Current status of breast implants

Introduction

Breast augmentation is the most performed procedure in cosmetic surgery worldwide. Approximately 300,000 breast augmentations are carried out in the US alone every year. Given the importance of the breast in terms of identity, image, fashion and sexuality, it is not surprising that it is in such demand. So strong is the desire for enlargement that historically, prior to implant development, almost anything that could be injected into the breast has been injected into it at some point, mostly with disastrous consequences. Even today, injectable solutions are offered in certain parts of Eastern Europe. Fortunately, implant development has progressed significantly since its inception in the early 1960s and continues to do so as our understanding of the shortcomings of existing devices evolves.

Breast augmentation has been littered with controversy at almost every stage of its development. Our knowledge of the interaction of these devices with the body changes constantly as data emerges over time. The silicone embargo in the 1990s in the USA was the first major event alerting to possible negative consequences of silicone implants. This was to last for 14 years (1992–2006) and changed the way implants were viewed – for the better, stimulating an extensive surge in research and development in order to further our understanding of the nature and possible consequences of introducing such devices into the breast. The embargo also saw the prominence of the use of the saline implant throughout this period in the US, an experience shared by few other countries. Outside of the US, the use of saline implants, has remained very sporadic and has never been commonplace.

Other notable events included the introduction of the soya-based implants known as Trilucent. These were introduced on the back of the silicone crisis as ‘natural’ alternatives. They gained great popularity in the late 1990s in the UK and other European countries. However, their lifespan on the market was short-lived as it was clear that in a rush to develop new technology, little had been understood about their interaction with the body. They had high rupture rates, their degradation was spectacular, and their breakdown products were carcinogenic. An enforced removal and replacement protocol was put in place and funded by the UK government.

The PIP crisis affected large parts of Europe and South America as fraudulent use of non-medical grade silicone was used to fill these French-manufactured implants as a cost-saving exercise. Implant manufacturing was also compromised resulting in very high rupture rates. The PIP scandal cast a shadow on the regulatory authorities and their lack of scrutiny of existing products on the market. Once CE marks were obtained, little was done to ensure continued maintenance of production standards. The PIP lesson has changed this approach with far more stringent observation and regulation of both new and existing products.

Undoubtedly the greatest shadow under which breast augmentation finds itself today is that of breast implant-associated anaplastic large cell lymphoma (BIA-ALCL). While in an in-depth discussion on this subject is beyond the remit of this chapter, it cannot go unmentioned as an important influence on implant selection and usage today. It is a subject which provokes much debate, not only among plastic surgeons themselves but with the wider public and the media. Our understanding of the condition remains limited. But once again it has laid focus on the plastic surgery and scientific communities to examine more greatly the issues around the safety of such devices. The remit of this chapter is to explore and give an account of available devices today tracing the origin of breast augmentation through history to the state of modern development as we know it today.

While many modern implants share several of the same properties, there are also some radical differences between them. It is important to understand these differences in order to be able to select appropriately for each patient and each clinical situation. As yet, the perfect implant does not exist, every device has its advantages and disadvantages; the key is understanding which compromises are worth accepting and which advantages to take in any given situation.

History of breast implants

The current status of breast implants today must be taken in context with the history and the developments in the field of breast augmentation to date.

Since the first recorded description by Czerny in 1895 of breast augmentation with an autologous lipoma, numerous techniques have been attempted to address a woman’s desire for breast augmentation and reconstruction. The era of ‘injectables’ preceded the onset of implant development. A wide variety of injectable substances including glycerin, ox cartilage, silicone oil, paraffin wax and even snake venom have all been utilized at great risk to the patients. The use of paraffin wax and free liquid silicone in the early twentieth century led to problems with migration, embolization, and granuloma formation. Diffuse infiltration of the breast with dispersed silicone resulted in solid formations distorting the breast and leading to infective sinus formation and even to mastectomy as the only resolution in extreme cases. Implantation of sponges made from a variety of plastic polymers was introduced and subsequently abandoned because of problems with infection, contracture, and tissue ingrowth, which often precluded complete explantation. In 1963, Cronin and Gerow (in conjunction with the Dow Corning Center for Aid to Medical Research) first implanted into a patient a device containing silicone gel confined within a separate silicone elastomer shell. This precursor to the modern breast implant was manufactured commercially by Dow Corning, starting in 1963, and was exempt from US Food and Drug Administration (FDA) regulations, as it was considered a medical device'rather than a drug. In 1963 the first breast augmentation was carried out in Houston Texas with Timmie Jean Lindsey as the first patient to be officially implanted.

The introduction of the silicone gel implant by Cronin and Gerow in 1963 began the modern era of breast augmentation, and over the past 60 years, breast implants have evolved to encompass a wide array of commercially available devices today. Peters et al. originally described three generations of silicone breast implants, which was further refined and described as five generations by Maxwell and Baker. The first-generation implants (1962–1970) were characterized by a dense, viscous silicone gel surrounded by a thick implant shell. As a response to requests from surgeons for a less firm implant with more natural feel, the second-generation implants (1970–1982) were round, less cross-linked gel implants covered with a thinner, much more permeable shell. These implant shells proved unreliable with increased rupture rates and high gel bleed. The subsequent third-generation implants (1982–1992) were created with a more viscous gel and a thicker smooth or textured shell, with a less permeable low-bleed barrier elastomer, in an attempt to reduce capsular contracture. The fourth-generation implants (1993 to present) are the current standard cohesive gel round implants available in the US today and are differentiated from the previous generation of pre-moratorium implants by refinements in the manufacturing process ( Fig. 2.1 ). Shaped implants were first introduced in the late 1980s as part of the fourth generation of implants. They were introduced because of their natural shape, mimicking more closely the shape of the breast. Throughout the 1990s they became increasingly popular in Europe and some parts of south America, as well as Australia and New Zealand. In the USA, however, probably as a result of the moratorium on silicone between 1992 and 2006, the use of anatomical implants was never adopted as diffusely as elsewhere.

