Fracture breaks continuity of bone and of important attached soft tissue--including blood vessels, which spill their contents into surrounding tissue.
Even before treatment, the body automatically seeks to repair the injury. Inflammatory cells rush to destroy, dilute or isolate invaders and injured tissue. Tiny new blood vessels called capillaries begin growing into the site. Cells proliferate. The injured person usually must endure pain, swelling, and increased heat at the breakage site for one to three days.
New tissue bonds the fractured bone ends with a soft callus, a mass of connective tissue and exudate (matter escaped through blood vessel walls). Remodeling begins. Within a few months, a hard callus replaces the soft one. Remodeling restores the inner canal.
Once restoration is complete, which may take years, the healed area is brand new, without a scar. Usually thicker, the new bone may even be stronger than the old.