bone healing

Question 1

What are the 3 phases of bone healing

Answer 1

1. inflammatory
2. restorative
3. remodelling

Question 2

Describe the inflammatory phase of bone healing

Answer 2

1. fracture causes damages to bone structures & surrounding soft tissues
2. at cellular level, lysis of osteocytes & cells of dead soft tissue leads to liberation of substances in fracture site that attract inflammatory cells & macrophages to clear away necrotic material
3. blood clot forms at fracture site within few hours of injury
   - clot important in neovascularisation to fracture site
4. phagocytes clean site of fracture

Question 3

Describe the restorative phase of bone healing

Answer 3

characterised by formation of callus

1. first soft callus produced is similar to hypercellular fibrocartilaginous tissue
2. callus (though elastic) starts to stabilise fracture site

Process takes 4 days to 3 weeks

3. as fracture is stabilised & blood supply is restored, newly formed cartilage is progressively substituted by bone tissue via endochondral ossification (osteoblasts)
4. results in formation of hard callus

Begins 2 weeks after fracture & ends between week 6 & 12

Question 4

What is compartmental syndrome?

Answer 4

a large bleed into the spaces between surrounding tissues => blood loss and hypovolaemic shock

Question 5

Describe the remodelling phase of bone healing

Answer 5

1. ends of bone are enveloped by a fusiform mass (callus)
2. remodelling occurs involving osteoclasts

slow process - months to years

Question 6

Label the stages of bone healing

Answer 6

Question 7

In the restorative phase, what types of healing occur?

Answer 7

First intention (minimal bone callus formation)

Second intention (most common natural type of healing)

Question 8

Describe healing by first intention

Answer 8

Characterised by direct formation of bone tissue in fracture line without creation of bone callus

Very important that blood supply is not excessively damaged (esp. intraosseous supply)

Ossification by first intention takes place much faster than by secondary intention but at first direct osteonal union is not as stable

Only achieved under following conditions:
- immediate stabilisation
- good blood supply
- perfect reduction of fracture edges (reducible fracture)
- absence of micro-movements at level of fracture line
- interfragmentary compression (Roux law)
- absence of infection

Question 9

What can be used to provide interfragmentary compression to a fracture?

Answer 9

Patients own weight

Application of osteosynthesis systems that compress fracture lines

Placement of osteosynthesis systems that redistribute weight

Question 10

What are the circumstances under which secondary intention healing occurs

Answer 10

late treatment

deficient reduction of fracture or loss of fragments

poor blood supply

infection

absence of forces of compression