Bone healing

Bone healing, or fracture healing, is a proliferative physiological process in which the body facilitates the repair of a bone fracture.Collagen fibers of woven boneOsteoclast displaying many nuclei within its 'foamy' cytoplasmOsteoblasts forming compact bone, containing two osteocytes, within a resorption pit in trabecular bone 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. Adaquate 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 which 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 remodeling 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 which 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. Osteoblasts fill up the cavities with the Haversian system. This causes the formation of lamellar bone that orients longitudinally along the long axis of the bone. Blood vessels form that penetrate the Harversian system. Remodelling of lamellar bone results in healing without callus formation. If the fracture gap is 800 μm to 1 mm, the fracture is filled by osteoclasts and then by lamellar bone oriented perpendicular to the axis of the bone. This orientation of lamellar bone is weak, thus a secondary osteonal reconstruction is required to re-orient the lamellar bone longitudinally. This process takes three to eight weeks. Secondary healing (also known as indirect fracture healing) is the most common form of bone healing. It usually consists of only endochondral ossification. Sometimes, intramembranous ossification occurs together with endochondral ossification. Intramembranous ossification, mediated by perisoteal layer of bone, occurs without formation of callus. For endochondral ossification, deposition of bone only occurs after the mineralised cartilage. This process of healing occurs when the fracture is treated conservatively using orthopaedic cast or immobilisation, external fixation, or internal fixation.