Biomedical Engineering Reference
In-Depth Information
which case they are Class III) and references an FDA
“Special Controls” guidance document for more
information about the typical testing that is expected.
IBFDs, or cages, are actually an example of
a device type that has been reclassified since the
original 1976 regulations were written. In cases
where clinical experience or history has revealed
additional risks associated with a device, or
conversely, established an increased level of comfort
with its ability to be used safely, there is a mechanism
by which devices can be moved to a new class. The
FDA, a manufacturer, or a third party can initiate this
process via a reclassification petition (described in 21
CFR Part 860, Subpart C). The evidence for and
against reclassification is usually brought before
a panel of experts who give the FDA their recom-
mendation. If the panel recommends reclassification,
the FDA publishes a proposed rule to reclassify in the
Federal Register (the daily publication of the federal
government that contains most public notices from
government agencies), which includes the scientific
justification for reclassification and which allows the
public to comment on the proposal. Assuming that
the decision is agreed upon, a final rule is published
in the Federal Register, which officially changes the
class of the device. In July 2007, spinal cages were
reclassified from Class III to Class II in response to
a proposal from the FDA based on the belief that
a sufficiently large body of clinical and preclinical
data had been collected on existing cages to suggest
that when used properly, the devices demonstrated
reasonable safety and effectiveness. The FDA
believed that all of the known risks associated with
cages could be addressed via “special controls,” or
a list of requirements in a guidance document.
When determining device classification, a manu-
facturer must consider what the device is indicated to
treat (i.e., what disease or condition, and what type of
patient) and how it will be used (i.e., how does it
achieve its desired function).
Table 17.1
gives some
examples of various medical devices in each of the
three classes, including those that have been
exempted from premarket review. Class I devices are
typically low risk, short term, and/or used to treat
illnesses that are not life threatening. The majority of
Class I devices (93%) are exempt from FDA review
and thus have a relatively simple path to market.
Class II devices have moderate risk, and Class III
devices are the highest risk and/or are used for life-
threatening diseases. Long-term implants are typi-
cally Class II or Class III. Roughly 46% of device
types are Class I, 47% are Class II, and 7% are Class
III. The Code of Federal Regulations, mentioned
above, is also available online as a searchable data-
base that manufacturers can use to determine the
correct class for their device.
17.6 Regulatory Approval Process
and Types of Applications
Depending on the classification of the device,
manufacturers are required to submit different types
of information to the FDA for review before they can
sell (or
market
) a new device in the United States.
As mentioned previously, many Class I devices and
some Class II devices are exempt from the
premarket review process and must only submit
basic information about the device and its type
(known as
device listing
) and the location(s) that
Table 17.1
Examples of Medical Devices in Each Class, Including Those Exempt from Premarket Review
Class I
Class II
Class III
Exempt
Surgical instruments
(general)
Stethoscopes
Gauze
Adjustable hospital
beds
Mercury
thermometers
Electric heating pads
n/a
Nonexempt
Surgical gloves
Dental mercury
Nonpowered
wheelchairs
X-ray machines
Blood pressure cuffs
Heart valves
Pacemakers
Spinal disc replacements
