Applied%20Human%20Anatomy%20and%20Biomechanics

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Applied Human Anatomy and Biomechanics
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Course Content

1. Introduction to the Course
2. Biomechanical Concepts Related to Human Movement
3. Anatomical Concepts Principles Related to the
   Analysis of Human Movement
4. Applications in Human Movement
5. Properties of Biological Materials
6. Functional Anatomy of Selected Joint Complexes

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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

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Application

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

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Properties of Biological Materials

1. Basic Concepts
2. Properties of Selected Biological Materials
3. Bone
4. Articular Cartilage
5. Ligaments Muscle-Tendon Units

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Structural vs. Material Properties

• Material Properties
• Stress-strain relationships of different tissues

• Structural Properties
• Load-deformation relationships of like tissues

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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

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Load-deformation relationship

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

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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

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Types of Loads

• Uniaxial Loads
• Axial
• Compression
• Tension
• Shear

• Multiaxial Loads
• Biaxial loading responses
• Triaxial loading responses
• Bending
• Torsion

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Types of Loads
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Axial Loads
Whiting Zernicke (1998)
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Shear Loads
Whiting Zernicke (1998)
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Axial Loads
Create shear load as well
Whiting Zernicke (1998)
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Biaxial Triaxial Loads
Whiting Zernicke (1998)
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Structural vs. Material Properties

• Structural Properties
• Load-deformation relationships of like tissues

• Material Properties
• Stress-strain relationships of different tissues

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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)

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Terminology Strain (?)

• ? ?dimension/original dimension
• normalized deformation
• change in shape of a tissue relative to its
  initial shape

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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

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Typical Stress-Strain Curve
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Elastic region Plastic region
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Stiffness
Fig. 3.26a, Whiting Zernicke, 1998
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Stiffness (Elastic Modulus)
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A
B
C
Load (N)
1 5 10 15 20
25
1 2 3 4 5
6 7
Deformation (cm)
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Strength
stiffness ? strength

• Yield
• Ultimate
• Strength
• Failure

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Apparent vs. Actual Strain
1. Ultimate Strength2. Yield Strength3.
Rupture4. Strain hardening region5. Necking
regionA Apparent stress B Actual stress
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Tissue Properties
A
B
C
Load (N)
1 5 10 15 20
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Deformation (cm)
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Extensibility Elasticity
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Extensibility
A
ligament
tendon
B
C
Load (N)
1 5 10 15 20
25
1 2 3 4 5
6 7
Deformation (cm)
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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.

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Bulk mechanical properties

• Stiffness
• Strength
• Elasticity
• Ductility
• Brittleness

• Malleability
• Toughness
• Resilience
• Hardness

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Ductility

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

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Brittleness

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

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Malleability

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

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Resilience
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Toughness
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Hardness

• Resistance of a material to scratching, wear, or
  penetration

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Uniqueness of Biological Materials

• Anisotropic
• Viscoelastic
• Time-dependent behavior
• Organic
• Self-repair
• Adaptation to changes in mechanical demands

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blast produce matrix clast resorb
matrix cyte mature cell
Distinguishes CT from other tissues
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Collagen vs. Elastin

• Elastin
• Great extensibility
• Strain 200
• Lack of creep

• 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

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• Bind cells
• Mechanical links
• Resist tensile loads

• Number type of cells
• Proportion of collagen, elastin, ground
  substance
• Arrangement of protein fibers

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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

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Application

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

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Properties of Biological Materials

1. Basic Concepts
2. Properties of Selected Biological Materials
3. Bone
4. Articular Cartilage
5. Ligaments Muscle-Tendon Units

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Mechanical Properties of Bone

• General
• Nonhomogenous
• Anisotropic
• Strongest
• Stiffest
• Tough
• Little elasticity

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Material Properties Bone Tissue

• Cortical Stiffer, stronger, less elastic (2
  vs. 50), low energy storage

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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

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• Stiffest?
• Strongest?
• Brittle?
• Ductile?

young
old
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Tensile Properties Bone
Stiffness
Ultimate stress (MPa) Modulus of elasticity (GPa) Strain to Fracture ()
Collagen 50 1.2 -
Osteons 38.8-116.6 - -
Axial
Femur (slow) (fast) 78.8-144 6.0-17.6 1.4-4.0
Tibia (slow) 140-174 18.4 1.5
Fibula (slow) 146-165.6 - -
Transverse
Femur (fast) 52 11.5 -
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Compressive Properties Bone
Ultimate stress (MPa) Modulus of elasticity (GPa) Strain to Fracture ()
Osteons 48-93 - -
Axial
Mixed 100-280 - 1-2.4
Femur 170-209 8.7-18.6 1.85
Tibia 213 15.2-35.3 -
Fibula 115 16.6 -
Transverse
Mixed 106-133 4.2 -
78.8-144
1.4-4.0
6.0-17.6
140-174
18.4
146-165.6
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Other Bone
Ultimate stress (MPa) Modulus of elasticity (GPa) Strain to Fracture ()
Shear 50-100 3.58 -
Bending 132-181 10.6-15.8 -
Torsion 54.1 3.2-4.5 0.4-1.2
Tension 78.8-174 6.0-18.4 1.4-4.0
Compression 100-280 8.7-35.3 1-2.4
From LeVeau (1992). Biomechanics of human motion
(3rd ed.). Philadelphia W.B. Saunders.
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Mechanical Properties of Selected Biomaterials
Ultimate stress (MPa) Modulus of elasticity (GPa) Strain to Fracture ()
Polymers (bone cement) 20 2.0 2-4
Ceramic (Alumina) 300 350 lt2
Titanium 900 110 15
Metals (Co-Cr alloy) Cast Forged Stainless steel 600 950 850 220 220 210 8 15 10
Cortical bone 100-150 10-15 1-3
Trabecular bone 8-50 - 2-4
Bones (mixed) 100-280 8.7-35.3 1-2.4
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Viscoelastic Properties Rate Dependency of
Cortical Bone

