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Dr. Gross video interview by Vicky
Marlow Freelance Patient Advocate Volunteer 2008
Vicky Marlowe’s Questions:
These are my belated responses to
your questions. You may post these on surface hippy. Please let me know if you
need any clarification
Thomas P. Gross M.D. 1/17/2007
Why do you choose to use the posterior approach over other
approaches?
I estimate that most total hip
resurfacing done worldwide is done through a posterior approach ( > 90 %). There
was an interesting report recently at the Annapolis MD HSR Meeting from Mr.
Ronan Treacy indicating no difference in results between posterior and
anterior-lateral approaches in a direct comparison looking at the rates of limp
and other complications. Therefore, I do not think anyone has shown that it
really matters which approach is used.
My current personal preference is
posterior minimally invasive (see my video) vascular sparing (as described
by Dr. Koen DeSmet). I believe, that with this approach, I can accomplish the
operation in virtually all case that are candidates ( only 2 of 1300 converted
to THR intraoperatively), return patients back to activity as rapidly as
possible, avoid a permanent limp, and place components in ideal position. This
is personal preference, not science. Every surgeon should use the approach that
he/she is most comfortable with.
How long do you feel it takes for the bone to be fully healed, grow into the
prosthesis?
It is a gradual process that proceeds
over 6-12 months. Dog studies have shown that the process has already begun by 6
weeks postop. At 6 months, I estimate that 90% of bone ingrowth has occurred.
After 12 months bone remodeling around an implant porous surface should be back
to the normal baseline with the implant well incorporated. Some impact early on
will likely stimulate bone ingrowth, while too much may cause implant – bone
micromotion and result in failure of ingrowth. How much then is too much?
What is the recommended time you
tell your patients before they can start to run again/do impact sports?
Six
months. This is not only because of bone ingrowth issues, but also because of
the femoral neck fracture risk which is present for 6 months after surgery in my
experience.
Although it is clear that M/M HSR is much more durable than most THRs, exactly
how much impact activities can be safely tolerated over the long term is
unclear. Therefore, patients should exercise caution.
What is your take on cementless
devices?
Derek McMinn’s comments on cementless HSR:
“Cementless
Components
At the beginning of my experience, all my resurfacings were cementless. The
results were not good for
cementless
femoral components, but cementless acetabular cups were excellent. Of course I
have occasional patients with a great result following a cementless femoral
component 16+ years post-op. For the total group of patients, however,
cementless femoral components were not successful.
In 1994 I started with hybrid fixation using a cemented femoral component and a
cementless cup. In my BHR series, i.e. commencing 1997, I continued with hybrid
fixation and I have had no loose cups and no loose femoral components. It would
be hard to do better than have a zero loosening rate in this large series of
BHRs in patients with varying bone quality. Thankfully patients who need
resurfacing today need not be the Guinea pigs for a new experiment. Hard
information does exist on this subject and should be used by surgeons and
patients alike. Those are the short answers to your questions, the long answers
are in a multi author book called Modern Hip Resurfacing which I have edited and
which will be published by Springer early next year. When it is published, I
will send you a signed copy.
Best Regards
Derek
Dr. Thomas Gross’s response:
Uncemented femoral resurfacing
components are a new development. The acetabular components used routinely are
uncemented, while the femoral components routinely have been cemented to bone.
Recently, I have developed a fully
porous coated femoral component with Biomet Inc. (Uncemented ReCap). This
component is FDA approved in the US for femoral resurfacing. I have been using
this together with the uncemented Magnum acetabular component for uncemented
total Hip Surface Replacement since April 2007. No other surgeons are yet using
this device. Corin also has a device available outside the US for uncemented
femoral resurfacing; it is partially porous coated plus HA coated (Corin Cormet
2000 uncemented femoral component [version 2]). Several early reports on the
Corin device out of England are promising.
Mr. Richard Villar has compared the
uncemented Corin Cormet 2000 version I (No porous, only HA coating) to a
cemented femoral component. This study showed less bone remodeling (neck
narrowing) with the uncemented component. The significance of this is completely
UNKNOWN. We will watch these developments with interest.
I also have a favorable experience
(fewer patients but 8year f/u) with this original Corin version I device which I
presented at the first Comprehensive US hip Resurfacing Course in Annapolis MD
in November 2007. I am currently working on a manuscript for publication.
Mr. Derek McMinn has recently added some insight into his past experience with
uncemented femoral components based on the Corin McMinn component, which was
made of cobalt chrome with no bone ingrowth or ongrowth surface whatsoever. Mr.
McMinn tried this about 15 years ago and it predictably failed with this
surface. At that point (early 1990’s) we already knew (from joint implant work
done in the 1950’s) that an uncemented uncoated press-fit implant of any sort
would not work reliably more than 1 – 2 years in most patients.
At this point uncemented fixation of the femoral component in total hip
resurfacing is an interesting concept. My hypothesis is that an implant that has
fixation to bone by an appropriate bone ingrowth surface may result in less
early complications because the thermal necrosis of bone with curing of cement
is avoided. Also it may be longer lasting, if cement is subject to late fatigue
failure in HSR as it is in most other joint replacement applications. But,
again, I stress that this is a hypothesis which can only be validated or refuted
by clinical data (That means 2+ year results in large numbers of patients).On
the negative side, we need to discover how reliable the bone ingrowth process is
(with these new implants and instruments) in the femoral head.
