Nonunion

Nonunion is a complication where a broken bone or bone fusion does not heal properly. The bone does not grow together.

If a nonunion occurs, there will usually be some very small amount of motion still between the bone ends, and that is usually painful. One cause of persistent pain after an arthrodesis operation is nonunion.

Causes
Nonunions occur with different frequencies in arthrodesis operations on different joints. Some bones have a high rate of healing, while others have a high rate of nonunion. That probably has most to do with the blood supply in each particular bone – some have a better blood supply than others.

There are some conditions that can increase the chance of a nonunion occurring. Smoking cigarettes, putting weight on the leg before the six weeks after surgery or taking some medications may increase the chance of a nonunion. Patients with diabetes, renal failure and vascular disease also have an increased risk of having a nonunion. These conditions also can lead to poor healing of bone if there is a fracture.

Treatment
If a nonunion occurs the initial treatment will be to extend the period of protected weightbearing. If that is not successful, there are external devices that can be put over the area to generate an electric field, which may promote the bone healing. To be effective these must usually be used for at least 4 months.

Sometimes it will be necessary to do further surgery, and use bone graft to obtain fusion.

If a nonunion occurs, any screws or wires at the site are in danger of breaking. They may need to be removed.