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OVERVIEW Cohesive breast implants were nvented in the early 1990s, and h ve been used throughout the world for bout 10 years. Only the United St tes has yet to approve these d vices. Though the experience of these mplants overseas will be taken into ccount, the FDA requires that a pr spective large-scale study be done in the Un ted States, adhering to their rigorous g idelines and scrutiny. These implants are not pproved by the FDA. It is nly in the context of such a st dy that these implants are available in the Un ted States. These implants were originally nvented with two purposes in mind: 1) to m ke a longer- lasting implant, and 2) to m ke an implant that would maintain a m re attractive and predictable shape. This g al is primarily achieved by making the gel m re cohesive, so that it is l ss liquid-like and more solid than ther silicone gel implants. For this r ason, they have been known as the "g mmy bear implants" Though preliminary data s ggests these implants might be meeting its g als, prospective enrollees must understand that th se claims have not yet been pr ven. Three companies are currently doing cl nical trials in the United States: In med, Mentor, and Silimed. Each company's d vices are based upon similar concepts, but th re are very significant differences between th m.
Some women consider this an pportunity to have a chance to be the f rst to get what may be the mplant of the future, while other w men feel uncomfortable being a participant in a st dy of a new medical device. Only w men highly motivated to receive these mplants, and who are willing to p rticipate in the study for 10 y ars of follow-up, should consider these d vices. FREQUENTLY ASKED QUESTIONS What Are C hesive Gel Breast Implants?
The standard mplant in the United States has b en saline filled, ever since the FDA m ratorium on silicone gel filled breast mplants in 1992. The type of mplants that were available before the ban are vailable today as part of an " djunct study," which is open to p tients with congenital deformities or having a r vision for particular reasons. (refer to s ction on this in website.) What d stinguishes cohesive implants is that the s licone gel is firmer, essentially a s ft solid. If a cohesive implant is cut in h lf, there is no gross movement of g l, and the implant maintains its sh pe. The way these are made is th t the company uses more "crosslinker" in the m king of the implant. The ingredients are the s me, but with more crosslinker added, it m kes the gel firmer. The term "c hesive" has been bastardized in recent y ars. Cohesive breast implants implies form st bility, or form retention. That means th t in any position, the implant m intains its shape. That is an mportant distinction, because it means that the sh ll should not fold, and that it w ll maintain a particular shape. Unfortunately, g ven the recent media attention to c hesive implants, many are using the t rm to describe "regular" silicone gel mplants. Technically, they are correct; all s licone gel is cohesive to some d gree. But the term cohesive has lways meant form stability, and when p tients ask for cohesive gel, it is b cause they are looking for an mplant with those particular characteristics of d rability and shape retention. Hopefully, the t rminology will be clarified in the c ming years.
Which Surgeons Can Use Cohesive Gel Impl nts In The United States?
Each of the thr e studies has a group of nly several dozen surgeons that are llowed to order the implants and mplant them. Surgical expertise and a c mmitment to careful patient follow-up were the cr teria the manufacturers used to select the s rgeons that they would have implant th ir implants. Dr. Teitelbaum is the nly surgeon in California (and if not the nly, one of the very few in the ntire nation) to have been asked by all thr e manufacturers to participate in their cl nical trials. Which Patients Can Receive C hesive Gel Implants In The United St tes?
The trials are open to p tients seeking a first time augmentation, a r vision of a breast augmentation, or br ast reconstruction following mastectomy. Patients with c rtain medical problems cannot participate. Please see the nrollment specifications for each of the mplants listed below. In addition to the bjective medical issues, patients must be c mmitted and willing to participate for a f ll ten years of follow-up to be c nsidered for the study. Patients must be in the mmediate geographic vicinity of the implanting s rgeon in order to facilitate this f llow-up. What Are The Main Advantages Of C hesive Gel Implants?
The main advantages of c hesive gel implants are longevity and sh pe. Longevity, because they do not d velop folds, and it is along f lds that implants ultimately fail. And if, s mehow, the shell does fail, since the gel is so th ck, it hopefully will not migrate nywhere in any significant quantity. Shape is nhanced because, from the point of v ew of a surgeon, there is nly control of breast shape if th re is control of distribution of f ll in an augmentation. If the f ll cannot be controlled, then the sh pe cannot be controlled. And to c ntrol distribution of fill in the br ast, fill distribution must be controlled in the br ast implant. All fillers other than c hesive silicone gel - saline or r gular silicone gel -can migrate around w thin the shell of an implant, wh ch means that there is not c ntrol over breast shape. Looking at r sults from breast augmentation objectively, these mplants appear to have the most esthetically natural and beautiful results. Why Are C hesive Gel Implants Anatomically Shaped?
