Applied Human Anatomy and Biomechanics by zku40248

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									Applied Human
  Anatomy and
 Biomechanics
Course Content
I.   Introduction to the Course
II.  Biomechanical Concepts Related to
     Human Movement
III. Anatomical Concepts & Principles Related
     to the Analysis of Human Movement
IV. Applications in Human Movement
V. Properties of Biological Materials
VI. Functional Anatomy of Selected Joint
     Complexes
Why study?
   Design structures that are safe against the
    combined effects of applied forces and
    moments

1. Selection of proper material
2. Determine safe & efficient loading conditions
Application
       occurs when an imposed
 Injury
 load exceeds the tolerance (load-
 carrying ability) of a tissue
    Training effects
    Drug effects
    Equipment Design effects
Properties of Biological Materials
A. Basic Concepts
B. Properties of Selected Biological Materials
  A. Bone
  B. Articular Cartilage
  C. Ligaments & Muscle-Tendon Units
Structural vs. Material
Properties
Structural Properties          Material Properties
 Load-deformation            Stress-strain
   relationships of like       relationships of
   tissues                     different tissues
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
Load-deformation relationship
   Changes in shape (deformation) experienced
    by a tissue or structure when it is subjected to
    various loads
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
Types of Loads
        Uniaxial Loads         Multiaxial Loads

   Axial                   Biaxial loading
       Compression          responses
       Tension             Triaxial loading
   Shear                    responses
                            Bending
                            Torsion
Types of Loads
Axial Loads




              Whiting & Zernicke (1998)
Shear Loads




              Whiting & Zernicke (1998)
    Axial Loads



                            Create
                            shear
                            load as
                            well


Whiting & Zernicke (1998)
Biaxial & Triaxial Loads




                           Whiting & Zernicke (1998)
Structural vs. Material
Properties
Structural Properties          Material Properties
 Load-deformation            Stress-strain
   relationships of like       relationships of
   tissues                     different tissues
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)
Terminology – Strain ()


                      = dimension/original
                             dimension

                        normalized
                         deformation
                        change in shape of a
                         tissue relative to its
                         initial shape
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
Typical Stress-Strain Curve


                        Fe  kx
Elastic region & Plastic region
Stiffness




            Fig. 3.26a, Whiting & Zernicke, 1998
Stiffness (Elastic Modulus)
           25


                                                   A
           20
Load (N)




                                               B
           15




                                                       C
           10
           5
           1




                1   2   3     4      5     6   7
                        Deformation (cm)
Strength   stiffness ≠ strength



                            •Yield
                            •Ultimate
                             Strength
                            •Failure
Apparent vs. Actual Strain

                    1. Ultimate Strength
                    2. Yield Strength
                    3. Rupture
                    4. Strain hardening
                    region
                    5. Necking region
                    A: Apparent stress
                    B: Actual stress
Tissue Properties
            25


                                        A
            20
 Load (N)




                                    B
            15




                                            C
            10
            5
            1




                 Deformation (cm)
Extensibility & Elasticity
Extensibility
             25


                                                        A
             20




                                         ligament           tendon
  Load (N)




                                                 B
             15




                                                                 C
             10
             5
             1




                  1   2   3     4      5     6      7
                          Deformation (cm)
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.
Bulk mechanical properties
   Stiffness        Malleability
   Strength         Toughness
   Elasticity       Resilience
   Ductility        Hardness
   Brittleness
Ductility
   Characteristic of a material that undergoes
    considerable plastic deformation under
    tensile load before rupture
   Can you draw???
Brittleness
   Absence of any plastic
    deformation prior to
    failure
   Can you draw???
Malleability
   Characteristic of a material that undergoes
    considerable plastic deformation under
    compressive load before rupture
   Can you draw???
Resilience
Toughness
Hardness
   Resistance of a material to scratching, wear,
    or penetration
Uniqueness of Biological
Materials
   Anisotropic
   Viscoelastic
       Time-dependent behavior
   Organic
       Self-repair
       Adaptation to changes in mechanical demands
…blast – produce matrix
…clast – resorb matrix                                          Distinguishes
…cyte – mature cell                                             CT from other
                             General Structure of               tissues
                              Connective Tissue

           Cellular Component                         Extracellular Matrix

   Resident Cells
                        Circulating Cells
                                             Protein Fibers            Ground
    fibroblasts,                                                      Substance
                        lymphocytes,
    osteocytes,                             collagen, elastin           (Fluid)
                       macrophages, etc.
 chondroblasts, etc.




