These implants are made with a silicone envelope and a valve that allows inflation by means of a physiological solution during the surgical procedure. The envelope may be either smooth or textured. The envelope has good elasticity, and allows variation of the inflation from the saline solution in order to obtain better symmetry with the contralateral breast. Overinflation of 10–20 % more than the volume recommended by the implant manufacturer is suitable as it causes better distension of the envelope and prevents the implant folding. These folds could subsequently cause rupture of or extrusion of material from the prosthesis, especially in the case of thin and irradiated tissue coverage. The shape might be round or anatomic, but it is more difficult to maintain an anatomic shape when saline solution is used as the implant does not have the same consistency as cohesive gel. The valve may be anterior or posterior according to the technique. Small incisions can be adequate for insertion of the implant, and it can then be inflated with the physiological solution.

Practically, it would be simpler to use implants with anterior valves or periareolar and posterior valves for axillary incision cases. The valve is one of the critical points of saline implants, as a rare production defect may cause partial or total leakage of the physiological solution. Usually, this leakage does not produce any pathological damage to the patient, as it is a physiological solution and can be reabsorbed. The main problem is a good aesthetic result; the deflation can lead to the necessity for a revision or substitution procedure (Fig. 20.1). Some studies reported different levels of leakage or disruption of saline implants. A French group has demonstrated leakage level of 15 % in 650 patients with an average follow-up of 5 years [10].

These implants have a fixed volume. They are made of an envelope of silicone gel. Currently, the thickness of the envelope is carefully considered. It can be more resistant and avoid the “perspiration” of silicone gel particles. Silicone gel is elastomeric and its viscosity depends on the molecular mass, so now it is possible to manufacture a more cohesive gel. This kind of gel is used in the manufacture of anatomic implants, which need to be slightly more rigid in order to maintain the anatomic shape. Anatomic implants with cohesive gel were a great advance in terms of improving the aesthetic results in breast reconstruction. It is possible to achieve a better shape with less projection of the upper pole of the breast. Implant manufactures are now using three types of cohesive gel: low, medium and high cohesive gel for both anatomic and round implants. For this reason, plastic surgeons have a very large choice depending on the shape and consistency of the breast.

A technical refinement is necessary when using this implant for breast reconstruction. When the mastectomy flaps are thick and well vascularized, it is possible to make a partial cover of the implant with only the pectoralis major muscle. This technical element contributes to a better aesthetic result, with more projection of the lower pole of the breast. Using a round prosthesis with complete coverage of the pectoralis major muscle and the serratus anterior muscle may create a round and less natural shape [11]. Another advantage of cohesive gel is increasing patient safety by reducing the phenomenon of perspiration of the particles. As it is more cohesive, this gel probably reduces migration to the lymph nodes even in cases of disruption of implants. The main advantage of anatomic implants is the possibility to choose different shapes and volumes, as some manufacturers supply different models of implants that differ according to three parameters: height, width, and anterior projection. It is easier to select the ideal implant according to the different morphological characteristics of the patient (Fig. 20.2). Other manufacturers provide innovative features such as prostheses for the right or the left breast and with a concave posterior wall for thoracic wall convexity (Poly Implant Prosthèse, PIP, implant). Although this was an interesting idea, this manufacturer suffered a crisis in 2010 owing to suspicion of the use of industrial (nonmedical and nonapproved use in humans) silicone in their implants [12].

The disadvantages of anatomic implants with cohesive gel are:

These implants are made with an internal coat of silicone gel and an external chamber that can be filled with 20–50 ml of physiological solution. The initial purpose was to create a more fragile external chamber that will degrade 3 or 4 months after implantation, therefore reducing the implant volume by 20–50 cm³ when the periprosthetic capsule stabilizes. There was no clear advantage of reducing periprosthetic capsular contracture when compared with single-chamber implants, so the use of double-chamber prostheses was discontinued.

These implants are made with an external coat of polyurethane, and they are more efficient in preventing capsular contracture than those with a smooth envelope. The physical characteristic of the polyurethane-coated implant causes disorientation of the direction of collagen fibers, which does not occur in smooth-envelope implants [14]. Some publications have demonstrated that the metabolism of polyurethane produced 2,4-toluenediamine and 2,6-toluenediamine, which could be carcinogenic [7, 15]. The incidence of periprosthetic contracture and other complications was reported to be less than 1 % [16]. In the case of infection with a polyurethane prosthesis, removal of the prosthesis with all polyurethane residues is mandatory to avoid cutaneous fistula.

These are relatively new implants, launched on the market in 2003, and they have the following characteristics: the internal part is silicone gel and the external envelope is silicone with a titanium microstructure. The aim is to reduce reactions to foreign bodies and consequently to decrease the incidence of periprosthetic capsules. An in vivo animal study show titanium-coated silicone grafts were not effective in protecting against infection; however, they might reduce the rate of capsular contracture [17].

These implants have an adjustable volume. The external chamber is filled with silicone gel and an internal chamber can be filled with physiological solution; therefore, it is easier to match the volume symmetry of the opposite breast. The internal chamber lies at the lower portion of the implant; therefore it creates the anatomic-shape-like prosthesis. An external valve connects with the internal chamber through a 2-mm silicone tube; this device can be removed (Becker’s prosthesis) or fixed to the prosthesis (Allergan style 150). The valve can be easily placed in the axillary region or other superficial locations. A parasternal placement may cause discomfort to the patient and should be avoided [18]. This type of implant is also useful for an immediate breast reconstruction with a fragile skin flap and high risk of necrosis if high tension is found. In such cases, the implant can be inserted without filling the internal chamber, and inflation can be done after 3 or 4 weeks when a viable skin flap is approved. There is also the possibility to correct the volume when the body weight changes in the postoperative period owing to chemotherapy or hormone therapy (Figs. 20.3, 20.4).

Two disadvantages in the use of implants of this type are

These are implants with an elastic silicone envelope and a filling valve that allows inflation by means of physiological solution. The postoperative skin can be expanded to match the volume symmetry of the contralateral skin. However, a second surgical procedure is needed to replace the expander with the definitive implant. There are different models and shapes of expanders: round or anatomic, with integrated valves or with separated valves. The older models are round and have separated valves which are connected with the device through a 2-mm-diameter silicone tube. The disadvantage of these models is that they not only produce distension of the lower pole but they also cause distension of the upper pole and the pectoralis major muscle. Such distension causes pain and discomfort when patients move their upper limbs; distension of the upper pole is more likely than distension of the lower pole (Fig. 20.5

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