Orthomech L2: Bones

  1. What are the types of bone
    • Flat
    • Long
    • Irregular
    • Short
  2. What is the function of bone?
    • Protect organs
    • Support body
    • Provide attachment
    • Hearing
    • Produce cells
    • Store calcium
  3. Draw a diagram of a long bone
    Image Upload 1
  4. What is an osteon and what is its structure?
    Fundamental unit of compact bone

    • Lamellae: Concentric ring of bone tissue
    • Cement lines: Outer rings of bone tissue
    • Volkmann canal: Contain transverse blood vessels connecting haversion canals
    • Haversion canal: Blood vessels 
    • Lacunae: Holes for osteocytes
    • Canaliculi:Osteocyte communication means
  5. What are the two components of long bone?
    • Cortical(compact)
    • Trabecular(spongy) bone
  6. Where do you find trabecular bone?
    In epiphysis or metaphysis of long bone
  7. Explain the heirarchical structure of bone and draw the diagram
    Each bone has secondary osteons ->fibre arrays -> collagen fibrils -> mineralised collagen molecues

    • Collagen fibrils and collagen fibres have enzymatic and non enzymatic cross links as well as hydroxyapatate
    • Image Upload 2
  8. What are the components of bone?
    Organic: Collagen for tensile strength and flexibility

    • Mineralised:
    • Hydroxyapatate for stiffness and compressive strength.
  9. What are the three types of cells in bone and what are their functions?
    • Osteoblasts:
    • Lay down bone
    • Make collagen fibrils and proteoglycans. 
    • Deposit apatite.
    • Can become osteocytes

    • Osteocytes: Perform mechanosensory and maintenance functions
    • Sit in bone matrix and communicate with each other via canaliculi
    • Long lived

    • Osteoclasts: Secrete H+ 
    • Secrete collagenase and proteinases to clear proteins
    • THey are multinucleated and larger than osteoblasts
  10. What are basic multicellular units? (BMUs)
    Bone lining cells (Type of Stem cells) lining the endosteum
  11. How does Bone turnover process work?
    • Originiation:Mechanical stimulus starts process.
    • Bone lining cells recruit osteoclasts
    • Osteoclasts resorb bone, creating resorption pit
    • Osteoclasts die
    • Osteoblasts fill the pit and secrete osteoids
    • Matrix is mineralised and matures
  12. Explain timeline of bone turnover
    • 3days: Activation
    • 30 days: Resorption
    • 90 days: Formation
    • 6months: Mineralisation
    • Maturation afterwards
  13. What is Wolff's law?
    Bone will adapt to any stimulus placed on it
  14. What are the factors that affect the biomechanical properties of bone?
    • Load rate: As load rate increases, so does young's modulus. Bone adapts to strain rates.
    • But this makes it more brittle
    • Orientation: Stronger in compression and stronger longitudinally due to anisotropic nature
    • Creep: Has visoplastic properties- dependent on time history of strain.
    • Strain changes under constant load.
    • Age: Bone is less stiff, less strong, more brittle
  15. Why does bone get weaker with age?
    • Loss of bone quality
    • Increased enzymatic cross linking between collagen fibrils
    • Collagen fibrils can no longer slide over each other as easily to absorb impact
    • This suppresses plascticity
  16. Draw the graph to show how bones adapt to mechanical stimulus
    • Image Upload 3
    • Higher daily stimulation leads to bone formation
    • Lower daily stimulus leads to bone resorption
  17. How does one measure bone mineral content?
    DEXA (dual x ray absoptionmetry)
  18. In what way will bone adapt to loads placed on it?
    • Orientation
    • Bone density: Spacing thickness, number
  19. What the the types of bone fracture?
    • Traumatic or non-traumatic
    • Simple: Transverse, spiral, oblique.

    • Comminuted
    • Segmental
    • Compression

    To describe location: Proximal middle, distal.
  20. What are the ways bone can detect mechanical stimulus
    • Strain: Cells attached to stiff matrix which strains stretch receptors on cells
    • Fluid flow: Canalicular channels have fluid. 
    • Osteoctes repond to fluid flow
    • Microdamage? Strain energy density? Stress?
  21. What approaches are there to bone fracture fixation
    Stabilise: With nails screws, plates wires

    Orthopaeidc hardware: Internal and external fixation methods
  22. What internal fixation methods are there for fracture fixation
    Compression plate, tendion banding, wires
  23. What is the mechanism for fracture healing in 5 steps?
    • Haematoma forms (blood clot)
    • Granualation tissue forms (loose connective tissue)
    • Cartilage formation
    • Bone formation
    • Remodelling
  24. WHat is osteoporosis defined as and why does it happen?
    Bone density less than 2.5 standard deviations below the peak bone mass

    • It happens due to too much resorption and too little formation
    • Image Upload 4
  25. What are the risk factors of osteoporosis?
    Gender: For women, estrogen normally regulates osteoclast apoptosis. Menopause causes decrease in estrogren. For men its decrease in testosterone

    Other factors: Genetic, age, malnutrition, physical inactivity
Card Set
Orthomech L2: Bones