what is femur
Femur Shaft Fractures (Broken Thighbone) Your thighbone (femur) is the longest and strongest bone in your body. Because the femur is so strong, it usually takes a lot of force to break it. Car crashes, for example, are the number one cause of femur fractures. The long, straight part of the femur is called the femoral shaft. When there is a break anywhere along this length of bone, it is called a femoral shaft fracture. The femoral shaft runs from below the hip to where the bone begins to widen at the knee.