Mr. McMinn’s statement that he has already tried uncemented femoral fixation and
that this did not work is not completely accurate. There is no doubt that he
showed that “a femoral component placed without cement and without a bone
ingrowth (or ongrowth) surface will not give reliable results.” He has not
published any results on a femoral component with a bone ingrowth coating, and
to my knowledge, his company (MMT, which makes the Birmingham hip) has not
marketed any such device.
The reference article is:
Derek McMinn; Ronan Treacy; Kyaw Lin; Paul Pynsnnt, Metal on Metal Surface
Replacement of the Hip. Experience of the McMinn Prosthesis CLINICAL
ORTHOPAEDICS AND RELATED RESEARCH, Number 329S, 1996,pp S89-S98
There is very little published data on the use of an uncemented femoral
component. I will need to gather data for at least three to four years before I
will be able to provide any useful data on this subject. Fixation of total
joint implants to bone can be accomplished by cement or by porous ingrowth
technology. Cement fixation is immediate, while permanent fixation with
uncemented components requires six to twelve months of bone ingrowth before it
is considered well fixed. Some total joint replacement components have had more
success with cement fixation, while others have done better with uncemented
technology.
In hip surface replacement at eight years, approximately 95% of implants are
still working in young patients with cemented femoral fixation. Only rarely can
these 5% failures be blamed directly on the cement fixation itself.
Dr
Rogerson, Madison Wisconsin comments
on
cementless devices:
" I
think the presentation and the xrays shown by Dr. Papavasileou were very
telling. Many of the xrays showed significant neck narrowing not seen on the
cemented BHR xrays. I think this is because the ingrowth on the cementless heads
is "spotty" and leads to variable stress shielding of the distal inferior neck
and calcar bone. Some of the xrays were very ominous appearing and will likely
result in delayed neck fracture. Therefore, I will stay with the thin cement
mantle produced by the BHR technique to spread out the forces coming down the
femoral neck and avoid the stress shielding."
Dr
Rogerson, Madison, WI
Dr. Thomas Gross response:
Dr. Rogerson is
mistaken. I suggest that he reads Mr. Richard Villar’s work. The reference is:
FEMORAL NECK RESORPTION
AFTER HIP RESURFACING ARTHROPLASTY – A COMPARISON OF CEMENTED AND UNCEMENTED
PROSTHESES. P Katrana; JR Crawford; S Vowler; A Lilikakis; and RN Villar. Journal of Bone and Joint Surgery - British
Volume, Vol 88-B, Issue SUPP_II, 234.
Copyright © 2006 by British Editorial Society of Bone and Joint Surgery
Mr. Richard Villar has compared the
uncemented Corin Cormet 2000 version I (no porous, only HA coating) to a
cemented femoral component. This study showed less bone remodeling (less
neck narrowing) with the uncemented component. The significance of this is
completely unknown. We will watch these developments with interest. Overall the
short term results are equivalent between these two types of femoral implants.
Recently,
comments have been made re: FDA status of implants. Can you clarify this issue?
Statements have been made that the only FDA approved hip resurfacing device is
the BHR with S&N. Furthermore, if patients get any other one the insurance
companies at any time can make them pay them back for non-FDA approved devices.
Both of these
statements are false.
The Birmingham
(Smith & Nephew, Richards) total HSR was the first to get FDA approval in the
US based on an unprecedented FDA decision to approve this implant on the basis
of single (developing) surgeon’s foreign data. Cormet 2000 ( Corin Ltd.,
Stryker) total HSR was the first to be approved based on the usual mechanism of
a US run Multi-center FDA study( approval 7/2007, I was the lead investigator).
Therefore, there are now 2 implants available in the US that have an FDA
indication for total HSR.
The Recap/Magnum
(Biomet), Conserve Plus (Wright Medical) and APR (Depuy) are all also FDA
approved implants in the USA. They may be legally used by any surgeon for the
purpose of total Hip Surface Replacement. (The FDA does not regulate how
surgeons may use approved implants.) However, the implant companies may not
promote them as total HSR devices. (The FDA does regulate how implant companies
may market approved implants.)
Approximately 20 different
companies sell total HSR implants on the worldwide market, including all of
those mentioned above.
A specific use of an implant
(or drug) that is approved by the FDA is termed an FDA approved indication. As
soon as a company has received one indication for use of their implant (or
drug), the implant (or drug) is FDA approved. The use of this same implant (or
drug) for a purpose other than for the approved indication is termed an off
–label use. Off-label use is legal. In fact, much of American medical practice
involves off-label use of drugs and implants. It would be impossible for the FDA
to regulate doctors’ practice in every situation. Actually the Supreme Court has
expressly stated that this is not the FDA role (see Rehnquist opinion).
Many insurance companies do
have contract clauses that deny payment for “experimental” treatment. How to
define what is experimental is very controversial. However, “experimental” is
something altogether different than off-label use of implants and drugs.
Therefore, an insurance
company would be treading on thin ice if they were to use FDA indications as a
basis to deny payment. |