It is the absence of union within the expected time frame or the lack of progress toward union within a certain period. It is influenced by many factors, such as the location of the fracture, which part of the bone is affected, the type of injury, and the presence of infection. In addition to causing deformity and pain, it causes the person to lose their ability to work for a long time. Treatment varies depending on the underlying cause and the type of nonunion. An experienced surgeon and a coordinated approach are important for achieving success.