| Fibro-cartilage metaplasia occurs in tendons that wrap around bony protruberances in the skeletal system. Within these regions of contact, tendons undergo a process of structural adaptation (i.e. metaplasia) into fibrocartilage. The mechanobiology of this transformation is key to developing a scientific understanding of structure-biomechanical function relationships in load bearing tissues. It is also of relevance in the area of “Functional Tissue Engineering ” wherein controlled mechanical signals are delivered to a cell therapy based construct to induce synthesis of appropriate extracellular matrix components.; Malaviya et al [2000] conducted in vivo experiments on reversing the formation of fibrocartilage in the rabbit flexor digitorum profundus tendon. This was achieved by translocating the tendon surgically away from its bony contact, which transformed the fibrocartilage (FC) region back to a tissue with tendon like characteristics. Developing an understanding of this unique transformation is the central theme of this dissertation.; The path towards developing a fundamental mechanics based understanding of the effect of translocation involved the formulation of an anisotropic poro-hyperelastic constitutive description of the fibrocartilage zone of the tendon. This constitutive model was implemented into an existing finite element code (ABAQUS™) for conducting poroelastic structural analysis of the tendon-fibrocartilage complex under realistic in vivo loading conditions. Changes that occurred to fluid pressures, fiber stresses, and dilatational and distortional stresses in the extrafibrillar matrix as a result of translocation surgery were investigated.; Based on the results seen, it appears that we can now advance a concept, i.e., fibrocartilage metaplasia most likely occurs in a tissue that is required to sustain large intermittent hydrostatic as well as distortional stresses, which may or may not act in unison. Cyclic hydrostatic stresses induce a cellular differentiation pathway that is chondrocytic in nature. However, in the presence of a distortional stress state, the tissue is also required to minimize the strain energy stored in distortion. Thus, a balance is struck leading to the development of fibrocartilage as a compromise between the two extremes, i.e., cartilage and tendon. Tissue forming cells within fibrocartilage are most likely seeded with a dual intent, i.e the ability to synthesize Type I collagen as well as Type II collagen along with associated EFM components.; The developed constitutive models can be employed for future analysis of in vivo model systems like the FDP tendon, and can also be applied to the analysis of loading pathways in tissue engineered implants. |