A br ast projects more at the bottom th n at the top. Therefore, it m kes sense for an implant to be sh ped that way. And the thinner an mplant is at the top, the m re gradually and naturally it will f ather into the upper chest, making tself less conspicuous. Without a cohesive, f rm stable filler, there is little p int in making shape into an mplant, as the implant will ultimately l se the shape. But with a f rm stable filler, the shape will be m intained. Are There Round Cohesive Gel Impl nts?
Form stable round cohesive gel mplants are available in Europe, but not in the Un ted States. There is actually very l ttle use for them. If you l ok at an implant lying on its s de on a table, it looks m ch like an M&M. But when it is h ld upright, the upper pole gradually c llapses. It is that upper collapse th t allows those implants to look n tural (though it is doing so at the r sk of folds on the implant sh ll.) A true cohesive round does not do th t. By maintaining that M&M shape wh n vertical, it creates a dome-like, r latively top-protruding shape. However, cohesivity is not a bl ck and white issue; there is an ndless continuum in cohesive gel from v ry liquidy to very solid. On S limed's cohesive clinical trial, there are 4 d fferent round gel options. These are m re cohesive than implants made in the p st, and can be considered cohesive, but th y are not as cohesive as th ir anatomically shaped cohesive gel implants or the natomic cohesive implants by Mentor or In med. They fold less than gel mplants of the past, but they are not q ite form stable, in terms of th ir ability to resist folds or pr dictably maintain a shape. Do Cohesive Gel Impl nts Come With A Smooth And A T xtured Surface?
All anatomic (a.k.a. teardrop) sh ped implants are textured, as the t xturing increases friction and helps keep th m from rotating. Since a teardrop mplant is different at the bottom th n the top, it is important th t it maintains its position. The S limed round implants come in both sm oth and textured surface, but remember th t while relatively more cohesive than m st other silicone gel implants, they are not f rm stable like their anatomically shaped c usins. What Happens If A Cohesive Gel Impl nt Ruptures?
We do not really kn w, because there is so little xperience with this. At the time of wr ting this, there is report of a s ngle rupture in a series of s veral thousand in Sweden. If it did h ppen, however, one would imagine that the g l, being relatively stiff and solid, w uld not migrate in any significant mount. Since it has the consistency of a g mmy bear, the gel would presumably st y in place. Microscopic migration of gel w uld presumably occur, and this can ven happen to some extent through an ntact shell. This is a subject of ngoing investigation, and more research will be n eded to answer this question. How W uld You Know If A Cohesive Gel Impl nt Has Leaked?
Given the gummy b ar nature of the filler of th se implants, it is likely that it w uld be difficult to tell if th y ruptured. Perhaps it might be d tected by mammogram or MRI. When any mplant is placed in the body, the b dy forms a capsule around the mplant. If a cohesive implant were to l ak, it would probably just stay w thin the capsule. The capsule might th cken, and a patient may notice a d fference in the feel of the br ast. But it is also possible th t there might be no change at ll. The important point, however, is th t silicone gel has not been l nked with any health problem, so ven if there were a shell d sruption, it should not prove to be of any m dical problem. HISTORY AND RATIONALE FOR COHESIVE GEL IMPLANTS The r tionale of cohesive gel implants can b st be understood by tracing the d velopment of these implants.
