Summary/Key Points

Introduction

Form stable high cohesive silicone gel implants were introduced in 1994. This resulted in a paradigm shift in breast augmentation surgery in spite of the fact that the fundamental differences in the use of these implants compared to traditional non-form stable breast implants were not understood at the time. The introduction of form stable implants was not global, as the United States and a few other countries were influenced by the 1992 FDA moratorium on the use of silicone breast implants. However, in Europe these implants were accepted and have reached a widespread acceptance and use.

With the introduction of shaped textured implants surgeons started to think in terms of shape and dimensions rather than volume and cup size.¹ In order to fully exploit the opportunity for creation of a natural breast shape offered by the shaped devices, careful attention must be given to the surgical techniques of pocket dissection and implant placement for shaped devices.^2–5

In the last decade much of the discussions in the plastic surgery literature has focused on the difference between shaped and round implants, however, a much greater divergence relates to the use of form stable versus non-form stable implants (Fig. 24.1). Basically most aspects of such breast augmentations are different. The way of selecting implants is different. Patient preoperative markings, surgical techniques and postoperative recommendations and results also differ. These are not just new type implants, they represent a new concept in breast augmentation surgery. Surgeons who believe that form stable implants behave in the same way as non-form stable implants will tend to plan, select implants and perform surgery in traditional ways. Unfortunately, they are bound to encounter significantly more complications and problems.

Fig. 24.1 A form stable (Allergan Style 410) implant on the right and a non-form stable responsive silicone gel on the left. Note that the form stable implant retains its upper pole fullness and shape even in a standing position without pressure.

Patient and Implant Selection

Ever since silicone breast implants were introduced in the early 1960s implant selection has been a relatively arbitrary process where the surgeon has estimated the volume of the implant in relation to patients’ desires and biological prerequisites based on his own experience. As form stable implants cannot be deformed (Fig. 24.2) dimensional planning and implant selection is necessary. Instead of estimating an appropriate volume the ideal dimensions of the implant are calculated.

Fig. 24.2 A A non-form stable breast implant can be deformed even if its base dimension is too wide for the implant pocket. Thus they are simpler to use as planning is less crucial. B A form stable breast implant with a too wide base plate cannot be deformed to fit into a too small implant pocket. Thus these implants necessitate new and fundamentally different implant selection and preoperative planning techniques.

The implant selection can be separated into several distinctly different steps. The first step includes definition of patient’s desires and evaluation of the biological prerequisites. This is followed by determination of ideal implant width, height and projection. Knowledge about ideal implant type and its width will provide information on implant volume.

Several implant manufacturers provide form stable shaped implants, but the Style 410 implant from Allergan was first on the market and it still has the widest range of form stable shaped implants available; twelve basic different cells are available. Three different heights (the vertical length in the direction of the clavicle) are available (low, moderate, and full). Each height of this Matrix system is available with four different projections (low, moderate, full, and extra) and each of these twelve different shapes is available in a large number of different implant widths. Breast augmentation has, by this great variability, become more versatile and customized than ever before.

The typical breast augmentation patient wants a proportionate and natural breast augmentation. Once a patient is deemed to be an appropriate candidate, the ‘selection’ process will depend on evaluating patient characteristics and then selecting the correct implant.

Definition of Patient Desires

Contrary to common beliefs and the stereotypical picture of a typical breast augmentation patient in the mind of the general public and the media, the typical breast augmentation patient wants a proportionate and natural breast augmentation. She is not mainly concerned with the size of the breast, but rather its shape and youthfulness. It is of fundamental importance for success in aesthetic breast augmentation that patients are well informed and have a realistic expectation about the outcome of the procedure. It is more important to recognize the patients that are not suitable for an operation than the ones that are. Patients who anticipate detailed, almost millimetre exact results and not just the general improvement of the procedure are usually not good candidates for aesthetic plastic surgery procedures. Also patients who do not listen and take in information should usually be avoided, as should be patients who describe minor defects as horrible. Another group to beware of are patients who have undergone surgery elsewhere and are extremely dissatisfied and complaining about previous procedures and physicians.

The general information about breast augmentation surgery can be conveyed in many different ways and well educated patient coordinators and/or in the written form and a patient information book have proved extremely useful.²⁸ A full size mirror in the doctor’s office is also an extremely important part of the consultation process as the dimension and proportions of the expected result can be demonstrated for the patient by displacing the breast medially and laterally, showing expected borders of the new breast and showing projection of different implants. To use sizers in a sports bra should not be part of the consultation in the first stages but final testing with suitable sizer in a sports bra can be a good way to create final trust in the implant selection for the patient.

