Implant historical timeline

Implant type

See Table 52.1.

Table 52.1B Mentor silicone implants (MemoryGel^™), smooth and textured (Siltex®)

Table 52.1D Allergan silicone implants (Natrelle^™ Collection), smooth round: style 10 – style 45. Textured (Biocell®): style 110 – style 120

Implant generations

Since the original silicone implants that were introduced in 1962, there have been many design modifications and advancements in their technology and production. Although there is variability in classification schemes for implant generations, it is universally agreed that the current generation of implants with thicker multilayered shells, barrier layers, more cohesive silicone gels, and numerous textures, and shapes represents a significant advancement from the first and second generation implants before 1993. Many of the complications that led to the implant crises and moratorium involved these early generation implants.

Despite the silicone gel-filled implant moratorium in the United States, these implants have generally maintained their availability in other countries and advances in design and manufacturing have continued to this date. These advances are apparent in current (3rd and later) generation implants. Some authors describe only three generations of implant designs with current implants falling into this third generation. Advances in manufacturing guidelines since 1993 that adhere to strict regulations governing shell thickness and gel cohesiveness is what characterizes 4th generation implants.

A new category or 5th generation includes the highly cohesive form-stable silicone implants that are currently under investigational use. These so-called “gummy bear” implants are enhanced cohesive silicone gel-filled breast implants with higher cross-linking of the silicone molecules. This form-stable gel helps maintain the shape of the implant. They include Allergan’s style 410 implant and Mentor’s 300 series CPG (Contoured Profile Gel – Cohesive III) implants. At this time, these breast implants are available only through clinical studies being conducted by Mentor and Allergan (Table 52.2, Figs 52.1–52.3).

Table 52.2 Implant generations

Breast implant rupture, connective tissue disease and breast cancer

The moratorium on silicone breast implant use instituted in January 1992 against the advice of the FDA expert panel demonstrated the contentious nature of the controversy surrounding silicone implants and associated disorders such as connective tissue diseases and breast cancer. Because of the scale of this controversy, breast implants have become the single most investigated medical implant device. Numerous large-scale epidemiologic studies have shown no statistically significant relevant increased risk of connective tissue disease in women who have undergone breast augmentation or reconstruction with silicone gel implants.

A literature review on the subject demonstrated numerous anecdotal and clinical reports from the 1980s and 1990s which hypothesize the possibility of an immunologic reaction from silicone exposure. More recently, however, comprehensive literature reviews such as that by Holmich et al., reinforce the large epidemiological studies and meta-analyses which conclude similarly that there is no connection between silicone implants and defined connective tissue diseases or atypical, undefined connective tissue syndromes.

Questions about the relationship of implants to breast cancer have also been raised over the years and anecdotal reports have suggested possible links. Delayed detection and decreased survival rates in breast cancer are common concerns for women contemplating breast augmentation. Deapen (2007) methodically reviewed 21 cohort and case–control studies, representing nine different populations from around the world. The data from numerous locations in the United States as well as Denmark, Sweden, Finland, Canada, Australia and Scotland consistently demonstrated no increased risk of cancer. In fact in many studies the relative risk was decreased. Furthermore, the risk of delayed detection and poorer prognosis was not borne out with any consistent evidence.

It must be noted that there are reports demonstrating that screening mammography is slightly impaired in patients with silicone or saline implants. The false negative rate can be higher as less tissue is visualized. Women with breast implants require special displacement techniques (i.e. the Eklin protocol) to increase the efficacy of mammography and may also require additional testing such as ultrasound or MRI to complete the workup of a questionable finding. Mammography, however, remains the first line diagnostic tool of choice for these women. Despite the increased difficulty in screening patients with breast augmentation, many studies have demonstrated that tumor size, disease stage, recurrence rates and survival remain equal in augmented patients.

Just as reassuring are the findings by the Institute of Medicine of the National Academy of Sciences which, in 1999, was commissioned through congressional legislation to study the safety of silicone breast implants. The Institute of Medicine’s 400-page report by an independent committee of 13 scientists demonstrated no causal link between silicone implants and systemic diseases. Similarly, implants were not felt to be the cause of any connective tissue disorder or cancer. They did, however, conclude that breast implants were responsible for localized problems such as capsular contracture.

