is
still considered a success by the registry. If a patient has
suffered three dislocations but has not been revised, this
is still considered a success by the registry.
2. Dislocation is the most common complication in THR but
almost never happens in hip resurfacing. A recent randomized
controlled study from Australia has shown the dislocation
rate of 28mm THR to be 5.2% within the first year after
surgery. The most common reason for revision for THR in the
US is dislocation. It accounts for more than 20% of all THR
revisions in the US. My rate of dislocation for HRA is <
0.5%. Only 1/3000 (0.03%) have required revision for this
problem.
In HRA, bearing size is the same as the natural hip and the
normal hip biomechanics are closely reproduced, leading to
normal hip stability. After a 6-month healing period,
patients can bend their hip how they like and engage safely
in all sports including gymnastics and kayaking. This is
simply not possible to do with a 28mm THA.
But the Lancet article suggests that resurfacing should be
abandoned? This is an ivory tower conclusion that ignores
the desires of many younger patients sidelined from an
active lifestyle or from physical work because of an
arthritic hip. These young people would be unable to return
to their desired activities after a standard THA. Apparently
the Lancet authors have not considered this fact. A 28mm
cemented THA simply does not meet the needs and desires of
many young patients. It does not compare to an HRA.
3. Patients with THR are usually not able to resume as high
a level of function as those with HRA. If they do manage to
return to impact activities, they have a high rate of
implant failure. HRA only has a higher rate of implant
failure at extreme levels of activity, and most of those are
from failure of femoral cement fixation.
Functional potential is much greater after HRA. If a patient
wishes to golf, walk or even use an elliptical it is
doubtful that they would notice the difference between a HRA
and a THR. But if they are interested in physical work or
impact sports they are much more likely to resume these
after HRA. 4/5 published gait studies have shown normal gait
with HRA, but abnormal gait with THR. 2 large comparative
survey studies by Barrack and Noble have shown a much higher
activity level achieved by young people if they had an HRA
compared with THR. In a 15-year comparative study Argenson
has recently shown that THR had a 6.5% loosening rate in low
activity patients and a 20% rate in patients with a high
UCLA Activity score (partaking in impact sports). Amstutz
was unable to show any difference in implant survivorship
after hip resurfacing at 10 years when using the UCLA
activity score, but could show a difference when using a
much more rigorous hip impact score (3.6% vs. 11.2% failure
at 8 years; 70% of failures were cement loosening of the
femur).
Resurfacing clearly allows better function and tolerates
higher level of activities. The primary remaining challenge
is failure of fixation of the cemented femoral component. I
predicted this 12 years ago and therefore have pursued
uncemented femoral fixation. The results at 5 years are
promising, but not yet conclusive.
4. Bone preservation for future revision surgery is still an
important consideration in young patients needing a hip
replacement. The amount of bone removed from the acetabulum
in the original THR is similar to that for HRA. But on the
femoral side much less bone is removed during HRA than in
THR where the entire head and half of the femoral neck are
removed. Removing a stem from inside the femoral canal can
lead to further bone destruction at the time of revision of
a THR. Many patients are justifiably not sufficiently
confident in the durability of THR to allow surgeons to
amputate their femoral head and neck at a young age. But the
authors of the Lancet article do not consider bone loss.
5. Patients that have an HRA with a cemented femoral
component can safely participate in impact sports, but
should refrain from extreme impact activities such as
running long distances. Patients with uncemented resurfacing
are not restricted from any activity after 1 year after
surgery. Because the hip ligament heals after 1 year, full
unrestricted range of motion is allowed for all HRA. Neither
impact activity nor extreme bending is advisable for
cemented 28mm THA. 40% of my patients choose to participate
in impact activities after HRA. When a registry study
compares THR to HRA can they possibly be comparing
equivalent patient populations?
