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. More commonly the tissue between the un-united fragments is scar tissue.
Since the process of bone healing is quite variable, a nonunion may go on to heal without intervention in a 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.
1. Hypertrophic non-union : Callus is formed, but the bone fractures have not joined. This can be due to inadequate fixation of the fracture, and treated with rigid immobilization.
2. Atrophic non-union : No callus is formed. This is often due to impaired bony healing, for example due to vascular causes (e.g. impaired blood supply to the bone fragments) or metabolic causes (e.g. diabetes or smoking). Failure of initial union, for example when bone fragments are separated by soft tissue may also lead to atrophic non-union.
Determining the cause of a nonunion is critical to determining the proper treatment. The most common causes of nonunion are:
2. Inadequate blood flow to the bone
3. Separation of the fractured ends of the bone
4. Inadequate stabilization of the fracture .