Biomedical Engineering Reference
In-Depth Information
Table 3.3. Effects of graft tissue processing on allograft mechanical performance
Processing
technique
Study
Observations
Lyophilization
Brantigan et al. 1993 [9]
Fresh frozen cancellous bone is 219% stronger than lyophilized
cancellous bone.
Simonian et al. 1994 [54]
Lyophilization significantly decreases screw pullout strength.
Kang and Kim 1995 [28]
In vivo lyophilized graft had decreases of 30.1% in bending
strength and 41.3% in compressive strength.
Thoren and Aspenberg
Lyophilization decreased mechanical stiffness by 19%, yield by
1995 [60]
16%, and energy to failure by 31%.
Nather et al. 2004 [41]
Lyophilized allografts significantly weaker than deep-frozen grafts.
Gamma-irradiation
Anderson et al. 1992 [5]
Failure stress and elastic moduli of cancellous bone significantly
decreased after 6.0 megarads but not after 2.5 megarads.
Rasmussen et al. 1994 [45]
12% decrease in stiffness and 26% decrease in maximum force
after 4.0 megarads.
Zhang et al. 1994 [68]
No significant difference in mechanical properties of iliac crest
wedge grafts after 2.0 to 2.5 megarads.
Fideler et al. 1995 [19]
Mechanical properties of fresh-frozen bone-patella-bone graft
reduced by 15% after 2.0 megarads, with further reduction of
46% after 4.0 megarads.
Hamer et al. 1996 [23]
Dose-dependent decreases of up to 46% in mechanical strength
after irradiation.
Currey et al. 1997 [13]
Virucidal irradiation levels decreased bending strength by 52% to
67%, work to fracture by 74% to 96%, and impact energy by
37% to 75%.
Pasteurization
Borcher et al. 1995 [7]
Boiling and autoclaving decreased allograft strength by 26% and
58%, respectively. Freezing did not compromise allograft
strength.
Ethylene oxide
Wittenberg et al. 1990 [66]
Ethylene oxide had no significant effect on immediate
compression strength of grafts.
logical evaluation was performed on
27
% of the
are placed in an anatomically appropriate site,
as in an area of large bone loss. In heterotopic
transplantation, bone allografts are placed in
an anatomically abnormal location, such as a
fi bular strut allograft used adjunctively during
a vertebral fusion [
1
osteoarthritic femoral heads donated by
patients undergoing elective total hip arthro-
plasty. More than
,
146
% of the samples exhibited
osteopenia on radiographic examination.
Marked, generalized osteopenia with thinning
of the cortical and cancellous bone was found
in
30
]. In general, cortical bone
allografts are stronger than cancellous bone
allografts. Cortical bone graft strength varies
according to anatomical location, with fi bular
struts being stronger than femoral rings, which
in turn are stronger than tricortical iliac bone
crest [
57
]. The increased inci-
dence of osteopenia clearly affects the bone
quality, but the effects of metabolic and infl am-
matory diseases noted in some specimens are
not known [
3
% of the samples [
43
43
]. Siddiqui et al. [
51
] observed
]. Additionally, iliac bone
grafts harvested close to the anterior superior
iliac spine are stronger than those harvested
near the posterior iliac spine [
21
,
46
,
52
,
66
that
allografts from screened donors
in their fi fties had osteoporosis. They suggested
that these allografts would not be suitable in
cases where graft strength is required.
Bone allografts can be used in either ortho-
topic or heterotopic transplantations. In ortho-
topic transplantation, cortical bone allografts
12
% of
40
]. Various com-
binations of cortical and cancellous bone
allografts can augment reconstructive proce-
dures, but terminal sterilization, though rec-
ommended, may reduce their strength.
31
