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Surgery I > Lec 19: Mechanisms of Bone Healing > Flashcards

Lec 19: Mechanisms of Bone Healing Flashcards

1
Q

this type of fracture undergoes osteonal reconstructions, requires rigid internal fixation, less than 2% strain, and minimal or no fracture gap.

A

direct (primary)

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2
Q

this type of fracture undergoes intermediate callus formation, direct bone formation (intramembranosus) and endochondral ossification

A

indirect (secondary)

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3
Q

in direct bone formation (intramembranous) there is no _____ ______.

A

cartilaginous intermediate.

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4
Q

the fracture gap length is the ___ in length / the original length

A

change

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5
Q

fracture gap length is described as a _____

A

percentage

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6
Q

granulation tissue can withstand ___% strain

A

100 - will survive through LOTS of stretching and movement

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7
Q

cartilage can withstand __% strain

A

10

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8
Q

bone can withstand __% strain

A

2

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9
Q

____ healing occurs in gaps less than 300 microns

A

contact

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10
Q

___ healing occurs in gaps less than 1 mm

A

gap

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11
Q

osteons (cutting cones), cross the fracture plane from one fragment to the other in ____ healing

A

contact

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12
Q

osteons (cutting cones) traverse the fracture plane in ____ healing

A

gap

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13
Q

contact healing is ___

A
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14
Q

direct healing consists of ___ healing and ___ healing.

A

contact ; gap

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15
Q

in gap healing, blood vessels and ____ tissue form

A

connective

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16
Q

osteblasts deposit _____ lamellar bone in the gap

A

perpendicular

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17
Q

once once lamellar bone is deposited in gap healing, cutting cones are able to ____ the fracture plane

A

traverse

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18
Q

once cutting cones traverse the fracture plane of the lamellar bone in gap healing, the lamellar bone becomes _____ oriented

A

longitudinally (this creates a stronger bone)

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19
Q

osteons (cutting cones) can move at _____ microns/day in contact healing

A

50-80 ; they move slowly

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20
Q

contact healing requires rigid ______ with a plate for direct healing to occur.

A

fixation

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21
Q

direct (primary) healing requires what 3 things?

A

rigid fixation, adequate reduction, and sufficient blood supply

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22
Q

what does rigid fixation do in primary healing?

A

decreases inter-fragmentary strain

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23
Q

adequate reduction is only possible with…

A

simple fractures

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24
Q

what is the most common type of fracture healing? (even in repaired fractures)

A

indirect (secondary) healing

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25
Q

indirect healing is enhanced by what?

A

motion

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26
Q

indirect healing is inhibited by what?

A

rigid stabilization

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27
Q

indirect healing requires ___ formation

A

callus

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28
Q

The 4 General Phases of Fracture Healing
1. ____ formation (inflammation phase)
2. soft callus formation (____ phase)
3. ____ formation (maturing or modeling phase)
4. ____ phase

A

hematoma ; proliferative ; hard callus ; remodeling

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29
Q

phase 1, hematoma formation/inflammation releases what types of cells along with mediators?

A

inflammatory cells

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30
Q

in the hematoma formation/inflammation phase, what important mediator is released?

A

BMP - bone morphogenetic protein (along with other TGF beta proteins)

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31
Q

phase 2 is ____

A
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32
Q

The 4 Specific Stages of Indirect Bone Healing
1. ____ formation/inflammation
2. ____ bone formation
3. ______
4. ______ ossification

A

hematoma ; intramembranous ; chondrogenesis ; endochondral

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33
Q

what is the endochondral ossification similar to?

A

metaphyseal growth plate

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34
Q

match the numbers with the phase of healing

A

1 - hematoma formation/inflammation
2 - intramembranous bone formation
3 - chondrogenesis
4 - endochondral ossification

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35
Q

which process is faster, direct bone healing or indirect bone healing?

A

INDIRECT

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36
Q

Direct fracture healing differs from indirect as it NEEDS

A

rigid stabilization of a bone plate

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37
Q

Indirect fracture healing differs from direct fracture healing as it requires….

A

LESS rigid fixation with callus formation
(ex: pins/wires, interlocking nail, external fixator - do not need to know these, just examples)

38
Q

true or false: fracture complications can occur even if repair principles are adhered to

A

TRUE

39
Q

to avoid fracture complications, we must understand

A

bone healing, bone blood supply, growth factors, and surgical principles

40
Q

when all evidence of osteogenic activity at the fracture site has stopped, this is called…

A

fracture nonunion

41
Q

true or false: fracture nonunion requires intervention for union to occur

A

TRUE

42
Q

viable nonunion means that it is

A

vascular

43
Q

nonviable nonunion means that it is

A

avascular

44
Q

what is depicted in the image

A

viable hypertrophic nonunion

45
Q

in viable, hypertrophic nonunions, an abundant ____ is notable but NOT bridging the fracture site

A

callus

46
Q

another name for viable, hypertrophic nonunion

A

elephant foot

47
Q

what are causes of viable hypertrophic nonunion (elephant foot)

A
  1. inadequate stabilization
  2. premature weight-bearing
  3. too much activity of the patient
48
Q

viable, mildly hypertrophic nonunion is also called

A

the horses foot

49
Q

in viable, mildly hypertrophic nonunion, mild callus but ___ bridging the fracture site

A

NOT

50
Q

causes of mildly hypertrophic nonunion:

A

inadequate stabilization usually due to implant failure (ex: plate breaks, screw pulls out)

51
Q

what is depicted in the image?

