What is Bone: fracture of bone, causes of fracture, types of reduction, phases of repair process, healing time & remodeling


The hardest tissue in the body composed of collagen, calcium, phosphorus salts and covered by periosteum is called bone.


The breaches in the structure of any bone produced by violence are called fracture despite strength the bone may break.

Causes of fracture

The fracture may occur during youth and old age:

  • During youth, most fractures result from trauma that may twist or break the bones e.g. support injured, automobile accident and fall, etc.
  • In old age, bones become thin/soft.

Treatment of fracture

A fracture is treated by reduction. It is allowed by realignment of the broken/cracked bone ends.

Types of reduction or traction

There are two types of reduction
  • Closed reduction
  • Open reduction

    Closed reduction

    In closed reduction, the bone end is coaxed back to their regular position by the physician's hand.

    Open reduction

    In open reduction, surgery is performed the bone ends are brought together with pins and wires.

    Healing Process

    After the broken/damaged/cracked bone is reduced. It is immobilized by a cast or by traction to allow the healing mechanism to begin.

    Healing time

    Healing time is 56-84 days but it is much longer for a large weight bearing bones. The same poorer blood dissemination or circulation.

    Phases of the repair process

    The repair process of a simple fracture takes place in four phases
    • Hematoma formation
    • Callus formation
    • Bony callus formation
    • Remodeling 

    Hematoma formation

    The mass of clotted RBCs is called hematoma. When a bone breaks/crack the blood vessels in the bone itself and perhaps in the surrounding is torn. It causes hemorrhage. As a result, a hematoma i.e. mass of clotted blood RBCs is formed at the fracture site. 
    Soon after bone cells deprived of food initiate to die. Thus the tissue at the fracture site becomes swollen and hence painful.

    Callus formation

    The tissue build around the fragments of a broken bone which develops into a bone to heal the fracture is called callus.

    Hematoma is followed by callus formation the soft callus begins to form in 3-4 weeks. Capillaries grow into the hematoma. The clear up the debris after removal of debris fibroblast and osteoblast migrate into the fracture site. They begin to the contract/regenerate bones.

    Bony callus formation

    The osteoblast i.e. bone-forming cells and osteoclasts i.e. bone-dissolving cells continue to migrate inward. They multiply speedily and gradually convert soft callus into a bony callus.


    Bone formation begins 3,4 weeks after injury it continues until a firm bony union is formed within 2 to 3 months later.


    After several months bony callus is remodeled by the excess of material on the outside of the bone final structure of remodeled area resembles that of the original unbroken bone. This is due to the fact it responds to the same set of mechanical stimuli.

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