A nonunion fracture occurs when a broken bone fails to heal long after the typical recovery period, usually four to six months. This stalling of the body’s natural repair process causes chronic pain, instability, and loss of function. Addressing a nonunion requires a precise diagnosis to determine why healing stopped, allowing the orthopedic surgeon to tailor an intervention that restarts bone regeneration.
Defining and Classifying Nonunion Fractures
Orthopedic specialists define a nonunion as a fracture that has persisted for a minimum of nine months without showing healing progression for the last three months. Diagnosis relies on clinical symptoms, such as persistent pain and instability, and radiographic evidence, typically X-rays or CT scans. Imaging is used to classify the nonunion into distinct types, which guides the appropriate treatment strategy.
The classification system focuses on the biological activity and mechanical stability at the fracture site. The two primary types are hypertrophic and atrophic nonunions. Hypertrophic nonunions are biologically active, producing callus, but the bone ends fail to bridge due to inadequate mechanical stability. This type often presents on an X-ray with an “elephant foot” appearance.
Conversely, an atrophic nonunion is biologically inactive, indicating poor blood supply and a lack of callus formation. The bone ends are resorbed, appearing smooth and tapered on imaging. Atrophic nonunions require biological enhancement, while hypertrophic nonunions primarily need improved mechanical fixation. Oligotrophic nonunions are a middle ground, showing minimal callus formation despite adequate vascularity.
Non-Invasive and Minimally Invasive Healing Options
Non-invasive or minimally invasive techniques can stimulate the stalled healing process, particularly for hypertrophic or oligotrophic nonunions. These methods enhance the biological environment without requiring major surgery and are often considered an initial step when the fracture site shows inherent healing potential.
Low-Intensity Pulsed Ultrasound (LIPUS) therapy involves applying low-frequency sound waves to the fracture site daily for about 20 minutes. The mechanical energy induces small stresses within the bone tissue, stimulating cellular activity and accelerating bone regeneration. This non-thermal treatment can be administered at home.
Pulsed Electromagnetic Field (PEMF) stimulation uses electromagnetic pulses to modulate cellular function at the nonunion site. PEMF enhances osteoblast activity (the cells responsible for forming new bone) and improves local blood flow. Both LIPUS and PEMF are used daily over several months and have shown comparable success rates to some surgical interventions.
Addressing systemic factors is also a fundamental component of nonunion treatment. Nutritional deficiencies, especially low levels of Vitamin D and calcium, require targeted supplementation. Smoking cessation is highly recommended because nicotine and carbon monoxide reduce blood flow and inhibit the cellular processes necessary for bone healing.
Surgical Strategies for Correcting Nonunion
When non-invasive methods are unsuccessful or the nonunion is atrophic or involves significant deformity, surgery becomes the definitive treatment. Successful surgery requires a two-pronged approach: correcting mechanical instability and supplying the necessary biological components for bone growth. This ensures the fracture environment is both stable and biologically active.
Mechanical Stability
A primary goal of surgery is to achieve rigid fixation, which is often lacking in hypertrophic nonunions. This frequently involves revising the existing internal fixation, such as replacing a plate and screws with a more robust implant or using a larger, stiffer intramedullary nail. For long bones, exchange nailing may be performed, where the existing rod is removed and a larger-diameter nail is inserted to increase stability and stimulate the bone marrow.
If the nonunion is associated with a deformity, an osteotomy may be required to re-cut the bone ends and restore proper anatomical alignment before applying fixation. Stability is essential because it eliminates the excessive motion that prevents the final bridging of the fracture site. Debridement is also performed to surgically remove any dead, sclerotic, or infected tissue, creating a clean, vascular bed capable of healing.
Biological Enhancement
For atrophic nonunions, where biological healing potential is low, a bone graft is necessary to restart the process. Autograft, bone harvested from the patient’s own body (most commonly the iliac crest), is considered the gold standard. Autograft provides a potent combination of osteoconduction (scaffold), osteoinduction (growth factors), and osteogenesis (living bone cells).
Although autograft is highly effective, its use is limited by the amount available and the potential for pain at the donor site. Allograft, processed bone from a deceased donor, provides an osteoconductive scaffold but lacks the living cells and potent growth factors of autograft. Allograft is often used to fill large bone defects, sometimes combined with autograft or bone graft substitutes to improve biological activity.
Alternative biological materials include bone graft substitutes, which act primarily as scaffolds, and Bone Morphogenetic Proteins (BMPs). BMPs are powerful growth factors used to stimulate bone formation, typically reserved for specific indications and complex cases. The surgical decision depends on the size of the bone defect, vascularity, and the location of the nonunion.
Post-Treatment Recovery and Management
Following intervention, a structured post-treatment plan is necessary to ensure the nonunion progresses to a complete union. This management phase involves closely monitored physical activity and consistent follow-up care. Patient adherence to the protocol significantly influences the final outcome.
Physical therapy is important, initially focusing on gentle exercises to maintain range of motion and prevent muscle atrophy without stressing the repair site. As healing progresses, the therapist introduces closed-chain exercises and a progressive strengthening regimen to restore functional mobility. Pain management and scar mobilization are also integral parts of rehabilitation.
Weight-bearing restrictions are gradually lifted based on radiographic evidence of healing and fixation stability. For lower extremity nonunions, this progression often involves using a scale to measure the precise percentage of body weight placed on the limb, advancing over several weeks to months. The time to full weight-bearing can range significantly, but the median time after complex surgery is often around 12 weeks.
Monitoring is performed through serial imaging, typically X-rays every four to six weeks to track bridging bone callus formation. In complex cases, a CT scan may be used to visualize bridging bone across the nonunion site, especially when obscured by surgical hardware. Continued attention to nutritional support, including adequate Vitamin D and calcium intake, remains important throughout recovery.