Analysis and Modeling of Inelasticity in Tendon: Viscoelasticity, Damage, and Plastic Deformation

Tendons are soft connective tissues that connect the muscular system to the skeleton. Tendons are abundant in human body and their primary function is to enable transmission of mechanical force. These tissues are prone to overuse and disease. To understand the relationships between tendon’s function and disease, one needs to clearly understand the mechanical behaviors in a physiological context. Despite decades of studies on tendon, a comprehensive framework for studying tendon mechanics that addresses its inelastic mechanical response in relationship to its structure is missing.

The objective of this dissertation was to analyze and model the inelastic behaviors in tendon, which can be categorized into viscoelasticity, damage, and plastic deformation, and study their underlying mechanisms by using state-of-the-art mechanical testing, constitutive modeling, and micro-structural imaging. I addressed this general objective through four specific aims: (1) developing a comprehensive and unifying structurally-inspired modeling framework, reactive inelasticity (RIE), that describes the major inelastic mechanical behaviors of tendon using kinetics of molecular bonds; (2) evaluating damage and plastic deformation as the potential mechanisms of tendon softening behavior during axial loading by using micro-mechanical experiments on tail tendon and RIE modeling; (3) evaluating the poroelastic parameters of tendon, particularly hydraulic permeability, using lateral osmotic loading and biphasic mixture finite element modeling; (4) visualizing and quantifying the 3D microstructure of tendon using serial block-face SEM, and providing a model for interfibrillar load transfer.

This study is innovative in comprehensively addressing the mechanisms of inelasticity in tendon by separately identifying and modeling inelastic behaviors, providing a unifying theoretical explanation for the underlying mechanisms, elucidating novel structure-mechanics relationships, and calculating the inelastic mechanical properties. The outcomes of this study provide novel understanding of tendon mechanics and its relationships to tendon’s multiscale structure. The results and tools developed in this dissertation can be used in further studying structure-mechanics relationships in tendon and other tissues, optimizing treatments for pathologies, and designing engineered tissues and materials.

Year	Entry
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2001	Huang C-Y, Mow VC, Ateshian GA. The role of flow-independent viscoelasticity in the biphasic tensile and compressive responses of articular cartilage. J Biomech Eng. October 2001;123(5):410-417.
2002	Provenzano PP, Heisey D, Hayashi K, Lakes R, Vanderby R Jr. Subfailure damage in ligament: a structural and cellular evaluation. J Appl Physiol. January 2002;92(1):362-371.
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Year

Entry

2006

Provenzano PP, Vanderby R Jr. Collagen fibril morphology and organization: implications for force transmission in ligament and tendon. Matrix Biol. March 2006;25(2):71-84.

2008

Shen ZL, Dodge MR, Kahn H, Ballarini R, Eppell SJ. Stress-strain experiments on individual collagen fibrils. Biophys J. October 2008;95(8):3956-3963.

2001

Huang C-Y, Mow VC, Ateshian GA. The role of flow-independent viscoelasticity in the biphasic tensile and compressive responses of articular cartilage. J Biomech Eng. October 2001;123(5):410-417.

2002

Provenzano PP, Heisey D, Hayashi K, Lakes R, Vanderby R Jr. Subfailure damage in ligament: a structural and cellular evaluation. J Appl Physiol. January 2002;92(1):362-371.

1997

Ateshian GA, Warden W, Kim JJ, Grelsamer RP, Mow VC. Finite deformation biphasic material properties of bovine articular cartilage from confined compression experiments. J Biomech. November–December 1997;30:1157.