Breast Implants Characteristics: New Implants Shapes, Gels, Surfaces
All breast implant associated complications (i.e., seroma, capsular contracture, double capsule, BIA-ALCL) appear to be related not only to the materials used to manufacture the implants but also to how this interacts with the host. Every breast implant has a distinctive 3D surface architecture, which elicits a unique host response at the cellular level that needs to be further studied to establish cellular response and biocompatibility. Eventually this may be elaborated into a unique classification that takes into consideration the level of host response to the physical characteristics of the surface.
Clinical indications for the use of breast implants are either reconstructive or aesthetic. Reconstructive surgery comprises approximately 25% of cases with the remaining 75% conducted for aesthetic reasons, or may be evenly distributed depending on the geographical region as indicated by a survey of plastic surgeons.
Examples of implant use for reconstructive surgery include restoration of a breast mount following mastectomy (i.e., removal of the breast), treatment for breast cancer, or to reduce breast cancer risk in women who are carriers of a BRCA gene mutation. Breast implants may also be employed to correct breast anomalies, such as women with asymmetrically developed breasts (anisomastia, Poland syndrome, tuberous breast), or completely undeveloped breasts (amastia). Finally, breast reconstruction with implants can also be performed following accidental or iatrogenic trauma sustained during paediatric surgery or radiotherapy, or for male to female gender reassignment surgery. A recent patient survey showed that after breast cancer therapy, quality of life was higher for women having undergone breast reconstruction compared to mastectomy without reconstruction.
Aesthetic indications include patients who wish to change their native body image, by increasing the breast volume and adjusting its shape. Some trends are apparent in the literature for the use of one or another type of breast implant. However, the clinical indications for the use of a specific type of breast implant should depend on a consultation between clinician and patient to allow informed decision making to take place with regards to the choice of an appropriate breast implant. For breast reconstruction, a shared consultation with a multidisciplinary healthcare team including a pathologist, oncologist, surgeon, breast care nurse, etc. should be held with the patient to allow informed decision making to take place with regards to the breast reconstruction procedure as well as the choice of implant. For both aesthetic and reconstructive surgery, all aspects of breast implants should be evaluated and discussed with the patient, expressly covering advantages, disadvantages, follow-up procedures and risk factors.
In summary, breast implants are used for:
Primary Reconstruction, i.e., the replacement of breast volume lost after accidental or iatrogenic trauma, mastectomy for breast cancer, and developmental anatomic anomalies such as amastia, tuberous breast and Poland syndrome.
Secondary reconstruction following a previous surgical procedure after breast cancer or preventive surgery in women with a BRCA mutation.
Correction of aesthetic variants such as hypomastia and anisomastia.
Aesthetic use for increasing breast volume and improving its shape.
Different types of Breast Implants
Breast implants have a limited number of characteristics that can be used for their categorisation. The most frequently used categories for breast implants include those that differentiate them by:
Fill
Shell Surface
Three-dimensional Shape
Fill
Breast implants can be filled with various materials with the most frequently used being silicone gels. These gels are designed to have differing levels of cohesiveness resulting in varying levels of viscosity and hence firmness. The second most commonly used filling material is a saline solution, although silicone accounts for the vast majority of fillings used in implants available on the European and USA markets. Besides silicone and saline, less commonly used filling materials sometimes include methylcellulose, polyvinylpyrrolidone (PVP), the now discarded soybean oil, or a combination of various filling materials.
Tissue expanders are temporary implants. They are empty shells that are filled after their placement in the breast area. The most commonly used filling material is saline that is injected through the skin into the device. As the volume increases, it expands and stretches the skin, and when fully expanded creates a “pocket” into which, after removal of the expander, the final breast implant or autologous tissue is placed.
