Breast Implant Placement - Over vs Under the Muscle

The final outcome and shape of breasts after breast enlargement or augmentation mammaplasty (popularly known as a "boob job") is in large part determined by the relationship of the implants to the pectoralis muscles of the chest wall.

Implants can either be placed above (over) the pectoral muscles, or beneath (under) the muscles. Furthermore, the route of breast implant placement under the muscle also determines whether the implant is totally covered or only partially covered by muscle when placed in the sub-pectoral plane.

A number of consequences may result, depending on the position and route of placement of implants. By adhering to certain principles of implant placement, surgeons can prevent some of the potential complications of breast augmentation. These include limiting risk of capsule contracture, limiting the "round" look of implants, preventing visible rippling or wrinkling of the implants, preventing "bottoming out" of the implants, and increased longevity.

Breast Implants Over the Muscle

The photo to the right shows breast implant placement over the muscle in the sub-glandular position, completely in contact with the breast tissue. The result of implants over the muscle provides a round, augmented look in many patients, though many women prefer the round and somewhat less natural look.

In the "over" approach, the implants are inside the breast. Advantages are ease of the surgery, which can be accomplished by almost any surgeon, avoidance of mastopexy in mild ptosis (although it usually makes the ptosis worse later), and less post-op discomfort, since only skin and fat are cut.

This approach allows insertion of oversize implants, which is what some women want.

Disadvantages are marked interference with mammograms (about 40% obstruction - see reference below), clear visibility and feel of implant edges, visible and palpable rippling of the skin over the breast implants, especially with any textured implants, higher rate of capsule contracture, high rate of implant downward migration or "bottoming-out," and difficulty correcting later ptosis problems when they occur.

Breast Implant Partially Under the Muscle

Photos to the right shows partial submuscular breast implant coverage with implants placed under the muscle via the areola (nipple) incision or an inframammary crease incision, thus disrupting the muscle support fascia at the lower pole of the implant and allowing it to enter the space under the muscle.

With this approach, the implants are mostly behind the breast. This approach has the advantage of mostly separating the implants from the muscle, facilitating unobstructed mammography, a more natural look, less rippling (except textured implants), and low risk of capsule contracture.

Disadvantages include greater discomfort, a higher difficulty in the technique, and the loss of the lower pole support fascia that leaves the implants supported by the same weak skin tissues as implants over the muscle, leading to later downward bottoming-out of the implants in a few patients, as is frequently seen in implants over the muscle.

Breast Implants Completely Under the Muscle

Complete implant muscle coverage is shown above with intact muscle fascia supporting the lower pole of the breast implant. This support fascia is the extension of the muscle envelope from the pectoralis muscles to the abdominal rectus muscles, and the finger shaped serratus anterior muscles to the sides. It is a stout collagen sheet which stretches slowly after implant placement, but provides reliable long-term internal bra-like support to prevent "bottoming-out".

With this approach, the implants are totally behind the breast. Complete muscle coverage of the implant, without cutting through the muscles, can only be achieved by Trans-Axillary approach, entering the space under the muscle where it lies closest to the skin in the anterior axillary fold.

Pros and Cons Of Breast Implant Placement: Over vs. Under the Muscle

Implant Location
Over Muscle Partial Under Muscle Complete Under Muscle
Mammography Marked interference even with Eklund distraction technique Minimal interference with Eklund distraction technique Minimal interference with Eklund distraction technique
Capsule Contracture Highest risk Lower risk Lowest risk
Rippling Highest risk especially with any textured implants Lowest risk even with textured implants Lowest risk even with textured implants
Natural Appearance
(not desired by all patients)
+/- Likely Likely
Implant Bottoming out Frequently seen - leads to inframammary scars riding up onto the breast Frequently seen - leads to inframammary scars riding up onto the breast Rarely seen
Use in presence of borderline sag May correct sag in short term, but usually requires later ptosis repair because breast support ligaments (of Cooper) are cut May correct borderline sag but may require immediate or later mastopexy May correct borderline sag by pectoral sweep maneuver, but may require immediate or later mastopexy
Late Sag requiring repair Frequently seen especially if over muscle was done to try to "fix" sag Less frequent, but may be needed after pregnancy Less frequent, but may be needed after pregnancy

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