The body naturally initiates a complex sequence of events to repair a broken bone, a process that typically progresses without complication. Healing begins immediately with inflammation and the formation of a blood clot (hematoma) at the fracture site. Specialized cells then create a soft callus of cartilage and fibrous tissue, which is replaced by a hard callus of woven bone, offering structural stability. While most fractures achieve union within six to twelve weeks, this regenerative process can sometimes falter, signaling a need for medical attention.
Identifying the Warning Signs
One persistent indicator that a broken bone is not healing properly is pain that fails to diminish as expected. While initial discomfort is normal, pain should progressively lessen as the hard callus forms. Continued, deep aching, or pain that intensifies with use, suggests the bone ends are not bridging. This persistent pain may also be accompanied by prolonged swelling, tenderness, or warmth at the fracture site.
A lack of mechanical stability is another warning sign that the healing process is compromised. Patients may notice an inability to bear weight or use the limb after the prescribed immobilization period. Alarming symptoms include feeling movement, instability, or a gritty, grinding sensation (crepitus) at the fracture site. These observations indicate that the fractured ends are not securely fused and are moving against each other.
If the limb shows a noticeable bend or curve where it should be straight, this indicates a potential malunion or nonunion fracture. Signs of infection, such as persistent redness, warmth, or drainage, can completely halt the healing process and require immediate medical evaluation. Any plateau or worsening of pain, function, or stability, compared to expected progressive improvement, should prompt a conversation with a physician.
Defining Delayed Union and Nonunion
When bone healing takes significantly longer than the average time frame, it is medically classified as a delayed union. A fracture is considered delayed when it has not consolidated within the expected period for that specific bone and fracture pattern, but it still shows signs of slow, progressive healing. This means that biological activity is ongoing, and the fracture is likely to heal, perhaps with extended immobilization.
A nonunion signifies that the healing process has completely stopped, and the bone will not achieve union without specific medical intervention. The U.S. Food and Drug Administration (FDA) typically defines a nonunion as a fracture site showing no progressive signs of healing for at least nine months. Imaging tests, such as X-rays or CT scans, confirm this stage by showing a persistent gap between bone fragments and a lack of callus formation. Nonunion is a definitive failure of the bone to repair itself, requiring treatment to restart the biological healing cascade.
Factors That Impede Bone Healing
The success of bone healing relies on adequate stability, sufficient blood flow, and a favorable biological environment. Smoking significantly impairs healing because nicotine causes vasoconstriction, which reduces blood flow and oxygen delivery to the fracture site. Chronic systemic diseases, such as poorly controlled diabetes mellitus, also compromise healing by affecting osteoblast function and impairing new blood vessel formation, leading to a weaker callus.
Specific medications can interfere with callus formation; for instance, nonsteroidal anti-inflammatory drugs (NSAIDs) and corticosteroids may negatively impact bone mineralization and slow the regenerative response. From a mechanical perspective, excessive movement or inadequate immobilization at the fracture site can disrupt the process of callus formation.
The characteristics of the injury itself can also lead to a nonunion. These include severe soft tissue damage, the presence of an infection, or a poor intrinsic blood supply to the fractured bone segment. Certain bones, like the scaphoid in the wrist, have a naturally limited blood supply, making them more prone to healing issues.
Medical Interventions for Nonunion
Once a nonunion is confirmed, the primary treatment goal is to restore stability and create a biological environment conducive to healing. Surgical intervention is often necessary, typically involving open reduction and internal fixation (ORIF). This procedure realigns bone fragments and holds them securely with metal hardware, such as plates, screws, or intramedullary rods. The surgeon may also perform debridement to remove any dead or infected tissue from the fracture site before fixation.
To stimulate the stalled biological process, the surgeon may use a bone graft, which provides a scaffold and introduces bone-forming cells and growth factors. An autograft, bone harvested from the patient’s own body, is often preferred because it contains living cells and is not rejected by the immune system. Donor bone (allograft) may also be used.
Non-surgical options include the use of bone stimulators, small devices that deliver pulsed electromagnetic fields (PEMF) or low-intensity pulsed ultrasound (LIPUS) waves to the nonunion site. These non-invasive methods encourage cellular activity and bone formation. They are used daily, often for twenty minutes to several hours, to help restart the repair process.