Nonunion Fracture: (When a Broken Bone Doesn't Heal)

What is nonunion fracture?

A nonunion fracture (which physicians more commonly call a “fracture nonunion” and is sometimes also referred to as a “nonhealing fracture”) occurs when pieces of a broken bone (fractured bone) do not heal solidly together.

After a fracture occurs, the body starts to heal the bone. The healing process, with or without surgery to repair the broken bone, typically takes 6 to 12 weeks. During this time, the body makes new bone to fill-in any spaces or gaps between the edges of the fractured bone pieces. This is similar to how a tree branch mends if it becomes cracked or bent. When a bone is “healed,” it is considered “united” back together.

There are times when the body cannot fully mend the fractured bone pieces back together to form a single solid piece of bone. This is called a nonunion: The bone has not “united” together. In a nonunion situation, X-rays at different points in time will typically show no progression of the fracture healing process. Generally speaking, nonunions are not likely to heal without further medical intervention because the body’s healing process has “petered out.”

In the situation of a nonunion, additional treatments are needed to stimulate the body to resume the healing process. These treatments usually entail surgical nonunion repair, but sometimes nonsurgical methods such as the use of bone stimulators can be effective at getting nonunions to fully heal.

What is the difference between nonunion, delayed union, and malunion of a fracture?

A nonunion is when a fractured bone does not heal solidly back together and X-rays show no progression towards healing. With nonunions, there is little chance the bone will fully heal with additional time. A delayed union means that the bone is healing more slowly than is typical, but the fracture shows progressive signs of healing. Delayed unions have the potential to heal without additional interventions. Malunion is when the bone has healed crooked.

How common are nonunions?

Bone fracture nonunions are not common, but they are not rare either.

What are signs a broken bone isn’t healing?

Clinical signs of nonunion are most commonly pain at the fracture site which is made worse by physical stress on the fractured bone (such as walking on a fractured leg bone). The severity of nonunion pain depends much on how the original fracture was treated. Sometimes, surgically stabilized fractures that go on to develop a nonunion produce very little pain, which can make them detectable primarily through radiological imaging. At other times, especially when there was no surgery to stabilize the bone, a nonunion can be very painful and debilitating.

Why do some bone fractures heal more slowly than others?

Different fractures have different risks for nonunion based on several factors, such as which bone is broken, what portion of the bone was broken, how severe the fracture was, and the general health of the person with the fracture. These same factors also impact the speed at which fractures heal. In general, adults, regardless of age, heal at similar rates. Children, especially those still growing, generally heal faster than adults.

Why do some broken bones fail to heal and develop a nonunion?

The more severe a fracture is, the higher the risk of nonunion. More severe fractures are those that result from higher energy impacts. For example, fractures that occur from a high-speed motor vehicle or motorcycle accident are considered “high energy,” are high severity, and have higher risk of nonunion than “lower energy” fractures such as a broken ankle from a twisting injury. Also, fractures that develop an infection often fail to heal.

There are certain medical conditions, medications, and habits that can slow fracture healing and potentially lead to nonunion. For example, diabetes, oral steroid medications, and smoking are all well known risk factors for developing a nonunion after a fracture.

Are some bones more prone to nonunion than others?

Although any bone can develop a nonunion, some bones are more prone than others. For example, the tibia bone (shin bone) and the scaphoid bone in the wrist have higher risks for nonunion than most other bones. This is mainly because these bones have less robust blood supply (circulation) than other bones. All tissues in the body require good circulation for healing. When blood supply is compromised, so is healing.

Can you walk on a nonunion fracture of the leg?

Walking on a leg nonunion is a very different situation from walking on a fresh fracture. In the situation of a fresh fracture, walking is typically not recommended because it may compromise good fracture healing and it would be very painful. With a nonunion, which is many months after the fracture originally occurred, the situation is very different. Often, pain is the primary limitation for walking on a nonunion. If it is not too painful, then walking on a nonunion may be recommended to help rehabilitate leg muscles. However, the safety of walking on a nonunion depends on many factors and an orthopedic surgeon with extensive experience treating nonunions should be consulted.

Are there different types of fracture nonunions?

Nonunions are generally classified in two ways based on:

1. Whether there is an associated infection or not
2. How much bone healing the body was able to produce.

An infected nonunion (also sometimes called a “septic nonunion”) is when there is an infection in the bone at the site of the fracture nonunion. An “aseptic nonunion” is when there is no infection at the nonunion site

The most common risk factor for an infected nonunion is when the original fracture pierced through the skin. These fractures are called compound fractures or “open fractures.” The bone in such cases is exposed to the “open air” and outside elements. The exposed bone can become contaminated with bacteria from the skin itself (all skin normally has bacteria in it) or any dirt that the bone may have come into contact with. Infection inhibits the healing process and can cause additional pain.

Septic nonunion: A complex condition that requires a complex care team

A septic nonunion refers to a nonhealing fracture complicated by an infection at the fracture site. Normally, the first priority in treating infected nonunions is to manage the associated infection. Once infection is controlled or eradicated, priority shifts to getting the nonunion to heal. Occasionally, both infection treatment and nonunion treatment can occur simultaneously. Infected nonunions are among the most difficult to treat.

At HSS, we have an experienced multidisciplinary team to manage the individual needs of each unique infected nonunion situation.

Our nonunion and bone healing team includes orthopedic surgeons who specialize in these complex problems. HSS infection disease specialists provide expert tailoring of antibiotic treatments, musculoskeletal radiologists provide state-of-the art imaging modalities such as CT, MRI, and bone scans, and metabolic bone specialists can treat underlying bone healing deficiencies and osteoporosis with targeted medications.

Patient case: Treating a complex, infected nonunion of the tibia

A healthy 67-year-old man sustained a compound fracture of his left tibia and fibula in a dirt-bike accident. Initial treatment at another hospital included cleaning of the wound, stabilization of the tibia with internal fixation, and graft of healthy muscle tissue from another section of his leg to cover and improve blood supply to the injured area and protect it from infection.