Mending a broken bone is somewhat like mending a broken saucer, except the doctor doesn't have to apply any glue. This is produced by connective tissue cells of the bone itself.
Bone tissue has an amazing ability to rebuild itself. When bone is broken, bone and soft tissues around the break are torn and injured.
Some of the injured tissue dies. The whole area containing the bone ends and the soft tissue is bound together by clotted blood and lymph.
Just a few hours after the break, young tissue cells begin to appear — the first step in repairing the fracture. These cells multiply quickly and become filled with calcium. Within 72 to 96 hours after the break, these cells form a tissue which unites the ends of the bones.
More calcium is deposited in this newly formed tissue which eventually helps form hard bone, developing into normal bone over a period of months.
A plaster (what we usually call POP) cast is usually applied to the broken limb in order not to move the bone and keep the edges in perfect alignment.
Credit : Tell Me how