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.20,21
The first textured implants were covered with polyurethane foam, but they were ultimately withdrawn from the US market because of concern for in vivo degradation to carcinogenic compounds.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. Smooth implants, by contrast, are manufactured by repeatedly dipping the implant shell into liquid silicone.2
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.21
Form-stable vs fluid-form
Silicone is a polymer. 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,2 but they require slightly larger incisions.7 “Fluid-form” refers to an implant with silicone filler with shorter chain length, less cross-linking, and more fluidity.6
As with silicone fillers, the properties of silicone implant shells also depend on chain length and cross-linking within the polymer. Silicone elastomer shells (Table 1) contain extensively cross-linked chains that impart a flexible yet rubbery character. Silicone elastomers can also be found in facial implants and tissue expanders.2
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.2
No anatomically shaped implant is manufactured with a smooth shell, but rather with a textured shell that resists malrotation.6,15 However, in the United States, 95% of patients receive round implants.16
Before breast augmentation surgery, the surgeon assesses a number of factors—physical and psychosocial—and helps the patient choose a type and size of implant. The surgeon and patient also plan where the implants will be placed—ie, above or beneath the chest wall muscle—and where the incisions will be made. Every decision is made in close consultation with the patient, taking into account the patient’s desires and expectations, as well as what the patient’s anatomy allows. An integral component of this shared decision-making process is a discussion of the possible complications, and often photographs to better illustrate what to expect postoperatively.
One must consider the patient’s psychology, motivations for surgery, and emotional stability. Here, we look for underlying body dysmorphic disorder; excessive or unusual encouragement to undergo the procedure by a spouse, friends, or others; a history of other aesthetic procedures; unrealistic expectations; and other factors influencing the desire to undergo this surgery.
Choosing an implant
Implant selection must take into account the patient’s height, weight,7 and overall body morphology: taller patients and those with wider hips or shoulders usually require larger implants. A reliable method for determining the appropriate implant must include the current breast shape, dimensions, volume, skin elasticity, soft-tissue thickness, and overall body habitus. Ultimately, the most important considerations include breast base diameter, implant volume,20 and soft-tissue envelope.
Preoperative sizing can involve placing sample implants within a brassiere so that the patient can preview possible outcomes. This method is particularly effective in minimizing dissatisfaction because it shares ownership of the decision-making process.15
A computerized implant selection program available in Europe suggests a “best-fit” implant based on a clinician’s measurements.7