Fracture Healing

Question 1

Name some of the functions of bone.

Answer 1

Support
Protection Movement
Calcium and phosphate storage

Question 2

What is cortical bone?

Answer 2

Compact or tubular bone
- 80% of the skeleton
Slow turnover rate/metabolic activity
Lines the outside of the bone

Question 3

What is cancellous bone?

Answer 3

Spongy or trabecular bone
High turnover rate
High remodelling rate 
Elastic 
Found at the centre of bones (contains bone marrow)

Question 4

Describe the composition of bone.

Answer 4

Matrix
- organic (collagen, mucopolysaccharides and non-collagenous proteins)
- inorganic (calcium and phosphate)
Cells
- osteoclasts
- osteoblasts
- osteocytes
- osteoprogenitor cells

Question 5

How much of the matrix is organic, and what is it composed of?

Answer 5

40% organic components
Collagen (type 1)
Proteoglycans
Noncollagenous protiens
Growth factors
Cytokines

Question 6

How much of the matrix is inorganic, and what is it composed of?

Answer 6

60% inorganic components
Calcium hydroxyapatite
Calcium phosphate

Question 7

What are the names for the three different parts of a long bone?

Answer 7

Diaphysis - shaft
Epiphysis - end of the bone
Metaphysis - transitional flared region between the diaphysis and epiphysis

Question 8

What is the physis of a bone?

Answer 8

Unique, cartilaginous feature of children’s bone
- responsible for skeletal growth
Allows remodelling of angular deformity after a fracture
If the physeal blood supply was damaged, it would cause growth arrest (partial or complete)
Is seen as a line of lucency at the metaphysis on an X-Ray

Question 9

What are the two methods of fracture healing?

Answer 9

Indirect - secondary
- via callus formation
Direct - primary

Question 10

What is the definition of indirect healing?

Answer 10

Formation of bone via a process of differential tissue formation until skeletal continuity is restored
Inflammation, repair and remodelling

Question 11

What are the four stages of indirect fracture healing?

Answer 11

1) Fracture haematoma and inflammation
2) Soft callus formation
3) Hard callus formation
4) Bone remodelling

Question 12

Describe the process of fracture haematoma and inflammation.

Answer 12

Blood from the broken vessels form a clot
- occurs 6-8 hours after injury
The dead bone cells cause swelling and inflammation to occur at the fracture site
- TNF-beta (regulatory protein in fracture healing)

Question 13

Describe the process of soft callus formation.

Answer 13

Fibrocartilage (soft) callus lasts for about 3 weeks

• new capillaries organise the fracture haematoma into granulation tissue (procallus)
• fibroblasts and osteogenic cells invade the pro-callus
• collagen fibres are made (connect the ends of the bone together)
• chondrocytes begin to produce fibrocartilage

Question 14

Describe the process of hard callus formation.

Answer 14

Bony (hard callus) lasts for around 3-4 months

- osteoblasts make woven bone, connecting the ends of the fracture together

Question 15

Describe the process of bone remodelling after a fracture.

Answer 15

Osteoclasts remodel woven bone into compact bone and trabecular bone
- often no trace of fracture line on the X-Ray

Question 16

What is direct fracture healing?

Answer 16

Artificial surgical situation
Holds the fracture stable directly (metal plates drilled into the bone)
- no movement at all is allowed
Relies on compression of the bone ends

Question 17

Define direct fracture healing/

Answer 17

Direct formation of bone, without the process of callus formation, to restore skeletal continuity

Question 18

How does direct fracture healing work?

Answer 18

The two ends of the fracture are pressed tightly together.
Bone is formed directly (without a callus) via osteoclastic absorption and osteoblastic formation
- osteblasts remove bone across the fracture site and osteoclasts trail behind and form bone across the fracture site
- ‘cutting cones’

Question 19

In both types of healing, what most the bone have in order to heal successfully?

Answer 19

A blood supply

Question 20

What are the names of the arteries that supply blood to the bone?

Answer 20

Inner 2/3rds
- endosteal
Outer 1/3rd
- periosteal

Question 21

What can compromise the blood supply?

Answer 21

Surgical factors (iatrogenic inhibition)
Anatomical fractures

Question 22

What anatomical factors can compromise the blood supply?

Answer 22

Proximal pole of scaphoid fractures
Talar neck fractures
Intracapsular hip fractures
Surgical neck of humerus fracture

Question 23

What are the risk factors that can inhibit fracture healing?

Answer 23

Increasing age
Diabetes
Anaemia
Malnutrition 
PVD
Hypothyroidism 
Smoking
Alcohol

Question 24

What medications often inhibit fracture healing?

Answer 24

NSAIDs
Steroids
Bisphosphonates

Question 25

How do NSAIDs inhibit fracture healing?

Answer 25

NSAIDs reduce local vascularity at the fracture site

May also affect healing independent of blood flow

Question 26

What action of NSAIDs seem to have the biggest effect on fracture healing?

Answer 26

COX-2 inhibition

Question 27

How do bisphosphonates inhibit fracture healing?

Answer 27

Inhibit osteoclastic activity
- remodelling can’t occur
- cutting cones cant occur in direct healing
These have a long half life, so patients may not heal properly for several months