FDA
and Mobile Bearing Devices
For at least the last quarter century the FDA has pursued
a policy which has prevented the general acceptance of mobile
bearings in condylar joint replacement, such as the knee and
ankle, in the USA. This major breakthrough was first made
in the UK for knee replacement devices and in the USA for
shoulder devices in 1974. Dr’s Buechel and Pappas first
used this concept for ankle replacement in 1976.
The mobile
bearing concept solves a fundamental dilemma facing the designers
of condylar replacement joints. It solves the problem of providing
needed mobility while keeping contact pressures on the plastic
bearing within limits consistent with long life. The need
for a mobile bearing is even greater for the ankle than for
the knee. This is the case since both the ankle and knee see
similar loads but the ankle is very much smaller than the
knee and thus lowering contact pressures is much more difficult.
Yet the
FDA has long resisted the general approval of devices designed
using this important concept even though it has been clear
for some time that overloaded fixed bearing condylar joints
wear excessively. Thus, the only knee replacement sold in
this country using a mobile bearing is the knee designed by
Drs Buechel and Pappas and a derivative.
FDA
and Mobile Bearing Ankle Devices
No mobile bearing ankles are generally available in this country.
Outside the USA mobile bearing ankle devices are used almost
exclusively. They are, to date however, not generally available
here. Thus, if a US citizen wishes to have a proven and universally
accepted device implanted they must normally go abroad for
proper treatment. Thus, the actions of the FDA in this matter
are injurious to our citizens and to the medical community.
In 1982
the FDA published criteria for determining the class of an
ankle device and thus whether its approval for the sale of
such a device can be granted by a 510(k) exemption. Such exemption
can be granted after a review of the design by the FDA. Otherwise,
one must use the means of a PMA which normally involves a
lengthy and almost prohibitively costly clinical trial. Almost
all devices sold in this county are sold under a 510(k) clearance
and are not subject to a formal clinical trial due to such
costs.
The decision
on these criteria was based on relatively short-term clinical
evidence supplied by certain orthopaedic device manufacturers.
This submission was based on the clinical experiences of the
developers of their ankle replacement devices. Unfortunately,
later clinical experience clearly demonstrated that all of
the devices involved were unsafe and all were withdrawn from
the market many years ago.
The FDA
has been unresponsive to the experience on ankle devices of
the last quarter century and still uses these same discredited
criteria today. More than five years ago Endotec filed a formal
petition to the FDA (See:  )
to revise these criteria in light of current information.
The FDA has been sitting on this petition since then. Further,
a recent conversation with an FDA official indicated that
success of such reclassification was unlikely and cited the
difficulties the industry was having in reclassifying mobile
bearing knees.
Endotec
has filed three requests for 510(k) clearance of different
mobile bearing ankle designs in the last 15 years. Two have
been rejected and the latest is pending. In the case of the
two rejected the grounds for rejections were unreasonable
and unscientific. Further, the reviewer of the pending 510(k)
told me that this application cannot succeed because it involves
a mobile bearing device. These actions appear to be based
on an unwritten FDA policy that mobile bearing devices can
only be approved by PMA. The reason for such a position is
unclear since mobile bearing condylar joints are clearly superior,
particularly in the case of the ankle, to the fixed bearing
types for which the FDA has granted 510(k) clearance. This
fact is clearly demonstrated in our ankle reclassification
petition and by the scientific and clinical literature of
the last quarter century (See:  ).
Write
to the FDA, Congress and Senate
We urge potential ankle patients to become involved in this
issue. Unless the FDA can be made to see the error of its
ways, superior ankle replacement devices will not be introduced
in the USA in the foreseeable future.
Please
write the FDA (See:  ),
your Congressman (See:  )
or Senator (See:  )
about this problem. The letters should encourage the FDA to
be guided by science and reason and not by inflexible bureaucracy.
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