Final answer:
Severe nerve injury is least likely following a femur fracture because major nerves are not typically situated where femur fractures occur. Complications such as deep vein thrombosis and pneumonia can arise during the recovery period due to immobility, especially in elderly patients.
Step-by-step explanation:
After a femur fracture, the most common complications are severe pain, expanding hematoma, and, rarely, absent distal pulses. Severe nerve injury is least likely because the major nerves are generally not located where the femur is likely to fracture. Fractures can lead to various complications such as deep vein thrombosis, pneumonia, pressure sores, and urinary tract infections, particularly in the elderly due to immobility during the recovery process. Femoral neck fractures are also common in the elderly, especially in those with weakened bones due to osteoporosis, and can be life-threatening.