• With ? loading rate

• ? brittleness
• Energy storage ? 2X (? toughness)
• Rupture strength ? 3X
• Rupture strain ?100
• Stiffness ? 2X

Fig 2-34, Nordin Frankel, (2001)
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Viscoelastic Properties Rate Dependency of
Cortical Bone

• With ? loading rate

• More energy to be absorbed, so fx pattern changes
  amt of soft tissue damage ?

Fig 2-34, Nordin Frankel, (2001)
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Effect of Structure

• Larger CSA distributes force over larger area,
• ? stress
• Tubular structure (vs. solid)
• More evenly distributes bending torsional
  stresses because the structural material is
  distributed away from the central axis
• ? bending stiffness without adding large amounts
  of bone mass
• Narrower middle section (long bones)
• ? bending stresses minimizes chance of fracture

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Effects of Acute Physical Activity
Fig 2-32a, Nordin Frankel (2001)
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Acute Physical Activity

• Tensile strength 140-174 MPa
• Comp strength 213 MPa
• Shear strength 50-100 MPa

Fig 2-32b, Nordin Frankel (2001)
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Acute Physical Activity

• As speed ?, ? and ? ?
• 5X? in ? with speed
• ?walk 0.001/s
• ?slow jog 0.03/s

Fig 2-32b, Nordin Frankel (2001)
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Acute Physical Activity

• In vivo, muscle contraction can exaggerate or
  mitigate the effect of external forces

Fig 2-33, Nordin Frankel (2001)
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Chronic Physical Activity

• ? bone density,
• ? compressive strength
• ? stiffness (to a certain threshold)

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Chronic Disuse

• ? bone density (1/wk for bed rest)
• ? strength
• ? stiffness

Fig 2-47, Nordin Frankel (2001)
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Repetitive Physical Activity
Muscle Fatigue
? Ability to Neutralize Stresses on Bone

• Injury cycle

? Load on Bone
? Tolerance for Repetitions
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Repetitive Physical Activity
Fig 2-38, Nordin Frankel (2001)
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Applications for Bone Injury

• Crack propagation occurs more easily in the
  transverse than in the longitudinal direction
• Bending
• For adults, failure begins on tension side, since
  tension strength lt compression strength
• For youth, failure begins on compression side,
  since immature bone more ductile
• Torsion
• Failure begins in shear, then tension direction

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Effects of Age

• ? brittleness
• ? strength
• (? cancellous bone thickness of cortical bone)
• ? ultimate strain
• ? energy storage

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Effects of Age on Yield Ultimate Stresses
(Tension)
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Effects of Age on Eelastic (Tension)
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Effects of Age on Ultimate Strain (Tension)
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Effects of Age on Energy (Tension)
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Properties of Biological Materials

1. Basic Concepts
2. Properties of Selected Biological Materials
3. Bone
4. Articular Cartilage
5. Ligaments Muscle-Tendon Units

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• Deforms more than bone since is 20X less stiff
  than bone
• ? congruency
• High water content causes even distribution of
  stress
• High elasticity in the direction of joint motion
  and where joint pressure is greatest
• Compressibility is 50-60

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Tensile Properties Cartilage
Ultimate stress (MPa) Modulus of elasticity (GPa) Strain to Fracture ()
Tension 4.41 - 10-100
Superficial 10-40 0.15-0.5 -
Deep 0-30 0-0.2 -
Costal 44 - 25.9
Disc 2.7 - -
Annulus 15.68 - -
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Compressive Properties Cartilage
Ultimate stress (MPa) Modulus of elasticity (GPa) Strain to Fracture ()
Compression 7-23 0.012-0.047 3-17
Patella - 0.00228 -
Femoral head - 0.0084-0.0153 -
Costal - - 15.0
Disc 11 - -
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Other Loading Properties Cartilage
Ultimate stress(MPa) Modulus of elasticity (GPa) Strain to Fracture ()
Shear
Normal - 0.00557-0.01022 -
Degenerated - 0.00137-0.00933 -
Torsion
Femoral - 0.01163 -
Disc 4.5-5.1 - -
Tension
From LeVeau (1992). Biomechanics of human motion
(3rd ed.). Philadelphia W.B. Saunders.
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Properties of Biological Materials

1. Basic Concepts
2. Properties of Selected Biological Materials
3. Bone
4. Articular Cartilage
5. Ligaments Muscle-Tendon Units
6. Skeletal Muscle

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Structure and Function Architecture

• The arrangement of collagen fibers differs
  between ligaments and tendons. What is the
  functional significance?

