An anatomic feature that most women do not think about is their chest shape. The shape of the chest is determined by the rib cage and sternum. With breast tissue and pectoralis muscle overlying, the true shape is difficult to assess. Most people have a fairly flat anterior with a rounded transition to the side wall. This makes a nice platform for breast implants for augmentation patients, or for expanders and then implants for reconstruction patients.
Many women, however, have significant asymmetries and shape differences which impact how a device fits their chest. The sternum may be prominent (pectus carinatum), or deeply indented (pectus excavatum), but these findings are unusual. More commonly, one side of the rib and sternum junction is more prominent than the other and contributes to the overall breast asymmetry which is very normal.
Another very common variant which I see is what we refer to as a keel (like the underside of a boat) shaped chest. This is where the sternum may be prominent and the ribs drop off more quickly to give a more triangular appearance. This is not a problem functionally and most women are not even aware of it. It becomes much more apparent, however, after a mastectomy.
Proper planning to address the keel shaped chest is important for the Plastic Surgeon. First, the patient must be made aware of the shape and its implications. With a flat surface, an implant or expander is more likely to stay where I put it. With the keel shaped chest, the device wants to slide to the side, like a rock off of a peaked roof. As I tell patients, gravity always wins. So, what to do?
For augmentations, using a textured device to encourage gripping to the chest wall and ingrowth of surrounding tissue may be helpful. Also, limiting size helps to limit gravitational pull. The lateral chest is minimally dissected and the inframamary fold incision is closed securely. The patient should then wear an underwire bra when instructed to help maximally support the implant until a scar capsule is well formed.
For delayed reconstruction, the same approach is used. For immediate reconstruction, a bra like sling may be formed with human cadaver dermis (almost a standard maneuver now), or with a latissimus flap. If possible, the expander is then filled slowly.
I have found these approaches to be helpful, and most patients do well (see the case of the month). Nonetheless, a keel shaped chest puts the patient at a higher risk for lateral movement of her implant.