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In permanent bending tests, veStAKeeP® holds up three times
as long as a comparable competing PeeK product
veStAKeeP® Ultimate Standard PeeK polymer
Bending force [n]
30
25
20
15
10
5
0
0 100,000 200,000 300,000 400,000
Cycles
On the computer, 3D X-ray scans are used to
reconstruct the exact three-dimensional anatomy
of the skull. this is done for the purpose of
manufacturing skull implants, where the implant is
adapted to this form. CnC milling technology is
used to make the implant from one block of PeeK
Visible thanks to
barium sulfate
MedICAL teCHnoLoGY
the primary stability of a spine cage to make sure it
is properly seated, and whether the bones are actually
growing through it. This is why tantalum pins are
used in PEEK cages to make the implant visible. However,
incorporating the pins is a pretty tedious, laborintensive
post-processing step because they have to
be seated perfectly flush—the cavities around the pins
could cause problems during cleaning and sterilization.
For such cases, Evonik has developed a new
VESTAKEEP® PEEK variant that contains barium sulfate.
The idea comes from diagnostic radiology: Physicians
give patients a suspension made of barium
sulfate to display the esophagus, stomach and small
and large intestines, as well as mobility disorders of
these organs, in a CT image. Decades of experience
have proven the safety of using barium sulfate.
Studies by Evonik have shown that a content of
less than ten percent barium sulfate is enough to make
the implant visible on an X-ray, without generating
the kinds of disruptive artifacts caused by metals.
While the quality of the X-ray depends on a number
of factors—such as the strength of the X-ray radiation
and geometry, and the wall thickness of the implant—
a filling level of six percent barium sulfate is wellsuited
to a majority of applications. For example, a
spine cage can be portrayed clearly in an X-ray image,
and at the same time allows the monitoring of
bone growth in the cavity.
Osteointegration—the healing process in the bones
in which the bone cells graft to the implant and implant
surface, which normally takes about six to
twelve months—is essential for a stable fit for an implant
in the spinal column. The factors that influence
osteointegration are the individual properties of the
bone, the construction of the implant, and its surface
condition. With regard to the latter, titanium is
superior to PEEK, because the metal surface shows
improved grafting behavior, and the bone substance
anchors faster to the metal. Consequently, the 333
Coating should accelerate
bone growth
31
elements39 Issue 2|2012