nonunions

Nonunions are fractures that fail to achieve healing within an expected time and do not show progressive healing on serial imaging. They are typically suspected when pain and deformity persist at the fracture site months after injury, and radiographs show a persistent fracture line with limited or no callus formation.

Classification commonly uses biology and stability. Hypertrophic nonunions have abundant callus and usually reflect inadequate stability, while atrophic nonunions show little or no callus, indicating poor biology or blood supply. An oligotrophic or normotrophic category describes intermediate biology with varying healing potential.

Causes and risk factors include insufficient stabilization or fixation, large bone gaps, infection, and compromised blood supply. Systemic factors such as smoking, diabetes, malnutrition, osteoporosis, and certain medications can impair healing. Open fractures and injuries to the tibia or femur carry higher risk in some settings.

Diagnosis relies on history, examination, and imaging. Symptoms include persistent pain and instability at the fracture site months after injury. X-rays and computed tomography help assess stability, alignment, and the presence or absence of healing; bone scans or MRIs may be used in select cases to evaluate biology and blood supply.

Management aims to restore stability and stimulate bone healing while addressing underlying factors. Treatment is often surgical and may include revision fixation, bone grafting (autograft, allograft, or bone graft substitutes), and, in selected cases, vascularized bone grafts for large defects. Biological adjuvants such as bone morphogenetic proteins or growth factors may be used in some situations. Electrical bone growth stimulators or low-intensity pulsed ultrasound can be considered as adjuncts. Prognosis improves with timely, appropriate intervention, though some nonunions require multiple procedures.