Most breast implants are placed under the pectoral muscle, but the decision isn’t as simple as over or under: There are four variations including dual plane, split muscle, subfascial, and subglandular. Knowing the specifics of each of these will help you to make an informed decision.
The pectoral muscle is fan-shaped with the gathered end – the “handle” – attaching to the upper
arm, and the outer edge attaching along the sides of the sternum (breastbone) and the rib cage, usually just above the bottom edge of the breast. The muscle provides a more gradual transition from the chest wall into the upper breast for a more natural look as compared to over the muscle. But what many patients are not told is that with the dual-plane technique, the portion of the muscle that attaches to the ribs is detached. That allows the implant to be centered behind the nipple, and minimizes flattening of the implant with muscle contraction. (It is called dual plane because the upper part of the implant is under muscle, and the lower and outer parts are under breast tissue.)
However the detached portion of the muscle, now in front of the implant, will heal into the scar capsule as it forms. The muscle can then pull on the capsule, causing double bubble and animation distortions in a high percentage of cases. This does not occur with implants above the muscle, but because the breast tissue often does not add enough coverage, many years ago I started looking into an alternative called subfascial. The fascia (pronounced like “fashion”) is a thin but tough membrane on the surface of the muscle, and it can be separated to go over the implant and behind the breast while leaving the muscle undisturbed. If you are going over the muscle, this may add a little bit better support but not much coverage.
The best of both is a technique I developed called the split muscle, which I started doing in 2004. With this technique, the muscle attachments are left intact (so no sacrifice of muscle function or strength) but the upper portion of the muscle is lifted over the implant by splitting between the muscle fibers. The central and lower parts are subfascial. This allows for better upper pole implant coverage as with the dual plane but without the potential for animation or distortion. I have used this method on more than 1000 augmentations, and as a corrective procedure for animation/double bubble in several dozen.
Baxter R. Subfascial breast augmentation: Theme and variations. Aesthetic Surgery Journal 2005; 25(5):447-53.
Baxter R. Update on the split muscle technique for breast augmentation: Prevention and correction of animation distortion and double-bubble deformity. Aesthetic Plastic Surgery 2011; 35(3):426-9.