After generally at least 6 months of fracture healing and no changes are seen on x-ray examination for over one month your physician may tell you that you have a non-union, basically meaning that your fracture is not healing and will not unless something else is done. Three basic types of non-unions exist: atrophic, oligotrophic, and hypertrophic non-unions. A non-union may also be called by some as a pseudarthrosis (false joint), although the two terms are distinctly different.
An atrophic non-union is one in which no bone growth is occurring. There is usually a lack of vascular (blood) flow at the site hindering growth. No external callous is seen. The bones may become pencil-shaped on x-ray due to resorption of the bone ends. This type of fracture usually requires a surgical procedure to use a bone graft to promote healing.
An oligotrophic non-union the external callous is limited but some exists. This type of non-union also would require a bone graft for healing.
Hypertrophic non-unions have excessive callous formation with adequate blood supply for healing. Healing may be hindered in this type of fracture if it is not stablized and not given a chance to heal. Typically immobilization with a cast or surgical stabilization is needed for complete healing.
A pseudoarthrosis is much like a hypertrophic non-union, except that a false joint has been formed where a cartilaginous cap is formed over the ends for the fracture fragments or fibrous tissue interposed between them. Just stabilizing the bones would not be adequate for healing as the cartilage or soft tissue must be removed for end to end bone contact.