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Wong M.Y.W.,University of New South Wales | Yu Y.,University of New South Wales | Yang J.-L.,University of New South Wales | Woolford T.,Queensland Bone Bank | And 2 more authors.
European Journal of Orthopaedic Surgery and Traumatology

Background: Demineralized bone matrix (DBM) allografts are widely used in orthopaedic clinics. However, the biological impact on its osteoinductivity after its sterilization process by gamma irradiation is not well studied. Furthermore, little is known about the relationship between residual calcium levels on osteoinductivity. Hypothesis: We hypothesize that low-dose gamma irradiation retains the osteoinducitivity properties of DBM and causes ectopic bone formation. Materials and methods: A randomised animal trial was performed to compare tissue and molecular responses of low-dose (11 kGy) gamma irradiated and non-irradiated human DBM at 6 weeks post-intramuscular implantation using an athymic rat model. In addition, we correlated residual calcium levels and bone formation in gamma irradiated DBM. Results: A modified haematoxylin and eosin stain identified ectopic bony capsules at all implanted sites with no significant difference on the amount of new bone formed between the groups. Statistically significantly lower ratio of alkaline phosphatase expression over tartrate-resistant acid phosphatase and/or cathepsin K expressions was found between the groups. Discussion: This study found that low-dose gamma irradiated DBM, which provides a sterility assurance level of 10-6 for bone allografts, retained osteoinductivity but exhibited significantly enhanced osteoclastic activity. Furthermore, this is the first study to find a positive correlation between residual calcium levels and bone formation in gamma irradiated DBM. © 2013 Springer-Verlag. Source

Nguyen H.,Queensland Bone Bank | Nguyen H.,Griffith University | Morgan D.A.F.,Queensland Bone Bank | Cull S.,Queensland Bone Bank | And 2 more authors.
Journal of Industrial Microbiology and Biotechnology

Sterility testing is the final, and critical, step in quality control of tissue banking. It informs the decision whether to release the tissue allografts for clinical use, or not. The most common method for sterility testing of structural bone and tendon allografts is to swab using cotton tip streaks. This method provides low recovery efficiency; and therefore may pass allografts with low bioburden, providing false negatives. Our pilot data revealed organism recovery efficiencies of 60, 30 and 100% from cotton swab, membrane filtration and sponge swaps, respectively. Our aim was to develop a high sensitivity sterility test for structural bone and tendon allografts using a sponge sampling method. Eighty-one bone and tendon allograft samples were inoculated with organism suspensions (10 2 or less organisms per 0.1 mL) of Clostridium sporogenes, Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, Bacillus subtilis, Aspergillus niger, Staphylococcus epidermidis and Micrococcus spp. Nasco sponges (4 × 8 cm) were used to aseptically sample the whole surface of allograft samples. The sponges were cut in half and cultured in either tryptone soya or fluid thioglycollate broths for 14 days. Positive culture samples were further examined for microbial morphology. The results showed that the sensitivity of the method, and negative predictive value, is 100% for all inoculated organisms incubated with thioglycollate. We conclude that this sponge sampling method should be applied as the standard for sterility testing of structural bone and tendon allografts. © 2011 Society for Industrial Microbiology. Source

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