Bone Healing/Grafting

Question 1

What are the three long bone blood supply sources in mature animals?

Answer 1

Principle nutrient artery
Metaphyseal arteries
Periosteal arteries

Question 2

What are the long bone blood supply sources in immature animals?

Answer 2

Epiphyseal and metaphyseal arteries

Question 3

What occurs in terms of blood supply with fractured bone?

Answer 3

Development of extraosseous blood supply

Question 4

What are the two types of bone healing?

Answer 4

Direct- primary osteonal reconstruction

Indirect- callus formation

Question 5

When does indirect bone healing (callus formation) occur?

Answer 5

Unstable mechanical environment and motion between fracture fragments

• > 1mm gap between fragments
• impaired blood supply or revascularization

Question 6

What are the three stages of indirect bone healing?

Answer 6

Inflammation
Repair
Remodeling

Question 7

When does the inflammation stage of indirect bone healing occur?

Answer 7

IMMEDIATELY after fracture, lasts 3-4 days

Question 8

What occurs in the inflammation stage of indirect bone healing?

Answer 8

Clot at fracture site

• Osteoinductive growth: angiogenesis, bone formation
• Abundant mast cells: vasoactive substances (new vessel formation)

Question 9

When does the remodeling phase of indirect bone healing occur?

Answer 9

Around 2 months

Question 10

What occurs during the remodeling phase of indirect bone healing?

Answer 10

Clot differentiates into granulation tissue, gain strength, soft callus, mesenchymal cells become osteoblasts (lay down fibrocartilage)

Question 11

What is the governing law of remodeling?

Answer 11

Wolfe’s law
Compression- osteoblasts
Tension- osteoclasts

Question 12

What is the difference of direct and indirect bone healing?

Answer 12

Direct bone healing fills fracture sites with no callus formation

Question 13

How long does it take to gain mechanical strength?

Answer 13

6-12 months

Question 14

What size are the fracture gaps with direct gap healing?

Answer 14

< 1 mm

Question 15

What size are fracture gaps with direct contact healing?

Answer 15

< 0.01 mm

Question 16

What is contact healing initiated by?

Answer 16

Cutting cones of osteclasts directly followed by osteoblasts

Question 17

How far do cones travel per day? (micrometers/day)

Answer 17

50-100

Question 18

What are characteristics of cancellous bone healing?

Answer 18

More stable than cortical bone
No callus formation
Fracture gap filled then cortical shell

Question 19

Fractured zone of hypertorphy will heal how?

Answer 19

Continued growth of physeal cartilage

Question 20

Fractured zone of proliferation will heal how?

Answer 20

Endochondral ossification

Question 21

What is a disadvantage to physeal fractures?

Answer 21

Premature physeal closure (stunted growth)

Question 22

What are factors that affect fracture healing?

Answer 22

Location of fracture
Stability
Method of fixation
Biological environment
Blood supply
Biomechanical vs. Biological Osteosynthesis

Question 23

What is biological osteosynthesis?

Answer 23

Restores overall length and alignment

Limits soft tissue disruption

Question 24

What are the different types of repairs used on fractures?

Answer 24

Intermedullary pins with wire
Cast/splints/no fixation
Bone plates
External skeletal fixator

Question 25

Which repairs utilize indirect healing?

Answer 25

IM pins/wires Casts/splints/no fixation External skeletal fixator

Question 26

What repair heals by direct healing?

Answer 26

bone plates

Question 27

What effect does IM pins/nails have on the blood supply?

Answer 27

Disrupts endosteal blood supply and medullary blood flow

Question 28

What effect does bone plates have on the blood supply?

Answer 28

Disrupt perioseal bone supply

Question 29

What does improper bone implants do to blood supply?

Answer 29

damage blood supply

Question 30

When are bone grafts used?

Answer 30

Bone loss Arthrodesis Delayed/non-union fractures Old age

Question 31

What are the three bone graft origins?

Answer 31

Autograft Allograft Xenograft

Question 32

What are the three functions of bone grafts?

Answer 32

Osteogenesis (osteoblasts) Osteoinduction (mesenchymal cells) Osteoconduction

Question 33

What are the three bone graft types?

Answer 33

Cancellous Cortical Combination

Question 34

What is the gold standard of bone grafts?

Answer 34

Autogenous cancellous bone graft

Question 35

What does Autogenous cancellous bone graft promote?

Answer 35

Osteogenesis

Question 36

What are the four phases of cancellous graft?

Answer 36

Inflammatino (hours) Revascularization (1-2 weeks) Osteoconduction (2-4 weeks) Mechanical support (up to 12 weeks)

Question 37

Where are autograft cortical bone grafts used?

Answer 37

Ribs ulna Fibula Ilial wing

Question 38

What patients are cortical bone grafts indicated in?

Answer 38

Devascularized comminuted fractures | OSA patients and limb sparing procedures where dz is caught early and hasn't metastasized

Question 39

What are the phases of cortical bone graft effects?

Answer 39

Osteoclasts move into graft and resorb bone Osteoblasts follow and lay down new bone Mechanical strength of graft maintained Termed "creeping substitution"