Silicone breast implants: pathology

The Evolution of Breast Implants

The present review traces the evolution of breast implants over the past 50 years. During the early years (from 1951 to 1962), a number of different sponges were used for breast augmentation. The first of these was Ivalon, a polyvinyl alcohol sponge. Other sponges were introduced subsequently, including Etheron (a poly-ether sponge popularized by Dr Paule Regnault in Montreal) and Polystan (fabric tapes that were wound into a ball). Subsequently, polyethylene strips enclosed in a fabric or polyethylene casing were also used for breast augmentation. All of these materials had similar outcomes. Although the initial results were encouraging, within one year of augmentation, breasts became very firm and lost over 25% of their volume. This was due to capsular contracture, a process that would lead to the collapse of the sponge and would continue to plague plastic surgeons and their patients for the next 50 years. In 1963, Cronin and Gerow introduced the silicone gel ‘natural feel’ implant, which revolutionized breast augmentation surgery. Approximately 10 companies have manufactured many types of silicone gel breast implants over the years. They obtained their raw materials for gels and shells from a similar number of other companies that entered and left the market at intervals. Many of the suppliers and manufactures changed their names and ownership over the years, and most of the companies no longer exist. No formal process of United States Food and Drug Administration premarket testing was in effect until 1988. There have been three generations of gel implants and a number of other lesser variations. First-generation implants (1963 to 1972) had a thick gel and a thick wall. They have generally remained intact over the years. Second-generation implants (1973 to the mid-1980s) had a thin gel and a thin wall. They have tended to disrupt over time. Third-generation implants (mid-1980s to 1992) had a thick wall and a thick gel. Except for those made by Surgitek, these implants remain intact. The breast implant business was competitive and companies introduced changes such as softer gels; barrier low-bleed shells; greater or lesser shell thickness; surface texturing; different sizes, contours and shapes; and multiple lumens in search of better aesthetics. Ultimately, more than 240 styles and 8300 models of silicone gel breast implants were manufactured in the United States alone. Inflatable breast implants were introduced in Toulons, France in 1965 (the Simaplast implant). There have been three main eras of inflatable implants: seamed, high-temperature vulcanized and room temperature vulcanized implants. In 1973, spontaneous deflation rates of 76% to 88% over three years were reported for many types of inflatable implants. Because of this, most plastic surgeons abandoned their use. From 1963 until the moratorium on gel implants (January 6, 1992), about 95% of all breast implants inserted were silicone gel filled. Only 5% were saline filled. Since the moratorium, this ratio has been reversed and 95% of all implants have been saline-filled, with only 5% being gel filled. Polyurethane-coated (PU) silicone gel implants were introduced in 1968. Over the next 20 years, they were shown to reduce the prevalence of capsular contracture to 2% to 3%. Other forms of surface texturing (Biocell, Siltex, multistructured implant) also appear to reduce capsular contracture with gel implants, but the reduction has been much less dramatic than that seen with PU implants. Contoured (anatomical) shaping appears to have advantages in some patients with gel implants. No such advantage has been seen for texturing or shaping with saline-filled implants. The story of gel implants has culminated in the largest class action lawsuit in medical history, with US$4.2 billion being awarded to women with silicone gel implants. During the past decade, there has been a tremendous amount of research on the reaction of a woman's body to gel implants. A plethora of studies have demonstrated that silicone gel implants are not associated with the development of any medical diseases. Silicone gel-filled implants have therefore been approved for use under Health Canada's Special Access Program. Silicone gel-filled implants may now be used in certain patients in whom they would provide advantages over saline implants. Silicone gel implants have not been approved for unrestricted general use. The evolution of breast implants occupies the past half century. It has been a stormy course, with many exciting advances and many bitter disappointments. The universe of breast implants is large and the variation among the implants is substantial. The purpose of the present review is to trace the evolution of breast implants over the past 50 years.

Does the surface structure of implants have an impact on the formation of a capsular contracture?

BACKGROUND

The formation of a fibrous capsule around a silicone breast implant is part of a physiologic foreign body reaction after breast augmentation. In contrast, the formation of a capsular contracture is a local complication of unknown cause. This study aimed to discover whether the surface structure of the implant (textured vs smooth) has any impact on the formation of a capsular contracture.