Shell Surface
The shell surface, or outer layer of the implant otherwise known as the envelope, contains the filling material. Processes employed to produce these surfaces are proprietary information. However, at present all shells are made of silicone and are fabricated by adding a number of different layers (3-5) on top of each other in order to increase their strength. The shell can rupture over time and there are reports of shells being permeable to silicones as well as to biomolecules from the surrounding tissues. The most outer layer represents the surface in contact with patient tissues and can be smooth or rough with different degrees of roughness ranging from macro (with deep texturing), micro (with shallow texturing) to smooth (with minimal texturing). In addition, the silicone shell surface may also be coated with polyurethane. The total surface area in contact with the patient is also affected to a certain extent by the volume of the implant and by the number of implants a patient has had in their lifetime. Textured surfaces and coatings were developed in an attempt to reduce implant-related complications such as rotation and capsular contraction.
Surface texture of objects can be characterised by the following features that may affect interactions between the implant and host cells:
pore size or diameter (μm);
peak maximum height (µm);
peak mean height (μm);
kurtosis (sharpness of the profile), measured by the number and height of peaks (μm);
skewness (profile symmetry), measured by the number and depth of valleys and peaks (μm);
density (profile topography), measured by the average distance between morphological features (μm);
roughness (µm).
Some of the above features are not applicable to all types of texture
Three-Dimensional (3D) Shape
Breast implants can either be round or anatomical in the latter case being teardrop shaped. Round implants have a lenticular shape, with a symmetrical curved anterior side (dome) and a flat round posterior base, with no apparent differences in the shape between the top and bottom of the implant. In contrast, anatomical breast implants have a teardrop shape with the upper half being “flatter”, with little projection and the lower half having an enhanced projection. They have an asymmetric curved anterior side and a flat, more often round or elliptic posterior base. These implants require a highly cohesive gel filling to maintain their anatomical shape and in order to prevent their rotation, they need to ‘stick’ to their surrounding tissue, which is generally achieved by roughening their surface (texturing).
Breast Implant Surface textures
Breast implant surface textures can be achieved with several different techniques.
The most commonly used methods are:
the salt-loss technique: refers to the application of sodium chloride to uncured silicone with different methods (dipping, spraying, sprinkling), and it can be performed both closed (extra layer of silicone is applied over the salt and abraded after curing to remove the salt) or open (the salt is washed away after curing).
gas diffusion (volatilisation/vulcanisation): refers to the application of ammonium carbonate to the uncured silicone surface, leaving grain-shaped openings when it thermally decomposes during curing. This can also be done at a subsurface level when the ammonium carbonate is embedded in the silicone and the gasses (ammonia and carbon dioxide) to which it decomposes, bubble through the uncured silicone during thermal curing.
imprint stamping: refers to the negative stamping of a structure onto uncured silicone. It can be done with polyurethane foam that is pressed onto the uncured silicone and removed before curing, or with a mandrel being sandblasted and the texture transferred to the silicone during curing (the shell is turned inside out). Imprint stamping with the process of turning the shell inside out can also produce low surface area and low roughness surfaces, including nano-surfaces with minimal surface area and roughness.
polyurethane foam coating: refers to the application of an extra layer of foam coating to the implant.
For the breast implants with a polyurethane (PU) coated surface, it was suggested that this cannot be considered a macro-textured implant, even though according to Figure 1 these PU coated implants do have a high surface area and high surface roughness (Hamdi 2019). For the PU coated Silimed implants, the highest surface roughness and surface area was observed when various brands of breast implants were compared with each other. Also, according to the ISO 14607 classification, PU coated breast implants should be considered macro-textured.
See below the implant surface texturing as it relates to the manufacturing method, surface area and surface roughness
Several different classifications for implant surfaces are available. However, none of these is fully satisfactory, as they don’t reflect the inflammatory mechanisms inducing adverse effects due to breast implants. To date the most credited and accepted classification by government authorities and manufacturers around the world is the ISO classification (ISO 14607:2018), and it is recommended that this is adhered to because it is the product/outcome of a wide consensus among the scientific and technical communities that deal with breast implants. The ISO 14607:2018 is currently under revision as this classification, based on surface roughness only, was considered too limited, as was also concluded in the TGA 2019 report.
