PS 1001:03 Lecture Notes - Lecture 6: Haversian Canal, Ultimate Tensile Strength, Hyaline Cartilage
Apply knowledge of bone structure to biomechanical
properties
Bones - osteology
Supportive framework for whole body
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Protection
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Attachment of muscles, tendons, ligaments and fascia
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Forms system of levers - allows movement of the joints
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RBC formation in marrow, WBC and platelets
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Mineral store - Ca, P, carbonate, Mg, F, all stored as salts with the bone structure
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Functions
Epiphysis - widened ends
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Articular hyaline cartilage
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Compact bone - outer shell, solid, compact, mineralised connective tissue with low
porosity
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Trabeculae bone found mainly in central skeleton, spine, pelvis, small bones
of hand and feet, long bones
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Spongy bone - inner, trabeculae, less compact, high porosity, found at ends
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Epiphyseal plate/line
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Metaphysis
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Diaphysis
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Medullary cavity
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Periosteum - tissue surrounding the bone except for joint surfaces, contains
osteoblasts
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Endosteum - lines central canal, contains osteoclasts (reabsorb bone)
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Structure
Screen clipping taken: 6/03/2018 9:54 AM
Central canal
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Concentric lamellae
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Lacunae - contain osteocyte
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Haversion canals - osteons with concentric lamellae
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Canaliculi opening on surface = links between osteons
Osteon units
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L2 - mechanical properties of bone and articular cartilage,
bone healing
Tuesday, 6 March 2018
9:47 AM
week 3 Page 1
Canaliculi opening on surface = links between osteons
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Osteoclasts dig tunnels - multinucleated, so work faster
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Osteoblasts build walls
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Osteocytes mature and form Haversian canals - mechanotransducers, detect
stimuli created by mechanical load, initiate bone remodelling (osteoblasts)
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As bone matures
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Screen clipping taken: 6/03/2018 10:00 AM
Long bone e.g. humerus, provide leverage
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Short bone e.g. carpus, thin cortex filled with cancellous bone
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Flat bone e.g. scapula, 2 thin layers of cortical bone with cancellous bone inside
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Irregular bone e.g. vertebrae of spine - structure same, shape irregular
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Pneumatic e.g. nasal cavity/sinuses
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Types
Calcium carbonate and calcium phosphate
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60% dry bone weight
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Gives rigidity, brittleness
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Mineral
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Type 1 collage
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40% dry bone weight
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Malleability
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Resists stressing
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Collagen resists pulling and stretching forces
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Organic
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Ground substance
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Triphasic
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Composition
Mechanical support system
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System of levelrs to transmit forces
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Protects vital organs
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Mechanically classified as an anisotropic material - mechanical properties in
different directions
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Composite material - collagen and calcium phosphate based, stronger in
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Bone summary
week 3 Page 2
Composite material - collagen and calcium phosphate based, stronger in
complresion than tension, collagen supports elastic behaviour and increased tensile
strength
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Define and apply the concepts of stress, strain, deformation;
Young's Modulus, plastic deformation & Wolff's Law to bone
biomechanical properties
Mechanical terminology
Strength
Sigma σ
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= force per unit area = force/cross-sectional area
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Measured in N/cm2or N/m2= Pa
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e.g. tendon stiffer than ligament which is stiffer than muscle
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Stress
ε
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Stretch or displacement of a material
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= (Length of bone - original length)/original length = % of stretch of material
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(L-Lo)/Lo
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Stress and strain are independent of the amount of a material
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Strain
Elasticity = stiffness = stress/strain = tensile strength/tensile strain
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= N/m2= Pa
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If you load parallel to the fibres along the grain, it will be stiffer
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If increase in E, then material is stiffer
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Young's Modulus (E)
Describe stress-strain, load-deformation, strain rate - failure
and repetitive loading - fatigue relationships as they apply to
bone and be able to describe the phases of each
No damage
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Toe region
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Can get microdamage
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Can return to original form
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Elastic zone/linear region
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Progressive failure of tissue
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Equivalent to grade II sprain
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Plastic zone
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Grade III sprain
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D and E
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General stress-strain curve
e.g. think of elastic band, don't go back to normal structure if fibres torn
Ie. If you load at an angle to the fibres, they will be less resistant to the fibres
Load according to the line of stress (trabeculae in the bone)
week 3 Page 3
Document Summary
L2 - mechanical properties of bone and articular cartilage, bone healing. Apply knowledge of bone structure to biomechanical properties. Forms system of levers - allows movement of the joints. Mineral store - ca, p, carbonate, mg, f, all stored as salts with the bone structure. Compact bone - outer shell, solid, compact, mineralised connective tissue with low porosity. Spongy bone - inner, trabeculae, less compact, high porosity, found at ends. Trabeculae bone found mainly in central skeleton, spine, pelvis, small bones of hand and feet, long bones. Periosteum - tissue surrounding the bone except for joint surfaces, contains osteoblasts. Endosteum - lines central canal, contains osteoclasts (reabsorb bone) Canaliculi opening on surface = links between osteons week 3 page 1. Canaliculi opening on surface = links between osteons. Osteoclasts dig tunnels - multinucleated, so work faster. Osteocytes mature and form haversian canals - mechanotransducers, detect stimuli created by mechanical load, initiate bone remodelling (osteoblasts)
