What pocket plane should be used – over the muscle or under the muscle?
Breast implants can be placed either in front of or behind the pectoral muscle. The muscle is thick and narrow where it forms the fold in front of the armpit. It then becomes thinner as it fans out to attach vertically to the breast bone. Implants placed under the muscle are only partially covered by it because the breast and muscle only partially overlap each other (Figure 12). Implants are easier to feel on the side and bottom of the breast because they lie directly under the skin in these areas. This is why the more viscous silicone implants are often preferred to saline. The latter feel more obvious and sometimes exhibit visible wrinkles on the side and bottom of the breast, particularly in very thin women with scant amounts of breast tissue.
There are three advantages to placing implants behind the muscle. First, the upper breast contour is smoother because the transition between the chest and implant is concealed by muscle padding. Second, multiple studies suggest that there is less tendency for breast hardening, or capsular contracture, to occur when the implant is placed under the muscle. Finally, mammograms are easier to interpret when the implant is under the muscle. It is for these three reasons that implant placement behind the muscle is almost always preferred.
Heavier women who have a lot of breast tissue to begin with and have breasts that either sag or are positioned low on the chest are reasonable candidates for having the implants placed in front of the muscle. There is not much overlap between the muscle and the breast in these cases anyway, and the greater tissue volume conceals the implant shape in the upper part of the breast adequately. Nevertheless, placement of the implant in front of the muscle is not recommended for the vast majority of women.