Briefly describe the basic healing process of fracture.

Fracture healing can be divided into three stages:

(1) Hematoma formation: Hematoma formation at and around the fracture end, often accompanied by mild inflammatory reaction.

(2) Fibrous callus formation: Hematoma was first replaced by granulation tissue and organized, and then fibrosis formed fibrous callus.

(3) Callus formation: Fibrous callus gradually differentiated into osteoblasts to form osteoid tissue, and then calcium salt was deposited, and the osteoid tissue was transformed into woven bone to form osteoid callus.

(4) Callus reconstruction: The woven bone structure is not compact enough, and the trabecular arrangement is disordered, which can not meet the needs of normal function. On the basis of osteoclasts absorbing original bone and osteoblasts to form new bone, woven bone forms mature lamellar bone which adapts to the stress required by bone activity, and restores the normal relationship between cortical bone and bone cavity and the normal arrangement of trabecular bone.