Tissue Mechanics Bone Flashcards
What is the intercellular calcified bone matrix composed of (3)
- Inorganic matter
- Water
- Organic matter
What percent of the intercellular matrix of bone is inorganic matter
60-70%
What is the inorganic matter of the intracellular matrix of bone
Hydroxyapatite crystals
What percent of the intercellular matrix of bone is water
5-8%
What percent of the intercellular matrix of bone is organic matter
22-35%
Where is inorganic matter embedded in
Variously oriented fibers of protein collagen (fibrous portion of extracellular matrix)
What is make up the greatest percentage of the ECM organic matter
Type I collagen
How much of the ECM organic matter does type I collagen make up
90%
How much of the dry weight of bone does type I collagen make up
25-30%
What composes the ECM organic matter of bone (4)
- Type I collagen
- GAGs
- PGs
- Glycoproteins
What do GAGs do in the ECM organic matter
Serve as cementing substance between osteons
What percent of the ECM are GAGs
About 5%
What do the glycoproteins contain in the ECM organic matter
Glutamic acid
What does glutamic acid do
Causes glycoproteins to bind to calcium
What do GAGs do for the bone
Give it the ability to absorb stress and share it across the bone
What is the main portion of the inorganic of the ICM
Calcium and phosphorus
What form do calcium and phosphorus take in the inorganic matter of the ICM
Hydroxyapatite crystals
What makes bone such a dynamic tissue
Bone cells
What are the 3 bone cells
- Osteocyte
- Osteoblast
- Osteaoclast
What are osteocytes
Mature cells
What are osteoblasts
Young cells for growth
What are osteoclasts
Phagocytic
What is constantly going on in existing bone hopefully inbalance
Bone tissue deposition and bone tissue resorption
What happens more during growth
Deposition
What happens more during aging
Resorption
What happens more during healing
Hopefully both are equal
What happens more during exercise
Resorption
What occurs when bone deposition decreases
Disuse atrophy
Following 8 weeks of immobilization what can happen to load to failure, stiffness, and energy storing capacity
A 3 fold decrease
What do plates do in fracture
Take up some of the force that would normally be experienced by the tissue
What is micromotion
Motion where the screw goes in and stimulates bone growth
What is another name for compact bone
Cortical bone
What is the stress strain curve of compact compared to cancellous bone
Steeper slope
What bone is stiffer
Cortical bone
Which type of bone has a greater capacity for energy storage
Cancellous
What is another name for cancellous bone
Trabecular bone
Does increased velocity of loading make bone more stable or brittle
Brittle
Does bone exhibit anisotropic or isotropic behaviors
Anisotropic
What does anisotropic meand
The tissue responds to the forces put on it
Which direction is strength the strongest for bone
The direction in which loading is most common
What is force (per unit area) applied to a structure
Stress
What is deformation (change in shape) of a structure produced by an applied force/stress
Strain
What is material stiffness of bone equal to
Slope of liner portion of curve points A to B
What does the inverse of material stiffness of bone equal
Compliance
Which bone can withstand great stress but less strain
Cortical
How much strain does it take cancellous bone to fail
75%
How much strain does it take cortical bone to fail
2%
What is stress
Load
What is strain
Deformation
True or False:
Constant compression can hinder growth
True
How do you determine if someone has a valgus/varus
Look at which way the distal segments points
Distal segment points toward midline
Varus
Distal segment points away from midline
Valgus
What causes valgus/varus
Unequal loading
What is the effect that occurs when bone bends
Piezo-electric effect
What happens on the side of compression
- charge
What happens on the side of tension
+ charge
Where do osteoblasts migrate to
- charge
Where do osteoclasts migrate to
+ charge
What does the piezo-electric effect cause
Bone deposition on side of compression
What is the usual function of muscle contractions on bone
Oppose antagonist or gravity to counterbalance bending
True or False:
Muscles pulling on bone overtime creates tuberosities/trochanters
True
What happens at the tissue level as a result of high tension load
Hopefully balance of osteoblast/clast activity
What does a constant compressive load produce in bone
Increase in endosteal diameter and intracortical porosity
Are constant compressive loads good for long bones
Not really
What does intermittent loading produce
Increased bone mass
True or False:
Spiral fractures are common with torsion loading
True
What part of the bone is most sensitive to torsion forces
Epiphyseal plate
What does a greater cross sectional area cause
Stiffer and stronger bone
What is clinical healing
Formation of the hard callus
What is the intensity for bone interventions (3)
- Load within tissue structural tolerance
- Move carefully into plastic zone
- Pain free loading
What is the duration for bone interventions
Many reps of cyclic loading
What is the mode for bone interventions
Attempt to mimic functional loading characteristics