RESUMO
Tissue engineering approaches are now being investigated for altering the course of intervertebral disc degeneration (IDD). Because the disease changes the mechanical properties of the load bearing tissues of the disc, viscoelastic tissue behavior is a key measure for comparing the efficacy of treatments. To investigate the basic viscoelastic behavior of nucleus pulposus tissue, tissue from the rabbit disc was tested in torsional creep. Both the Andrade and Nutting creep models had a good fit to the data, however, the Andrade creep model gave a much better prediction of the longer term creep. This is the first application of Andrade creep to biological tissue and results indicate that this model may be particularly well suited for characterizing the viscoelastic behavior of very soft biological tissues.