METHODS

This prospective study included 48 female patients with unilateral capsular fibrosis grades 1 to 4 in Baker's clinical scaling system. Of these patients, 14 received implants with a textured surface (Mentor), and 34 received implants with a smooth surface (Mentor). The implants all were placed in a submuscular position by the same experienced plastic surgeon. The clinical data were assessed using standardized patient questionnaires. For histologic diagnosis, operatively excised capsular tissue was examined. Preoperatively, venous blood samples for determining serum hyaluronan concentrations were taken from the patients. The control group consisted of 20 patients without capsular fibrosis.

RESULTS

The separate analysis of clinical data for the patients with textured and those with smooth-surfaced breast implants showed a slightly reduced degree of symptoms for the patients with textured silicone breast implants, as compared with those who had smooth-surfaced implants. The histologic assessment of the fibrosis showed a symmetric distribution for Wilflingseder scores 1 to 3 (29% each), whereas 13% of the capsular tissues could be assigned to Wilflingseder score 4. In contrast, the histologic assessment of the patients with smooth-surfaced implants predominantly showed a Wilflingseder score of 3 (65%). The serologic investigations via enzyme-linked immunoassay (ELISA) showed serum hyaluronan concentrations of 10 to 57 ng/ml (25.0 +/- 11.7 ng/ml). Therefore, no statistically significant differences in terms of serum hyaluronan levels could be determined between the two groups of patients. In comparison with the control group, the patients with implants showed elevated serum hyaluronan levels (p < 0.05).

CONCLUSIONS

The histologic examination and serum hyaluronan concentration analysis showed no statistically significant difference between smooth-surfaced and textured implants (Mentor) with respect to the development of capsular contracture. On the other hand, the severity of capsular contracture showed a positive linear correlation with the degree of local inflammatory reactions, which were independent of the implant surface.

The use of biomedical sensors to monitor capsule formation around soft tissue implants

Piezoelectric sensors have been shown to respond reproducibly to changes in tissue mechanical properties surrounding an implant over a 4-month period. The vibrational amplitude at a frequency corresponding to the radial resonance shows a statistically significant change over time. The initial period of inflammation is marked by a significant reduction in amplitude, which is indicative of an increase in viscous dissipation of the tissue. As collagen displaces the cellular response, the amplitude continues to decrease. Finally, as the tissue matures, the capsule becomes stiffer, and the viscous dissipation lessens. These results are consistent with qualitative assessments of explanted capsules. Strain gauges encased in a monolithic block of silicone exhibited a greater degree of variability, yet show similar trends over time. The strain increases in the initial 4-week period and remains relatively steady over the following 4 weeks. Beyond 8 weeks, the gauges begin to extrude from the animal or suffer a loss of electrical continuity. Steps are being taken to improve the strain sensor longevity in the animals.

Shur-clens: an agent to remove silicone gel after breast implant rupture

Removal of silicone gel from surrounding tissues after implant rupture is difficult. Local inflammation, infection, and silicone granulomas warrant thorough removal of the silicone gel. Shur-Clens (20% solution of the surfactant poloxamer 188), povidone-iodine, and saline are agents that are used to aid in the removal of silicone gel from tissue. The purpose of this study was to compare the efficacy of silicone gel removal by these three agents in vitro. Shur-Clens, povidone-iodine, and saline were compared as solvents for silicone gel. Four weight increments of silicone gel (0.02 g, 0.04 g, 0.06 g, and 0.08 g) were placed on glass slides. These slides were placed in separate beakers containing 40 ml test solution. The slides were soaked for 1 minute with gentle agitation. The slides were removed, rinsed gently with de-ionized water, and placed in a vacuum desiccator to dry. The slides were weighed to determine the amount of silicone removed after soaking in the solution. Analysis of variance was used to determine the significance between the three solvents. The percentages of silicone gel removed for the four weight increments (0.02 g, 0.04 g, 0.06 g, and 0.08 g) in saline were 5.6%, 2.9%, 2.1%, and 5.8%, respectively. In povidone-iodine solution, the percentages were 18.9%, 25.4%, 28.8%, and 51.9%. In Shur-Clens, the percentages were 31.3%, 43.0%, 63.5%, and 79.9%. The greater percentage of silicone gel removed by Shur-Clens was significant compared with the other solutions (p < or = 0.05). Shur-Clens was shown to be a more effective solvent for removal of silicone gel in vitro. This enhanced efficacy is a result of the fact that Shur-Clens contains 20% of the surfactant poloxamer 188. The authors' clinical experience with 7 patients who underwent ruptured silicone breast implant removal demonstrated the superiority of Shur-Clens. Shur-Clens is a surfactant cleanser that is widely available, is inexpensive, and has a good safety profile. They propose the use of Shur-Clens to clean silicone gel spillage to decrease local complications resulting from residual silicone gel.

