Bone healing

Bone healing, or fracture healing, is a proliferative physiological process in which the body facilitates the repair of a bone fracture. Generally, bone fracture treatment consists of a doctor reducing (pushing) displaced bones back into place via relocation with or without anaesthetic, stabilizing their position to aid union, and then waiting for the bone's natural healing process to occur. Adequate nutrient intake has been found to significantly affect the integrity of the fracture repair. Age, bone type, drug therapy and pre-existing bone pathology are factors that affect healing. The role of bone healing is to produce new bone without a scar as seen in other tissues which would be a structural weakness or deformity. The process of the entire regeneration of the bone can depend on the angle of dislocation or fracture. While the bone formation usually spans the entire duration of the healing process, in some instances, bone marrow within the fracture has healed two or fewer weeks before the final remodelling phase. While immobilization and surgery may facilitate healing, a fracture ultimately heals through physiological processes. The healing process is mainly determined by the periosteum (the connective tissue membrane covering the bone). The periosteum is one source of precursor cells that develop into chondroblasts and osteoblasts that are essential to the healing of bone. Other sources of precursor cells are the bone marrow (when present), endosteum, small blood vessels, and fibroblasts. Primary healing (also known as direct healing) requires a correct anatomical reduction which is stable, without any gap formation. Such healing requires only the remodeling of lamellar bone, the Haversian canals and the blood vessels without callus formation. This process may take a few months to a few years. When the gap between the bone ends is less than 0.01 mm, and interfragmentary strain is less than 2%, contact healing can occur. In this case, cutting cones, which consists of osteoclasts, form across the fracture lines, generating cavities at a rate of 50–100 μm/day.