Bone Healing And Bone Grafting Flashcards Preview

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Flashcards in Bone Healing And Bone Grafting Deck (33):
1

What is the blood supply to the long bones in a mature animal?

Principle nutrient artery
Metaphyseal arteries
Periosteal arteries

2

What is the blood supply to the long bones in immature animals?

Epiphyseal and metaphyseal arteries

3

How does blood supply change in a fractured bone?

Develops extraossecous blood supply —- supplying periosteal bone proliferation

4

What are the stages of indirect healing (aka callus formation)?

Inflammation
Repair
Remodeling

5

What type of bone healing occurs with unstable mechanical environment/motion between fracture fragments

Indirect

6

What occurs in the inflammatory stage of indirect bone healing?

From time of fracture, lasting 3-4days

Clot at fracture site
-osteoinductive growth factors causing angiogenesis and bone formation

-abundant mast cells with vasoactive substances

7

What occurs in the remodeling stage of indirect bone healing?

Takes about 2 months

Clot differentiates into granulation tissue

Gain in strength - soft callus

Mesenchymal cells become osteoblasts
-lay down fibrocartilage

Mineralizes forming a hard callus
-bony union

8

What is direct bone healing?

Filling of fracture site with no callus

Requires anatomical reduction and rigid fixation which minimize secondary healing phase (usually plate fixation)

Minimal interfragmentary strain

9

T/F: it take longer to gain mechanical strength when healing has occurred by direct bone healing rather than indirect bone healing

True

10

Reducing a fracture (increases/decreases) interfragmentary strain

Increases

We try to compensate for this by adding fixators

11

Gap healing occurs then the fracture gap is _______mm

<1

Interfragmentary strain must be <2%

12

What is the process of gap healing ?

Osteoblasts deposit lamina bone in fracture gap perpendicular to long axis

Mechanically week at fracture ends

Osteoclasts form cutting cones along osteoblasts to lay longitudinally oriented lamellar bone

13

Contact healing can only occurs if the defect between fracture sites is ______mm

<0.01

14

How does contact healing occur?

Lamellar bone is layer in normal axial direction

Bony union and remodeling simultaneous

Initiated by cutting cones of osteoblasts directly followed by osteoblasts

15

How does healing of cancellous bone occur?

Fracture gap is filled with new trabecular bone followed by the cortical shell

(Eg metaphyseal fractures)

16

How does healing of a physeal fracture occurs?

Fractures occur in this area because it is weaker than surrounding bone

Fracture of zone of hypertrophy will heal by continued growth of physeal cartilage

Fracture of zone of proliferation will heal by endochondrial ossification —> prevent normal physeal function and premature physeal closure

17

What type of healing usually occurs with bone plate fixation?

Direct healing

18

What type of healing occurs with external fixators?

Direct or indirect

19

What type of healing occurs with IM pins with wires/ cast/ splints/ no fixation

Indirect healing

20

Intramedulary pins/interlocking nails disrupt ________ blood supply

Endosteal/medullary

21

Bone plates disrupt _________ blood supply

Periosteal

22

Why do we use bone grafts?

Bone loss
Arthodesis
Delayed or non-union fractures
Old age

23

What are the disadvantages to using bone grafts?

Increased surgical time
Increased pain
Increased blood loss
Increased expense

24

What are the functions of bone grafts?

Osteogenesis — osteoblasts

Osteoinduction — recruitment of mesenchymal cells

Osteoconduction — scaffold

25

What is the gold standard for bone graphs?

Autogenous cancellous bone graft

Promotes osteogenesis and is readily available

26

What are the phases of cancellous grafts in healing and how long does each phase take?

Inflammation (hours)

Revascularization (1-2weeks)

Osteoconduction (2-4weeks)

Mechanical support (up to 12weeks)

27

How are cancellous bone grafts collected?

Drill hole through cortex (proximal humerus/ proximal tibia/ wing of ileum)

Scoop out cancellous bone with curette

Has short storage time!

28

What type of graft is available as frozen chips or powder and decreases surgical time?

Allograft

29

T/F: allograft lacks osteopenia properties

True

30

What sites can you get a cortical bone graft from?

Rib, ulna, fibula, ililal wing

31

T/F: cortical bone has more osteogenic properties than osteoconductive

False

Cortical bone — osteoconductive

32

What are the phases of healing witha cortical bone graft?

Osteoclasts move into graft and resort bone

Osteoblasts follow and lay down new bone

Mechanical strength of graft is maintained “creeping substitution”

33

Why type of bone graft provides immediate mechanical support and promotes osteogenesis, osteoindcutive, and osteoconductive function?

Cortical-cancellous bone graft

— usually autogenous