Experimental Study on the Osteosynthetic
Properities of Sterilized Allografts
Abstract
Serious problems associated with frozen allografts
include infection developing after implantation
and difficulty in obtaining them in Japan
because of religious and social factors.
If the osteosynthetic properties of sterilized
allografts, such as autoclaved allografts
(135 , 10 min) and ethylene oxide gas sterilized
allografts (EOG allografts), are similar
to those of frozen allografts (-80 ), such
allografts would overcome the problem mentioned
above. The purpose of this study is to compare
the osteosynthetic properties of sterilized
allografts with those of frozen allografts
in animal experiments. The allografts were
obtained from the 10 mm femoral diaphysis
of Wistar rats and treated with one of the
above-mentioned sterilization conditions.
The immunological response was checked by
the skin graft assay. Each allograft was
implanted into a 10 mm femoral diaphyseal
defect made in an SD rat. In other sterilized
allograft implanted groups, the reconstructions
were supplemented with autolysed antigen-extracted
allogeneic bone (AAA bone). The reconstructions
were investigated with respect to incorporation
by radiography, histology and microangiography
at 2, 4, 8, 12, 16, 24 weeks after reconstruction.
In the skin graft assay, the antigen level
of the sterilized allografts was similar
to that of the frozen allografts, but was
not completely extracted. Bony union was
achieved at 8 weeks after reconstruction
of the frozen allografts and at 12 weeks
after reconstruction of the sterilized allografts
radiographically. New appositional bone was
present at the border of the grafted bone
at 8 weeks after transplantation of the frozen
allografts. On the other hand, no appositional
bone was present at the border of the sterilized
allograft at 12 weeks after transplantation.
These findings suggest that frozen allografts,
but not sterilized allografts, have an osteoinductive
property which is largely destroyed by the
sterilization methods. The blood vessel density
of the sterilized allografts was lower than
that of the frozen allografts. The reason
for this difference is that sterilized allografts
have only osteoconduction. But new bone formation
after the invasion of new vessels occurred
in the sterilized allografts by osteoconduction.
Supplemented with AAA bone, each type of
allograft exhibited abundant new bone formation
and invasion of new vessels compared to the
nonsupplemented allografts. As the union
of the sterilized allografts was satisfactory
at the host-graft junction by osteoconduction,
it is concluded that these allografts can
be used for the reconstruction of large skeletal
defects. And the addition of osteoinductive
material can improve the incorporation of
the sterilized allograft.
JOURNAL OF THE JUZEN MEDICAL SOCIETY 101,
802-816i1992j
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