WHAT IS THE
BEST BONE FIXATION TYPE? 1/11/2011
A Comparison of cement vs. bone ingrowth
Thomas P. Gross, M.D.
At 2 years
of follow-up cemented and uncemented femoral resurfacing is equivalent.
cement failure is the most common late cause of failure in hip resurfacing
(3% @ 8 years).
Wear-related failures with the Corin or Biomet implant systems are rare in
demonstrated that failure of bone ingrowth does not occur in a properly
designed uncemented femoral resurfacing component (provided femoral neck
fracture or osteonecrosis does not occur).
fixation of implants in stemmed total hip replacement surgery is more
durable at 10 years than cement, especially in young active patients.
patient who is a candidate for hip resurfacing is a candidate for an
uncemented femoral resurfacing component.
Most clinical data on hip surfacing to date is based on an uncemented acetabular
component and a cemented femoral component.
femoral resurfacing components are now available from Biomet for any patient
who desires them.
Medical is beginning initial studies on an uncemented femoral component.
had an uncemented femoral component available in Europe for several years.
uncemented resurfacing for every patient who is a resurfacing candidate; I
don’t require cemented components or stemmed total hips as backups except in
unusual circumstances (2/2300 = 0.23%)
of the Biomet Magnum and Recap components for total hip resurfacing is
defined by the FDA as an off-label use.
uncemented fixation of both the femoral and acetabular components of
metal-on-metal hip resurfacing devices. Currently, the market standard used by
most surgeons around the world is uncemented fixation of the acetabular
component and cement fixation of the femoral component. I was one of the first
surgeons in America to begin performing metal-on-metal hip resurfacing in 1999.
I was the first to begin resurfacing with a fully porous coated uncemented
femoral component that I developed with BIOMET in 3/2007. I currently lead the
world in uncemented metal-on-metal hip resurfacing with over 1300 operations
performed. The initial results are excellent and other companies are beginning
to explore this technology as well. The speed of recovery is no different than
if a cemented femoral component is used. The early results are the same. I
believe (but have not proven) that the long-term fixation will be superior. Let
me explain why.
components for metal on metal total hip resurfacing have shown excellent results
during the initial 4 years that I have been using this new technology. The early
results that I have achieved in over 1300 cases since March 2007 are better than
the early results that I achieved with the same brand cemented femoral
component. But this may simply be due to greater surgical experience. In a
comparison study to be published in Orthopedic Clinics of North America in April
2011, we found no difference in the results of matched patient groups with
either cemented or uncemented femoral components implanted during the same time
period at early (2 year) follow-up. All uncemented femoral components were found
to be bone ingrown by XR criteria. This means that the attachment of these
uncemented femoral components is highly successful. My opinion is that they will
therefore outlast cemented components in the long run. We will provide a
detailed summary of the results of this study as well as the latest results in
the first 1000 uncemented hip resurfacings.
of implants to bone is a proven technology that has generally surpassed the
durability of cemented fixation to bone in traditional stemmed total hip
replacement surgery. In the long term (at 10 years) a higher percentage of hip
implants using uncemented fixation still remain attached to the bone than
cemented implants, especially in younger more active patients.
Fixation of total
hip implants to bone can be accomplished by cement or by porous ingrowth
technology (uncemented). Cement fixation is immediate. Cement is an acrylic
material (methylmethacrylate) that is very brittle and also fairly toxic to bone
cells. Cemented implants gradually loosen from the bone over time by reaction to
the cement itself and due to gradual fatigue failure of this material. This
process is faster in more active patients and faster in implant situations where
the cement is stressed by shear forces rather than by compression forces.
components are initially held to the bone by a very tight press fit, which is
achieved by accurately preparing the bone so that the implant can be tightly
hammered-on. The implants are so tightly wedged–on that the patient can bear
full weight on them immediately. They do require a period of six to twelve
months of bone ingrowth before they are considered well fixed. There is usually
a small chance of failure of this bone ingrowth process in uncemented implants
(<1%). But if ingrowth occurs, it is much more durable than cemented fixation
and rarely fails in the long term.
surgeons in America have come to a consensus on the superiority of uncemented
fixation in total hips, uncemented fixation has virtually completely replaced
cemented fixation in stemmed total hip replacements, despite the fact that these
implants are more expensive. 99% of acetabular (socket) components that are used
today are of the uncemented type, as are about 90% of femoral stems. In hip
resurfacing there is also universal agreement that uncemented fixation is
superior for the acetabular component. However, until recently, uncemented
femoral components have not been available, therefore most hip resurfacing
operations in the past have employed cemented fixation of the femoral
At the time that I
began hip resurfacing in 1999, there was not yet general agreement that
uncemented fixation was superior to cement in hip replacements. However, the
evidence was mounting that uncemented fixation was better. I therefore did not
think it was logical to use cemented fixation in hip resurfacing, an operation
developed specifically with the more active younger patient in mind. The only
companies pursuing hip resurfacing at the time were two small English companies:
Corin and Midland Medical Technology (maker of the Birmingham implant). I
suspect that they did not have the financial resources to develop a more
complicated uncemented femoral component. I began working with Corin 12 years
ago, but they were unable to manufacture a porous coated femoral component at
that time. I therefore worked with Biomet on an uncemented femoral component and
the precision instrumentation required for this implant for five years. I first
began implanting it in March 2007. The Biomet component has a full
coating of Titanium plasma spray under the entire under-surface of the femoral
component. Recently they have added an additional layer of hydroxylappatite (HA)
to increase the speed and extent of bone ingrowth. This is the best implant
available to maximize the chance of bone ingrowth.
