- Stage 1 - Haematoma
formation - Immediately following trauma. A variable amount of bleeding
from torn vessels; if the periosteum is torn this blood may extend into
the surrounding muscles.
- Stage 2 -
Traumatic inflammation - The tissue damage excites an inflammatory
response, the exudate adding more fibrin to the clot already present.
There is an increased blood flow and a polymorphonuclear leucocytic
infiltration.(12hours)
- Stage 3 - Demolition -
Macrophages invade the clot and remove the fibrin, red cells,
inflammatory exudate and debris.(12-36 hours)
- Stage 4 - Formation of
granulation tissue - Following demolition there is an in growth of
capillary loops and mesenchymal cells derived from the periosteum and
the endosteum of the cancellous bone. This contributes to the
granulation tissue formation.( <2 weeks)
- Stage 5 - Woven bone
and cartilage formation- The mesenchymal osteoblasts differentiate to
form woven bone. The collagen fibers and ground substances laid by
osteoblasts makes the callus hard. ( 2-3 weeks)
- Stage 6 - Formation of
lamellar bone - The disorganised collagen fibers are arranged in a
lamellar fashion and more calcification occures.(1-3 months)
- Stage 7 Remodelling -
The continued osteoclastic removal and osteoblastic laying down of bone
results in final bone formation.(>3 months)
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