Bone Growth and Fracture healing

Question 1

What is the role of the medullary cavity?

Answer 1

> Lightens bone
Haematopoeitic centre
Contains blood vessels

Question 2

What is the role of spongy bone?

Answer 2

Acts to absorb excessive mechanical stress/load

Question 3

Bone growth?

Answer 3

1) Hyaline cartilage “model”
2) Primary ossification centre
3) Secondary ossification centre
4) Epiphyseal plate
5) Compact bone and spongy bone

Question 4

What is the name of the shaft of a bone?

Answer 4

Diaphysis

Question 5

What is the name of the end of the shaft of a bone?

Answer 5

Metaphysis

Question 6

What type of bone makes up the diaphysis?

Answer 6

Cortical bone

Question 7

What type of bone makes up the metaphysics?

Answer 7

Cancellous/spongy bone

Question 8

What does cortical bone resist?

Answer 8

Bending and torsion

Question 9

What does cancellous bone/spongy bone resist?

Answer 9

Compression

Question 10

Which type of bone is more biologically active?

Answer 10

Cancellous bone

Question 11

How is cortical bone laid down ?

Answer 11

Circumferentially

Question 12

How is cancellous bone laid down?

Answer 12

Site of longitudinal growth (Physis)

Question 13

What is a fracture?

Answer 13

> Break in structural continuity of bone

> May be a crack, break, split, crumpling, buckle

Question 14

What does # indicate?

Answer 14

Shorthand for a fracture

Question 15

Why do bones fail/fracture?

Answer 15

> High energy transfer in normal bones (Takes a lot)

> Repetitive stress in normal bones (Stress fracture)

> Low energy transfer in abnormal bones:

• Osteoporosis
• Osteomalacia, metastatic tumour
• Other bone disorders

Question 16

How many stages are there in bone repair?

Answer 16

Four stages:

1) Inflammation
2) Soft callus
3) Hard callus
4) Bone remodelling

Question 17

What occurs during stage 1 (Inflammation) of bone repair?

Answer 17

> Hematoma and fibrin clot
Platelets, PMN’s, Neutrophils, Monocytes, Macrophages
Fibroblasts
Mesenchymal & Osteoprogenitor cells
Angiogenesis

Question 18

What is required for angiogenesis to occur in stage 1 on bone repair?

Answer 18

Low oxygen gradients, hypoxic conditions stimulate macrophage to produce angiogenic factors

Question 19

What can affect stage 1 (inflammation) in bone repair leading to slowing of bone repair?

Answer 19

> NSAID’s

> Loss haematoma

• Open fractures
• Surgery

> Extensive tissue damage
- Poor blood supply

Question 20

What can be used to affect stage 1 (inflammation) in bone repair aiding bone repair?

Answer 20

Inject platelet concentrates into the fracture site:
> Buffy coat”
> Platelet-derived growth factor (PDGF)
> Transforming growth factor-beta (TGF-B)
> Insulin like growth factor (IGF)
> Vascular endothelial growth factor (VEGF)

Question 21

When does stage 2 (Soft callus) of bone repair begin?

Answer 21

When pain and swelling have subsided

Question 22

When does stage 2 (Soft callus) of bone repair last until?

Answer 22

Lasts until bony fragments are united by cartilage or fibrous tissue

Question 23

What is the gold standard in aided repair of bone in stage 2 (soft callus) of repair?

Answer 23

Autogenous Cancellous bone graft:
> Osteoconductive = Bone grows through it
> Osteoinductive = Stimulate bone growth

Best from the patient themselves

Question 24

Options in spending up/aiding stage 2 (Soft callus) of bone repair?

Answer 24

> Replace cartilage
- DMB (demineralised bone matrix)

> Jump straight to bone

• Bone graft
• Bone substitutes

Question 25

What is meant by an allograft?

Answer 25

From someone else (Or cadaver)

Question 26

What are the risks we think of when using an allograft?

Answer 26

Risk of disease transfer = Think of prions and Mad cows disease

Question 27

What type of bone formation is there in allograft bone repair?

Answer 27

> Osteoconductive

> Creeping substitution

Question 28

What is meant by cancellous?

Answer 28

Cancellous = “cut up” into small pieces

Question 29

What is meant by osteoconductive?

Answer 29

Doesn’t have the cells within it to stimulate osteoinduction (growth)

Question 30

What is meant by creeping substitution?

Answer 30

Creeping substitution = Removal of dead bone and replaced within living

Occurs within allograft bone repair

Question 31

What occurs during stage 3 (hard callus) bone repair?

Answer 31

> Conversion of cartilage to woven bone

> Typical long bone fracture

• Endochondral bone formation
• Membranous bone formation

Question 32

What is the main role of stage 3 bone (Hard callus) repair?

Answer 32

Increasing bone rigidity

Question 33

What is meant by primary and secondary bone healing in stage 3 (Hard callus) of bone healing?

Answer 33

Secondary = Normal bone healing

Surgery = Primary bone healing

Question 34

What occurs in stage 4 (Remodelling) of bone healing/

Answer 34

> Conversion of woven bone to lamellar bone

> Medullary canal is reconstituted

> Bone responds to loading characteristics Wolff’s Law

Question 35

What is critical in progression of fracture repair?

Answer 35

> Mechanical properties of tissue and their environment are critical for the progression of fracture healing described by Wolff’s law

> If strain is too low mechanical induction of tissue differentiation fails

> Too high and healing process does not progress to bone formation

Question 36

The may delayed union occur in fractures?

Answer 36

>  high energy injury
 distraction 
(increased osteogenic jumping!)
>  instability
>  infection
> steroids
> immune suppressants
> smoking
> warfarin
> NSAID
> Ciprofloxacin

Question 37

What should you do when there is delayed healing in a fracture?

Answer 37

Consider an alternative management:
> different fixation
> dynamisation
> bone grafting

Question 38

Non-union?

Answer 38

Failure of fracture to heal

> failure calcification fibrocartilage 
> instability 
	-excessive osteoclasis
> abundant callus formation
> pain + tenderness
> persistent fracture line
 sclerosis