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YR2: Musculoskeletal > Fracture through the Ages > Flashcards

Fracture through the Ages Flashcards

1
Q

Define bone strength.

A

Ability of bone to resist fracture

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2
Q

What factors contribute to bone strength?

A

Density

Structure

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3
Q

What method has been used for diagnosing osteoporosis and what are the limitations of this method?

A

DEXA scans

Measures bone mineral density (BMD) but doesn’t tell anything about bone structure

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4
Q

Describe the effects of oestrogen on osteoclasts.

A

Oestrogen stimulates apoptosis in osteoclasts

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5
Q

What are the two main divisions of bone composition?

A

Cell (10% of volume)

Matrix (90%)

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6
Q

What are the two subsets of bone matrix and what falls undereach?

A

Organic: collagen, non-collagenous proteins, mucopolysaccharides
Inorganic: hydroxyapatite crystals (calcium + phosphorus)

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7
Q

What are the four types of bone cells?

A

Osteoprogenitor cells
Osteocytes
Osteoblasts
Osteoclasts

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8
Q

What is the role of osteoprogenitor cells?

A

Differentiate into the other types of bone cell

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9
Q

What is the role of osteocytes?

A

Bone homeostasis (found in the lacunae + have projections into the canaliculi)

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10
Q

How often does bone normally turnover?

A

120 days

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11
Q

Describe normal bone turnover.

A

Osteoclasts dissolve away old bone
Preosteoblasts move in + differentiate into osteoblasts
Osteoblasts will lay down more bone than the osteoclasts dissolved (so no bone loss)

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12
Q

How is bone turnover different in an elderly person?

A

Less apoptosis of osteoclasts + resorption pits are very big + don’t get filled in by osteoblasts = loss of bone

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13
Q

What effect do bisphosphonates have on osteoclasts?

A

Encourage cell death in osteoclasts

Damage their cytoskeleton they lose their RUFFLED BORDER, without which they can’t function

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14
Q

What is a major problem with bisphosphonate use?

What causes this?

A

Atypical fractures:
Reduce bone remodelling (which replaces old + damaged bone) results in premature ageing of the bone
Microcracks
Form due to day-to-day use + if not filled in they eventually join + cause stress fractures

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15
Q

What is the half-life of alendronate? (bisphosphonate)

A

Long ~ 10 years

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16
Q

What new drug has come onto the market that has a similar action to bisphosphonates but with a shorter half-life?

A

Denusomab (half-life = 6 months)

17
Q

Describe the action of RANKL.

A

RANKL binds to RANK receptors on osteoclast precursors + promotes maturation to osteoclasts

18
Q

What protein is responsible for regulating the bone remodelling process and how does it do this?

A

Osteoprotegrin

Prevents RANKL binding to RANK receptor (same as denusomab)

19
Q

State Wolff’s Law.

A

Bone remodels according to the stresses applied to it

20
Q

At what age is peak bone mass reached?

A

30-40 years

21
Q

State 4 factors that contribute to bone mass

A

Genetics
Nutrition
Vitamin D
Exercise

22
Q

What are the 4 stages of callus fracture healing? What are the relative time periods from date of fracture?

A 
Haematoma + Inflammation  (1 week)
Soft Callus   (1-4 weeks)
Hard Callus  (1-4 months)
Remodelling (up to several years)
23
Q

Which type of collagen is deposited in the soft callus?

A

Type 2 collagen

24
Q

What prevents mineralisation in the soft callus?

A

Proteoglycans

25
Q

What happens in stage 3 of callus fracture healing?

A

Hard callus
Soft callus is invaded by blood vessels
Chondroblasts break down calcified callus
It is replaced by osteoid (type I collagen) produced by osteoblasts
Osteoid calcifies to form woven bone

26
Q

What happens in stage 4 of callus fracture healing?

A

Woven bone remodels to lamellar bone
It is shaped relative to the load (Wolff’s law)
Medullar canal reforms

27
Q

Name four types of fracture and their common causes

A

Spiral (twisting)
Oblique (compression)
Butterfly (direct impact)
Transverse (pulling)

28
Q

What type of fracture can occur in the bones of children due to their plasticity?

A

Greenstick fractures

One cortex could break but the other cortex could bend + stay intact

29
Q

What are the 2 ways in which fractures can heal?

A

Surgical: rigid fixation, 2 bones compressed against each other with a plate
Callus: non rigid fixation, when there is a degree of movement at the fracture site e.g. a rod inserted

30
Q

What happens in stage 1 of callus fracture healing?

A

Haematoma containing macrophages, leukocytes etc.
Granulation tissue forms
Progenitor cells invade

31
Q

What happens in stage 2 of callus fracture healing?

A

Soft callus
Chondroblasts + fibroblasts differentiate to form type II collagen + fibrous tissue
Proteoglycans produced to prevent mineralisation
Chondrocytes release calcium into ECM + degrading enzymes to breakdown proteoglycans to allow mineralisation

YR2: Musculoskeletal (10 decks)

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