   synthesis &          defense &                   determines the
   maintenance           clean up             functional characteristics
                                               of the connective tissue
Collagen vs. Elastin
         Collagen                         Elastin
   Great tensile strength        Great extensibility
   1 mm2 cross-section 
    withstand 980 N tension
   Cross-linked structure 
     stiffness
   Tensile strain ~ 8-10%        Strain ~ 200%
   Weak in torsion and           Lack of creep
    bending
•Bind cells
•Mechanical links                       Types of
•Resist tensile loads                Connective Tissue
                               Ordinary                                Special

Irregular Ordinary               Regular Ordinary          Cartilage             Bone

                     Loose                   Regular Collagenous

                     Adipose                    Regular Elastic

             Irregular Collagenous

               Irregular Elastic




•Number & type of cells
•Proportion of collagen, elastin, & ground substance
•Arrangement of protein fibers
Why study?
   Design structures that are safe against the
    combined effects of applied forces and
    moments

1. Selection of proper material
2. Determine safe & efficient loading conditions
Application
       occurs when an imposed
 Injury
 load exceeds the tolerance (load-
 carrying ability) of a tissue
    Training effects
    Drug effects
    Equipment Design effects
Properties of Biological Materials
A. Basic Concepts
B. Properties of Selected Biological Materials
  A. Bone
  B. Articular Cartilage
  C. Ligaments & Muscle-Tendon Units
Mechanical Properties of Bone
   General
       Nonhomogenous
       Anisotropic
   Strongest
   Stiffest
   Tough
   Little elasticity
Material Properties: Bone Tissue
   Cortical: Stiffer, stronger, less elastic (~2% vs.
              50%), low energy storage
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
                      Metal



          Glass           •Stiffest?
                          •Strongest?
                         •Brittle?
                          •Ductile?

                  young
    old
             Bone


            
Tensile Properties: Bone
                                    Stiffness
                    Ultimate       Modulus of         Strain to
                  stress (MPa)   elasticity (GPa)   Fracture (%)

Collagen              50               1.2               -
Osteons            38.8-116.6           -                -
Axial
  Femur (slow)      78.8-144        6.0-17.6          1.4-4.0
         (fast)
  Tibia (slow)      140-174           18.4              1.5
  Fibula (slow)    146-165.6            -                -
Transverse
  Femur (fast)        52              11.5               -
Compressive Properties: Bone
                 Ultimate       Modulus of         Strain to
               stress (MPa)   elasticity (GPa)   Fracture (%)
Osteons           48-93              -                -
Axial
   Mixed         100-280             -              1-2.4
   Femur78.8-144 170-209 6.0-17.6 8.7-18.6 1.4-4.0 1.85
   Tibia 140-174 213        18.4 15.2-35.3           -
   Fibula 146-165.6 115            16.6               -
Transverse
   Mixed         106-133            4.2               -
 Other: Bone
                            Ultimate           Modulus of               Strain to
                             stress             elasticity              Fracture
                             (MPa)                (GPa)                    (%)
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.
 Mechanical Properties of Selected Biomaterials
                         Ultimate     Modulus of       Strain to
                       stress (MPa) elasticity (GPa) Fracture (%)
Polymers (bone             20             2.0            2-4
cement)
Ceramic (Alumina)          300            350            <2
Titanium                   900            110            15
Metals (Co-Cr alloy)
 Cast                      600            220             8
 Forged                    950            220            15
 Stainless steel           850            210            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
     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)
    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)
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
    Effects of Acute Physical Activity




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




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




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



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



Fig 2-33, Nordin & Frankel (2001)
Chronic Physical Activity
    bone density,
    compressive strength
    stiffness (to a certain threshold)
    Chronic Disuse




    bone density (1%/wk for bed rest)
    strength
    stiffness                   Fig 2-47, Nordin & Frankel (2001)
Repetitive Physical Activity
                     Muscle Fatigue




          Ability to Neutralize Stresses on Bone
Injury
cycle
                      Load on Bone




                Tolerance for Repetitions
    Repetitive Physical Activity




Fig 2-38, Nordin & Frankel (2001)
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 < compression strength
       For youth, failure begins on compression side,
        since immature bone more ductile
   Torsion
       Failure begins in shear, then tension direction
Effects of Age
    brittleness
    strength
       ( cancellous bone & thickness of cortical bone)
    ultimate strain
    energy storage
               Effects of Age on Yield & Ultimate
               Stresses (Tension)
               180


