To compare the effect of different preservation methods on the biomechanical properties of rat Achilles tendons, and recommend the best tendon preservation method.

Achilles tendons from 25 SD rats were randomly divided into 5 groups: fresh, -20℃ preservation, -80℃ preservation, liquid nitrogen preservation and 10% formalin preservation group. Tendons in the fresh group were set out for biomechanical test immediately after dissection. Tendons in the rest four groups were preserved accordingly before being subject to biomechanical tests. The length and width of the tendons were measured to calculate the cross sectional areas. After preloading, the tendon was straightened and the initial length was recorded. The tendon was then stretched at a rate of 3 mm/min until the middle position of the tendon ruptured. The load and displacement were recorded, and the maximum strain, maximum stress and stiffness of tendons were calculated.

There were no significant differences of the initial length of the tendons (F=0.217, P=0.921). The cross sectional areas of tendons in the cryopreservation groups increased, while the ones in the formalin preservation group decreased. These differences were significant (P<0.05). The maximum tensile length, maximum strain and maximum stress of the preserved groups were lower when compared to those of the fresh group, the differences being significant for liquid nitrogen preservation group and formalin preservation group (P<0.05). Tendon stiffness in -20℃ group and -80℃ group was higher, compared to the fresh group (P<0.05). Tendon stiffness in the liquid nitrogen group and formalin group was lower than that in the fresh group, the difference being significant (P<0.05).

Comparing to liquid nitrogen group and 10% formalin group, the biomechanical properties of tendons in -20℃ group and -80℃ group were closer to those of fresh tendons. Cryopreservation is the recommended method for tendon preservation.

Achilles tendon; Biomechanics; Low temperature cryopreservation; Formalin preservation