6. HRA is widely acknowledged to be a more complicated
operation to master than THR. There are few if any
orthopedic residents that learn this operation during their
training. If a surgeon is interested in resurfacing, he has
to mostly learn it himself. Numerous studies have indicated
that the learning curve is long. In a study of my first 373
HRA, my failure rate continued to fall after the first 200
cases. The Lancet study reports on 26,119 HRA done by 698
surgeons over 8 years; an average of 37 cases per surgeon or
4.6 cases/surgeon/year. They claim to account for the
“learning curve” effect. This is a ridiculous claim when
most British surgeons in this study have performed fewer
than 100 HRA.
7. In a recent study evaluating the same English and Wales
registry, McMinn has found that life expectancy for men
after HRA is greater than after THR. Results were adjusted
for age, gender and level of health but not for activity.
There are several possible explanations.
• Perhaps patient populations in the British registry who
have HRA are not the same as those that have THR despite the
fact that age and health status were controlled. If this is
true, how can the Lancet article then compare failure rates
between two different groups of patients in a meaningful
fashion?
• If young patients who receive HRA have a higher functional
level than THR patients, perhaps the positive effects of
exercise account for their lower mortality?
• Perhaps there is something in the technique or materials
of a THR that are deleterious. For example, fat embolism
occurs with femoral preparation in THR but not in HRA. This
may cause previously unrecognized permanent cardiopulmonary
dysfunction. Critics of metal on metal bearings have long
speculated that cobalt and chromium released by HRA bearings
may cause cancer or other ill effects. The potential cancer
effect has long been disproven with studies up to 30 years.
Now it appears that patients with these metal bearings
actually live longer! It will be interesting to learn why
patients with THR have a shorter life expectancy than
patients with HRA.
In summary, the conclusions of the Lancet study are based on
a very limited and superficial analysis of THR vs. HRA. The
Lancet study only illustrates that a patient should not
allow an inexperienced hip-resurfacing surgeon to perform
his/ her operation. It confirms what many other studies have
already shown: that women have a higher failure rate than
men with HRA, but it adds no new information on why this may
be true. There are numerous advantages of resurfacing that
are simply not evaluated by this study. The Australian hip
registry shows a better survivorship for young men with HRA.
Young active people are not able to resume their desired
lifestyle with THR.
Young sporting people or physical workers should be advised
that THR will relieve their pain but will not safely allow
them to resume their lifestyle. Surgeons who are not
experienced with HRA should not attempt to perform this
operation without warning their patients that their failure
rate is probably much higher than that demonstrated in
specialist centers. Data from this Lancet study suggests
that young active patients should be referred to specialist
centers for hip resurfacing with demonstrated low failure
rates with this procedure. In England, for example, a vast
difference in outcomes is seen between Oxford and
Birmingham. More than with most other procedures, it is
critical for the patient to do their homework before
undertaking HRA and to select a surgeon who can demonstrate
a high success rate with this operation.
References:
1. Ollivier et al; CORR 2012. Does Impact sorts Activity
Influence Total Hip arthroplasty Durability?
2. LeDuff et al; JBJS Am 2012. The relationship of sporting
activity and implant Survivorship After Hip Resurfacing.
3. Smith et al; The Lancet 2012. Failure rates of
metal-on-metal hip resurfacings: analysis of data from the
National Joint Registry for England and Wales.
4. McMinn et al; British Medical Journal 2012. Mortality and
implant revision rates of hip arthroplasty in patients with
osteoarthritis: registry based cohort study.
5. Gross et al; Journal of arthroplasty 2012 Hip resurfacing
with the Biomet Hybrid Recap-Magnum System
6. Gross et al; Journal of arthroplasty 2011. Clinical
Outcome of the Metal-on-metal Hybrid Corin Cormet 2000 Hip
Resurfacing System
7. Brekke, Noble et al; ISTA 25th Congress Sydney Australia
2012. Patient Function and Satisfaction After Large Head
Total Hip Arthroplasty versus Hip resurfacing.
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