After a bone breaks, modern treatment allows almost all to heal completely. In rare cases, however, a fracture does not heal, resulting in a nonunion. In other cases, the fracture takes far longer to heal than usual, which is called a delayed union.


Nonunions usually lead to a continuation of the pain at the site of a break, even after the initial pain of the fracture has passed. 

The pain from a nonunion may last months or even years if treatment is not sought.

Causes and Risk Factors

For a fracture to heal, the bone needs to be stabilized, usually with a cast or, in some cases, surgery is required to use plates, screws or nails to stabilize the bone. The bone also needs a steady blood supply. Blood brings oxygen, healing cells and growth factors to the bone to allow it to heal. If a fractured bone is left unstable or lacks blood supply, it can lead to a nonunion.

Factors including the use of tobacco or nicotine can impede bone healing and increase the risk of nonunion. Older individuals and those with diabetes, severe anemia or a infection also face an increased risk of nonunion if they break a bone. Medications such as anti-inflammatory drugs, including aspirin, ibuprofin and prednisone, also increase the risk of nonunion, since they affect blood flow.

Nutrition can also affect the risk of nonunion, since bones need protein, calcium, vitamin C and D, and other minerals to ensure proper healing.

Some bones, such as toe bones, have excellent stability and blood flow and almost never lead to a nonunion. Other bones, such as the upper thighbone (femoral head and neck) and small bones of the wrist have limited blood supply and are at higher risk after a fracture of developing a nonunion.


Persistent pain at the site of a fracture or a fracture that does not heal in the usual time frame will lead a physician to order an X ray,  MRI and/or CT scans to check to see if a nonunion has occurred. A blood test may also be used to determine if an infection has caused the nonunion.


In some cases, a bone stimulator can be used to treat a nonunion. A bone stimulator is a small device that delivers ultrasonic or pulsed electromagnetic waves to a bone to stimulate healing. The stimulator is placed over the skin near the nonunion for between 20 minutes and several ours each day. The stimulator must be used every day to be effective until the nonunion heals.

If a bone stimulator fails to heal a nonunion or if the fracture is severe, surgery may be required. Several types of surgery can be used to treat a nonunion depending on the individual case.

A surgeon may perform a bone graft to provide a framework upon which new bone can grow. Bone grafts provide fresh bone cells and other naturally occurring chemicals in the bone that can aid growth to heal a nonunion. In the procedure, small pieces of bone are taken or harvested from different parts of the patient's body, usually from the rim of the pelvis or iliac crest. The amount of bone removed does not cause any functional, structural or cosmetic damage to the bone.

Since harvesting bone from a patient can be painful, a second option is to use bone harvested from a cadaver, called an allograft. The bone from the cadaver is processed and sterilized to minimize the risk of infection to the patient.

In some cases, a surgeon may recommend the use of bone graft substitutes or osteobiologics, which are commercially made bone-like substances. They provide a framework for new bone to grow and can be supplemented with other products that mimic the chemicals found in real bone that stimulate growth.

Besides grafting bone to the fracture site, the nonunion is also usually stabilized during a surgical procedure. The stabilization can be done internally, by using metal plates and screws attached to the bone or by placing a rod in the inside canal of the bone. A surgeon may also recommend external fixation of a nonunion, which uses a scaffold-like rigid frame outside the injured arm or leg to stabilize the fracture. The frame is attached to the bone with wires or pins.

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