Biomedical Engineering Reference
In-Depth Information
Figure 14.15
Effective (von Mises)
strain
distributions
in
the
Cambridge
-PCR
Cups. The upper images
represent sections taken through
the cup and the pelvis in the
plane parallel to the support fins
of the MITCH-PCR Cup. The
lower images represent views
into the acetabulum, with anterior
directed to the left of figure.
and MITCH
reasonably successful, with survival rates in the
elderly population exceeding 90% at 10 years
[100,101]
. The clinical needs for the orthopedic
community, therefore, have been focused on
extending the longevity of existing implants for the
elderly patient population, as well as on expanding
the clinical success of total joint replacements to
younger and more active patients. Consequently, in
orthopedics, novel implant technologies need to
demonstrate sustained, long-term improved perfor-
mance relative to historical alternatives
[100,101]
.
Only within the past decade have animal studies and
clinical data started gradually accumulating to
demonstrate the viability of composite stems incor-
porating PEEK biomaterials as an alternative to
monolithic metal alloys in hip stems
[30,31,33,34]
.
Other novel designs of PEEK implants are still in the
early stages of clinical evaluation.
As the studies highlighted in this chapter have
illustrated, PEEK and CFR-PEEK composites are
now established as sufficiently versatile and durable
for isoelastic orthopedic implants. The design ideal
of isoelastic femoral stems, conceived in the 1960s, is
now beginning to show clinical evidence of reason-
ably sustained fixation and reduced stress shielding
when compared with traditional metallic stems. Of
the variety of polymers that have been evaluated for
composite hip stems over the past 40 years, only
PEEK has demonstrated the requisite combination of
mechanical properties, biocompatibility, manu-
facturability, and consistent availability throughout
this time period. Long-term clinical data are awaited
to determine whether PEEK orthopedic implants will
continue to provide extended benefits to patients
undergoing total hip arthroplasty as have been
observed in early and intermediate follow-up.
