| This thesis presents four studies that investigate the relationships between composition and microstructure, material properties, and mechanical loading for soft skeletal connective tissues. The first study relates tensile behavior to composition and microstructure. It presents a mathematical model that describes the uniaxial tensile constitutive and failure behavior of tendon, meniscus, and articular cartilage based on microstructural parameters including fiber volume fraction, fiber orientations, fiber crimping and failure strain, fiber modulus, and ground substance resistance to fiber reorientation. The second study examines the effects of tensile loading on the geometric and material properties of tendons and ligaments. It presents a computational model that relates changes in the tendon or ligament cross-sectional area, modulus, and strength during development and functional adaptation to biological influences and cyclic tensile strains. The third study relates compressive behavior to composition and microstructure. It proposes relationships for determining tissue permeability from water content, glycosaminoglycan content, and collagen fiber diameter, and it examines the effects of permeability and load rate on the compressive behavior of tissue specimens loaded at a fixed rate in uniaxial confined compression. The fourth study considers the effects of compressive loading on the material properties of tendons that wrap around bones. It proposes a remodeling rule that predicts the development of a low permeability region in the tendon in response to high cyclic hydrostatic pressures. Finite element analyses of the rabbit flexor digitorum profundus tendon suggest that the low permeability protects the solid constituents of the extracellular matrix from deformations that might damage the matrix organization. These four studies lay the groundwork for understanding the interplay between composition and microstructure, material properties, and mechanical loading. A more complete understanding of these relationships may allow the development of innovative treatments for maintaining, rehabilitating, repairing, and regenerating soft skeletal connective tissues. |
