Breast Implant Placement Options The chest wall consists of the breast, the muscle layer (pectoralis major) and then the rib cage. The vast majority of breast implants are placed partially behind the muscle layer. This is also called dual plane, behind the muscle or partial retropectoral. The implant can go into either one of two spaces: Submuscular – the most common site of placement because a woman presenting for breast augmentation often has very thin tissues of the chest wall. Therefore, in order to protect and camouflage the implant, it needs to be placed deep to the muscle.Retromammary / Subfascial / Pre-pectoral – if you have adequate intrinsic breast tissue to protect the upper pole of the breast implant or specific activities such as a female bodybuilder, or if you are undergoing this procedure to correct a specific type of breast tissue deformity, then the implant can also be placed immediately deep to the breast tissue, superficial to the muscle.