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Chou Siaw Meng
04-24-1997, 11:52 AM
Question: I would appreciate if anyone can suggest useful equipment and
procedure
for the testing of spinal implants.
Thank you for all your replies. I believe my query has been fully
answered.
Replies are:
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I believe there is an ASTM standard for fatigue/ static testing of
spinal fixation systems, although I haven't got the number to hand.
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You should have a look to the ASTM Standards (American Society fot
Testing and Materials). They have a whole set of standards about spinal
implants testing. (Which are currently proposed as ISO standards).
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You have to make various fixtures to hold the parts, which are
defined in the standards. Depending on your material and the parts
you are testing, you may need a temperature controlled water bath and
circulating system to immerse the components in Ringer's solution or
similar while you test them. For polymers or composites, you will
need to soak them before testing.
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have you looked at the protocols being developed by ASTM Committee F04
on
Medical Devices? ASTM is in West Conshohocken, PA and you can reach
their
WEB page to get names and e-mail addresses by accessing www.astm.org.
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I just realized that I only answered half of your question in my first
message. We test spinal implants using test machines from MTS Systems
Corporation and I know that they have developed some special fixturing
for
theit Mini-Bionix machine to assist in spinal testing.
They can be reached by e-mail at lito.mejia@mts.com (Lito Mejia,
Biomaterails Testing Systems) or:
MTS Systems Corporation
14000 Technology Drive
Eden Prairie, MN 55344-2290
612-937-4000
FAX: 612-937-4515
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I have tested spinal implants in porcine spinal segments in torsion,
compression and fatigue. Basically the spinal segment consists of two
vertebrae and one intervertebral disc. A discetomy is performed to
remove
the disc nucleus, and the replacment disc inserted. The spinal segment
is
then mounted inbetween two holding jigs using both screws and a medical
cement (dental or bone cement) set around the cut ends of the two
vertebrae
A compressive load is applied, using typically a MTS or Instron testing
machine, and if you have the capability, a rotation can be applied for
several cycles to simulate fatigue loading. The magnitude of loads
depends
on your model (animal or human cadaver), which values can readily be
found
in the literature.
If you want to test the implant on its own, that depends on what your
artificial disc is made of.
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