The fractured bone heals by different stages.
healing starts by hematoma and ends by remodeling
this Educational video describing the mechanisms and stages of fracture healing by secondary bone healing. it will explain both types of bone healing.
Primary bone healing
Cutting cone mechanism
There is no motion at the fracture site. Seen in rigid fixation of fractures such as in plate fixation. Minimal callus formation.
What is a cutting cone?
Osteoclasts at the front remove the dead bone. Osteoblasts lay down new bone at the site of the old bone. Osteoclast eat up or dissolve the bone tissue with their powerful enzyme systems. Osteoblasts lay down new bone stimulated by hormones and growth factors.
Cutting cones are formed that cross the fracture site. This is a slow process often taking months to years to complete.
Contact healing
Contact between the fracture ends allows healing to begin immediately.
Gap healing
•Larger gaps do not heal very well.
•Could be filled with fibrous tissue.
Secondary bone healing
Endochondral mechanism
•Seen in flexible fixation of fractures such as fractures stabilized by rods and casts. Occurs with abundant callus.
•Undergoes endochondral ossification.
•Chondrocytes hypertrophy and degenerates then calcify followed by vascular invasion and ossification.
Stages of fracture healing
1-Hematoma
2-Inflammation
3-Soft callus
4-Hard callus: woven bone = hard callus
5-Remodeling: remodeling is a process by which immature or woven bone is converted to mature or lamellar bone. The meduallry cavity is reconstituted and bone is reconstructed in response to stress. There is more remodeling potential in children.

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