Biomedical Engineering Reference
In-Depth Information
manufacture of IBFDs to the point that nearly every
large spinal company has at least one IBFD manu-
factured from PEEK. There are two main perceived
benefits of using a polymer to manufacture IBFDs as
opposed to metals. First, many polymers are radiolu-
cent, whichmeans they are transparent on X-ray; thus,
bony fusions can be better assessed when a polymer
IBFD is used. The drawback of a radiolucent implant
is that the placement of the device is less apparent on
X-ray and thus it is difficult to determine whether the
device has shifted from its intended location. Manu-
facturers often address this issue by placing small
metal (e.g., tantalum) markers at specific locations in
the device that allow the location and orientation of the
device to be determined on radiographs. The second
perceived benefit of using PEEK to manufacture an
IBFD is that the modulus (stiffness) of the material is
closer than titanium's modulus is to that of cortical
bone. The theorized advantage over a metal IBFD is
that the PEEK IBFD will allow better load sharing
between the IBFD and the bone graft, thus allowing
for faster fusions to occur.
column, which is thought to potentially yield a faster,
more effective fusion.
Although the possibility of lower stiffness rods
positively affecting fusion results does exist, the
concern from a safety and efficacy standpoint is that
the lower stiffness could instead result in lower
stability and poorer fusion results. For this reason, the
FDA currently requires clinical data to support the
clearance of all spinal fusion rods that have lower
stiffness than traditional metallic fusion rods,
because the latter have a longer established clinical
history of successful fusions and the former do not.
17.10 The Use of Master Files in
Supplying Material Data for FDA
Regulation
Master Files are a mechanism that allows the
sharing of proprietary information with the FDA that
can be referenced by a third-party applicant. A
normal example of Master File use occurs when
a company submits a premarket application (i.e.,
510(k), PMA, IDE) to the CDRH for a device man-
ufactured from PEEK material that is provided, in
raw form, by another company. In this situation, the
supplier of the
material
may not want the manufac-
turer of the
device
to be privy to all aspects of the raw
material information required for review by the FDA
and may consider some information as trade secret,
such as the material formulation or processing tech-
niques. In order for the FDA to be able to review this
information without also allowing the device manu-
facturer to see the information, the material supplier
can submit a Master File. Master Files are not
approved or disapproved by the FDA as other regu-
latory submissions are, but they act as sources of
information that the FDA can use in its regulatory
decisions regarding an actual IDE, 510(k), or PMA.
The use of Master Files is common by material
suppliers, so that multiple device manufacturers can
reference material-specific information in their
submissions to the FDA. There are not many limi-
tations regarding the type of information a Master
File can contain, as long as the information is
substantive in nature and can be considered trade
secret or confidential.
Table 17.3
lists examples of
what a Master File for a material might contain.
To reiterate, the FDA approves devices (for specific
intended uses with specific technological character-
istics),
not
materials. Use of a material in a particular
17.9.2 Vertebral Body
Replacements
Vertebral body replacement (VBR) devices have
a similar function to IBFDs, except that instead of
simply replacing a single diseased spinal disc, VBRs
replace one or more entire vertebral bodies along with
their adjacent discs. Metals such as titanium alloy are
commonly used to manufacture VBRs. However, just
as with IBFDs, PEEK has become a very popular
alternative. Because fusion is often the goal of a VBR
procedure, the same advantages of using a polymer, or
specifically PEEK, for IBFDs apply to VBRs as well.
17.9.3 Spinal Fusion Rods
Spinal fusion rods are anchored to the posterior
spine with screws, hooks, or other connectors to
stabilize the spine to promote a fusion and/or correct
deformities. Traditionally, spinal fusion rods have
been manufactured from metals such as titanium
alloy, stainless steel, or cobalt chromium. However,
just as with the devices discussed above, some spinal
device manufacturers theorize that the lower stiffness
of the PEEK material will be beneficial for fusion
procedures. In this case, the decreased stiffness of the
PEEK rods as compared to metal rods is thought to
allow better load sharing with the anterior spinal