The fifth generation of implants (1993 to present) saw the introduction of more cohesive gel in order to maintain better shape, as well as more aggressive texturization in order to improve interaction with the soft tissues of the breast to minimize rotation of the shaped devices, but also in the belief that there were lower rates of capsular contracture. The fifth-generation implants have the same silicone elastomer and low-bleed shell present in previous generations, filled with a silicone gel of greater cohesiveness that better retains its shape in varying positions. This led to the creation of an array of anatomically shaped devices to accommodate a variety of different breast forms and chest dimensions ( Fig. 2.2 ). It is, however, the increased cohesiveness of the gel and not the shape that defines this generation of implants. In the US, Sientra’s round and shaped gel implants were the first of the fifth-generation implants to gain approval in 2012, followed by Allergan’s and Mentor’s shaped implants in 2013.

The latest technological advances have seen the development of the B-lite implant, which incorporates air-filled borosilicate microspheres bound to silicone polymers to render the implants 30% lighter than standard silicon.

Implant shape

Round vs. anatomical implants

There are many differences between round and anatomical devices. Clearly, they are shaped differently ( Fig. 2.3 ), but it is important to understand the significance of this shape difference and the implications that go with it.

Surface

As already mentioned, for anatomical implants, by definition, a degree of texturization is required to minimize rotation risk. The texture can be anything from microtextured, macrotextured (not Biocell any longer), to the increasing popularity and resurgence of polyurethane in many parts of Europe and South America. There is currently a ‘smooth’ surfaced anatomical implant produced by Establishment labs with tabs for fixation. However, these implants have had limited appeal as the lack of reliability of the tabs and the complications associated with them have negated their widespread use.

For round implants, although the same texturization is also available, it is perhaps less ‘necessary’ than for the shaped devices, as rotation is not a risk, and therefore the option of a smooth surface is available for users of round implants who seek to avoid texture.

Gel

For anatomical devices, form stability of the gel is critical and arguably more important than for round devices. Form stability maintains the asymmetric shape of the anatomical device and allows it to impart its shape to the breast tissue. This constitutes the key feature of the anatomical implant (see projection point and volume distribution below). For a round device, the imposition of the shape of the device is less important and therefore, the gel is often able to be softer. For some this may also be an advantage.

Dimensionality

A major advantage of anatomical devices is that they can be varied in three dimensions as opposed to two dimensions for round implants. For the latter, because the height and the width are always the same, the only other independent variable is the projection of the implant. For anatomical implants the height, the width, and the projection can all be varied independently of each other. This combination gives great versatility in being able to select an implant more precisely for certain anatomical situations, and for complex asymmetries.

Projection point and volume distribution

The difference in volume distribution between the two devices results in a significant difference in the point of maximum projection. This is perhaps the most critical element in being able to select a device, which can achieve optimal volume distribution above and below the nipple areola complex (NAC) especially in difficult anatomical situations. Anatomical implants have low projection points – short height anatomical devices have even lower projection points than full height anatomical devices. Round implants have relatively higher projection points ( Fig. 2.4 ).

The significance of the projection point is that ideally the maximum point of projection should be just below the NAC. This allows a forward and upward projection of the NAC on the breast mound (image) as well as a harmonious volume distribution in keeping with the authors’ 45:55 ratio of ideal volume distribution above and below the nipple meridian. If the projection point lies above the NAC the nipple will be pushed in a downward direction, which is highly undesirable ( Fig. 2.5 ). In addition, a high projection point with a downward pointing nipple often results in an inadequately filled lower pole and a subsequent waterfall deformity. By contrast certain anatomical situations will dictate that lower pole volume is essential for resolution of the problem at hand.

Why are we told there is no difference between the devices?

Various publications in the literature suggest that, as plastic surgeons, we are not able to discern a round implant from an anatomical implant when looking at postoperative images of women with implants. The implication of this is that if there is no difference between the two devices, why use an anatomical implant at all? The major flaw of these studies is a lack of control imagery. In other words, in a postoperative image where the result seems as if it might be round, but in fact it is anatomical, the image might have appeared even more round with a round implant; however, this comparison is never presented. The fact that an anatomical implant can look round and vice versa is simply an interplay of anatomy and tissue-based implant selection. All anatomical implants look round if they are too large ( Fig. 2.6 ), almost all round implants look natural when they are small enough and the starting anatomy is favorable ( Fig. 2.7 ). This absolutely does not mean that there is no difference between the devices. If that really were the case, then rotation could not be cited as a complication, as it would go unnoticed. However, we know this is not the case. It is important therefore to understand based on the volume distribution and projection point discussed earlier, when and how to use anatomical implants.

Indications for anatomical implants

Natural look

Anatomical implants are classically suited to those seeking a natural look. The volume distribution of the device lends itself to recreation of the 45:55 volume distribution previously defined by the author as being indicative of ideal natural breast beauty. The ICE principle was devised to plan for anatomical implant placement in order to replicate this distribution predictably. This is especially the case in those who have amastia or very little breast development ( Fig. 2.8 ).