Hi Pat,
Thanks very much for the mail. I wanted to write to you for a long time
regarding the updating of the ASR component write up. It is a good thing that
you wrote to me.
I was not keen to do the ASR when it was introduced. After a couple of years
when surgeon friends told me that it was good and I saw the results, I tried it
out in a phased manner.
Currently I use the BHR and ASR to almost about 50% each.
I make the decision based on technical preference in the particular patient. I
think the BHR and ASR are best suited for opposite ends of the spectrum of
patient and bone size.
One important advantage of the ASR is the small stem (peg) it has for the
smaller sizes. This is the huge advantage in small built individuals as the
proportion of the stem (peg) to the residual bone is less. In contrast the BHR
has a same size peg through all sizes. A large peg in a small head size has the
potential problem of causing stress shielding . I almost never use the very
small size BHR like the 38 anymore.
In very big built patients who are bound to return to sports etc very soon the
BHR is the preferred option as the cup has a more high profile surface for bone
contact with a plastic disc for heavy impaction. The ASR is more fine and seats
without much impaction. This may be an advantage in relatively soft bone.
The other important way to harvest the advantage of prosthesis design is the
selecting the prosthesis based on the amount of head bone involved. The ASR
certainly removes less bone in the head than the BHR. This could be used to the
advantage of the patient in a condition like ankylosing spondylitis where the
problem is only in the articular cartilage with the bone being intact. Here the
ASR scores over the BHR.
However in a pathology like AVN there is significant head involvement, the BHR
has a distinct superiority as one would like to remove the diseased bone and
replace it with the metal.
Osteoarthritis lies somewhere inbetween where some patients have significant
head involvement where the BHR would be superior and in some others the head
bone may be largely intact and the ASR would be a better option.
Thus I choose the prosthesis based on technical issues and employ it to the
patient’s advantage. Thus in my practice both the ASR and BHR complement each
other. After doing more than 200 ASR over the last 2-3 yrs , I am as impressed
with the ASR as with the BHR.
I was one of the first to try out computer aided surgery for resurfacing. This
has no advantage except in patient who have had previous surgery like a
osteotomy . It has a very important disadvantage of removing all the capsule and
soft tissues on the neck of the femur ( to take a computer reading known as bone
morphing). This will compromise blood supply. I have to say that currently for
resurfacing computer aided navigation is only a marketing tool for surgeons/
companies. Computer aided navigation is very beneficial in knee replacements
where one has to align the knee components to the hip and ankle and I use it
routinely for knee replacements.
Wishing you the very best
With best regards
Vijay bose
chennai
Asian Regional
Center for Hip Resurfacing (ARCH)
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