Ultrastructural anatomy of contracted capsules around textured implants in augmented breasts

The development of a capsule around an implant is part of the physiological response to a foreign body. Capsular contracture is the most specific and frustrating complication of augmentation mammaplasty, and a lot of studies have been devoted to it. The aim of the current study is to examine the fine architecture of the contracted capsule around textured implants in humans. Eight capsules from augmented and contracted breasts with gel-filled, textured-surface silicone implants were studied after standard preparation for light and scanning electron microscopy, and after partial digestion in sodium hydroxide. Two capsules from contracted breasts around smooth implants and two noncontracted capsules around textured implants were prepared and studied in the same fashion as controls. A multilayer structure of the contracted capsule was seen, and the architecture of the various layers is described. The inner surface presents irregular craterlike depressions. The arrangement of collagen fibers varies in capsule layers. The effect of a textured-surface implant on the mechanism of capsule contraction based on the observed capsular architecture is that only part of the capsule is effective mechanically in producing a contracting force. A thin vascular layer was identified near the inner surface in contracted capsules around textured implants, and the authors' think that this layer is probably the key structure in the histological development and growth of the capsule.

Analysis of silicon in human tissues with special reference to silicone breast implants

The increase, in the last two decades, in the application of silicones (polysiloxanes) and inorganic silicon compounds in medicine and the food industry, has exposed the human body to extensive contacts with these substances. Most silicone breast implants contain a gel consisting of a crosslinked silicone elastomer swollen by silicone oil (PDMS). Diffusion of PDMS through the silicone elastomer envelope and rupture of the envelope with release of the gel contents both occur clinically. The amount and distribution of silicone compounds in various tissues are key issues in the assessment of health problems connected with silicone implants. We have measured by GFAAS the Si content of tissues from normal and implant patients and the organic solvent extractable Si levels (assumed to be silicone), using careful control of sample collection and preparation. Whole blood levels were: implant patients mean 38.8 (SD 25.6) (microg/kg), controls mean 24.2 (SD 26.7) (microg/kg) in one study and subsequently 103.8 (SD 112.1) and 74.3 (SD 86.5) (microg/kg) in another study. Capsular tissue levels were: gel implants 25047 (SD 39313) (mg/kg of dry tissue), saline implants 20.0 (SD 27.3) (mg/kg of dry tissue) and controls 0.24 (SD 0.39) (mg/kg of dry tissue). Breast milk levels were: implant patients mean 58.7 (SD 33.8) (microg/kg), controls mean 51.1 (SD 31.0) (microg/kg); infant formula mean was 4.40 (mg/kg). Various precautions were undertaken to avoid Si contamination in this work, the most important being a) the use of a Class 100 laboratory for sample preparation and b) application of strict and elaborate washing procedure for specimen collection tools and laboratory plasticware. This data demonstrated that to properly interpret the importance of these numbers for human health, a larger study of "normal" levels of Si in human tissues should be undertaken and factors such as diet, water, race and geographical location should be considered.

The immunopathology of siliconosis. History, clinical presentation, and relation to silicosis and the chemistry of silicon and silicone

Recent evidence confirms the fundamental involvement of the human immune system in the reaction to implantation of silicone-based medical devices. An as yet-to-be particularized epitope of many complex substances sharing siloxane structures is presented through the MHC-II apparatus with development and retention of T cell memory. This memory can be tested for in practical terms using one or more forms of silica, which links the immuno-histopathology and autoimmune attributes of "silicosis" with those of "siliconosis." The lesions of siliconosis are typical of those for persistent antigens and delayed, cell mediated hypersensitivity. The basic descriptive pathology of the reaction to silicone has been known since soon after introduction of silicones in medical procedures, with the exception of some details related to the more recent discoveries on the role of cytokines in the immunopathic process. The clinical consequences of siliconosis are common and can be severe in some individuals implanted with silicone devices.