Prepectoral (above-the-muscle) implants
Breast implants can also be placed above the pectoralis muscle, in the same location as the breast tissue. In breast augmentation, a breast implant over the pectoralis muscle is called a "subglandular" or "prepectoral" implant, because it is under the breast gland but over the pectoralis muscle. In breast reconstruction, a breast implant over the pectoralis muscle is just called a "prepectoral" implant, because it is over the pectoralis muscle but there is no glandular breast tissue after a mastectomy.
Prepectoral breast implants have the advantage of being more comfortable, because there is no tightness from a foreign body being placed underneath the pectoralis muscle. There is no hypermobility with the implant being deformed and displaced by the pectoralis muscle, because the breast implant is over the muscle. The disadvantage is that there is not as much soft tissue coverage. Thus, it may be easier to see the outlines of the breast implant itself. This can be addressed by using a shaped implant with an acellular dermal matrix (ADM) wrapped around the implant. The ADM provides an extra layer of soft tissue coverage over the implant, and can also soften the edges of the implant itself.
Breast reconstruction with prepectoral cohesive gel implants wrapped in ADM is the newest type of implant-based breast reconstruction. ADM is composed of the dermal layer of skin that has been stripped of reactive cell components but retains the biologic qualities and structure of natural collagen. ADM eventually integrates with the body and is replaced with the patient's own tissue. Since the implant is placed above the muscle, the normal pain and tightness from a subpectoral implant is eliminated. In addition, the cohesive gel implant retains a teardrop shape underneath the thin mastectomy skin.