               170


               160


               150
Stress (MPa)




               140


               130


               120


               110


               100
                     20-29          30-39    40-49            50-59       60-69          70-79          80-89
                                                        Age (yrs)

                             Femur - Yield    Tibia - Yield           Femur - Ultimate           Tibia - Ultimate
Effects of Age on Eelastic (Tension)
                         35.0



                         30.0
 Elastic Modulus (GPa)




                         25.0



                         20.0



                         15.0



                         10.0
                                20-29   30-39   40-49     50-59        60-69   70-79   80-89
                                                        Age (yrs)

                                                        Femur       Tibia
Effects of Age on Ultimate Strain (Tension)

                   0.045

                   0.040

                   0.035

                   0.030
Ultim ate Strain




                   0.025

                   0.020

                   0.015

                   0.010

                   0.005

                   0.000
                           20-29   30-39   40-49     50-59        60-69   70-79   80-89
                                                   Age (yrs)

                                                   Femur       Tibia
Effects of Age on Energy (Tension)
                6


               5.5


                5


               4.5
Energy (MPa)




                4


               3.5


                3


               2.5


                2
                     20-29   30-39   40-49     50-59         60-69   70-79   80-89
                                             Age (yrs)


                                             Femur       Tibia
Properties of Biological Materials
A. Basic Concepts
B. Properties of Selected Biological Materials
  A. Bone
  B. Articular Cartilage
  C. Ligaments & Muscle-Tendon Units
   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%
Tensile Properties: Cartilage

                  Ultimate       Modulus of         Strain to
                stress (MPa)   elasticity (GPa)   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              -                -
Compressive Properties:
Cartilage
                   Ultimate       Modulus of         Strain to
                 stress (MPa)   elasticity (GPa)   Fracture (%)

Compression         7-23          0.012-0.047         3-17
  Patella             -             0.00228             -
  Femoral head        -         0.0084-0.0153           -
  Costal              -                -              15.0
  Disc               11                -                -
 Other Loading Properties:
 Cartilage
                           Ultimate             Modulus of               Strain to
                         stress(MPa)          elasticity (GPa)         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.
Properties of Biological Materials
A. Basic Concepts
B. Properties of Selected Biological Materials
  A.   Bone
  B.   Articular Cartilage
  C.   Ligaments & Muscle-Tendon Units
  D.   Skeletal Muscle
Structure and Function:
Architecture
   The arrangement
    of collagen fibers
    differs between
    ligaments and
    tendons. What is
    the functional
    significance?
Biomechanical Properties and
Behavior
   Tendons: withstand
    unidirectional loads
   Ligaments: resist
    tensile stress in one
    direction and smaller
    stresses in other
    directions.
Viscoelastic Properties :
Rate Dependent Behavior
   Moderate strain-rate sensitivity
   With  loading rate:
       Energy storage  ( toughness)
       Rupture strength 
       Rupture strain 
       Stiffness 
     Viscoelastic Properties:
     Repetitive Loading Effects




                                                              • stiffness




Enoka (2002), Figure 5.3, p. 219, From Butler et al. (1978)
                                                                Idealized
                                         Very small           Stress-Strain
                                         plastic                   for
                                         region               Collagenous
                                                                 Tissue




Enoka (2002), Figure 5.3, p. 219, From Butler et al. (1978)
    Ligamentum flavum




Nordin & Frankel (2001), Figure 4-10, p. 110, From Nachemson & Evans (1968)
Tensile Properties: Ligaments

                 Ultimate       Modulus of         Strain to
               stress (MPa)   elasticity (GPa)   Fracture (%)
Nonelastic       60-100            0.111            5-14
ACL                37.8              -             23-35.8
Anterior                           .0123
Longitudinal
Collagen           50               1.2               -
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.
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)
Tensile Properties:
Muscles & Tendons
                Ultimate       Modulus of         Strain to
              stress (MPa)   elasticity (GPa)   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              -                -
Enoka (2002), Figure 5.12, p. 227, From Noyes (1977); Noyes et al. (1984)
                         EDL Tendon




Enoka (2002), Figure 3.9, p. 134,
From Schechtman & Bader (1997)
                         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
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
    Effects of Disuse




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




Nordin & Frankel (2001), Figure 4-15b, p. 110, From Noyes (1977)
Effects of corticosteroids
    stiffness
    rupture strength
    energy absorption

   Time & dosage dependent
     Effect of Structure




Whiting & Zernicke (1998), Figure 4.8a,b, p. 104, From Butler et al. (1978).
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?
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.

								
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