What happens when a Bone Fractures


A fracture is the medical term, used for a broken bone. They are so common that  average person has two during a lifetime as per statistics. It is a phenomenon which always occurs suddenly when the physical force exerted on the bone is stronger than the bone itself may be even for a moment.

Types of major fracture:

A Greenstick fracture  is an incomplete fracture in which only one side of  bone is bent. It occurs in infants and in young children whose bones are very soft like a green stick.

A transverse fracture (Oblique) where broken piece of  bone is at a 90° to the bone’s axis.

An oblique fracture where the bone is broken in curved or sloped shape.

A comminuted fracture where the bone is broken into several pieces.

A buckled fracture (impacted fracture)  where ends are driven into each other (in children).

A pathologic fracture occurs due to any disease where bones are severely weakened.

A stress fracture (hairline crack) when broken bone is attached to its parent body.

Closed or simple fracture where skin remains intact.

Opened or Compound fracture where one end of broken bone tears through the skin.

Overall, in almost all fractures, the broken bone heals up itself but, the only precaution required is to make sure that the pieces of bone are lined up correctly. The bone needs to recover fully in strength, movement and sensitivity. However, some complicated fractures may need bone grafting, surgery or surgical traction (or both) also.

How the Bone is Repaired:

When a bone breaks, the blood starts flowing from vessel which is broken by the fracture. These vessels could be in the periosteum (a thick layer of vascular connective tissue covering the bones except at the surfaces of joints), osteons, and/or medullary cavity. The blood begins to clot, and about six to eight hours after the fracture, the clotting blood has formed a fracture hematoma. The disruption of blood flow to bone results in death of bone cells around the fracture. The healing of a bone fracture follows a series of following steps:


(A)  fracture hematoma forms > (B) Internal and external Calli forms >  (C) Cartilage of the calli is replaced by trabecular bone > (D) Remodeling occurs.

Within about 48 hours after the occurrence of any fracture, Chondrocytes (Collagen and Proteoglycans). From the endosteum have created an internal callus by secreting a fibrocartilaginous matrix between 2 ends of broken bone, while, the periosteal chondrocytes and Osteoblasts create an external callus of hyaline cartilage and bone, respectively, around the outside of the break. This is how the fracture is stabilized.

Over the next several weeks, Osteoclasts resorb (dissolve & assimilate) the dead bone & Osteogenic cells become active, divide, and differentiate into Osteoblasts. The cartilaginous calli (pleural of callus) is replaced by Trabecular bone (also called Cancellous bone) via endochondral Ossification.

Finally, the internal and external calli unite, compact the bone, replaces spongy bone at the outer margins of fracture, and healing is complete. A slight swelling may remain on the outer surface of the bone, but quite often, that region undergoes remodeling and no external evidence of the fracture remains in that area.