Biomedical Engineering Reference
In-Depth Information
Anderson, “Most biomaterials of potential clinical
interest typically elicit the foreign body reaction
(FBR), a special form of non-specific inflammation.
The most prominent cells in the FBR are macro-
phages
.
Multinucleated giant cells in the vicinity of
a foreign body are generally considered evidence of
a more severe FBR”
[21]
.
Much of the PEEK particulate debris in the series
of X-STOP PEEK IPD explants was of the order of
less than 1
m in size, and appeared to be agglom-
erated or clumped by transmitted light microscopy.
As seen in
Figs 7.15 through 7.17
, the polymeric
debris was found to be birefringent upon examination
with polarized light microscopy. The observed bire-
fringence of the PEEK polymeric debris is consistent
with the previous literature cited, as the PEEK
material is known to be a crystalline polymer. When
compared with transmitted light microscopy, polar-
ized light microscopy was more capable of recog-
nizing individual birefringent particulates in the
tissues. Polarized light microscopy revealed that
much of the PEEK particulate debris was of the order
of several microns to less than 1
m
Figure 7.16
Periprosthetic tissues from an X-STOP
PEEK Interspinous Process Distraction (IPD) explant
showing intracellular birefringent PEEK polymeric
debris in the tissue sample received with the device
(H&E stain, partially polarized light, original magnifica-
tion
200
).
¼
Based on the population and type of inflammatory
cells observed in the histology, the chronic inflam-
matory host response (macrophages almost exclu-
sively) to the PEEK particulate debris dispersed
throughout the fibrous connective tissues varied from
“no reaction” to “mild reaction” to “moderate reac-
tion” (as characterized by ASTM standard F981-04)
[20]
. As so eloquently stated by pathologist Dr James
m in size. Quali-
tative optical microscopy of birefringent polymeric
debris showed that the debris was almost always less
than 1
m
m, and submicron size particulate predomi-
nated. Thus, quantitative analysis of particle size was
not possible by light microscopy. The ASTM stan-
dard F1877-98 calls for a magnification of 10,000
(which cannot be obtained by optical light micros-
copy methods) to characterize particles in the size
range of 0.1
e
1.0
m
m
[22]
. Thus, quantitative image
analysis of optical microscopic fields is inadequate to
fully characterize the number and size of particulate
debris. Qualitatively, particulate shape would be best
characterized as granular irregular fines per ASTM
standard F1877-98
[22]
.
Birefringent polymeric debris was a frequent
finding in the connective tissue samples in the series
of X-STOP PEEK IPD explants. Despite the ubi-
quitous nature of the polymeric debris, the overall
rating of the host response varied from “no reaction”
to a focal “moderate reaction” chronic inflammatory
response (macrophages almost exclusively) by
ASTM standard F981-04
[20]
. Similar to the rabbit
nonclinical study reported by Jockish et al.
[16]
,
nonpolarizable hemosiderin was found in the
connective tissue samples adjacent to metallic and
polymeric particulate debris in a few patients.
Hemosiderin (iron storage granules) may be present
in areas of old hemorrhage or may be deposited in
m
Figure 7.17
Periprosthetic tissues from an X-STOP
PEEK Interspinous Process Distraction (IPD) explant
showing intracellular birefringent PEEK polymeric
debris in the tissue sample received with the device
(H&E stain, partially polarized light, original magnifica-
tion
500
).
¼
