Applied Human Anatomy and Biomechanics

Applied Human Anatomy and

Biomechanics

Course Content

I. Introduction to the CourseII. Biomechanical Concepts Related to

Human MovementIII. Anatomical Concepts & Principles Related

to the Analysis of Human MovementIV. Applications in Human MovementV. Properties of Biological MaterialsVI. 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

ApplicationInjury occurs when an imposed

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 MaterialsA. Bone

B. Articular Cartilage

C. Ligaments & Muscle-Tendon Units

Structural vs. Material Properties

Structural Properties Load-deformation

relationships of like tissues

Material Properties Stress-strain

relationships of 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

Axial Compression Tension

Shear

Multiaxial Loads

Biaxial loading responses

Triaxial loading responses

Bending Torsion

Types of Loads

Axial Loads

Whiting & Zernicke (1998)

Shear Loads


Axial Loads

Create shear load as well


Biaxial & Triaxial Loads


Structural vs. Material Properties

Structural Properties Load-deformation

relationships of like tissues

Material Properties Stress-strain

relationships of 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

kxFe

Elastic region & Plastic region

Stiffness

Fig. 3.26a, Whiting & Zernicke, 1998

Stiffness (Elastic Modulus)

Lo

ad (

N)

Deformation (cm)

1

5

10

15

20

25

A

B C

1 2 3 4 5 6 7

Strength stiffness ≠ strength

•Yield•Ultimate Strength•Failure

Apparent vs. Actual Strain

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

http://en.wikipedia.org/wiki/Yield_(engineering)

http://en.wikipedia.org/wiki/Rupture

http://en.wikipedia.org/wiki/Strain_hardening

http://en.wikipedia.org/wiki/Necking_(engineering)

Tissue PropertiesL

oad

(N

)

Deformation (cm)

1

5

10

15

20

25

A

B C

Extensibility & Elasticity

ExtensibilityL

oad

(N

)

Deformation (cm)

1

5

10

15

20

25

A

B C

1 2 3 4 5 6 7

ligament tendon

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 Strength Elasticity Ductility Brittleness

Malleability Toughness Resilience Hardness

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

General Structure of Connective Tissue

Cellular Component Extracellular Matrix

Protein Fibers

collagen, elastin

Ground Substance

(Fluid)

Resident Cells

fibroblasts, osteocytes,

chondroblasts, etc.

Circulating Cells

lymphocytes, macrophages, etc.

synthesis &maintenance

defense &clean up

determines the functional

characteristics of the connective tissue

Distinguishes CT from other tissues

…blast – produce matrix…clast – resorb matrix…cyte – mature cell

Collagen vs. Elastin

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

Types of Connective Tissue

Types of Connective Tissue

OrdinaryOrdinary SpecialSpecial

Irregular OrdinaryIrregular Ordinary Regular OrdinaryRegular Ordinary CartilageCartilage BoneBone

Regular CollagenousRegular Collagenous

Regular ElasticRegular Elastic

LooseLoose

AdiposeAdipose

Irregular CollagenousIrregular Collagenous

Irregular ElasticIrregular Elastic

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

•Bind cells•Mechanical links•Resist tensile loads

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

ApplicationInjury occurs when an imposed

load exceeds the tolerance (load-carrying ability) of a tissue Training effects Drug effects Equipment Design effects


A. Basic Concepts




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

Glass

Bone

Metal

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

old

young

Tensile Properties: Bone

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 -

Stiffness

Compressive Properties: Bone




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 -

140-174

146-165.6

78.8-144 1.4-4.06.0-17.6

18.4

Other: Bone


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.




Polymers (bone cement)

20 2.0 2-4

Ceramic (Alumina) 300 350 <2

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

Mechanical Properties of Selected Biomaterials

Viscoelastic Properties :Rate Dependency of Cortical Bone

Fig 2-34, Nordin & Frankel, (2001)

•With loading rate:

brittleness Energy storage 2X (

toughness) Rupture strength 3X Rupture strain 100% Stiffness 2X

Viscoelastic Properties :Rate Dependency of Cortical Bone

Fig 2-34, Nordin & Frankel, (2001)

•With loading rate:

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

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

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

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


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

•As speed , and •5X in with speedwalk = 0.001/s

slow jog = 0.03/s


Fig 2-33, Nordin & Frankel (2001)

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

Chronic Physical Activity

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

Chronic Disuse

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


Repetitive Physical Activity

Injury cycle

Muscle Fatigue

Ability to Neutralize Stresses on Bone

Load on Bone

Tolerance for Repetitions

Repetitive Physical Activity


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)

100

110

120

130

140

150

160

170

180

20-29 30-39 40-49 50-59 60-69 70-79 80-89

Age (yrs)

Str

es

s (

MP

a)

Femur - Yield Tibia - Yield Femur - Ultimate Tibia - Ultimate

Effects of Age on Eelastic (Tension)

10.0

15.0

20.0

25.0

30.0

35.0

20-29 30-39 40-49 50-59 60-69 70-79 80-89

Age (yrs)

Elas

tic

Mo

du

lus

(G

Pa)

Femur Tibia

0.000

0.005

0.010

0.015

0.020

0.025

0.030

0.035

0.040

0.045

20-29 30-39 40-49 50-59 60-69 70-79 80-89

Age (yrs)

Ult

imat

e S

trai

n

Femur Tibia

Effects of Age on Ultimate Strain (Tension)

2

2.5

3

3.5

4

4.5

5

5.5

6

20-29 30-39 40-49 50-59 60-69 70-79 80-89

Age (yrs)

Ene

rgy

(MP

a)

Femur Tibia

Effects of Age on Energy (Tension)


A. Basic Concepts




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




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




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 stress(MPa)



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.


A. Basic Concepts




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

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

stiffness

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

Idealized Stress-Strain

for Collagenous

Tissue

Very small plastic region

Ligamentum flavum

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

Tensile Properties: Ligaments




Nonelastic 60-100 0.111 5-14

ACL 37.8 - 23-35.8

Anterior

Longitudinal

.0123

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

Sprains1st degree – 25% tissue failure; no clinical

instability2nd degree – 50% tissue failure; 50% in

strength & stiffness3rd degree – 75% tissue failure; easily

detectable instabilty Bony avulsion failure (young people –

more likely if tensile load applied slowly)

Tensile Properties: Muscles & Tendons




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)

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

EDL Tendon

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.

Date post:	19-Jan-2016
Category:	Documents
Upload:	paulos
View:	104 times
Download:	1 times

Applied Human Anatomy and Biomechanics

Documents