bone healing Flashcards
What are the 3 phases of bone healing
- inflammatory
- restorative
- remodelling
Describe the inflammatory phase of bone healing
- fracture causes damages to bone structures & surrounding soft tissues
- 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
- blood clot forms at fracture site within few hours of injury
- clot important in neovascularisation to fracture site - phagocytes clean site of fracture
Describe the restorative phase of bone healing
characterised by formation of callus
- first soft callus produced is similar to hypercellular fibrocartilaginous tissue
- callus (though elastic) starts to stabilise fracture site
Process takes 4 days to 3 weeks
- as fracture is stabilised & blood supply is restored, newly formed cartilage is progressively substituted by bone tissue via endochondral ossification (osteoblasts)
- results in formation of hard callus
Begins 2 weeks after fracture & ends between week 6 & 12
What is compartmental syndrome?
a large bleed into the spaces between surrounding tissues => blood loss and hypovolaemic shock
Describe the remodelling phase of bone healing
- ends of bone are enveloped by a fusiform mass (callus)
- remodelling occurs involving osteoclasts
slow process - months to years
Label the stages of bone healing
In the restorative phase, what types of healing occur?
First intention (minimal bone callus formation)
Second intention (most common natural type of healing)
Describe healing by first intention
Direct bone formation at fracture line without callus
Faster than secondary healing but initially less stable
Requires:
- Immediate stabilization & good blood supply (esp. intraosseous)
- Perfect fracture reduction (reducible fracture)
- No micro-movements at fracture site
- Interfragmentary compression (Roux law)
- No infection
What can be used to provide interfragmentary compression to a fracture?
Patients own weight
Application of osteosynthesis systems that compress fracture lines
Placement of osteosynthesis systems that redistribute weight
What are the circumstances under which secondary intention healing occurs
late treatment
deficient reduction of fracture or loss of fragments
poor blood supply
infection
absence of forces of compression