The Effect of Freeze Storage on the Tensile Properties of Tendons

The objective of the current study is to elucidate the influence of freeze storage on the tensile properties of tendons by testing specimens at numerous adjacent durations to eliminate the influence of biological variation and experimental errors. Chicken flexor digitorum profundus tendons were stored intact in the digits at -20°C and specimens were tensile tested at 33 durations over 360 days. Scanning electron microscopy was done on fresh specimens and specimens freeze-stored for 30, 233 and 427 days to investigate microstructure change after freeze storage. The tensile properties of tendons, as represented by ultimate tensile strength, strained at ultimate tensile strength. The elastic modulus did not deviate significantly (p>0.01) after freeze storage while the collagen fiber density of specimens stored for 233 and 427 days decreased with porosity growth. In contrast, no obvious microstructure difference was observed between fresh tendons and tendons stored for 30 days. These findings suggest that the postmortem degradation incurred a minor effect on the structural integrity of the tendons and therefore did not affect the overall tensile properties. We conclude that freeze storage at -20°C does not alter the tensile properties of tendons for as many as 360 days.