Dear Vicky
It was a pleasure to talk to you in Miami just over a week ago and I hope you
enjoyed your time there.
Here is my view on the questions you pose:
Surgical Approach
I started back in 1991 with the antero-lateral approach to the hip for
resurfacing. At that time we were worried about blood supply to the femoral head
and on theoretical grounds the antero-lateral approach preserved the blood
supply well. For many patients the approach was satisfactory but there were some
problems. The exposure obtained in large patients was not good. This meant that
heavy retraction had to be used, and heavy retraction caused trauma to muscle
and other soft tissues which in turn led to heterotopic ossification. The other
problem was that some patients had a permanent limp after my surgery as a result
of the surgical approach. Please understand that the instruments were crude back
then compared to today where newer designs of instruments would cause less
tissue trauma and make the antero-lateral approach a better option. The sight of
limping patients persuaded me to change my approach to the posterior approach.
The theoretical objection to this approach was that it may cause more damage to
the femoral head blood supply. It turns out that the problems with femoral head
blood supply using the posterior approach are very rare, as you heard at the
conference. The big advantage is that an excellent exposure can be obtained,
giving the surgeon the best opportunity for perfect component positioning. As
you heard, inaccuracy with respect to acetabular component positioning is badly
tolerated and a high acetabular component inclination angle is the single
biggest reason for early bearing failure following a metal on metal resurfacing.
The other great advantage is that very little trauma to the soft tissues need
occur with a posterior approach resurfacing. The other thing is that a
mini-incision posterior approach can be done by those surgeons experienced in
the resurfacing operation with good exposure and minimal tissue trauma. My unit
published our mini-incision resurfacing results a few years ago, the average
incision length was under 12 cm and measured component position was good.
There are two other surgical approaches to be considered by surgeons, but for
different reasons these are not reasonable at this time.
The other issue is how well an inexperienced surgeon can be taught to reliably
perform an uncomplicated resurfacing operation. It's no use talking about Ronan
Treacy's or my own abilities in this regard as we have each performed well over
3,000 resurfacing procedures, and no matter how hard we work, we cannot make any
impact on the world demand for this procedure. New surgeons therefore must be
trained. As you heard, we tested how good newcomers to the BHR using the
posterior approach really were and over 100 new surgeons, as well as Ronan and
myself, entered our patients on the Oswestry Outcome Centre database. All those
patients have been independently followed up. At 9 years post-op Ronan's and my
results are still statistically significantly better, both with regard to
failure requiring revision and also with regard to hip function. Never mind
statistics, the fact is that the newcomer surgeons achieved very creditable
outcomes, which means that the whole package with respect to training, patient
selection, surgical technique and implant durability really does work. If
anything in that mixture changes then the outcomes achieved may significantly
change. To give you one example, during 1996, one year before I started the BHR,
I carried out the Corin, double heat treated resurfacing which I designed. All
the other ingredients of the package were the same.
Now that time has passed we can see the effect of one factor, implant design, on
the outcomes. At 5 years there is no difference between the Corin and the BHR
design on my outcomes. At 10 years, however, the Corin series has an 86 %
implant survival whereas the BHR series has a 96 % implant survival. In
addition, in the patients who have had the Corin resurfacing and have not been
revised at 10 years, 20 % have osteolysis or early loosening. These features
bode badly for the future. Heat treatment of the metal of the implant is not
something that the surgeon can see, and I wasn't aware that the manufacturer had
started to use this even though I was the implant designer! The implant looks
the same as the historically proven, as-cast alloy and the early results give no
cause for concern. The longer term sadly is a different matter. I understand
your interest in the surgical approach, but it's the complete package that
counts. For a patient, therefore, the key questions for their surgeon are: How
long have you done metal on metal resurfacing? Am I a good candidate for hip
resurfacing? Is my bone good enough? Do I have avascular necrosis which may
increase the failure rate with hip resurfacing? Do I have dysplasia or any other
condition which may seriously complicate the procedure and are you confident you
can handle any difficulties? What surgical approach do you use and why? How were
you trained and what was the resurfacing experience of your trainer? What are
your results--- how many have you done and how many failures have you had? What
are the hip scores in your resurfacing patients? What complications have you had
with hip resurfacing? What type of hip resurfacing do you propose using on me?
What are the results of that design used in a) the inventor’s hands and b) what
are the results of that design of implant in the hands of independent surgeons
e.g. what are that implants results on the Australian national register? If your
surgeon is using a device with either no independent results or poor results on
the Australian register the question to be answered is: Why are you using it
e.g. are you paid to use it or is your hospital paid to use it by the
manufacturer of the device?
Bone Recovery and Return To Sport
The evidence from a DEXA study on BHR patients published from Japan is that the
bone density in the proximal femur returns to normal 1 year after operation. The
at-risk period for femoral neck fracture following the BHR is in the 6 months
after surgery. I advise patients not to return to impact sport for 1 year after
surgery. For those patients who want to road run, I get them running on a
treadmill at 10 months post-op and they resume road running at 12 months
post-op. My unit published on activity level after resurfacing some years ago in
a group of patients who followed those rules. In young men with a single
osteoarthritic hip resurfaced, 92 % played sport and 62 % played impact sport.
The ladies were not quite as active, but you can see from the publication that
they still had an impressive activity level. In the total group their 10 year
implant survival is 99.8 % showing that high activity introduced at a sensible
time does not deteriorate the results.
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
