Fracture repair is usually divided into 3 or 4 significant steps or stages. These stages include the inflammatory phase, the repairing phase, and bone remodeling. In some cases, the repairing phase is divided into two steps, which are soft callus formation and hard callus formation. The entire process typically lasts for 4-5 weeks and usually results in complete bone restoration.
As already mentioned, the first stage is the inflammatory phase. It is also called fracture hematoma formation, and that preliminary healing stage follows the injury for approximately two days. The hematoma formation process involves blood release caused by the destruction of blood vessels by the fracture. Blood clotting leads to the formation of a fracture hematoma. In some cases, the bone fracture may prevent blood flow killing bone cells in the fracture area. The inflammatory stage usually lasts for approximately seven days after the injury.
The repairing phase may begin during the inflammatory phase and usually lasts for fifteen to twenty days. The stage consists of two steps, which result in hard and soft callus formation. During these steps, the fracture hematoma causes blood vessel ingrowth from nearby vessels. The process also forms a cartilage intermediate by endochondral ossification. Soft callus stabilizes the fracture while a bony callus called trabecular bone replaces it.
The last stage is bone remodeling, during which the primary lamellar bone is replaced with secondary lamellar bone. The bone fracture repair is normally complete after that stage, and the vascular supply is fully restored. Nonetheless, in some cases, minor swelling may remain on the outer bone surface. Such an issue normally sorts itself out during a short period.