| Collagenous connective tissues like the Achilles tendon have a highly complex and intricate microstructure. Their anatomy, biomechanical load response and regional-scale material properties have been investigated in detail. Available studies on the Achilles tendon generally focus on the tissue's macroscopic behavior. Macroscopic scale studies are useful, however, despite best efforts, they remain unable to provide accurate and reproducible information on the biomechanical properties and loading behavior of the tendon's sub-macroscopic scale components. Knowledge of the tissue's biomechanical properties at these scales is critical to address the clinical problems of injury, particularly sub-failure injury, and repair. Historically, challenges of experimental testing and analytical modeling have precluded detailed analyses or studies at sub-macroscopic scales.;The objective of this work is to characterize the fascicle-scale biomechanical properties and load response of the human Achilles tendon by addressing the following three specific goals: (1) develop and implement experimental protocols for performing fascicle-scale studies of the Achilles tendon, (2) formulate a viscoelastic model to characterize the cyclic stress response of Achilles tendon fascicles and (3) model realistic fascicle deformation patterns using a 3-D computational model of the heterogeneous tendon microstructure. The experimental techniques and protocols presented can be extended to other connective tissues and structural scales. In addition to the application to sub-failure injury and repair, the results of this thesis work are applicable to microstructural models investigating localized cellular stress fields for tissue engineering applications. |
