What causes someone to get a leg amputation after car wreck?

Injuries. People may sustain injuries that cannot be repaired or reconstructed. In bad accidents the legs can be pinched when the motor is pushed into the cabin.
Complex injury. Although there can be several reasons, the most common cause is severe non repairable injury to the blood vessels that supply the leg. Sometimes severe nerve injury or loss of muscle and tissue can be the reason for amputation. A severe infection can be the reason for a amputation after an attempt to save a limb after a severe leg injury.