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Mechanisms of Disease > Bone Healing and Grafting > Flashcards

Bone Healing and Grafting Flashcards

1
Q

What is the long bone blood supply in mature animals? (3 things)

A

Principle nutrient artery
Metaphyseal arteries
Periosteal arteries

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2
Q

What is the long bone blood supply in immature animals? (2 things)

A

Epiphyseal arteries

Metaphyseal arteries

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3
Q

What is the blood supply in a fractured bone?

A

Extraosseous blood supply develops

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4
Q

What are the 2 types of bone healing?

A

Indirect

Direct

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5
Q

What is indirect bone healing?

A

Healing by intermediate callus formation

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6
Q

What is direct bone healing?

A

Primary osteonal reconstruction, no callus formation.

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7
Q

When does indirect healing happen?

A

Unstable mechanical environment with motion between fragments.

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8
Q

What are the 3 stages of indirect bone healing?

A

Inflammatory
Repair
Remodeling

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9
Q

When does the inflammatory stage being?

A

Immediately

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10
Q

How long does the inflammatory stage last?

A

3-4 days

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11
Q

What happens in the inflammatory stage?

A

Clot develops at the fracture (helps the healing process) and extraosseous blood supply develops within hours.

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12
Q

How long does the repair stage last?

A

approx. 2 months

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13
Q

What happens in the repair stage?

A

The clot becomes granulation tissue and there is a slight gain in mechanical strength as the soft callus is mineralized into a hard callus,

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14
Q

What is achieved in the repair stage?

A

Bony union

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15
Q

What is bony union?

A

Callus has formed, but fracture line is still visible on RADs.

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16
Q

How long does the remodeling stage last?

A

Up to 7-9 years

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17
Q

What is the function of the remodeling stage?

A

To provide optimal function and strength

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18
Q

What governs the remodeling stage and what is it?

A

Wolfe’s Law

Compression (osteoblasts) and Tnesion (osteoclasts)

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19
Q

How does direct healing occur?

A

By direct osteonal proliferation

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20
Q

How long can direct bone healing take?

A

6-12 months

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21
Q

What does direct bone healing require?

A

Precise reduction and rigid fixation

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22
Q

What is contact healing?

A

Defect is < 0.01mm

Interfragmentary strain is <2%

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23
Q

What does contact healing result in?

A

lamellar bone in normal axial direction with “cutting cones” of osteoclasts followed by osteoblasts.

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24
Q

What occurs simultaneously in contact healing?

A

Bony union and remodeling.

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25
Q

What is gap healing?

A

Defect is < 1mm

Interfragmentary strain is <2%

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26
Q

How is lamellar bone deposited in gap healing?

A

Perpendicular to long axis

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27
Q

Are the fracture ends weak or strong?

A

Weak

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28
Q

How long does it take for cutting cones to allow longitudinal lamellar bone to be laid down?

A

3-8 weeks

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29
Q

What are separate steps in gap healing?

A

Bony union and remodeling

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30
Q

What is a cancellous bone fracture?

A

Metaphyseal fracture involving trabecular/cancellous bone

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31
Q

T/F: Cancellous fractures are more stable than cortical fractures.

A

True

32
Q

T/F: Cancellous fractures heal by callus formation.

A

False, they don not heal by callus formation.

33
Q

How do cancellous fractures heal?

A

Woven bone deposited on trabeculae, fracture is bridged before the cortical shell heals.

34
Q

What are the 2 types of physeal fracture?

A

Zone of Hypertrophy

Zone of Proliferation

35
Q

Why do physeal fractures occur?

A

Because the area is weaker than the surrounding bone.

36
Q

What can a physeal fracture result in?

A

Prevention of normal physeal function

Premature closure

37
Q

What is another name for a physeal fracture?

A

A Salter-Harris fracture

38
Q

What type of healing occurs with an absolutely stable fracture?

A

Direct

39
Q

What type of healing occurs with an unstable fracture?

A

Indirect

40
Q

What are 6 factors affecting fracture healing?

A 
Location
Stability
Method of fixation
Biological environment
Blood supply
Biomechanical vs. biological Osteosynthesis
41
Q

What 3 things comprise biomechanical approach to healing?

A

Anatomical reduction
Rigid fixation
Compromise soft tissue

42
Q

What 2 things does biological osteosynthesis restore?

A

Overall length

Overall alignment

43
Q

What 2 things does biological osteosynthesis emphasize?

