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Hyaline Cartilage articular cartilage larynx rib and costal cartilage nasal septum Elastic Cartilage epiglottis Fibrocar

Cortical Bone. Trabecular Bone. Hyaline Cartilage articular cartilage larynx rib and costal cartilage nasal septum Elastic Cartilage epiglottis Fibrocartilage Intervertebral disk meniscus. Meniscus. Articular Cartilage.

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Hyaline Cartilage articular cartilage larynx rib and costal cartilage nasal septum Elastic Cartilage epiglottis Fibrocar

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  1. Cortical Bone Trabecular Bone • Hyaline Cartilage • articular cartilage • larynx • rib and costal cartilage • nasal septum • Elastic Cartilage • epiglottis • Fibrocartilage • Intervertebral disk • meniscus Meniscus Articular Cartilage Tissues are classified by their biochemical composition, molecular microstructure, biomechanical properties and function.

  2. AC/Meniscus Functions: • Support large loads • gymnastics • Walking • Lubrication Interested in these structures because when they “breakdown” we get osteoarthritis

  3. Articular Cartilage • Important to understand • Mechanical properties of normal cartilage • Manner by which biochemical and structural factors contribute to the material properties of cartilage • Manner by which changes in tissue composition affect the mechanical properties of cartilage

  4. Diarthrodial joint • Fibrous capsule • Inside lined with synovium which secretes synovial fluid

  5. Microstructure (Solid and Fluid Phase) • Interstitial water • Articular cartilage 68-85%, meniscus 60-70%

  6. Interstitial Water • Constant with age • Increases with OA or degeneration • Amount of water is dependent on

  7. Interstitial water • Ions- • As tissue is compressed-Frictional drag force on walls of the pores of the solid matrix due to interstitial fluid flow through the pores of collagen-PG matrix

  8. Microstructure (Solid and Fluid Phase) • Collagen • Proteoglycans • Cells No blood or nerves in cartilage

  9. Collagen: made up of molecules (tropocollagen--1.4 nm) that polymerize to form fibrils • Type II (AC), forms bundles, with diam.=2 to 10 microns • Type I (meniscus), forms fibrils, with diam. = 20-200 nm

  10. Collagen Orientation

  11. Collagen Orientation

  12. Proteoglycan: protein with bound side chains (glycosaminoglycans)

  13. Proteoglycans • Negative charge attracts +ions (K and Na) • Swelling pressure • PG want to be 5-10 times larger, but not enough room in cartilage

  14. Cells: Chondrocytes

  15. Material Properties • Steel is linear elastic (E,) • Soft tissues ARE NOT!! • Water movement (forces depend on rate-damping) STEEL

  16. Material Properties • Viscoelastic behavior are dominated by frictional drag of interstitial fluid flow through the porous collagen-proteoglycan solid matrix, thus causing viscous dissipation

  17. Material Properties-Anisotropy/Inhomogeneous • Transversely Isotropic • Inhomogeneous

  18. Constitutive Equation: • Linear Elastic Materials (Steel) • Hookes’ Law:  = E • Viscoelastic materials (AC/meniscus) • Biphasic Theory (2 phase) • Triphasic Theory (3 phase)

  19. Deform. Force time time Tensile Stress Relaxation Test Tension • Equilibrium Tensile Modulus (1-30 MPa) • Type of tissue • Age of animal • Type of joint • Sample location • Depth of sample (surface = 10MPa, Middle =4.5MPa) • Relative orientation • Biochemical comp/ molecular structure • State of degeneration (Normal =10MPa, OA=1.4MPa)

  20. Tension

  21. Compression • Compressive Aggregate Modulus (HA)(0.4-1.5 MPa) Force Deform time time Confined Compression Creep Test

  22. Compression • HA varies inversely with water content *OA patients have increased water • HA varies directly with PG content • Not dependent on collagen content

  23. Shear

  24. Shear

  25. Methods of Failure-Cartilage Fracture – Fracture with Bone Wear Degeneration Blunt Trauma (intense compression and shear forces) Bone Bone

  26. Methods of Failure - Meniscus • Degeneration • Tearing

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