In the 1980s, Replicon implants were the most popular. Replicon is an anatomically shaped, polyurethane coated, silicone gel-filled implant. Many surgeons felt that the initial results were very beautiful, but short-lived, because the polyurethane, which was bonded to the surface of the shell helped to maintain the anatomic shape of the implant, eventually deteriorated, and once it was absorbed off of the shell, the remaining thin and pliable shell could not hold the silicone gel in place, and so its shape was lost. Further, gravity forced the gel to the bottom of the shell, collapsing the upper breast, and expanding the lower breast. Folds developed in the collapsed upper pole. The shell was very thin, and with time, the shell weakened along those folds, and eventually could break, allowing the relatively liquid-like contents of the implant to leak outside of the shell. In addition to the effects of gravity, the forces of the breast acted upon the implant, deforming its initial anatomical shape. The implant accommodated to the shape of the breast, rather than the breast taking on the shape of the implant.
Dr.Fisher was directly involved in a long and tedious process – far beyond the scope of this article, or this site, to describe in detail – which involved experimentation with diverse silicone gel fillers. Silicone can be made in virtually any firmness, from a liquid lubricant to almost a rock-hard solid. The aim was achieved in making the filler more stable and avoiding collapse of the shell. Further, the modern cohesive shell can be formed into a particular shape and maintain it.
In the past, shape was of only moderate importance, because the forces of the body and of gravity would shape the implant. However, the modern cohesive filler allows for various ratios of width, height, and projection.
The FDA moratorium on silicone gel filled breast implants in 1992 also contributed to increase in competitiveness and invention in this area. The type of implants that were available before the ban are available today as part of an “adjunct study,” which is open to patients with congenital deformities or having a revision for particular reasons.
What distinguishes the modern cohesive implants is that the silicone gel is firmer, essentially a soft solid. If a cohesive implant is cut in half, there is no gross movement of gel, and the implant maintains its shape. The way these are made is that the company uses more “crosslinker” in the making of the implant. The ingredients are the same, but with more crosslinker added, it makes the gel firmer.
Cohesive breast implants implies form stability, or form retention. That means that in any position, the implant maintains its shape. That is an important distinction, because it means that the shell should not fold, and that it will maintain a particular shape. All breast implants are “cohesive” to a different extent. More cohesive are not necessarily better. The bottom line here is the desirability of shape and firmness, which must be in proportion to the body’s natural qualities.