A

The role of soft tissues integrity

The use of bone grafts

44
Q

What 2 things does biological osteosynthesis limit?

A

Surgical approach

Soft tissue disruption

45
Q

What type of healing do plates and ESF result in?

A

Direct (contact of gap)

46
Q

What type of healing do pins with wires, ESF, or interlocking nails result in?

A

Direct and/or indirect healing

47
Q

What type of healing do casts and splints result in?

A

Indirect healing

48
Q

What type of healing do you see with no fixation?

A

Indirect healing

49
Q

What term is used for the use of splinting and casting?

A

External coaptation

50
Q

How do pins and nails affect blood supply?

A

They disrupt the endosteal blood supply

51
Q

How do cerclage wires and external fixator pins affect blood supply?

A

Not significant, unless wires and loose

52
Q

How do bone plates affect blood supply?

A

Impair blood supply to the outer layer of the cortical bone.

Stabilization allows early reformation of the medullary blood supply

53
Q

T/F: Bone grafts enhance healing and compensate for unstable mechanical environment.

A

False. Bone grafts enhance healing, but do not compensate for unstable mechanical environment.

54
Q

What are 4 indications for a bone graft?

A

Comminuted fractures
Fractures with bone loss
Delayed or non-union fractures
Arthrodeses (removed cartillage, want to fuse the bone)

55
Q

What are 3 origins of a bone graft?

A

Autograft (patient’s own bone)
Allograft (same species)
Xenograft (different species)

56
Q

What are the 3 types of bone graft?

A

Cancellous
Cortical
Cortical-cancellous

57
Q

What are the 3 functions of bone grafts?

A

Osteogenesis
Osteoinduction
Osteoconduction

58
Q

What is osteogenesis?

A

Laying down new bone

59
Q

What is osteoinduction?

A

Recruiting cells to form new bone

60
Q

What is osteoconduction?

A

Providing a scaffold for the growth of new bone

61
Q

What is the gold standard of bone grafts?

A

Cancellous Autograft

62
Q

What type of bone graft is the only one to promote osteogenesis?

A

Cancellou Autograft

63
Q

What are 2 benefits of cancellous autografts?

A

Readily available

Avoids immune reaction

64
Q

What are 5 drawbacks to cancellous autografts?

A 
Mechanically weak
Increased surgical time
Limited storage time (repair fracture first)
Pain at the donor site
Intraoperative blood loss
65
Q

How are cancellous allografts available?

A

Frozen chips or powder

66
Q

What are 4 benefits to cancellous allografts?

A

Decreased surgical time
Readily available
No donor site problems
Can mix with an autograft to increase the volume

67
Q

What are 2 drawbacks to cancellous allografts?

A

Expensive

Lack osteogenic properties

68
Q

What are the 4 phases of cancellous bone grafts and their time-frames?

A

Phase I: Inflammation (within hours)
Phase II: Revascularization and osteoinduction (2 weeks)
Phase III: Osteoconduction (3-4 weeks)
Phase IV: Mechanical support (up to 12 weeks)

69
Q

What 2 things are cortical bone grafts used for?

A

Providing structural support

Osteoconductive properties

70
Q

What 2 type of fractures are cortical bone grafts used in?

A

Highly comminuted fractures

Bone tumors

71
Q

What sites are cortical allografts from?

A

Ribs (9th)
Ulna
Fibula
Ilial wing

72
Q

How do you calculate the length of a cortical allograft needed?

A

length of normal bone - (length of normal bone left on fractured bone)

73
Q

What are the 3 phases we see with cortical bone grafts?

A

Phase I: Osteoclasts move into graft and resorb bone
Phase II: Osteoblasts follow and lay down new bone
Phase III: Mechanical strength of graft maintained

74
Q

What is the term used for cortical bone graft healing?

A

Creeping substitution

75
Q

What are the 5 benefits of a cortical-cancellous bone graft?

A 
Provides immediate mechanical support
Promotes osteogenesis
Osteoinductive
Osteoconductive
Autogenous graft obtained from the patient
76
Q

What are 5 key points for cancellous autografts?

A 
Most commonly used
Readily available
Highly cellular, mechanically weak
Superior osteogenic and osteoinductive properties
Less osteoconductive
77
Q

What are 3 key points for cortical bone grafts?

A

Excellent mechanical support
Osteoconductive
Acellular with no osteogenic properties

Mechanisms of Disease (7 decks)

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