Anatomy of a Breast Implant
While patients have a major choice between saline or silicone filler materials today in breast implants for breast augmentation, there is another component of a breast implant that is frequently overlooked and can have a big impact on how a breast augmentation feels….and that is the bag or shell which contains the filler material. And occasionally I do have a potential breast augmentation patient ask about the shell, particularly if they have some ‘old fears’ about silicone breast implants.
The shell (containment bag if you will) of a breast implant is made up of silicone oil (technically siloxane), but it is a highly cross-linked formulation giving it a rubbery or rubber consistency. From an elemental standpoint (for you chemistry enthusiasts), silicone does contain some silicon atoms (semimetallic element #14) but it is combined with oxygen and methyl groups which give it characteristics completely different from silicon on the periodic table. When cross-linked together to create a solid, it is known as polysiloxane. And it can be made in any consistency from an oil (what was used in antiquated breast implants and is now still used in ophthalmology for eyeball fluid replacement and in some countries as a soft tissue injectable filler) to any stiffness of a rubber material. As a result, silicone rubber is used in a large number of medical devices and implants. In plastic surgery, for example, many facial implants (cheeks, chins) are made of it. Silicone rubber has been consistently proven to be safe…..which is particularly evident from the intense evaluations done of it from the breast implant issues from the 1990s. It is fair to say, silicone breast implants have been the most studied medical implants in history…and it has now been proven that women with silicone breast implants are no more likely to develop ill health than women without breast implants. Which is why they are now again approved by the FDA and are now widely used in breast augmentation again.
But back to the shell, it is silicone and the shell is the same for either silicone breast implants or saline breast implants. When there is only one shell, it is called a single lumen breast implant, which is by far the most commonly used. In single -umen breast implants, it is only what lies in it that differs. When saline is used, the breast implant is placed ‘deflated’ and filled after it is in place. This is why saline breast implants can be placed through very small incision off of the breast. (through the armpit or bellybutton) It is like inserting a burrito through a small hole. In silicone breast implants, the semi-solid silicone material is placed in the implant at the factory, therefore they are pre-filled. As a result, a larger incision somewhere on the breast (lower fold usually) must be used to get them in place.
As opposed to a single-lumen breast implant, a double-lumen breast implant has a shell within a shell, or a ‘bag within a bag’. There is a smaller bag that floats inside a bigger bag. Usually the big or outer bag (the one you would hold in your hand) contains silicone (for the softness and lack or ripples) and the smaller inner bag contains saline (which can be added to at the time of surgery to offer some adjustability of size.The inner lumen (bag) is filled during surgery through a valve in the implant. This implant type combines the benefits of saline and silicone fillers in one breast implant.
As for filler materials, saline is just salt water. (although this is not entirely accurate, saline is 0.9%, salt water is around a 3% concentration of salt solution) Even if it leaks out, it is as safe as water. Silicone gel (oil is no longer used) is much like jello. It is still silicone, but it is somewhere between oil and rubber in consistency. If you cut a silicone gel implant with a knife and hold it upside down, it will act like meringue pie. The gel is ‘cohesive’ and it stays together. So if you get a hole in your silicone gel breast implant, it is not going to leak out. Increased firmness of the silicone gel is what makes a ‘gummy bear’ implant. It is still silicone but it is firmer or stiffer. Whether differing firmness of the silicone gels is any advantage in breast implants is a cosmetic matter, not any safety issue.
Remember that breast implants are medical devices that are highly regulated by the FDA today and are manufactured with high standards. That being said, I never tell a patient that a breast implant is permanent. They have a lifespan and can always fail and need to ber replaced. What makes a breast implant need to be replaced is failure (tear, rupture) of the shell. This would obviously be kost evident in saline breast implants (i.e., a flat tire) vs a silicone breast implant. (which may not even be detectable as it doesn’t change size)
Dr Barry Eppley
Indianapolis, Indiana