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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
What is gap healing?
Defect is < 1mm | Interfragmentary strain is <2%
26
How is lamellar bone deposited in gap healing?
Perpendicular to long axis
27
Are the fracture ends weak or strong?
Weak
28
How long does it take for cutting cones to allow longitudinal lamellar bone to be laid down?
3-8 weeks
29
What are separate steps in gap healing?
Bony union and remodeling
30
What is a cancellous bone fracture?
Metaphyseal fracture involving trabecular/cancellous bone
31
T/F: Cancellous fractures are more stable than cortical fractures.
True
32
T/F: Cancellous fractures heal by callus formation.
False, they don not heal by callus formation.
33
How do cancellous fractures heal?
Woven bone deposited on trabeculae, fracture is bridged before the cortical shell heals.
34
What are the 2 types of physeal fracture?
Zone of Hypertrophy | Zone of Proliferation
35
Why do physeal fractures occur?
Because the area is weaker than the surrounding bone.
36
What can a physeal fracture result in?
Prevention of normal physeal function | Premature closure
37
What is another name for a physeal fracture?
A Salter-Harris fracture
38
What type of healing occurs with an absolutely stable fracture?
Direct
39
What type of healing occurs with an unstable fracture?
Indirect
40
What are 6 factors affecting fracture healing?
``` Location Stability Method of fixation Biological environment Blood supply Biomechanical vs. biological Osteosynthesis ```
41
What 3 things comprise biomechanical approach to healing?
Anatomical reduction Rigid fixation Compromise soft tissue
42
What 2 things does biological osteosynthesis restore?
Overall length | Overall alignment
43
What 2 things does biological osteosynthesis emphasize?
The role of soft tissues integrity | The use of bone grafts
44
What 2 things does biological osteosynthesis limit?
Surgical approach | Soft tissue disruption
45
What type of healing do plates and ESF result in?
Direct (contact of gap)
46
What type of healing do pins with wires, ESF, or interlocking nails result in?
Direct and/or indirect healing
47
What type of healing do casts and splints result in?
Indirect healing
48
What type of healing do you see with no fixation?
Indirect healing
49
What term is used for the use of splinting and casting?
External coaptation
50
How do pins and nails affect blood supply?
They disrupt the endosteal blood supply
51
How do cerclage wires and external fixator pins affect blood supply?
Not significant, unless wires and loose
52
How do bone plates affect blood supply?
Impair blood supply to the outer layer of the cortical bone. Stabilization allows early reformation of the medullary blood supply
53
T/F: Bone grafts enhance healing and compensate for unstable mechanical environment.
False. Bone grafts enhance healing, but do not compensate for unstable mechanical environment.
54
What are 4 indications for a bone graft?
Comminuted fractures Fractures with bone loss Delayed or non-union fractures Arthrodeses (removed cartillage, want to fuse the bone)
55
What are 3 origins of a bone graft?
Autograft (patient's own bone) Allograft (same species) Xenograft (different species)
56
What are the 3 types of bone graft?
Cancellous Cortical Cortical-cancellous
57
What are the 3 functions of bone grafts?
Osteogenesis Osteoinduction Osteoconduction
58
What is osteogenesis?
Laying down new bone
59
What is osteoinduction?
Recruiting cells to form new bone
60
What is osteoconduction?
Providing a scaffold for the growth of new bone
61
What is the gold standard of bone grafts?
Cancellous Autograft
62
What type of bone graft is the only one to promote osteogenesis?
Cancellou Autograft
63
What are 2 benefits of cancellous autografts?
Readily available | Avoids immune reaction
64
What are 5 drawbacks to cancellous autografts?
``` Mechanically weak Increased surgical time Limited storage time (repair fracture first) Pain at the donor site Intraoperative blood loss ```
65
How are cancellous allografts available?
Frozen chips or powder
66
What are 4 benefits to cancellous allografts?
Decreased surgical time Readily available No donor site problems Can mix with an autograft to increase the volume
67
What are 2 drawbacks to cancellous allografts?
Expensive | Lack osteogenic properties
68
What are the 4 phases of cancellous bone grafts and their time-frames?
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
What 2 things are cortical bone grafts used for?
Providing structural support | Osteoconductive properties
70
What 2 type of fractures are cortical bone grafts used in?
Highly comminuted fractures | Bone tumors
71
What sites are cortical allografts from?
Ribs (9th) Ulna Fibula Ilial wing
72
How do you calculate the length of a cortical allograft needed?
length of normal bone - (length of normal bone left on fractured bone)
73
What are the 3 phases we see with cortical bone grafts?
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
What is the term used for cortical bone graft healing?
Creeping substitution
75
What are the 5 benefits of a cortical-cancellous bone graft?
``` Provides immediate mechanical support Promotes osteogenesis Osteoinductive Osteoconductive Autogenous graft obtained from the patient ```
76
What are 5 key points for cancellous autografts?
``` Most commonly used Readily available Highly cellular, mechanically weak Superior osteogenic and osteoinductive properties Less osteoconductive ```
77
What are 3 key points for cortical bone grafts?
Excellent mechanical support Osteoconductive Acellular with no osteogenic properties

Mechanisms of Disease (7 decks)

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