PRESERVATION AND STERILIZATION OF CORTICA L BONE - BIOMECHANICAL STUDIES IN RATS

The biomechanical properties of cryopreserved, autoclaved, irradiated and chemically treated cortical bone harvested from rat tibiae were ev aluated in three-point bending. Biomechanical parameters (maximum bend ing load, deflection, failure energy and stiffness) are not altered by cryopreservation (- 70-degrees-C, 28 days) or irradiation with doses of 1 kGy or 5 kGy. The maximum bending load of autoclaved (134-degrees -C, 3 min) or irradiated (25 kGy) cortical bone is reduced to 82% and 74% compared that of controls tested immediately after death (100% = 7 4.4 +/- 6.6 N). Extension of the autoclaving time from 3 to 5 min or i rradiation with 50 kGy diminishes the bending load (28% after autoclav ing, 48% after irradiation), deflection and failure energy. Stiffness is altered by autoclaving only. If a sterilization process is combined with deep freezing, better biomechanical values are obtained by steri lizing the bone before deep freezing than vice versa. The bending load s for autoclaving and irradiation before deep freezing are 68.8 +/- 9. 4 N and 50.8 +/- 7.9 N, as against 51.7 +/- 2.7 N and 43.1 +/- 3.9 N f or autoclaving and irradiation of previously cryopreserved bone. Where as treating bone with tetrahydrofurane does not alter its biomechanica l behavior, 80% ethanol leads to a reduction of structural properties.