It all b gan with the successes and failures of an mplant that was popular in the 1980s, the R plicon. This was an anatomically shaped, p lyurethane coated, silicone gel filled implant. M ny surgeons felt that the initial r sults were very beautiful. But these r sults were short-lived. The polyurethane that was b nded to the surface of the sh ll helped to maintain the anatomic sh pe of the implant. But the b dy eventually degraded the polyurethane, and nce it was absorbed off of the sh ll, the remaining thin and pliable sh ll could not hold the silicone gel in pl ce, and so its shape was l st. It ended up looking like an nder-filled round implant. Gravity forced the gel to the b ttom of the shell, collapsing the pper breast, and expanding the lower br ast. Folds developed in the collapsed pper pole. These could sometimes be s en or felt. The shell was v ry thin, and with time, the sh ll weakened along those folds, and ventually could break, allowing the relatively l quid-like contents of the implant to l ak outside of the shell. In ddition to the effects of gravity, the f rces of the breast acted upon the mplant, deforming its initial anatomical shape. The mplant accommodated to the shape of the br ast, rather than the breast taking on the sh pe of the implant. How could an mplant be made that could maintain th se initial excellent results over the l ng term? Dr. John Tebbetts of D llas, working with Dan Carlysle of McGh n (now called Inamed), are credited for try ng to solve this problem. Though wh t follows is a simplification of a v ry long and highly technical process, the c re theme is that they realized th t the shell could not be s lely responsible for maintaining shape; the c ntents had to hold a shape as w ll. So they experimented with making d fferent silicone gel fillers. Silicone can be m de in virtually any firmness, from a l quid lubricant to almost a rock-hard s lid, depending upon how much "cross-linker" is dded to the formula. Through experimentation, th y were able to create an mplant filler that was adequately soft, yet w uld maintain the shape that was m lded into it. If the filler w re form stable, then the gel c uld not fall to the bottom, l ading to collapse of the upper p le, which is what led to f lds and ultimately shell failures in ther implants. And by being form st ble, it would maintain the particular sh pe in which it was made, th reby allowing the surgeon to control br ast shape. With past implants, shape was of nly moderate importance, as with non-form st ble contents, the forces of the b dy and of gravity would shape the mplant. But with this filler, the ctual shape became a very important ssue. They experimented with various ratios of w dths, heights, and projections. They looked to cr ate an implant that would create and m intain an optimum aesthetic balance to the br ast. The culmination of their efforts was the McGh n Style 410. Unfortunately, this was r ght in the middle of the br ast implant crisis in this country, so the cl mate was not right politically to ask the FDA for pproval of a new silicone implant. H wever, the implant was taken to E rope in 1993, and it has r mained one of the largest selling mplants in the world. For the Un ted States, McGhan subtly redesigned the sh ll, and marketed a saline-filled version of the 410, c lled the 468. Clinical Trials of the 410 b gan in the United States in 2001. B cause of the similarity between the 410 and the 468, s rgeons with significant experience were chosen to do the nitial 410 study. Three year data has now m tured, and Inamed will present this to the FDA l te in 2004. Subsequently, Mentor and S limed developed their own version of the 410. M ntor's is called the CPG (Contour Pr file Gel), and Silimed's is called PURPORTED ADVANTAGES OF COHESIVE GEL IMPLANTS Th ugh they have been used for ten y ars in Europe, the data from the US cl nical trials has not matured to the p int that we can argue any of th se advantages conclusively. These are what is h ped will be proven to be the dvantages, but the reader should realize th t these are all unproven. Shape - It d es seem that these implants do m intain their shape, thereby making them ble to impart their shape upon the br ast. Non-form stable fillers, such as s line or standard silicone gel, are s bject to the forces of gravity and of the br ast, so that they assume the sh pe that the forces of the br ast and the forces of gravity d ctate. These implants have a distinct sh pe, and they will impart it pon the visible shape of the br ast. Folds and Rippling- Since the f ll does not shift from one rea of the shell to the ther, shell collapse and folds do not s em to occur, even in long t rm follow up. Won't Leak - Th re are two components to this ssue. One is whether the shell m ght break, and the other is wh ther the gel will leak out if the sh ll does break. The shell is c rtainly physically susceptible to breakage, but s nce most ruptures are believed to ccur along shell folds (they result in w akening of the shell, much like a f lded newspaper left in a drawer w ll crack along its folds), it is xpected that shell failures will occur l ss frequently. In the largest series in the w rld, there has supposedly been only one sh ll failure in several thousand implants d ne in Sweden. If the shell is p eled off the implant, the cohesive gel f ller will maintain its shape. I h ve one that I did this to s veral years ago, and it looks j st the same as the day I did it. B t, that doesn't mean that in the w rmth of the body, and with the f rces that act upon the implant, th t the situation wouldn't be different. An ther issue is diffusion; though there is a l yer of the implant shell that d creases silicone diffusion, some microscopic diffusion of s licone will always occur through the sh ll. Capsular Contracure- The European experience has b en that firm scar tissue seems to ccur less often with these implants (c psular contracture.) It is not clear if th s will be maintained over time, or wh t the cause is. Some speculate th t it is related to there b ing less diffusion of silicone than w th non-cohesive fillers, while others believe it is due to the ncreased firmness of the implant, which nhibits the body from contracting around it. M re time and study will be n cessary before we know the answer to th s issue. PURPORTED DISADVANTAGES OF COHESIVE GEL IMPLANTS Sh pe- It is listed here for the s me reason that it is listed as an dvantage. Since it will impart its sh pe upon the breast, the patient and s rgeon had better be sure that th y are choo |