Biomedical Engineering Reference
In-Depth Information
hydroxyapatite (
Fig. 16.10
)
[56]
. This dual-layer Ti/
HA coating combination is compatible with PEEK
and also has a successful clinical track record in
achieving stable long-term fixation in traditional
acetabular components
[58]
.
The MITCH cup has been tested in a hip simulator
under conditions comparable to previous PEEK
acetabular components
[18]
. After 25 million cycles,
the total extent of wear for the MITCH cup articu-
lating against alumina femoral heads ranged between
16 and 28 mm
3
, corresponding to an average wear rate
of 1.16 mm
3
/million cycles (range: 0.81
e
1.39 mm
3
/
million cycles). These tests indicated that the cups had
an initial surface roughness of 2.4
e
4.3
m
mpriorto
the tests; however, the surface became substantially
smoother and negatively skewed after the first million
cycles. Finite element analysis of the MITCH cup
demonstrated that the stress distribution in the
acetabulum was comparable to the Cambridge
Cup
[59]
, as detailed in Chapter 14 (see Section 14.6).
In summary, the MITCH PCR cup illustrates how
CFR-PEEK can potentially overcome the historical
wear and biomechanical constraints of contemporary
bearing materials for a novel arthroplasty design. It
remains to be determined whether the long-term
clinical findings previously observed with the Cam-
bridge Cup will also occur with the MITCH PCR.
Following preclinical validation, a staged clinical
trial was initiated by Messrs Field and Rushton in the
United Kingdom. The first implantations were per-
formed in February 2007. Twenty-five cups were
implanted in total as part of a limited clinical trial.
Personal communication with the investigators
(A)
(B)
Figure 16.11
Anterioreposterior radiograph of a patient
implanted with a well-functioning MITCH PCR cup,
3 years after implantation. Note that the CFR-PEEK
cup is radiolucent, with the exception of radiographic
marker beads in the stabilization fins. Image courtesy
of Richard Field.
Figure 16.10
Oblique (A) and backside (B) views of
HA/Ti coated CFR-PEEK composite acetabular
component (MITCH PCR). Images courtesy of Stryker
Orthopedics (Mahwah, NJ).
