Sunday, January 28, 2007

Building a better breast implant

The advances in the technology of silicone breast implant design and manufacturing have progressed significantly since the original was introduced in the late 1950's. We are now in what's called either the 4th or 5th distinct generation of implants as identified in our literature.

Most of the problems seen in the "implant crisis" of the early 1990's were those of the 2nd generation which had very liquid (non-cohesive) silicone gel fillers with thin shells that had a propensity to "bleed" or leak small amounts of silicone even when intact. The FDA endorsed 3rd/4th generation devices in October which have thicker, more-cohesive gel and thicker shells with coating that radically reduces gel bleeding. The high-cohesive "gummy bear" implants contain even thicker gel filler and are pending US approval while widely used elsewhere.

Saline implants are destined for the historical dustbin and have never been used widely outside of the United States.

Other then the form-stable devices, what are the new areas for improvement in implant science and use? Manufacturers report on electron microscopy of explanted devices suggests that many ruptured implants are ultimately caused from trauma during insertion years prior. That may or may not in fact be true as surgical trauma from removal could be hard to distinguish from preexisting device architecture. This assertion has had the effect of stimulation a great deal of educational efforts on proper techniques for insertion, implant handling, and other technical maneuvers.

A chemist, Dr. Judit Puskas, at the University of Akron, is trying to push the scientific envelope developing implants made of a biorubber called polyisobutylene. This compound purports to be lighter, less likely to rupture and less permeable than silicone implants. A write-up of this can be found here.

An interesting property of these biorubber implants would be the ability to design them to contain and release drugs that could inhibit the growth of the implant capsules, akin to how a drug-coated stents prevent scar tissue from blocking coronary arteries. In fact, polyisobutylene is already used in such stents with little side-effects.


Anonymous said...

I am a student at the U of A and when I read about this in our paper, The Buchtelite I was excited. I really hope that she receives the funding that she needs. I would even be interested in the clinical trials.

Kate said...

The research into alternative materials is very exciting, and long overdue. Not sure about making the rubber so it has drug-releasing properties though; those drug-eluting stents have actually caused additional problems (after they were FDA approved and in wide use).

What I like about the gummybear implants is, from what I've seen, they have so many size/width choices and they're sort of "tear-drop" shape, so you don't get that half-cantaloupe fakey roundness at the top of the breast, especially on slender women. Drs Grant and Stoker in California are approved to do these implants in the U.S. for the 10-year FDA study, and so far the before and after photos I've seen where these have been used look really good.

Is the situation that these won't have a chance at being approved for widespread use in the U.S. until after this 10 year study?

A little confused about the statistics of capsular contraction, though:

From a study done on these new implants (Breast augmentation with anatomical cohesive gel implants, Per Heden, MD, PhD, et al, Clinics in Plastic Surgery, Vol. 28, No. 3, July 2001, pp 531-552), they're saying "...The largest published study looking at complication rates with cohesive gel implants showed an overall capsular contracture rate of <5%."

Dr. Judit Puskas states "The real problem is the capsule formation around the implant...It actually happens to 100 percent of women over time.''

I realize she's talking not specifically the "gummybear" implants but all silicone implants, but which is it? Is the <5% on the largest study of the strong gel ones because the study was over such a short period of time?


Dr. Rob Oliver said...


all foreign bodies form capsules to some degree so in that sense she is correct with the "100% figure". That is a normal biologic process with all implants (pace makers, artifical joints, suture material, etc...). An exageration of that process with implants produces capsular contracture and the firm, hard feel and appearence that can develop.

Older low viscosity gel implants had a tendency to do this from a local reaction to rupture or "gel bleed" (microparticle leaking) thru the implant shell even when intact. We think that post-operative hematoma (bleeding) or subclinical infection are the most likely culprit in most high grade capsular contractures. As we've adopted more refined surgical techniques and began bathing the implants in potent anti-biotic solutions, we've seen capsule rates decrease signifigantly.

The form-stable ("gummy bear") implants seem to be even less prone to contracture for a couple reasones including:

* they do not rupture in the same way older devices do. There is little potential for migration of the gel outside of the shell or implant capsule

* they're all textured surfaced devices, which has some protective effect (we think)

* The structural rigidity of the implant may resist deformation from a capsule and make a capsule less noticible, even when they develop.

There's no firm time table on US approval of the form-stable devices. Presumably it could come this year as it's safety profile clearly appears to be an improvement over recently approved devices. Never underestimate the political groups who are violently objecting to breast implants though. They successfully stalled reapproval of silicone implants for a decade despite overwhelming evidence and international consensus