| ABSTRACT: Aiming at assuring the safety and effectiveness of the reconstituted bone xenograft (RBX) in its clinical use, especially in searching for a better way to sterilize bone graft, this paper has compared the sterilization effect of gaseous ethylene oxide (EO) and cobalt-60γ radiation on RBX. The bone chips were contaminated with 10~7 per milliliter bacteria of staphylococcus Aureus ATCC 25923, Bacillus Subtilis globigii 8017 and Bacillus Cereus 4001, then sterilized with various doses of gaseous EO or cobalt-60 γ radiation. The bacteriocidal capacity was determined, and the osteoinductive properties were studied by evaluating the alkaline phosphatase activity and calcium content of heterotopic ossification after implanting of RBX into muscle pouch in the mouse, and by bone histomorphometric analysis . The results revealed that both EO and cobalt-60 γ radiation had strong microbicidal properties. The process of lyophilization could not decrease the number of the bacteria in the bone grafts distinctly, but rather increase their resistance to EO and γ irradiation. The bone inductive properties were reduced in a dose-dependent manner. The radiation of fully bacteriocidal doses destroyed the bone induction properties completely while the EO didn't. The moderate doses of EO for sterilizing the paniculate bone grafts are desirable, which possesses fully bacteriocidal properties with little interfering with the osteoinductive potential. Based on this,a set of methods for sterilizing RBX was worked out, which served as the guide for the safety and effectiveness of RBX.For further expanding the clinical application of RBX, a sort of massive reconstituted bone xenograft (MRBX) was developed, and the changes in T lymphocyte count in the recipients after implantation of bone xenografts were... |
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