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Why Indian Surgeons Have Better Results with Hip
Resurfacing AVN Patients The longest followup has been
7&1/2 yrs and a lot of patients have crossed 5 yrs.
I am not the only one who is having a good result with AVN.
Prof Yoo from korea has not had a single failure yet for AVN resurfacing. The
same goes for Dr. Sugano from Osaka, japan.
The 3 of us together have done more than 1,000 resurfacings for AVN.
AVN is much more common in Asia when compared to the rest of the world.
Derek McMinn has a 10% failure rate for AVN when compared to 1% for
osteoarthritis.
The Australian joint replacement registry also shows a slightly higher failure
rate for AVN than for OA among the Australian surgeons.
In my opinion, I attribute the following reasons for the disparity in outcomes
in Asia when compared to the rest of the world.
With best regards
Vijay bose
chennai
July 20, 2005
Resurfacing in AVN - explanation Dr. V.C. Bose
I have
given the explanation of how a resurfacing works in AVN. I must apologise that
it is long - winded and a little technical . However with the best of my efforts
I could not make it any easier as it a complex concept to explain.
I have now done about 185 resurfacings for AVN cases over a 5 year period with
many patients crossing the 4 yrs mark. It is interesting to note there has not
been a collapse or fracture neck of femur even in a single patient.
It is wrong to think that the AVN continues forever in the femoral head. AVN is
a one time event in which a strikingly similar sector of necrosis occurs in most
femoral heads ( anteo supero lateral
part) due to blockage of presumably the same vessel in all patients. This sets
off a series of changes which are is marked by sectoral collapse. This is
primary collapse of AVN and most patients are likely to develop it. Any kind of
core decompression / bone grafting is a surgical attempt at preventing
/postponing this event. These joint salvage procedures ( according to
literature) achieves their goal in about 30 - 50% of cases.
The rest of the collapse - which at times is confused with primary AVN collapse
- even by medical personnel is actually secondary mechanical collapse and this
occurs because of 3 factors: 1.hip stiffness, (more the stiffness the more the likelihood of secondary
collapse)
2.wrong biomechanics leading to point loading. 3.soft bone ( non wt bearing and NSAID abuse).
However once resurfacing is done secondary collapse will not continue as the
normal biomechanics and range of movement is re established. The portion that
is already collapsed ( primary or
secondary) has to be taken out and substitued with cement or bone graft at the
time of surgery. This is a simplisitic explanation for peaple not familiar with
the concept. However this does not represent the complete story. Please read on if you are a medical personnel.
The 3rd type of collapse that can occur is specific to resurfacing and is called
as 'Global AVN' tertiary collapse ,or delayed primary failure of resurfacing. In
this the resurfaced head slowely tilts and falls off over a period of months.
This is the number one concern today in the field of hip resurfacing. There are
many theories as to why this occurs but the most plausible one is that it is
procedure induced and it involves disturbing the soft tissues of the neck and
the head-neck junction of the femur ( not the head of
femur) at the time of surgery.
One must keep in mind that AVN occurs in individuals following pretty trivial
reasons like a fall, a single dose of steroid or surgery in the vicinity of the
hip joint like intramedullary nailing of the femur. To assume that the varied
approaches described for resurfacing ( anterior , lateral , posterior &
trochanteric
osteotomy) will not cause AVN in the femoral head is naive. It is now
increasingly becoming obvious that Apical , sectoral primary AVN is caused
during the surgical approach in a very significant proportion of patients of any
surgeon's series of hip resurfacings.
However, this is not of any consequence and does not compromise the result.
In summary- the primary, sectoral classical AVN occurs in a majority of
resurfacings during the surgical exposure even in cases which did not have AVN
to begin with.
However with the usage of low viscosity cement one performs a 'capituloplasty'
on the head, similar to the vertebroplasty done in the spinal vertabrae with the
injection of cement.
This transforms the material under the resurfacing head into a composite of live
bone, dead bone and cement.
If this composite is seated on a vascular and biologically favourable neck and
head neck junction , then this composite performs well. (The biological status
of the neck and head neck junciton is similar to health of a fracture fragment
in fracture plating surgery.ie Soft tissue cover of a bone fragment is essential
for the end arteries to supply no matter from where the blood is coming from)
However for some resion the neck capsule and soft tissues get damaged then one
gets 'global AVN' and the component drifts and fails. - termed as delayed
primary failure . This is independent of the fact as to whether primary ,
sectoral AVN in the head was present before surgery or occured during the time
of the surgery.
Therefore , resurfacings in AVN are no different from resurfacings done for
other indications. However if secondary collapse has been left for too long it
destroys the femoral head bone stock completely precluding hip resurfacing. If
there is sufficient bone stock at the time of surgery a AVN resurfacing is
likely to perform as well as any other resurfacing.
The 185 AVN resurfacing represents roughly half of my series of about 400 cases.
Vijay Bose
consultant orthopaedic surgeon
chennai
July 21, 2005
Resurfacing in AVN by
DR AMEET PISPATI
As a Specialist in Hip Resurfacing myself, I thought I should highlight a few
facts:
Fact 1 - Ortho surgeons all over the world are still not completely sure about
AVN and how it progresses. We all fight with each other on this issue in our
resurfacing symposia and meetings. So the jury is still out, to be honest.
Fact 2 - AVN is not always a one time event - we have seen many cases of AVN
with serial MRI scans actually showing progress of AVN over a period of time. So
if resurfacing were done for such patients, the AVN could continue to progress,
causing persistent pain and eventual failure
Fact 3 - once the AVN has led to
arthritis, then the AVN itself does not progress. Further progress of damage
seen on x rays is purely mechanical. Such patients can safely have a
resurfacing.
In conclusion - AVN with advanced arthritis can be treated exceptionally well
with resurfacing. AVN itself (in the stage where arthritis has not
occured)should not be treated with resurfacing.
DR. AMEET PISPATI
Specialist in Hip Resurfacing and Joint Replacement, Mumbai, India
www.hipresurfacing.info
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