Changes in the cyclic and static relaxations of the rabbit medial collateral ligament complex during maturation

There is at present no information on how the viscoelastic properties of bone-ligament-bone complexes change during maturation. Changes in the static and the cyclic relaxation behaviours of rabbit bone-medial-collateral-ligament-bone complexes at 3, 6, 9 and 12 months of age are described. These ages cover maturation and initial ageing of this complex. The specimens were subject to 30 cycles of uniaxial tension between zero and 0.68 mm extension at 10 mm min-1. Immediately after the cyclic test, the specimens were held at a constant 0.68 mm extension for 1200 s. The results showed that in both the cyclic and the static tests, specimens from 3-month-old animals relaxed significantly more than specimens at 6, 9 or 12 months of age, whereas those 6, 9 and 12 months old were not significantly different from each other. When the results of the cyclic tests were compared to those of the static tests, cyclic relaxation was higher than static relaxation for each of the 6-, 9- and 12-month-old specimens. For specimens 3 months of age, the opposite was observed. An explanation is offered whereby the total relaxation is suggested to be comprised of two parts: a material relaxation and a water flux component. Differing contributions by each of the two components at particular ages can explain the observed results.