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Semester 2 systems > Bone growth > Flashcards

Bone growth Flashcards

1
Q

When does bone growth start?

A

Before birth

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2
Q

When does bone growth end?

A

Puberty

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3
Q

Which part of bone is very poorly vascularised?

A

The hyaline cartilage

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4
Q

What effect do sex steroids have on bone?

A

They stimulate bone growth spurt but also promotes the closure of epiphyseal plates

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5
Q

What happens to the growth plate towards the end of bone growth?

A
  • Growth in cells ceases, cell proliferation slows and the plate thins
  • The plate is invaded by blood vessels, epiphyseal and diaphysial vessels unite
  • A visible line may be left on an X ray
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6
Q

Which bones have one ossification centre

A
  • Capals
  • Tarsals
  • Ear ossicles
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7
Q

How many ossification centres do most bones have?

A

More than 2

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8
Q

How many ossification centres does the humerus have?

A

3

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9
Q

What are the effects on bone growth caused by having multiple ossification centres?

A
  • Rate of bone growth varies both bone to bone and within the same bone
  • Weak points within the bone change
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10
Q

What are the zones of the epiphyseal plate?

A
  • Ossification zone
  • Calcification zone
  • Hypertrophic zone
  • Growth (proliferating) zone
  • Resting zone
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11
Q

What happens in the resting zone?

A

Matrix production

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12
Q

What are the defects associated with the resting zone?

A

Diatrophic dysplasia: defective collagen synthesis/processing of proteaglycans
Results in shortened stature and shorter arms and legs

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13
Q

What happens in the Growth zone?

A

Cell proliferation

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14
Q

What are the defects associated with the growth zone?

A 
• Achondroplasia
• Malnutrition 
• Irradiation injures
All above result from the deficiency of proliferation and/or matrix synthesis 
• Gigantism: Increased proliferation
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15
Q

What happens in the hypertrophic zone?

A

Calcification of the matrix

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16
Q

What are the defects associated with the hypertrophic zone?

A

• Rickets
• Osteomalacia
Both caused by an insufficiency of calcium or phosphate for normal calcification

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17
Q

What is the difference between rickets and osteomalacia?

A
  • Rickets is more paediatrics related because of the growth plates
  • Osteomalacia involves the periosteum
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18
Q

What happens in the Metaphysis?

A

Bone formation and vascularisation

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19
Q

What are the defects associated with the metaphysis?

A
  • Osteomyelitis: bacterial infection
  • Osteogenesis imperfecta: Abnormalities with the osteoblasts and collagen synthesis (brittle bone disease)
  • Scurvy: Inadequate collagen turnover(which is why it also affects the skin)
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20
Q

What does bone growth and development require?

A
  • Calcium
  • Phosphorus
  • Vitamins A, C and D
  • Balance between growth hormone, thyroid and parathyroid hormones, oestrogen and androgens
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21
Q

What percentage of bone is cortical bone?

A

80

22
Q

Where is cortical bone found?

A

In the shafts of long bones

23
Q

Describe the structure of cortical bone

A

Concentrically arranged in lamellae- Haversian system

24
Q

What is the function of cortical bone?

A

Mechanic strength

25
Q

What may cause damage to the bone/ cause the bone to fracture?

A

Direct or indirect violence may result in deficits at the fracture sit leading to non-union

26
Q

What percentage of bone is cancellous/trabecular bone?

A

20%

27
Q

Where is cancellous/trabecular bone located?

A

At the ends of long bones, vertebral bodies and flat bones

28
Q

Describe the structure of cancellous/trabecular bone

A

Meshwork of trabecular with intercommunicating spaces

29
Q

What is the function of cancellous/trabecular bone?

A

Metabolic

30
Q

How would cancellous/trabecular bone likely be damaged?

