All of the following factors fascilitate non union except:

A i.e. Hematoma formation Fracture healing process passes through several stages. In which the, first is stage of hematoma formationQ and the last is stage of remodelingQ Fracture Healing Bone is a unique tissue because it heals by the formation of normal bone, as opposed to scar tissue. Infact it is considered a nonunion when a bone heals by fibroblastic response. The majority of fractures heal by secondary (callus) healing through a combination of intramembranous - ossification (hard callus formation) & endochondral ossificaion (soft callus formation). Bone healing can be divided into following phases depending on the biological events. * There are two sources of repair tissues (callus), medullary & periosteal. The former is most marked in cancellous hone, while the later predominates in diaphyseal fracture. Periosteal callus may be of two types - primary callus (from DOPC) & external bridging callus (from IOPC), its appearance is inhibited by rigid fixation as plate and is predominant form of healing in cast immobilization &intramedullary nailing. (i.e. micromovements present) * Late medullary callus is more dependent on intramedullary vascularity (not on external soft trissue) and is impoant in fractures immobilized by rigid plating (i.e. no micrmovements)* Phenomenon of Creeping Substitution occurs in cancellous bone (i.e. blood vessels invading the trabeculae of bone directly causing bone apposition)* The modification of previously undifferentiated soft tissue cells in to osteogenic cells (IOPC) is termed bone induction.