When large implants are placed behind the muscle, it may be necessary to detach the pectoral muscle from its origin along the 5th rib and the lower sternum.  When the patient flexes her pectoral muscles, the pectoral muscle may lift the entire breast upward and outward because the muscle is still attached to the upper arm but no longer anchored on the sternum and rib.  This visual appearance of the entire breast sliding upward and outward across the chest reminded the plastic surgeon of the action of a windshield wiper, hence the name.  It can be corrected by reataching the pectoral muscle to the sternum and rib or by moving the implant to a position in front of the muscle.