A

Honeycomb structure fails as the result of compression

31
Q

In cortical and cancellous bone, what are the differences between:

1) The periosteum
2) Cell turnover
3) Blood supply

A

1) Cortical bone has a thicker periosteum, Cancellous bone has a thin periosteum
2) Cortical bone has a slow turnover, Cancellous bone has a rapid turnover
3) Cortical bone has a slow blood supply and Cancellous bone has a rich blood supply

32
Q

What needs to be thought about in the mechanism of injury of a fracture?

A

Direction of force:
• Direct vs angular?
• Rotational?
• Was there compression?

Energy transfer:
• Cause?
• Site? (how close was it to other tissues?)

33
Q

What is imaging used for in fracture treatment?

A
  • Site and the bones involved
  • Clues on any soft bone injury (e.g. are there fragments? Can it be realigned? etc.)
  • Clues on energy transfer: Wide displacement? Comminuted? Multiple fracture sites?
  • Pathological bone?
  • Paediatric bone: What are the effects on the growth plates and bone density
34
Q

What are the different definitions of a fracture?

A
  • Complete or incomplete
  • Site
  • Open to surface
  • Contaminated
  • Soft tissue injury
  • Joint involvement
  • No. of pieces
  • Alignment
  • Degree of separation
35
Q

What are the types of fracture?

A
  • Transverse- across the bone horizontally
  • Linear - across vertically
  • Oblique non displaced - Diagonally
  • Oblique displaced - Diagonally and separated
  • Greenstick (mainly in children) chunk on side of bone
  • Communited - broken into fragments
  • Spiral - Around the bone and twisted
36
Q

What are avulsion fractures?

A

Fragment of the bone is separated from the main mass

37
Q

What is a buckled fracture?

A
  • Otherwise known as an impacted fracture, torus fracture

* Ends are driven into each other, commonly seen in arm fractures in children

38
Q

What is a compression/ wedge fracture?

A

Usually involves vertebrae (seen more commonly in patients with osteoporosis or in cancer patients)

39
Q

What is a pathologic fracture?

A

Caused by a disease that weakens the bones

40
Q

What is a stress fracture?

A

Hairline crack

41
Q

What complications are limb threatening/ a non-union risk?

A
  • Dislocation
  • Comminuted
  • Compound
  • Compartment syndrome
  • Vascular/nerve injury
  • Soft tissue injury
  • Pathological bone
42
Q

How long does a fracture take to heal and what is the healing time dependent on?

A
  • 2-10 weeks
  • Severity and position
  • Age
43
Q

What effect on bone cells does age have?

A

• Decrease of osteoblasts

44
Q

What effect on bone cells does osteoporosis have?

A

• Increases osteoclasts

45
Q

What are the 3 major phases of fractures and callus formation?

A

1) Reactive phase
2) Reparative phase
3) Remodelling phase

46
Q

What happens in the reactive phase of callus formation ?

A
  • Fracture and inflammatory phase (haematoma)

* Fibroblasts in the periosteum proliferate to form granulation tissue around fracture site

47
Q

What happens in the reparative phase of callus formation?

A

30-40% of callus formation
• Callus formation: osteoblasts quickly form woven bone to bridge the gap
• Woven bone is weak as the collagen fibres are arranged irregularly
• Lamellar bone is laid down - collagen is organised in regular sheets to give strength and resilience

48
Q

What determines if osteoblast or chondroblasts are the main cell in callus formation?

A
  • Osteoblasts = loading/ forces being applied

* Chondroblasts = less weight bearing

49
Q

What happens in the remodelling phase?

A

Remodelling by osteoclasts restore original bone shape

50
Q

What is conservative treatment?

A
  • Simple fracture with low risk of non-union
  • Dependent on natural healing process
  • +/- immobilisation
  • Rehabilitation
51
Q

What happens in intervention?

A
  • Fractures with limb threat or risk of non union
  • Augment natural healing with replacement or strengthening
  • +/- immobilisation
  • Rehabilitation

Semester 2 systems (6 decks)

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