Biomedical Engineering Reference
In-Depth Information
Table 3.1. Graft donor infectious pathogens screened
Mandated by FDA
Human immunodeficiency virus (HIV) types 1 and 2
Hepatitis B virus (HBV)
Hepatitis C virus (HCV)
Additional AATB screening
[
], and viruses in transplants pro-
cured from acceptable donors.
HIV infection is one of the most serious risks
associated with allograft transplantation. There
is currently no cure or vaccine for this lifelong,
disabling disease. With proper donor screening
and HIV antibody and antigen testing, the esti-
mated risk of HIV transmission in musculosk-
eletal transplantation is
4
,
24
,
26
,
65
Human T-lymphocytic virus (HTLV) types 1 and 2
Syphilis
1
in
150
,
471
and can be
reduced to
million with lymph node
testing, serology, and checking for complica-
tions associated with grafts from the same
donor [
1
in
1
.
67
are resorbed more quickly than cortical grafts
and are typically available as small, porous,
spongy blocks that are used to fi ll segmental
bone defects.
After terminal sterilization, bone allografts
can be demineralized to make osteoinductive
biological molecules, such as bone morphoge-
netic proteins (BMPs), more readily available to
augment new bone formation [
]. The risk of infection following
allograft transplantation is comparable to the
risk of HIV infection from screened whole red
blood cell transfusion; it is thought to be
between
10
1
in
250
,
000
and
1
in
2
,
000
,
000
[
10
].
Between
, four cases of HIV
transmission were reported resulting from
procedures that utilized fresh-frozen bone
allografts in
1988
and
1992
]. The
demineralization process is thought to destroy
the antigenic surface of the bone graft, which
reduces the host immune response. Like
gamma-irradiation and lyophilization, the
demineralization process weakens musculo-
skeletal allografts [
17
,
37
,
50
1984
and
1985
, which were traced
to two donors [
]. These investigations were
initiated after the allograft recipients, whose
only risk for HIV was transplantation, were
found to be positive for HIV several years later.
Other infected allograft recipients were then
identifi ed through analysis of banked tissue.
The donors of these tissues were screened for
HIV and tested negative. It is believed that the
infection occurred during an early stage when
HIV antibodies were not yet detectable. In
another case, a fresh-frozen bone allograft was
implanted that had been subjected to extensive
intramedullary reaming prior to implantation
and did not test positive, yet became the source
of the HIV infection. Conceivably, the removal
of blood and bone marrow from the allograft
prior to implantation cleared infectious cells
from the tissue and thus led to a negative test
result [
2
,
53
]. Thus, choosing an
appropriate allograft becomes critical when
the
14
,
44
primary
requirement
is
structural
augmentation.
Quality control of tissue banks is maintained
through documentation and periodic audits of
stored allografts. Some tissue banks routinely
test stored tissues as new laboratory methods
become available [
]. These periodic audits
increase the chance of detection of potential
cases of HIV transmission and/or epidemio-
logical exposures to other previously unde-
tected infections.
12
]. To date, there have been no reports
of HIV transmission from musculoskeletal
allografts obtained from seronegative donors
that were subjected to freeze-drying or other
terminal sterilization methods [
53
3.3 Infection from
Musculoskeletal Transplants
8
,
32
,
47
,
48
,
53
,
62
]. Since then, tests have been devel-
oped for other markers of HIV, including the
p
,
63
,
64
Musculoskeletal transplantation is a safe, com-
prehensively regulated practice with a low inci-
dence of infections, especially in light of its
substantial usage in reconstructive procedures.
However, the risk of potentially fatal complica-
tions from infectious transmission does exist.
The literature describes many cases of contam-
ination with HIV [
antigen assay and the use of the polymerase
chain reaction (PCR) [
24
20
,
32
,
47
,
48
,
53
,
62
,
63
].
Hepatitis C is a chronic hepatic disease that
for several years after infection may exhibit no
clinical signs or symptoms, yet ultimately lead
to severe morbidity and mortality. There is
no cure or vaccine for hepatitis C. Nine cases
2
,
32
,
53
], HCV [
1
,
12
],
Clos-
tridium
species [
4
,
27
,
38
], and other bacteria