When I started
working with Biomet to develop an uncemented femoral component, Corin also
started to work on one. They were able to bring it to market in Europe first;
however, their component is only partially porous-coated (less than 50%) with
Titanium (but it does have complete hydroxyl appetite coating). I personally do
not believe this is good enough for long-term fixation (>10years), but nobody
knows for sure yet. It is not yet available in the US.
There have been
limited trials of uncemented femoral components in resurfacing in the past. Most
of these did not have adequate porous surfaces for ingrowth fixation. This was
true, for example, for the early uncemented femoral McMinn device which was
cement is the weak link when long-term (> 10 years) fixation of the femoral
component is contemplated. I have found this to be true when evaluating my 5-8
year results with the Corin system. In 2001 I started the US FDA study that led
to the approval of the Corin resurfacing device in this country. My success rate
at the 8-year mark is 94% in 373 cases. Half of all failures, at 3%, are due to
loosening of the cemented femoral component. In my experience, this has been the
primary cause of failure overall, and the most common source of late failure.
Recently, there have been some reports of wear-related failures from the Oxford
Group and others; in the Corin study, I had only 0.5% failures due to this
problem (for a detailed discussion of this topic, please see my article on"wear")
1: COMPARISON STUDY
Group Cemented Group
cases: 191 96
Follow-up: 2 years 2 years
Score: 94± 10 96±6
Score: 8 ±2 7 ±2
Failures: 2% 2%
FIRST 1000 BIOMET UNCEMENTED HIP RESURFACINGS:
Follow-up: Average: 18 months // Minimum 2 years: 46%
Survivorship: 98.5% at 3 years
score: 95 + 8 after 2 years
resulting in revision surgery:
Femoral neck fractures: 6 (0.6%)
Femoral head osteonecrosis: 2 (0.2%)
3.Acetabular failure of ingrowth: 3 (0.3%)
infections: 3 (0.3%)
DVT (blood clots in the leg): 2 (0.2%)
(blood clots in the lung): 2 (0.2%)
Dislocations (isolated 1 time): 2 (0.2%)
none of the following complications in the first 1000 cases:
Loose femoral components after 1 year (either by XR or otherwise)
Adverse wear problems (“pseudotumors”)
Implant revision due to infection
Implant revision due to recurrent dislocation.
Other significant medical complications
SURVIVORSHIP CURVES OF DR. GROSS’ HIP RESURFACING GROUPS:
1: Corin cemented femur: 2001- 2005 #373
2: Biomet cemented femur: 2005- 2008 #740
3: Biomet uncemented femur: 2007- present #1300 cases
Results can be
improved by preselecting for certain subsets of patients who are known to be
better candidates. The results above, however, were achieved in a relatively
unselected group of patients. My criteria for hip resurfacing are relatively
broad; men and women up to age 65 with any type of hip arthritis who have
not lost more than 1/3 of their femoral head due to the arthritic process.
In all patients
signed up for uncemented hip resurfacing, a tight initial press-fit was
achieved. In no cases did we abandon uncemented fixation and have to rely on
cement. In no cases did we decide to convert to a stemmed total hip at the time
These are my
updated most recent results with hip resurfacing. The success rate is much
higher than most series of hip resurfacing or stemmed total hip replacement. As
with any implant system, increasing failures will occur as we follow patients
longer. Late failures that we may expect are loosening of components or adverse
wear problems. Late failures due to loosening of uncemented implants has been
rare in past studies of uncemented stemmed total hips, therefore we are hopeful
that the early results with this uncemented hip resurfacing will remain durable.
Magnum and Recap components are FDA approved. Their use together as a total hip
resurfacing combination is not FDA approved. This combination is approved for
use in most other countries in the world. When a US surgeon decides to use them
together this is defined as an off-label use. The FDA role is to regulate how
implant companies market their devices in the US market; they are not empowered
to regulate surgeon practice. Therefore Biomet may not promote off-label use,
but surgeons are free to use their best judgment in treating patients.
advisors like to say, past results do not guarantee future success. I have
reviewed the most common complications that have or can be expected to occur. Of
course, biological systems, such as the human body are extremely complex and
sometimes react unexpectedly despite our best efforts and intentions. Therefore
the problems listed above cannot be assumed to be the only complications that
might occur. I am happy to answer any individual questions that you have about
your special case. Most importantly, retaining the most skilled and experienced
surgeon that you can find will maximize your chance of an excellent result. All
other factors are secondary. I encourage you to compare results.