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MD1 Locomotor > Bone Pathology > Flashcards

Bone Pathology Flashcards

1
Q

Where are osteocytes found?

A

In lacunae

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2
Q

How are osteocytes sustained?

A

Canaliculi

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3
Q

What do osteocytes do?

A

Maintain matrix

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4
Q

What is mechanotransduction?

A

Osteocytes can tell if stress moving through bone

Initiate bone modelling in response

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5
Q

What are active osteoblasts involved in?

A

Growth
Remodelling
Fracture healing

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6
Q

What can osteoprogenitor cells differentiate into?

A

Osteoblasts

Chondrocytes

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7
Q

Where are osteoprogenitor cells found?

A

Periosteum

Endosteum

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8
Q

What do osteoclasts do?

A

Resorb bone

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9
Q

How many nuclei do osteoclasts have?

A

Multinucleated

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10
Q

Which hormone stimulates osteoclasts?

A

Parathyroid hormone

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11
Q

Which cells express RANK-L?

A

Osteoblasts

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12
Q

Which cells express RANK?

A

Osteoclast precursor

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13
Q

What is osteoprotegrin (OPG)?

A

Binds to RANK-L > blocks it from interacting with RANK

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14
Q

How does parathyroid hormone stimulate osteoclasts?

A

Increases expression of RANK-L on osteoblasts > bind to RANK on osteoclast precursor > stimulate osteoclast differentiation

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15
Q

What cells do the periosteum and endosteum contain?

A

Osteoprogenitor cells

Resting osteoblasts

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16
Q

What is in the dense outer layer of the periosteum?

A

Fibroblasts
Fibrous tissue
Blood supply
Nerves

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17
Q

What type of cartilage is the model built from in endochondral ossification?

A

Hyaline

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18
Q

How does endochondral ossification work?

A 
Chondrocytes
- Proliferate
- Hypertrophy
- Degenerate
Osteoblasts move in
- Colonise strips of cartilage left by growth plate > ossify cartilage
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19
Q

How do flat bones develop?

A

Intramembranous ossification

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20
Q

What is intramembranous ossification?

A

Mesenchymal stem cells differentiate directly into osteoprogenitor cells
- Start producing osteoid

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21
Q

What is osteoid?

A

Bone matrix

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22
Q

What cell lays down osteoid?

A

Osteoblasts

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23
Q

What does osteoid contain?

A

Type I collagen
Other proteins
- Few glycosaminoglycans
- Growth factors and cytokines

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24
Q

How is osteoid secreted by osteoblasts?

A

Secrete

  • Collagen
  • Secretory vessels
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25
Q

What do the secretory vessels released by osteoblasts contain?

A

Alkaline phosphatase

Pyrophosphatase

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26
Q

What do the proteins in the secretory vessels of osteoblasts do?

A

Increase concentration of calcium and phosphate locally to cause precipitation

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27
Q

What is the most common form of calcium phosphate found in bone?

A

Hydroxyapatite

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28
Q

What is woven bone?

A

Growing/healing bone

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29
Q

Compared to woven bone, what is the strength and production rate of lamellar bone?

A

Stronger

Slower production

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30
Q

What is the normal annual turnover of bone?

A

5-10%

31
Q

How is bone remodelled?

A

Removes tunnel of bone
Rebuilds new osteon
Occurs in lamellar, not woven bone

32
Q

What is a fracture?

A

Disruption in integrity of living bone

33
Q

What are the fracture types by orientation of the fracture line?

A

Transverse
Oblique
Spiral

34
Q

Other than by the orientation of the fracture line, what other fracture types are there?

A 
Displaced
Open (compound) vs closed (simple)
Comminuted
Pathological
Stress
35
Q

What is a comminuted fracture?

A

Bone broke into 2+ pieces

36
Q

What is a pathological fracture?

A

Something wrong with bone and it fractures

37
Q

What is a stress fracture?

A

Repeated low force injury to normal bone

38
Q

Can stress fractures be seen in an x-ray?

