Does Intramedullary Nail Diameter to Canal Ratio Predict the Incidence of Femoral Nonunion?

Femoral intramedullary nail fixation is currently considered the ''gold standard'' for treatment of femoral shaft fractures in adult population. Clinical outcomes after operative treatment of proximal femur fracture have been shown to be dependent on achieving optimal mechanical alignment and union. Patient independent risk factors associated with nonunion after intramedullary fixation includes: open fracture, undreamed intramedullary nailing, fracture comminution, non-isthmal and particularly infra-isthma fracture location and infection. Patient dependent risk factors include smoking, diabetes, nonsteroidal anti-inflammatory medications, closed head injury and delayed weight. Unreamed nailing allows for better maintenance of the endosteal circulation at the expense of smaller diameter implants; in contrast, reamed applications permit a larger diameter nail, resulting in stronger fixation constructs and earlier fracture union. After reaming, a larger diameter intramedullary nail is placed. When initially reported, this treatment resulted in high success rates.