Breast Implants: From Glass Balls to 3D Printing

By Demetrius Coombs, MD, Ritwik Grover, MD, and Raffi Gurunluoglu, MD, PhD

Reports of breast augmentation surgery date back to 1895, when a fatty tumor was successfully transplanted from a patient’s back to a breast defect in a mastectomy patient. In the 1930s, implantation of a glass ball into a patient’s breast marked the first implant-based breast augmentation. By 1954, attempts at breast augmentation using local dermal-fat flaps, adipose tissue and even omentum were described.

Alloplastic materials gained popularity throughout the 1950s and 1960s and included polyurethane, polytetrafluoroethylene (Teflon) and other synthetics. Adverse reactions associated with alloplastic materials were plentiful: local tissue reactions, distortion of the breast mound, increased firmness and discomfort all contributed to the eventual discontinuation of their use. The history of alloplastic breast augmentation also included epoxy resin, shellac, beeswax, paraffin, rubber, petroleum jelly and liquefied silicone. Outcomes were not good, and many patients ultimately needed mastectomy.

The first modern breast prosthesis was developed in 1961, and since then, implant composition and design have evolved significantly.

From silicone to saline, and back again

The first silicone gel implants, introduced in the early 1960s, had high complication rates — some centers reported an incidence of capsular contracture of up to 70%. This is a foreign body reaction in which pathologic scar tissue encases the implant, causing it to distort, appear misshapen, harden and even become painful. Attempts to minimize this reaction led to later generations of silicone implants with polyurethane shells.

Inflatable implants filled with sterile saline solution were originally developed in France in 1965. Unlike silicone implants, saline implants have undergone minimal changes since their inception, and grew in popularity during the 1970s in view of the high rates of capsular contracture with silicone implants. However, saline implants have their own problems, and as they became increasingly popular, deflation and the unnatural feel of saline sparked a renewed interest in silicone gel.

By the late 1980s, the thinner-shelled generation of silicone implants displayed its own frustrating complications including implant rupture, capsular contracture, infection and possible systemic and disseminated granulomatous disease. From 1992 to 2006, the US Food and Drug Administration (FDA) placed a moratorium on silicone implants due to concerns about a possible link with autoimmune and connective tissue diseases and the possible carcinogenic nature of silicone.

While silicone implants were prohibited in the United States, development continued abroad, and eventually the moratorium was lifted after several meta-analyses failed to reveal any link regarding the aforementioned concerns.

Today, silicone gel implants dominate the world market. In the United States, approximately 60% of implants contain silicone gel filler, and trends are similar in Europe.

Current implant options

Currently, three companies (Allergan, Mentor, Sientra) manufacture and distribute breast implants and implant-associated products such as tissue expanders and sizers in the U.S. market.

Another company, Motiva, makes an implant that is available in Europe, Asia and Australia, and the device is currently undergoing a 10-year clinical trial in the U.S. that began recruiting patients in 16 centers in April 2018. Pending final approval, Cleveland Clinic’s Department of Plastic Surgery may be among the centers involved in the clinical trial of the Motiva implant. Innovations in the Motiva implant include a high-performance shell that maintains consistent strength and includes a proprietary barrier layer, improved silicone gel filler, 3D imprinted surface texturing and an implant shape that adapts with vertical and horizontal movement. It also contains radio-frequency identification transponders that can transmit data about the implant wirelessly.

Surface (textured vs. smooth)

Developed in the 1980s, texturing of the implant surface disrupts capsule formation around the prosthesis. Additionally, texturing stabilizes an anatomically shaped (teardrop) implant within the breast pocket, reducing malrotation.

The first textured implants were covered with polyurethane foam, but they were ultimately withdrawn from the U.S. market because of concern for in vivo degradation to carcinogenic compounds. The focus subsequently turned to texturing implant shells by mechanically creating pores of different sizes.

The capsular contraction rate has been shown to be lower with textured silicone than with smooth silicone (number needed to treat = 7–9), and evidence suggests a lower risk of needing a secondary procedure.

Form-stable vs. fluid-form

The physical properties of polymers vary greatly and depend on the length of the individual chains and the degree to which those chains are cross-linked. Liquid silicone contains short chains and sparse cross-linking, resulting in an oily compound well suited for lubrication. Silicone gel contains longer chains and more cross-linking and is therefore more viscous.

In “form-stable” implants, the silicone interior has sufficient chain length and cross-linking to retain the designed shape even at rest, but they require slightly larger incisions. “Fluid-form” refers to an implant with silicone filler with shorter chain length, less cross-linking and more fluidity.

Shell

As with silicone fillers, the properties of silicone implant shells also depend on chain length and cross-linking within the polymer. Silicone elastomer shells contain extensively cross-linked chains that impart a flexible yet rubbery character. Silicone elastomers can also be found in facial implants and tissue expanders.

Implant shape (round vs. anatomic)

The shape of an implant is determined by the gel distribution inside of it. To understand gel distribution and implant shape, one must understand the gel-shell ratio. This ratio increases as cohesivity of the filler increases, and it represents increased bonding of the gel filler to the shell and a preserved implant shape at rest.

The gel-shell ratio varies among manufacturers, and a less-viscous filler may be more prone to rippling or loss of upper pole fullness in some patients. For this reason, careful analysis, patient and implant selection, and discussion of complications remain paramount.

No anatomically shaped implant is manufactured with a smooth shell, but rather with a textured shell that resists malrotation. However, in the U.S., 95% of patients receive round implants.

Future posts will discuss assessment of patients for breast augmentation and complications of implants.

Drs. Coombs and Grover are plastic surgery residents. Dr. Gurunluoglu is staff in the Department of Plastic Surgery.

This abridged article was originally published in Cleveland Clinic Journal of Medicine.