The number of women in the United States who have breast implants is unknown, but current estimates are derived from national surveys of up to 4 million+. This is more than 3% of the adult female population. It is estimated that 70-80% of breast implant procedures were performed for cosmetic purposes and 20-30% for reconstruction of post-mastectomy congenital anomalies or defects. Following adverse publicity in the early 1990s, interest in the procedure dropped by almost 50%, but appears to have gradually recovered. In 1998, approximately 350,000 pairs were sold in the United States for augmentation.
Prior to 1963, various plastic foam materials were used, however it became apparent that air would collapse and the cells, combined with the growing tissue, would shrink and squeeze the device. These materials were wrapped in plastic to minimize this effect to no avail. Surprisingly, some of these implants were well tolerated and have remained in place to this day.
Modern silicone breast implants have been available since 1963 and have gone through an evolution of changes and improvements. Various types of devices have been created, with many variations and styles within each class. Basic to all silicone implants is a rubber (rubber) shell, which can be single or double, smooth or textured, barrier coated, or covered with polyurethane foam.
The contents are factory filled with silicone gel of various consistencies or inflated for surgery with normal saline. A foreign-made brand was briefly marketed in the United States and was pre-salted at the factory. This device was later withdrawn when the FDA denied approval.
Dual-lumen devices consist of concentric balloons containing silicone in one chamber and saline in the other. The only one still in use is Becker, which has an outer layer of gel on the inside and a ball valve that is to allow gradual postoperative inflation with saline. This is called a “permanent tissue expander” as it allows for gradual and temporary over-inflation to create the pocket, then you can leave a permanent implant after the size is adjusted correctly.
gel implants
Three generations of basic design of this device have been created, with many variations within each type.
first generation
The first models marketed have thick, smooth-walled silicone elastomer envelopes, made in 2 sections, filled with viscous silicone gel material, and glued together. In the early years, researchers believed that the device required adherence to tissues to prevent migration. The growing scar was fixed for fixation by means of patches of material, such as Dacron mesh or perforated silicone, which were adhered to the back of the device or by means of an outer cover of polyurethane foam. Dacron and silicone patches were later found to be unnecessary and in fact held up in the quality of the result. Some patches or tabs created a stress point that caused the envelope to tear. Repair patches were removed in the early 1970s.
second generation
Evolution brought changes in gel consistency and shell thickness in an attempt to improve performance. Since the mid-1970s, gel capsules have been thinner and less viscous (ie, more “sensitive”), especially in an ill-conceived attempt to control capsular contracture. This trend was reversed in the early 1980s with the realization that it was not effective in reducing contracture and resulted in increased frailty. Most broke 10 years later.
third generation
The new formulations of the peel before it was strong and significantly less “bleeding” or spread are usually small amounts of silicone oil fraction of the gel content. The gel content also became more viscous and cohesive.
By 1989, envelopes with the surface texture that many surgeons expected to minimize the incidence of unwanted firmness from capsular contracture were available. Recent studies are somewhat confused about whether this is effective. They are also available with removable subcutaneous fill port devices, which allow for post-surgical sizing. Texture devices seem to have a higher break rate than those with good covers.
Polyurethane coated implants
In the late 1960s, a variation of the device was developed that contains a layer of polyurethane over a standard gel-filled implant. Although the coating was originally intended as a fixation layer, more surgeons came to believe that the foam pad resulted in a lower incidence (or at least delayed onset) of capsular contracture. These implants also evolved in shape and design, culminating in the 1980s with Meme Optimam and styles. In April 1991, the manufacturer with lottery voluntarily covered the market for foam implants.
A style, MemeME had a unique construction. There was a shell, but a type of skin was formed in situ by spraying the surface with silicone containing additional catalyst before curing. This increase in the area cross-links to create a shell-like membrane. Without the silica filler, this membrane is not as strong as a shell. Polyurethane foam is formed and stamped on the surface. Implants of this type are known to occasionally pull some of their contents through the gel foam when squeezed. This is one possible explanation for the reports of blood found on the underside of apparently intact gel implants. The MemeME model was marketed between 1983 and 1988.
Although silicone remained the only available shell material, newer fillers were in use in Europe and South America, while under development or pilot testing in the United States. Various hydrogels and a pure form of triglycerides are the 2 main formulations. The main advantage of the triglyceride formulation (Trilucent) was that it had a Z-number (far from radiolucency) similar to that of fat, so little or nothing compromised mammography. Another filler, pyrrolidone polychloride in saline, was briefly available in the United States under the trade name Misty Gold. Neither of these products is currently available in the United States. All currently considered fillers are designed to be aggressively absorbed and excreted if the cover cracks or leaks. Other than the time-honored non-absorbable silicone gel fillers, these are not currently available in this country.
The documents presented in clinical trials is a new formulation of gel filler that is thicker and more consistent in order to minimize the spread of the gel in case of rupture.
As evidenced by sales figures before the moratorium, approximately 80-85% of surgeons and patients prefer the quality of results obtained by gel implants. Gel devices appear to be the implant option to use after mastectomy. In 1997, sales figures for Europe, where use is free, show an allocation of 70% gel, 15% saline, and 15% alternative fillers such as triglycerides (then still available) and hydrogels for cosmetic use.
At the time of this writing, due to restrictions placed on the sale of the gel device by the FDA, these implants are only available for reconstruction or replacement under strict protocol. The FDA recently concluded hearings in which both manufacturers presented the latest safety data on gel implants. The panel approved the corporation’s Mentor devices for cosmetic purposes under strict regulation and monitoring needs, but denied approval for the Inamed product. The panel’s recommendations are advisory only, and it remains to be seen whether the FDA accepts their advice or, as it has done before, continues to ban cosmetic use.
