Failure of initial union, as when bone fragments are separated by soft tissue, may also lead to an atrophic non-union. Atrophic non-unions can be treated by stimulating blood flow and encouraging healing. This is often done surgically by removing the end layer of bone to provide raw ends for healing and the use of bone grafts. Oligotrophic nonunion
As the name implies, an oligotrophic nonunion demonstrates some attempt by the body to heal the fracture. These are thought to arise from adequate biology but displacement at the fracture site. Diagnosis
A diagnosis of nonunion is made when the clinician feels there will be no further bone healing without intervention. The FDA defines it as a fracture at least 9 months old that has not shown any signs of radiographic healing within the last 3 months. CT scans offer a closer look at the fracture and may also be used to evaluate how much of the fracture has healed. Blood tests can evaluate if the patient has adequate levels of nutrients such as calcium and vitamin D.  Blood tests can also look for markers of infection such as ESR and CRP. Treatment
Surgery
Currently, there are different strategies to augment the bone-regeneration process, however, there is no standardised clinical treatment guideline yet. Surgical treatment options include:
Debridement: radical surgical removal of necrotic or infected soft tissue and bone tissue is deemed essential for the healing process. Immobilization of the fracture with internal or external fixation.
Nonunion is permanent failure of healing following a broken bone unless intervention (such as surgery) is performed. A fracture with nonunion generally forms a structural resemblance to a fibrous joint, and is therefore often called a "false joint" or pseudoarthrosis (from Greek pseudo-, meaning false, and arthrosis, meaning joint). The diagnosis is generally made when there is no healing between two sets of medical imaging, such as X-ray or CT scan. This is generally after 6–8 months.Nonunion is a serious complication of a fracture and may occur when the fracture moves too much, has a poor blood supply or gets infected. Patients who smoke have a higher incidence of nonunion. The normal process of bone healing is interrupted or stalled.Since the process of bone healing is quite variable, a nonunion may go on to heal without intervention in very few cases. In general, if a nonunion is still evident at 6 months post-injury it will remain unhealed without specific treatment, usually orthopedic surgery. A non-union which does go on to heal is called a delayed union. Signs and symptoms
A history of a broken bone is usually apparent. The patient complains of persistent pain at the fracture site and may also notice abnormal movement or clicking at the level of the fracture. An x-ray plate of the fractured bone shows a persistent radiolucent line at the fracture. Callus formation may be evident but callus does not bridge across the fracture.