A

viable, mildly hypertrophic nonunion (horses foot)

52
Q

what is depicted in the image?

A

nonviable dystrophic nonunion

53
Q

in this type of nonunion, intermediate fragments of fracture heal to 1 main fragment and not the other

A

nonviable dystrophic nonunion

54
Q

what are causes of nonviable dystrophic nonunion?

A
  1. poor blood supply on non-healing side
  2. instability on avascular side
55
Q

what nonunions are more common in older animals with poorer blood supply?

A

nonviable dystrophic nonunion

56
Q

what is depicted in the image?

A

nonviable, necrotic nonunion

57
Q

which type of nonunion fragments have NO blood supply and cannot heal to any main fragments?

A

nonviable necrotic nonunions

58
Q

which type of nonunion represents the classical sequestrum?

A

nonviable necrotic nonunion

59
Q

what can the avascularity of the fragment lead to in a nonviable necrotic nonunion?

A

implant loosening

60
Q

what are the causes of a nonviable necrotic nonunion

A
  1. poor blood supply
  2. infection at the fracture site
61
Q

what is depicted in the image?

A

nonviable defect nonunion

62
Q

what is depicted in the image below?

A

nonviable atrophic nonunion

63
Q

what is the end result of the three nonviable nonunions, extremely uncommon and one of the most difficult cases to resolve?

A

nonviable atrophic nonunion

64
Q

overall causes of nonunions

A

infection, ischemia, distraction of bone ends, excessive compression of bone ends, interposition of soft tissue at the fracture, improper implant fixation, systemic factors

65
Q

pain at the fracture site, lameness (usually non weight bearing), disuse atrophy of the limb, and movement felt at the fracture site are all clinical signs of _____.

A

nonunion

66
Q

what signs will you see on radiography of a nonunion?

A

fracture gap, no activity at fracture ends, obliteration of marrow cavity, osteopenia of surrounding bone

and if there is a callus present, it does not bridge the fracture gap

67
Q

Ways we can treat nonunions
1. ___ stabilization of fracture
2. Enhancing ____ _____. (bone grafting)
3. Treat _____ cause of nonunion

A

rigid ; blood supply ; underlying

68
Q

what are some possible underlying causes of nonunions?

A
  1. infection (contaminated wounds in open fracture are 5X more likely to develop complications)
  2. fracture gaps
  3. metabolically unhealthy
69
Q

a ____ is a fracture that heals in a non-anatomic position

A

malunion

70
Q

causes of a malunion include
1. ____ fracture
2. ____ treated fracture
3. premature ____ weight bearing on fracture

A

untreated ; improperly ; excessive

71
Q

what are some clinical signs seen in malunion

A

angular limb deformities, limb shortening, gait abnormalities, degenerative joint disease

72
Q

a fracture that has not healed in expected time considering the patient and the fracture environment is called a _____ union.

A

delayed

73
Q

what provides the majority of blood supply to the bone marrow?

A

nutrient artery

74
Q

what vessels are involved in blood supply to the bone?

A

nutrient artery, periosteal vessels, epiphyseal & metaphyseal vessels

75
Q

TRUE OR FALSE differences in blood supply do not exist depending on growth versus maturity phase

A

FALSE - they do exist

76
Q

what is blood supply is most important after injury to the bone?

A

extraosseous - which supplies early periosteal callus

77
Q

true or false: medullary blood supply eventually takes back over after extraosseous steps in after an injury to the bone.

A

TRUE

78
Q

what is a very important tool for fracture complications?

A

bone grafts

79
Q

autogenous graft transplant occurs….
A. within the same individual
B. different individuals, same species
C. different individuals, different species

A

A

80
Q

allograft occurs with…
A. within the same individual
B. different individuals, same species
C. different individuals, different species

A

B

81
Q

xenograft occurs with…
A. within the same individual
B. different individuals, same species
C. different individuals, different species

A

C

82
Q

what are the 4 “O’s” of bone grafting?

A

osteogenesis, osteoconduction, osteoinduction, osteopromotion

83
Q

osteoconduction is where the graft acts as a ______ in which new bone is laid down

A

scaffold

84
Q

osteoinduction is where a graft induces cell to promote new ___. BMP works here.

A

bone ; BMP = bone morphogeneic protein

85
Q

osteopromotion is where material enhances the ______ of new bone.

A

generation

86
Q

platelet rich plasma is important in enhancing the regeneration of bone in _______.

A

osteopromotion

87
Q

cancellous bone grafts from the trabecular bone work by….

A

the O’s of bone grafting

88
Q

few cells survive once the bone graft is separated from its blood supply, these cells are called ________.

A

osteogenic cells

89
Q

what cells are induced to form bone cell lines in bone grafts?

A

mesenchymal stem cells, BMP’s also play an important role here

90
Q

depositing of new bone occurs via ____ cells.

A

osteoprogenitor

91
Q

what are some indications for bone grafts?

A
  1. any orthopedic fracture or arthrodesis
  2. infected fractures
  3. bone loss - cysts, fractures
  4. limb sparing for bone tumors
92
Q

what are the most common places to harvest a cancellous bone graft from?

A

wing of ileum, proximal tibia, humerus

Surgery I (10 decks)

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