Numerous independent reviews of breast implant safety such as that by the Institute of Medicine have been conducted. These include the World Health Organization, Health Canada, and the European Committee on Quality Assurance and Medical Devices in Plastic Surgery. They have all reached similar conclusions regarding the safety and efficacy of silicone breast implants.

The concerns of patients regarding the safety of these devices should be seriously addressed in any consultation for breast augmentation. Many patients will not be assuaged by the confluence of evidence demonstrating the safety of silicone implants, nor should they be convinced. They will sleep better at night after choosing saline for breast augmentation. On the other hand, the advantages of silicone implant augmentation can dramatically improve satisfaction in patients who are interested in silicone but harbor reservations about its safety. The surgeon must be able to review past controversies and current scientific evidence supporting their safety so that these patients feel comfortable with their decision.

Diagnosis of silicone breast implant rupture

Although current data indicate that the risk of silicone gel implant rupture in the latest generation implants is relatively low (0.5–3.5%), past studies have included earlier generation implants and have indicated rupture rates ranging from 0 to 69%. Later generation implant rupture rates tend to range in the single digit range with one study by Heden et al. demonstrating a 1% rupture rate in the Inamed silicone style 410 implants at six years. The ability to properly diagnose implant rupture is critical for surgical management and patient reassurance. Furthermore, the reintroduction of silicone implants onto the US market has come with specific guidelines set by the FDA for surveillance and tracking of their use. All patients must be informed that the FDA recommends MRI surveillance every two years starting three years after breast augmentation.

Magnetic resonance imaging of the breast has the highest sensitivity and specificity for detection of rupture and is the modality of choice; however; other modalities such as CT scan, ultrasound, and mammography can be used and may be appropriate in various settings.

Early generation implants had higher rates of rupture than current silicone implants and various radiological findings became classic in diagnosing these ruptures. Silicone released from a ruptured silicone implant can remain intracapsular or escape out of the fibrous capsule and become extracapsular. About 80% to 90% of all silicone implant ruptures tend to be intracapsular without silicone spreading into the surrounding parenchyma. Ruptures can be accompanied by a collapsed implant shell, common in second generation implants with soft shells, resulting in the classic “linguine” sign on MRI or CT. Ultrasound diagnosis is more technically demanding and user-dependent, but can also be made in this case with the classic “stepladder” sign. A non-collapsed implant rupture may demonstrate silicone gel pooling around the implant in the implant folds which subsequently has the classic inverted tear drop sign, but does not demonstrate a linguine sign as there is no collapse of implant shell floating in the silicone gel. This is more common with later generation implants that have more cohesive gel.

There are numerous limitations and contraindications to MRI such as implanted metallic devices, claustrophobia, weight limitations and cost. CT scan can be an excellent substitute, but exposes the patient to radiation. Given the current FDA recommendations for serial imaging surveillance to rule out implant rupture, the cumulative radiation exposure with CT scan could become concerning. Ultrasound, while very cost-effective, is highly user dependent and limited by interference in cases of extracapsular rupture. Finally, mammography is excellent for extracapsular rupture and leakage, but severely limited in identifying intracapsular processes. Ultimately, MRI remains the modality of choice with a specificity and sensitivity greater than 90%.

Patient measurements and implant size

When evaluating a patient preoperatively for implant size, it is critical to balance the patient’s desires with that of her tissue and body characteristics. The desired result is often simplified into a bra cup size or volume by both the surgeon and the patient, and this should be avoided. Attempting to achieve a result based on an arbitrary cup size may leave the patient disappointed if it is not fulfilled. Furthermore, an overzealous attempt to achieve the desired cup size or volume without regard to tissue characteristics can lead to an unnatural result.

Proper evaluation of a patient preoperatively includes recording key measurements and landmarks. The surgeon should evaluate and demonstrate to the patient any asymmetry that exists preoperatively, specifically breast size, shape and nipple areola position. Such asymmetries are common and may not have been recognized by the patient prior to consultation. If not photo documented and demonstrated to the patient preoperatively, they may be noticed after surgery and blamed on the surgeon.

