Causes / typical injury mechanism: Femoral shaft fractures in the adult population require a high-energy mechanism. These include motor vehicle accidents (MVAs), falls from heights, and gunshot wounds. Femur fractures are serious injuries and should be addressed immediately due to the high possibility of complications, including hemorrhage, associated internal organ injury, wound infection (if there is an open fracture), fat embolism, and acute respiratory distress syndrome (ARDS), if left untreated. Nonoperative treatment can result in pressure sores, malunion, limited mobility, and deep vein thrombosis.

Classic history and presentation: The condition presents as severe pain, swelling, and deformity of the affected thigh. Due to the trauma that frequently causes these fractures, soft tissue injury and bleeding are usually present and may lead to shock.

Prevalence: The estimated incidence of femoral shaft fractures is 9-22 fractures per 1000 people worldwide each year.

• Age – These fractures most commonly occur in the young (< 40 years) due to high-energy trauma (eg, MVAs), but incidence increases again in individuals older than 75 years due to low-energy trauma (eg, falls).
• Sex / gender – This condition can occur in either sex but is more common in young males.

Risk factors:

• If younger than 40 years, high-energy trauma such as MVAs.
• If older than 75 years, low-energy trauma such as falls.
• Osteopenia or osteoporosis, general or localized.
• Long-term use of bisphosphonates can result in atypical femur fractures.

Pathophysiology: The condition occurs as a result of trauma, usually a direct blow to the thigh or a force on the knee that is transmitted to the thigh. Given the size and strength of the femur, the force required to fracture the bone is significant, as in an MVA, but lower-force traumas have also served as significant contributors to femur fractures in the older population. The type and location of the force determines the type of fracture that results and the complications that may occur. Due to the location of the femur and its relationship to anatomical structures, surrounding muscles, ligaments, soft tissues, and nerves can also be damaged.

Classification system: There is no formal classification, but these injuries are described by location and fracture pattern. Location of the fracture is often described as proximal third, middle third, and distal third. Fracture patterns can be described as spiral, oblique, transverse, or multifragmentary. It should be noted if the fracture is open or closed.

An AO Foundation / Orthopaedic Trauma Association classification is available for research purposes only and is not used to describe injuries in the clinical setting.