Callus formation is seen between what duration of fracture healing -
Ans. is 'c' i.e., 4-12 weeks Healing of a fractureo The process of fracture healing varies according to the type of bone involved and the amount of movement at the fracture site. Following healing processes are thereA) Indirect fracture healing (healing bv callus)o This is the 'natural' form of healing in tubular bones and in the absence of rigid fixation when there is micromovement at fracture site. There is formation of internal and external callus. This stage is divided in three phases w hich are further subdivided into five stages :Reactive phase (phase 1)It consists ofHematoma stage (stage 1)o Blood seeps out through tom vessels and forms a haematoma between and around the fracture surface. This stage lasts from few hours to days.Inflammatory and granulation stage (stage 2)o The most prominent feature in the early stages of repair is inflammatory reaction with migration of inflammatory cells and the initiation of proliferation and differentiation of mesenchymal stem cells from the periosteum, the breached medullary canal and surrounding muscle. These inflammatory cells are precursors of osteoblasts. The clotted haematoma is slowly absorbed and fine new capillaries grow into the area, i.e. formation of granulation tissue. This stage begins within 8 hours and lasts up to 2-3 weeks. Fracture is still mobile.Reparative phase (phase 2)It consists ofStage of callus / cartilage callus formation (stage 3)o As the cellular tissue matures, the basic cells give rise to osteoblast and in places chondroblasts. The osteoblasts Say down an intercellular matrix which soon becomes impregnated with calcium salts to form callus, also called woven bone (immature bone). The woven bone imparts rigidity to the fracture and fracture is no more labile. The callus is the first sign of union visible on X-ray, usually 3-4 weeks after the fracture.This stage lasts for about 4-12 weeks.Stage of consolidation / lamellar bone deposition (stage 4)o The woven bone that forms the primary callus is gradually transformed by the combined activity of osteoblasts and osteoclasts into more mature bone with a typical lamellar structure (lamellar bone).Remodeling phase (phase 3)This phase consists of >Remodelling to original bone contour (stage 5)o The fracture has been bridged by a cuff of solid bone. Over a period of months, or even years, this crude 'weld' is reshaped by a continuous process of alternating bone resorption and formation. The bone is gradually strengthened along the lines of stress at the expense of the surplus bone outside the lines of stresses, which is slowly removed.Medullary canal is reconstituted.B) Direct bone healing iPrimary bone healing / healing bv primary intention)o This type of bone repair is seen when bone fragments are anatomically reduced and rigidly fixed, i.e. there is no micromovement at fracture site. No external callus forms and the fracture site is bridged by direct baversian remodelling which is almost a direct osteon to osteon hook up. The osteoclasts act as cutter heads to remove the bone and are in the forefront promptly followred by osteoblasts behind laying down new bone. This type of healing (union ) cannot be obtained by closed reduction, but is only by open reduction and rigid internal fixation.
0 - 2 weeks
2 - 4 weeks
4-12 weeks
12- 16 weeks
Anatomy of Bone & Fracture Healing