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Queen Mary University of LondonQueen Mary University of London
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School of Engineering and Materials Science
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PhD Thesis: Dynamic characterisation of rat-tail tendon fascicles

Author: TAMIWA, Masami

Year: 2007

Supervisor(s): Dan Bader

Reliable methodologies were established for testing tendon fascicles, with particular attention paid to the testing environment. These studies enabled a suitable test protocol to be developed to predict the ultimate tensile strength of a tendon fascicle and thereby investigate their fatigue life. Damage accumulation that occurs during long-term cyclic loading was examined, as well as the viscoelastic behaviour of the fascicles.

It was demonstrated that the mechanical properties of tendon fascicles were dependent on the age and the individual source of the rat tail, as well as the nature of the test hydration solutions. Indeed, incubation in a 5% sucrose solution was found to regulate the swelling of the fascicles to immediate post-dissection levels. The test solution also influenced their viscoelastic behaviour, with fascicles exhibiting an increase of approximately 6% in the load decay ratio when incubated in EBSS compared to the 5% sucrose solution. The fatigue life (N) of tendon fascicles was found to decrease exponentially with the normal stress level (S), in the form of a log-linear model, S = 187 – 30log(N). The fatigue tests also yielded an index of damage measured as a change in dynamic modulus. Results indicated that damage was established rapidly, before 3600 cycles, or 1 hour of testing.

This study has highlighted the importance of the testing environment for tendon fascicles. It has suggested that major damage may occur very early in a fatigue test and that the failure mechanisms of a tendon fascicle may differ from those of a whole tendon. Indeed the damage that occurs in tendon fascicles does not seem to directly influence the mechanical integrity of a whole tendon. These considerations should be taken into account when employing fascicles as an experimental model, particularly when using mechanical conditioning to up-regulate cell activity for the tissue engineering of tendons.