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Total
hip arthroplasty is one of the most rewarding surgical procedures
offered to patients at the present time. Over 300,000 total hip
arthroplasties are performed in the U.S. annually. There has been an
active campaign by various physicians and orthopaedic companies
bombarding the media with various opinions regarding total hip
components and even worse, suggesting what surgical procedures are
appropriate to patients.
While it is
now definite that total hip arthroplasty can be performed through
smaller incisions, thus creating less pain and decreasing recovery
time, what has become more confusing is "which of the various prostheses are indicated for an individual patient".
In
order to understand the situation, think of the total hip as a modular
system. The modular system consists of a shell, which is inserted into
the pelvis, a stem that is inserted into the upper femur, an insert
that goes into the shell, and a head that goes onto the stem. Now,
believe it or not, when it comes to the shell and the femoral component
(stem), there is little disagreement over the fact that these
components can be placed with or without cement and work well. The
issue becomes what to do with the bearing surface. The bearing surface
simply is the ball and the insert that move on each other. This does
not include the stem and the shell. When it comes to the bearing
surface, we know that with time, any bearing surface will wear out. The
question therefore, becomes which bearing surface is appropriate to
which individual so that the individual has a chance for one operation
to last a lifetime. So let's start with the basics.
A
conventional polyethylene on metal total hip arthroplasty from the
1970's would have an average longevity of 12-15 years. If we introduce
the new polyethylene coupled with a metal femoral head, there is a 90%
decrease in the wear of the polyethylene, thus, theoretically, the
longevity should be increased by as much as 90%. Therefore, we now have
a prosthesis with a bearing surface that should last somewhere in the
neighbourhood of 20 years or more. Now, if we use a ceramic femoral
head coupled with the new generation polyehtylene, the wear is even
better and although there are no solid statistics available, it stands
to reason that this bearing surface should last in excess of 20 years
and probably 25 years. When we deal with a patient whose demand is
higher than this, we have ceramic-on-ceramic bearing surface which
wears 200 times less than a conventional total hip, which means it
should last 200 times longer than 15 years. Do the math. In other
words, it should last anybody's lifetime.!
The
last bearing surface combination is metal-on-metal. Metal-on-metal as a
bearing surface wears almost as well as ceramic-on-ceramic and
therefore, as a bearing surface should last almost indefinitely as with
ceramics. The problem with metal-on-metal is there is one unanswered
question: Does the metal ion released with such a large surface area of
metal-on-metal cause systemic problems down the road? This is an
unanswered question of much concern.
The
bottom line is this: The prosthesis that is recommended to an
individual must be recommended on the basis of the patient's life
expectance, activity level, and bone quality. When choosing the
appropriate prosthesis, not only do we have to consider the patient,
but we have to consider the cost to society. Like it or not, the choice
of the prosthesis is now gradually becoming dictated by insurance
carriers and hospitals. Throughout the country as I present lecture
series on ceramic prostheses, I am constantly informed about the
difficulty other orthopaedic surgeons are having trying to choose which
prosthesis is indicated based on what hospital and insurance carriers
offer them.
The universal concern is
that the more expensive prostheses will not be available to the patient
regardless of their total life expectancy and activity level. To give
you an example, a standard cemented generic total hip would run
approximately $2000.00, while a ceramic-on-ceramic, non-cemented hip
would run approximately $6800.00. Remember the hospitals are reimbursed
approximately $11,000.00 for total hip arthroplasty which includes all
costs (obviously including the prosthesis), therefore there is a
disincentive to use more expensive prostheses.
Fortunately,
the Boca Raton Community Hospital, Delray Medical Center, and Bethesda
Memorial Hospital still value patient care and allow the orthopaedic
surgeons to choose the appropriate components for a given individual
patient. The luxury may not last forever and is based on mutual trust
between the hospital and physician making sure that the components are
chosen in an intelligent and scientific manner.
As
a final thought, I believe that the patient should remember that simply
because a prosthesis may last many years beyond their expected life
expectancy, that this may not be cost effective, and simply may not be
indicated for them. With technology as it is today, choosing the
appropriate components is not difficult and should simply be a matter
of common sense.
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