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Biomechanical Properties and Behavior

• Tendons withstand unidirectional loads
• Ligaments resist tensile stress in one
  direction and smaller stresses in other
  directions.

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Viscoelastic Properties Rate Dependent Behavior

• Moderate strain-rate sensitivity
• With ? loading rate
• Energy storage ? (? toughness)
• Rupture strength ?
• Rupture strain ?
• Stiffness ?

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Viscoelastic Properties Repetitive Loading
Effects

• ? stiffness

Enoka (2002), Figure 5.3, p. 219, From Butler et
al. (1978)
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Idealized Stress-Strain for Collagenous Tissue
Very small plastic region
Enoka (2002), Figure 5.3, p. 219, From Butler et
al. (1978)
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Ligamentum flavum
Nordin Frankel (2001), Figure 4-10, p. 110,
From Nachemson Evans (1968)
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Tensile Properties Ligaments
Ultimate stress (MPa) Modulus of elasticity (GPa) Strain to Fracture ()
Nonelastic 60-100 0.111 5-14
ACL 37.8 - 23-35.8
Anterior Longitudinal .0123
Collagen 50 1.2 -
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Viscoelastic Behavior of Bone-Ligament-Bone
Complex

• Fast loading rate
• Ligament weakest
• Slow loading rate
• Bony insertion of ligament weakest
• Load to failure ? 20
• Energy storage ? 30
• Stiffness similar

As loading rate ?, bone strength ? more than
ligament strength.
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Ligament-capsule injuries

• Sprains
• 1st degree 25 tissue failure no clinical
  instability
• 2nd degree 50 tissue failure 50? in strength
  stiffness
• 3rd degree 75 tissue failure easily
  detectable instabilty
• Bony avulsion failure (young people more likely
  if tensile load applied slowly)

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Tensile Properties Muscles Tendons
Ultimate stress (MPa) Modulus of elasticity (GPa) Strain to Fracture ()
Muscle 0.147-3.50 - 58-65
Fascia 15 - -
Tendon
Various 45-125 0.8-2.0 8-10
Various 50-150 - 9.4-9.9
Various 19.1-88.5 - -
Mammalian 0.8-2
Achilles 34-55 - -
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Enoka (2002), Figure 5.12, p. 227, From Noyes
(1977) Noyes et al. (1984)
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EDL Tendon
Enoka (2002), Figure 3.9, p. 134, From Schechtman
Bader (1997)
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ECRB Achilles
Max muscle force (N) 58.00 5000.0
Tendon length (mm) 204.00 350.0
Tendon thickness (mm2) 14.60 65.0
Elastic modulus (MPa) 726.00 1500.0
Stress (MPa) 4.06 76.9
Strain () 2.70 5.0
Stiffness (N/cm) 105.00 2875.0
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Muscle-Tendon Interaction

• Stiffer tendon ? more brisk, accurate movements
• Less stiff, ? muscle contraction velocity, ?
  efficiency
• ? tendon compliance, small ? muscle length (as
  compared to ? M-T unit length
• High resilience
• Limited viscoelastic behavior, therefore, tendon
  in major site of storage of elastic energy in M-T
  unit
• Tensile strength of tendon 2X that of its muscle

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Role of Elasticity in Human Movement

• Elasticity of tendon
• responsible for force transfer from muscle to
  bone
• enables storage and release of energy, reducing
  metabolic cost
• Material structural properties of tendon
  determine the amount of resistance to stretch
  and, thus, amount of elastic force transferred to
  bone

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Muscle Mechanical Stiffness

• Instantaneous rate of change of force with length
• Unstimulated muscles are very compliant
• Stiffness increases with tension
• High rates of change of force have high muscle
  stiffness, particularly during eccentric actions
• Stiffness controlled by stretch and tendon
  reflexes

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Effects of Disuse
Nordin Frankel (2001), Figure 4-15a, p. 110,
From Noyes (1977)
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Effects of Disuse
Nordin Frankel (2001), Figure 4-15b, p. 110,
From Noyes (1977)
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Effects of corticosteroids

• ? stiffness
• ? rupture strength
• ? energy absorption
• Time dosage dependent

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Effect of Structure
Whiting Zernicke (1998), Figure 4.8a,b, p. 104,
From Butler et al. (1978).
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Miscellaneous Effects

• Age effects
• More compliant / less strong before maturity
• Insertion site becomes weak link in middle age
• ? stiffness strength in pregnancy in rabbits
• Hormonal?

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Summary

• Mechanical properties of biological materials
  vary across tissues and structures due to
  material and geometry differences.
• Understanding how age, physical activity,
  nutrition, and disease alter mechanical
  properties enables us to design appropriate
  interventions and rehabilitations.
• Understanding these mechanical properties allows
  us to design appropriate prosthetic devices to
  for joint replacement and repair.