Alternatives for Breast Implant
Alternatives exist for both the aesthetic and reconstructive use of breast implants. The goal of breast reconstruction is to restore the breast’s volume and shape. Typically, reconstruction is performed after a mastectomy, following breast conserving therapy or quadrantectomy/lumpectomy following breast cancer.
There are three popular techniques for breast reconstruction:
implant-based,
autologous tissues,
a combination of implants and autologous tissues.
The choice of technique is decided in a shared decision-making process between clinicians and patients taking into consideration several aspects, including preoperative clinical conditions:
the type of breast defect (size and location);
the general condition of the patient;
the characteristics of the contralateral breast;
the necessity for radiotherapy;
the availability of donor autologous tissues.
Alternatives to breast implants following breast conserving surgery: Plastic Surgery Techniques
Breast conserving surgery for the treatment of breast cancer shows a higher level of patient satisfaction than breast mastectomy alone. Therefore, several techniques have been developed to increase the use of breast conserving surgery over mastectomy. For small resections, the breast mount remains relatively undisturbed. However, as the size of the resected tissue increases, the shape of the breast and the position of the nipple are disturbed and outcomes of surgery are, in general, less pleasing. For larger resections, adding so-called tissue remodelling plastic surgery techniques can prevent major deformities. Defects can be reconstructed using a breast reduction mammaplasty technique that restores the shape of the breast and the position of the nipple. This results in a smaller breast with immediate reconstruction and often excellent aesthetic results. However, it should be noted that the need for radiotherapy in any type of surgery may hamper tissue healing/regeneration.
Besides using breast size reduction techniques, the addition of new tissue to the breast can be carried out in cases where the resected tissues are greater in size. The defect is filled by adding tissue from the surrounding area, for example, tissue flaps vascularized by the rib vasculature or lateral intercostal artery perforator flaps. Certain patient characteristics (e.g., a slim body with a low Body Mass Index) can limit the use of such techniques.
Autologous fat transfer (AFT)
Autologous fat transfer (AFT) can be used for total breast reconstruction mainly in patients with a small to medium-sized breast (Colemann and Saboeiro 2007). It can also be used as a complementary procedure during plastic surgery techniques to offer aesthetic refinements, or in flaps to increase their volume and hence, the final breast volume. AFT involves aspiration of fat tissue from available donor areas, and its reinjection into the recipient site through micro incisions using cannulas. The harvested fat is injected into the recipient area in tiny droplets. To survive, these droplets must be surrounded by live tissues in order to form connections with the local vascular framework. Usually, to form a proper connection, the amount of fat needed to restore the required breast volume cannot be transferred in a single procedure, instead requiring more surgical procedures. Hence the volume of fat that can be transferred depends not only on donor site availability, but also on the capacity of the recipient site to accommodate it, thus generating a need for more surgical procedures to produce a breast of the same volume as could easily be obtained with a flap. The advantage of AFT over flap surgery is that it produces fewer scars although, like all surgical procedures there is a risk of complications.
Alternatives in aesthetic cases
Breast implants are used in aesthetic procedures for the correction of developmental anomalies of the breast such as amastia, hypoplasia, breast asymmetry, tuberous breast and when breast volume augmentation is desired. AFT, as in breast reconstruction, is an autologous alternative to breast implants, offering comparable results. However, the predictability of outcomes with autologous fat transfer may be uncertain, especially in cases in which radiotherapy was applied. Also, patients have to undergo several operative sessions for aesthetic purposes. Moreover, repetitive fat graft sessions might not be possible in some patients because of a lack of availability of the required fat volume (e.g. a slim body with a low Body Mass Index).
Fat transfer can be combined with a non-surgical external expansion by sustained tension (generated by a low negative pressure) on the natural breast tissue to cause the cells to proliferate.
Reference
FINAL Opinion on the safety of breast implants in relation to anaplastic large cell lymphoma (2021)
Functional biocompatibility testing of silicone breast implants and a novel classification system based on surface roughness(2017)
Breast Implant-Associated Anaplastic Large Cell Lymphoma: Case Report and Review of the Literature (2018)
Moving breast implant registries forward: Are they FAIR and Functional? (2020)
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