A

Usually, no

39
Q

What are the stages of fracture healing?

A

1) Inflammatory phase
- Bleeding and haematoma formation
- Vascular granulation tissue
2) Reparative phase
- Soft callus
- Hard callus
3) Remodelling phase

40
Q

What does a haematoma contain in a fracture?

A

Growth factors

Cytokines

41
Q

What does vascular granulation tissue contain?

A

Fibroblasts

New capillaries

42
Q

What is soft callus made of?

A

Cartilage

43
Q

What is hard callus made of?

A

Bone

44
Q

What happens during haematoma formation?

A

Fibrin mesh creates framework
Damaged matrix releases trapped growth factors and cytokines
Stem cells activated to start repair
Stem cells start to differentiate very early depending on local stability

45
Q

What can osteoprogenitor cells differentiate into during the inflammatory phase, from most to least stable?

A

Osteoblast
Chondroblast
Fibroblast

46
Q

When does the inflammatory phase occur?

A

Hours-days

47
Q

What does the soft callus do?

A

Holds fractured ends together but poor structural stability

48
Q

What happens to the periosteum during soft callus formation?

A

Repairs itself over outside

49
Q

When does soft callus formation occur?

A

Days-weeks

50
Q

What kind of ossification occurs to form the hard callus?

A

Endochondral in unstable areas

Intramembranous in stable areas

51
Q

What kind of bone is a hard callus?

A

Woven

52
Q

What is the shape of the hard callus?

A

Thickened spindle

53
Q

What is the structural integrity of a hard callus?

A

Stable and (pain-free) but not as strong as normal bone

54
Q

When does hard callus formation occur?

A

Weeks-months

55
Q

What happens during remodelling in fracture healing?

A

Osteoclasts followed by osteoblasts
Woven bone > lamellar bone
Along lines of stress

56
Q

What is the result of remodelling in fracture healing?

A

Completely reconstituted bone

57
Q

When does remodelling occur?

A

Months-years

58
Q

What is the goal of clinical management of fractures?

A

Union = unite broken ends

To allow bone healing as fast as possible and without complications

59
Q

How are the goals of clinical management of fractures achieved?

A

Minimise gap = reduction of fracture
Minimise strain/movement = fixation
Minimise any other factors slowing healing

60
Q

What are factors that slow healing?

A 
Age >40 years
Multiple medical comorbidites
NSAIDs and corticosteroids
Smoker
Poor nutrition
Open fracture with poor blood supply
Multiple traumatic injuries
Local infection
61
Q

What is non-union?

A

Fracture which will not heal, no matter how long you persist with primary management

62
Q

What is pseudoarthrosis?

A

Also called non-union and false joint
Has no chance of mending without intervention
Body perceives fragments as separate bones and doesn’t attempt to unite them

63
Q

What interventions can be done in non-union?

A

Bone grafting
Further stabilisation
Treat infection
Stop smoking

64
Q

What is delayed union?

A

Fracture which isn’t healing as fast as expected

65
Q

What are the risk factors for delayed union?

A

Similar to those for non-union

66
Q

What can delayed union result in?

A

Non-union

67
Q

What is mal-union?

A

Healing of bone in unacceptable position

68
Q

What problems can mal-union cause for the patient?

A

Disability
Post-traumatic osteoarthritis
Cosmetic

69
Q

Which type of fracture is especially at risk of infection?

A

Open

70
Q

What effect does osteomyelitis have on healing bone?

A

Disrupts vessels in periosteum/Haversian canals > infected fragments of necrotic bone

71
Q

What is the most common bacteria causing osteomyelitis?

A

Staphylococcus aureus

72
Q

What other infection can osteomyelitis lead to?

A

Sepsis

73
Q

What is osteonecrosis/avascular necrosis?

A

Fractures can interrupt blood supply > leave part of bone ischaemic

74
Q

Which bones are particularly at risk of avascular necrosis?

A

Neck of femur

Scaphoid

MD1 Locomotor (17 decks)

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