Engaging in activity that requires putting weight on a nonunion fracture is strongly discouraged until explicit medical clearance is received from an orthopedic specialist. A nonunion represents a failure of the bone to heal after a significant period, typically six to nine months. Attempting to use the limb normally can lead to serious complications, as continued stress on the unstable bone fragments can worsen the underlying problem.
Understanding Nonunion Fractures
A nonunion fracture is defined as a broken bone that has stopped the healing process and shows no further signs of progression, often persisting for a minimum of nine months without radiological evidence of union for the last three months. This condition is distinct from a delayed union, where the bone is taking longer than expected but is still showing signs of progress. The failure to heal is often due to a combination of mechanical and biological factors, which halt the natural repair cycle.
Fracture healing depends on adequate stability and a sufficient blood supply to the bone fragments. Nonunion can occur if there is excessive movement at the fracture site or if the blood flow, which provides oxygen and growth factors, is severely compromised. High-energy injuries, infection at the fracture site, smoking, diabetes, or nutritional deficiencies can all contribute to this complication. Diagnosis typically involves imaging studies like X-rays and CT scans to confirm the lack of bridging bone across the fracture gap.
The Immediate Risks of Weight Bearing
Attempting to walk or bear weight on a lower extremity nonunion fracture before it has been successfully treated carries risks. The underlying lack of structural integrity means the bone cannot withstand the forces generated by movement or body weight. This continued stress frequently results in increased chronic pain and a significant loss of function in the affected limb.
One concerning outcome is the worsening of the fracture’s existing deformity, potentially causing angulation or shortening of the limb. Repeated motion at the nonunion site can cause the bone ends to rub against each other, grinding away healing tissue and forming a “false joint” known as a pseudoarthrosis. This excessive motion also poses a danger to the surrounding soft tissue, including nearby nerves and blood vessels, which can be stretched or damaged by the constant instability of the bone fragments.
For fractures initially stabilized with internal fixation hardware, such as plates, screws, or rods, weight bearing can lead to catastrophic hardware failure. The implants are designed to hold the bone fragments until biological healing occurs, not to bear full load indefinitely. Increased stress can cause screws to loosen, plates to bend or break, or rods to fail, which necessitates revision surgery to remove the failed components. Allowing the condition to deteriorate by stressing the nonunion can convert a localized problem into a highly unstable, chronic condition, requiring far more complex and invasive reconstructive surgery later.
Strategies for Nonunion Repair
Since simple rest is insufficient for a nonunion, medical intervention is necessary to restart the healing cascade and achieve bone continuity. The treatment strategy is tailored to the specific type of nonunion, such as hypertrophic (ample callus but unstable) or atrophic (little to no callus and poor blood supply). Surgical intervention is often the definitive approach, aiming to provide a better biological environment and mechanical stability.
Surgery frequently involves debridement, which is the removal of dead or scarred tissue from the fracture ends to expose viable, bleeding bone. This is often paired with a bone graft, which supplies the necessary cellular and structural components for new bone formation. Autograft, taken from the patient’s own body, is considered the gold standard because it provides living cells and growth factors. Allograft, from a donor, offers structural support.
To enhance stability, revision of the fixation hardware is common, often involving stronger plates, intramedullary rods, or external fixation devices to rigidly hold the bone fragments. Non-surgical stimulation methods, such as pulsed electromagnetic fields or low-intensity pulsed ultrasound, may be used as an adjunct to surgery or as a primary treatment for specific nonunion types. Addressing underlying contributing factors, such as infection, nutritional deficiencies, or smoking habits, is also an important part of the repair process to maximize the chance of a successful outcome.