Applied Human Anatomy and Biomechanics

1. Applied Human Anatomy and Biomechanics

2. Course Content • Introduction to the Course • Biomechanical Concepts Related to Human Movement • Anatomical Concepts & Principles Related to the Analysis of Human Movement • Applications in Human Movement • Properties of Biological Materials • Functional Anatomy of Selected Joint Complexes

3. Why study? • Design structures that are safe against the combined effects of applied forces and moments • Selection of proper material • Determine safe & efficient loading conditions

4. Application • Injury occurs when an imposed load exceeds the tolerance (load-carrying ability) of a tissue • Training effects • Drug effects • Equipment Design effects

5. Properties of Biological Materials • Basic Concepts • Properties of Selected Biological Materials • Bone • Articular Cartilage • Ligaments & Muscle-Tendon Units

6. Structural Properties Load-deformation relationships of like tissues Material Properties Stress-strain relationships of different tissues Structural vs. Material Properties

7. Terminology • load – the sum of all the external forces and moments acting on the body or system • deformation – local changes of shape within a body

8. Load-deformation relationship • Changes in shape (deformation) experienced by a tissue or structure when it is subjected to various loads

9. Extent of deformation dependent on: • Size and shape (geometry) • Material • Structure • Environmental factors (temperature, humidity) • Nutrition • Load application • Magnitude, direction, and duration of applied force • Point of application (location) • Rate of force application • Frequency of load application • Variability of magnitude of force

10. Uniaxial Loads Axial Compression Tension Shear Multiaxial Loads Biaxial loading responses Triaxial loading responses Bending Torsion Types of Loads

11. Types of Loads

12. Axial Loads Whiting & Zernicke (1998)

13. Shear Loads Whiting & Zernicke (1998)

14. Axial Loads Create shear load as well Whiting & Zernicke (1998)

15. Biaxial & Triaxial Loads Whiting & Zernicke (1998)

16. Structural Properties Load-deformation relationships of like tissues Material Properties Stress-strain relationships of different tissues Structural vs. Material Properties

17. Terminology – Stress ()  = F/A (N/m2 or Pa) • normalized load • force applied per unit area, where area is measured in the plane that is perpendicular to force vector (CSA)

18. Terminology – Strain ()  = dimension/original dimension • normalized deformation • change in shape of a tissue relative to its initial shape

19. How are Stress () and Strain () related? • “Stress is what is done to an object, strain is how the object responds”. • Stress and Strain are proportional to each other. Modulus of elasticity = stress/strain

20. Typical Stress-Strain Curve

21. Elastic region & Plastic region

22. Stiffness Fig. 3.26a, Whiting & Zernicke, 1998

23. Stiffness (Elastic Modulus)

24. A B C Load (N) 1 5 10 15 20 25 1 2 3 4 5 6 7 Deformation (cm)

25. Strength stiffness ≠ strength • Yield • Ultimate Strength • Failure

26. Apparent vs. Actual Strain 1. Ultimate Strength2. Yield Strength3. Rupture4. Strain hardening region5. Necking regionA: Apparent stress B: Actual stress

27. Tissue Properties A B C Load (N) 1 5 10 15 20 25 Deformation (cm)

28. Extensibility & Elasticity

29. Extensibility A ligament tendon B C Load (N) 1 5 10 15 20 25 1 2 3 4 5 6 7 Deformation (cm)

30. Rate of Loading • Bone is stiffer, sustains a higher load to failure, and stores more energy when it is loaded with a high strain rate.

31. Stiffness Strength Elasticity Ductility Brittleness Malleability Toughness Resilience Hardness Bulk mechanical properties

32. Ductility • Characteristic of a material that undergoes considerable plastic deformation under tensile load before rupture • Can you draw???

33. Brittleness • Absence of any plastic deformation prior to failure • Can you draw???

34. Malleability • Characteristic of a material that undergoes considerable plastic deformation under compressive load before rupture • Can you draw???

35. Resilience

36. Toughness

37. Hardness • Resistance of a material to scratching, wear, or penetration

38. Uniqueness of Biological Materials • Anisotropic • Viscoelastic • Time-dependent behavior • Organic • Self-repair • Adaptation to changes in mechanical demands

39. …blast – produce matrix …clast – resorb matrix …cyte – mature cell synthesis & maintenance defense & clean up determines the functional characteristics of the connective tissue Distinguishes CT from other tissues

40. Collagen Great tensile strength 1 mm2 cross-section  withstand 980 N tension Cross-linked structure   stiffness Tensile strain ~ 8-10% Weak in torsion and bending Elastin Great extensibility Strain ~ 200% Lack of creep Collagen vs. Elastin

41. Bind cells • Mechanical links • Resist tensile loads • Number & type of cells • Proportion of collagen, elastin, & ground substance • Arrangement of protein fibers

42. Why study? • Design structures that are safe against the combined effects of applied forces and moments • Selection of proper material • Determine safe & efficient loading conditions

43. Application • Injury occurs when an imposed load exceeds the tolerance (load-carrying ability) of a tissue • Training effects • Drug effects • Equipment Design effects

44. Properties of Biological Materials • Basic Concepts • Properties of Selected Biological Materials • Bone • Articular Cartilage • Ligaments & Muscle-Tendon Units

45. Mechanical Properties of Bone • General • Nonhomogenous • Anisotropic • Strongest • Stiffest • Tough • Little elasticity

46. Material Properties: Bone Tissue • Cortical: Stiffer, stronger, less elastic (~2% vs. 50%), low energy storage

47. Mechanical Properties of Bone • Ductile vs. Brittle • Depends on age and rate at which it is loaded • Younger bone is more ductile • Bone is more brittle at high speeds

48. Metal Glass  Bone  • Stiffest? • Strongest? • Brittle? • Ductile? young old

49. Tensile Properties: Bone Stiffness

50. Compressive Properties: Bone 78.8-144 6.0-17.6 1.4-4.0 140-174 18.4 146-165.6