# Bone Repair --- **Bone repair** is the process that [[bone|bones]] undergo when they have been [[bone fracture|fractured]]. The healing process is similar to regular [[healing|tissue healing]] and will begin with or without medical intervention. If it is not set, or "fixated" into the correct anatomical position it will heal up in a deformed position. ## Step 1: Fracture Hematoma The bone fracture will be accompanied by torn a [[blood vessels]]—either from the [[bone#Endosteum Periosteium|periosteum]] osteon (??), and/or the [[bone#Structure|medullary cavity]]—and this blood forms a clot called a **fracture hematoma**. ## Step 2: Internal & External Callus An **internal callus** and **external callus** work to stabilize the fracture, and they are usually formed within 48 hours in. The internal callus is made from [[cartilage|chondrocytes]] from the [[bone#Endosteum Periosteium|endosteum]] which secrete a [[cartilage#Types|fibrocartilaginous matrix]], which attaches to the inside edges of the fracture and connects them together. The external callus is made from chondrocytes and [[bone|osteoblasts]] from the [[bone#Endosteum Periosteium|periosteum]] which make [[cartilage#types|hyaline cartilage]] and [[bone]] matrix that encircles the bone at the level of the fracture in order to stabilize from the outside. ## Step 3: Retortion & Ossification The next step takes place over several weeks. [[bone|Osteoclasts]] resorb dead bone and [[bone|osteoblasts]] lay down new bone. Cartilage in the calli undergoes [[ossification|endochondral ossification]] and forms [[bone|spongy bone]]. The internal and external calli eventually unite, and the spongy bone on the outside edges is replaced with [[bone|compact bone]]. When this is done the bone is structurally intact again and can withstand normal stresses. ## Step 4: Remodeling There is still a bulge at the fracture site after the bone is knit back together from where the calli were. This last stage takes place from four months to over a year after the initial fracture, where osteoblasts perform [[bone remodeling]] the callus and bulges of the fracture site. ___