Effects of supercritical fluid CO2 and 25kGy gamma irradiation on the initial mechanical properties and histological appearance of tendon allograft

Tendon allografts, when autograft options are limited or when obtaining an autograft is not aligned with the patients' best interest, play an important role in tendon and ligament reconstruction. To minimize the risk of infectious disease transmission tissue banks perform screening tests and the allografts cleaned are sterilized. The current study examines and compares the initial mechanical properties and histological appearance of supercritical CO2 (SCCO2)-treated and gamma-irradiated porcine extensor tendons. Thirty intact porcine forelimb extensor tendons randomized equally into three groups: control group, gamma-irradiation group, and SCCO2-treated group. Once treated, histological assessment and histomorphologic measurements were made on the histological sections obtained from each tendon while stiffness and ultimate failure loads were evaluated from tensile testing. Histological evaluation of gamma-irradiated tendons showed significant disruption to the hierarchical morphology of the fascicle bundles, which was not evident in SCCO2-treated specimens. Histomorphologic measurements showed a significant increase for measured dead space (void) between tendon fibrils of the gamma-irradiated group comparing to both control and SCCO2 treated groups (p<0.01). There was a significant reduction in the ultimate failure load for tendons treated by gamma-irradiation compared to the control group (p<0.05). No statistically significant difference was detected between control and SCCO2-treated tendons in the ultimate failure load. Stiffness values were not significantly different between three-study groups. This study suggests that while gamma-irradiation has a deleterious effect on mechanical properties of tendon tissue, SCCO2 does not alter the biomechanical properties and the histological structure of porcine extensor tendons.