Long bone fractures heal without complications in most patients. Only a small percentage of fractures, between 2 % and 10 %, result in delayed union or non-union. The process of fracture healing involves several stages, including inflammatory reaction, production of soft callus and then rigid bone, and remodelling. Delayed union is defined as the absence of radiographic progression of healing or the instability of a fracture upon clinical examination between 4 and 6 months after injury. Non-union is defined as a fracture that does not unite within 9–12 months. or the extension of the healing process beyond the expected rate. Mal-union refers to the healing of a fracture with incorrect anatomical alignment. Various aspects of the stages of fracture healing, aetiology and pathogenesis of delayed union, non-union and mal-union and the optional treatment modalities of these pathologies are reviewed and discussed.
