Posted: 25 July
2013
By Alexander Gaffney, RF News Editor FiDA Highlight
One of the largest medical
device scandals in the last decade has involved
metal-on-metal hip implants,
so-named because of the metal (usually chromium)
attachment that attaches a
leg to a metal socket.
In the wake of their failures, the
US Food and Drug Administration (FDA) moved to examine its regulatory
processes, eventually deciding
to require premarket approval (PMA) applications for all such implants.
But now evidence has emerged that the agency still has further questions about
what more it could have done to prevent the devices from ever having reached
the market.
Background
Medical devices are a relatively
recent addition to FDA's regulatory authority, with FDA only receiving the
authority to vigorously regulate them in 1976 under the Medical Device
Amendments. Because some medical devices were already marketed at that
time, FDA classified them all as class III, high-risk medical devices until it
could review and classify them properly.
Some of those devices went on to
serve as predicates for 510(k) premarket notification applications, which
claimed that they were substantially equivalent to already-approved devices and
were thus able to avoid conducting clinical trials to re-prove their safety and
efficacy.
The problem with that, some researchers
claim, is that many
of the original devices which metal-on-metal hips claimed to be ancestors of
have since been recalled from the market under dubious circumstances, meaning
the devices might never have been safe to begin with. Further, the
metal-on-metal hips were not so similar to the original device as to be clearly
substantially equivalent. Devices of this sort are routinely approved and are
referred to as "split predicates."
In light of those concerns—and a lack of action on the part of
Congress during the 2012 passage of the Food and Drug Administration
Safety and Innovation Act to explicitly close the so-called loophole—FDA
announced on 17 January 2013 that it would move to require all metal-on-metal
implant devices to be submitted in the form of a PMA or PDP, which typically
require clinical trials in support of the application and thus an
investigational device exemption (IDE) application as well.
A New Study
But even with these new
requirements, FDA said it is still concerned about hip implants in general, and
most especially with respect to how they are worn down. In the case of metal-on-metal
hips, the chromium coatings of the device wore each other down, in some cases
dislodging metal chromium shavings that caused tissue damage and raised fears
about metal ions entering the bloodstream and causing cancer.
In a solicitation notice posted on
the Federal Business Opportunities (FBO) website, FDA noted that "there is
renewed concern of wear and corrosion of conical head/stem taper junctions in
modern modular total hip replacements." While not a "new
phenomenon," FDA said new design changes like metal-on-metal bearings,
larger femoral heads and modular designs have reintroduced the issue even as
the new features more closely approximate patient features.
As a result, FDA said it's embarking
on a new project to "investigate the potential link between volumetric
wear and corrosion of conical head/stem taper junctions in explanted total hip
replacements and clinical outcomes."
As with nearly all solicitation
notices, it's looking to
the private sector to help it design and run the study, the results of
which will be used to "aid development of standard test methodologies for
preclinical evaluation of total hip implants."
The study will reportedly look at 250 explanted metal-on-metal hip
replacements of various sizes and genders and use the American Society
for Testing and Materials (ASTM) protocol for corrosion testing to analyze
them. "De-identified patient data and radiographs must be available or
obtainable for all devices," the notice explains.
The end goal of the project, which
should take about two years total to conduct, is to generate a peer-reviewed journal article
explaining correlations between wear and corrosion and relevant parameters
(e.g. implantation time, lateral offset, head size, materials, and modularity).
Solicitations are due to FDA by 1 August
2013.
REGULATORY FOCUS Departments: Under RAPS
Quality &
Compliance Science &
Technology Perspective
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