The sternum, often referred to as the breastbone, is a long bone running down the middle of the chest. It connects to the ribs through a cartilaginous connection. The most common aesthetic deformity of the sternum is pectus excavatum. This is where the sternum and, to some degree, the attached ribs grow abnormally inward. This produces a well known sunken in appearance to the chest.
Pectus excavatum presents in a wide variety of manifestations. It can present as a relatively minor and isolated sternal depression to a much larger and even functionally limiting central chest concavity. While there are well known invasive treatments for pectus excavatum if significant enough (e.g., Nuss procedure), treatments for more minor sternal depressions are not as well chronicled.
Treatment options for lower sternal depressions include injectable fat grafting, injectable bone cements and custom sternal implants. While there are a large number of advocates for fat grafting, the sternum is a challenging area for fat survival due to the extreme tightness of the overlying soft tissues and the lack of natural fat in them. Multiple fat injection treatments would certainly be needed. Injectable bone cements are less well known and having used them, they offer permanent volume enhancement. But if any irregular contours develop or over correction occur, they can be hard to revise successfully.
A sternal implant composed of a solid but flexible silicone material offers a precise shape that is also easily reversible. Such sternal implants can be made by two different methods. A silicone elastomer moulage can be made by direct shaping on the patient. From this moulage the silicone custom sternal implant is made. The key to its design is to prevent an over correction or the appearance of a sternal ‘hump’. Its design should be to lessen the sternal depression to that of a more natural concavity that exists between the pectoralis muscles. Therefore, the moulage design should not have a flat top appearance but still maintain an inward curve to it across its outer surface. Because of its narrow shape it can be introduced through a small 1.5 cm incision at the level of the xiphoid process in a horizontal skin crease.
The other technique for fabrication of custom sternal implants is through a computer design from a 3D CT scan of the patient’s chest. This allows a custom fit to the underlying sternum but does not account for the overlying soft tissue and the adjoining cartilages in its design. For smaller sternal defects, the added cost may not justify any increased aesthetic benefit in some cases.
Dr. Barry Eppley