Key landmarks and measurements should be documented to help in evaluating implant size and need for possible mastopexy. Some of these measurements include sternal notch to nipple–areola complex distance (SN : NAC), nipple to inframammary fold distance (N : IMF), and breast width or base diameter (BW).

Ultimately the benefit of these measurements is to allow the surgeon to match the patient’s characteristics with the correct implant with corresponding dimensions which will achieve the best aesthetic result. The breast width is one such measurement which combined with the patient’s desired projection, can be compared to implant diameter and projection to allow the surgeon to choose the appropriate size of implant. Using implant and breast dimensions rather than volumes will allow for a more natural result.

Various methods have been described for determining implant size. Ultimately, implant size should be determined by the patient’s breast and chest wall characteristics. Other characteristics that may be taken into account include the breast envelope thickness and compliance. The Tebbetts’ TEPID system and the associated Inamed BioDimensional® preoperative planning system as well as the more recent High Five preoperative evaluation system include measurements which quantify breast envelope thickness and compliance as well as parenchymal quantity.

Ultimately any system of preoperative measurements to determine implant size must be based on tissue characteristics. The implants available today are available in low, medium and high profile with varying base widths and shapes to accommodate for patient variability. Disregarding these variables will lead to poor aesthetic results and increased rates of complications over the long term, as breast tissue reacts to implants that are poorly matched in size or dimension.

Implant position

When choosing the optimal implant pocket location, there are certain factors to keep in mind. Most important is achieving adequate soft tissue coverage. The options available include subglandular, submuscular or biplanar (dual-plane) (Fig. 52.4). Most early breast augmentation was subglandular. Benefits of this position include anatomic placement that is not affected by pectoral muscle contraction and a more natural appearance under certain circumstances. Poor soft tissue coverage, especially in the upper pole, however can lead to implant palpability as well as rippling.

Fig. 52.4 Options for implant position include subglandular, submuscular, and biplanar (dual-plane). The dual plane position provides the benefits of submuscular and subglandular positioning. It has become the most popular method for implant placement. Complete submuscular coverage is uncommon.

Today a subpectoral or dual-plane placement is more common. By placing the implant under the muscle it is less palpable, rippling is decreased, and there is less potential for capsule contracture. In the dual-plane approach, the implant is not completely covered by muscle in the inferior pole where the breast parenchyma is maximal. This allows for a more natural appearance while keeping the benefits of the submuscular position described above.

Access incision

There are four possible access incisions and surgical approaches for breast augmentation. The three most common are inframammary, periareola and axillary. Transumbilical is less popular and does not allow for direct visualization and dissection of the implant pocket.

All three of the above access sites allow for subglandular, subpectoral and dual-plane implant placement. Blunt dissection of the implant pocket should be avoided in favor of sharp dissection under direct visualization to minimize bleeding and maximize control over the implant pocket. This minimizes tissue inflammation which may occur secondary to hemorrhage and theoretically reduces associated contracture rates. It will also allow for more accurate implant positioning.

Choice of incision site is largely dependent on patient and surgeon preference. Certain physical findings should play a role in the decision process. For example, if the nipple areolar complex is small, a large silicone implant will be difficult to introduce through this site and an IMF incision is preferable. Conversely, the periareolar incision tends to heal nicely with excellent camouflage. When using the IMF approach, the incision should be lowered approximately 1 cm onto the chest wall if the IMF is being lowered, as often happens in small breasted women without significant ptosis. This allows the scar to be hidden in the new IMF or slightly above it. A woman who does not want any scars on her breasts or is highly concerned about nipple sensation may be an excellent candidate for a transaxillary incision. Although the transaxillary approach is a tried and true method, there are numerous neurovascular structures that are at risk of injury from dissection, traction, bleeding or improper arm positioning.

Ultimately, excellent aesthetic results can be achieved from any of these approaches. Proper surgical control and exposure should be the primary concern when choosing an incision.