Examination of the Breast Tissue and its Envelope

As breast asymmetries are extremely common but not always noted by patients, these smaller asymmetries should be noted and pointed out to the patient. The characteristics and distribution of the glandular tissue should be examined as it has implications on implant selection. A patient with a dense, relatively constricted gland and short nipple inframammary fold distance has increased risk for a double bubble deformity in the lower pole and they may do better with a more projecting implant and shorter implant heights. The surgeon may also need to modify the gland with scoring or unfolding of a glandular flap.⁶ When selecting implants it is also very important to consider the envelope’s characteristics. A lax envelope may need more implant projection to fill it. A simplified way of estimating envelope laxity is to do an anterior pull stretch test (APSS) according to the TEPID-system.⁷ By grabbing the areola tissue beside the nipple and pulling firmly (warn the patient before doing this procedure as it may be uncomfortable), the extensibility of the envelope can be measured. This will provide information on suitable implant projection. An alternative to this is to measure the nipple–inframammary fold distance on the relaxed tissue and maximum stretch and put this in relation to implant dimension (see LVC and N-ILP measurements below). Obviously the selected implant has to suit the characteristics of the gland and envelope in accordance with all tissue based planning systems.^7,8 However, it should also be remembered that patient desires must be considered and for a patient with relatively lax tissue who desires a small augmentation, but needs a larger implant to fill the envelope an alternative is to combine a small augmentation with a mastopexy, which both takes patient desires and the envelope characteristics into consideration. Also, patients with very tight tissue could be treated with more projecting implants than the anterior pull test indicates as the tissue will expand over time (Fig. 24.3).

Fig. 24.3 A Patient with tight skin envelope (anterior pull stretch only 2.8 cm), but with a desire for 6 cm extra projecting implants (Style 410 FX 410 g). B Six months later – after an initial period of tightness, the tight tissues are expanded and soft.

Examination of Thoracic Shape and Surrounding Tissue Conditions

It should be remembered that the thoracic shape greatly could influence the shape of the breast after the augmentation. Also excess fat distribution and a thick pectoralis muscle in the upper pole may influence the shape of the upper pole of the breast after the augmentation and this should thus be considered when selecting implant height. Also asymmetries in the thoracic shape should be examined and different shaped implants may be considered to compensate for such asymmetries.

Operative Technique I: Selection of Adequate Implant Dimensions

Selection of ideal implant width

Having communicated with the patient and examined the biological prerequisites, the next step is the definition of the ideal implant dimension. The first and most important part of this is to define the ideal implant width. This is equal to the desired breast width minus the tissue cover on the implant (Fig. 24.4). Thus the medial and lateral thickness of tissue has to be examined. This is done at the height of the nipple–areola complex at the expected inner and lateral border of the implant (Fig. 24.5). Tissue cover is measured with a pinch and as a pinch of tissue is a double fold of skin and subcutaneous tissue, the measurement in the medial and lateral part of the breast should be divided by two when subtracting this number from the desired breast width. The desired breast width usually should leave an intermammary distance between 2 and 3 cm and the lateral protrusion of the breast should respect the anterior axillary line (Fig. 24.6). The distance between these two points can be measured with a caliper and the tissue cover, as mentioned according to the description above, is then subtracted for information about ideal implant width. The existing breast width should also be measured as implant selections that are considerably wider than the existing breast width should be avoided as it increases the risk for complications such as palpability and visibility of the implant.

Fig. 24.4 The desired breast width measured with a caliper minus the tissue cover medially and laterally is equal to the desired implant width.

Fig. 24.5 Tissue cover is measured medially and laterally at the estimated border of the implant. This is done with a pinch test, with a pressure that simulates the implant compression on the glandular tissue. The pinch A medially and B laterally is added together. As these represent double folds of tissue this number is divided by two to provide information on how much distance should be subtracted from desired breast width to provide information on implant width.

Fig. 24.6 A In a proportionate breast augmentation, desired breast width should respect an intramammary distance of between 2 and 3 cm and B the lateral protrusion of the breast should respect the anterior axillary line.

When it comes to selection of the ideal implant width it should be recognized that even form stable devices have a certain amount of plasticity. Usually, increasing the ideally measured implant width or reducing it by 0.5 cm is possible without increased risks in most patients. If the calculated ideal implant width is exceeded by more than one centimeter this can create problems. It can create a too small intermammary distance with implant visibility and palpability. Also narrowing the implant width a centimeter or more produces too large an intermammary distance with a more artificial and operated appearance.

Selection of implant height

Having defined and communicated ideal implant width with the patient, the next step is to recommend a suitable implant height. It should be remembered that preoperative upper and lower pole appearance is of great importance for the implant height selection. For example, bulging upper thoraxes may be exaggerated by selection of full height implants whereas depressions in the upper thorax more favorably could be treated with full height implants. When selecting implant height it is important to measure and localize where the lower and upper pole of different implants will be located and compare this to how the upper pole shape is estimated to appear and how the implant correlates to the existing submammary fold and the lower pole appearance of the breast (Fig. 24.8). To be able to estimate where the upper and lower pole of different implants will be located during the consultation, the patient is asked to put her hands on top of her head. This 45° elevation of the arms above the horizontal plane is an accurate estimation of where the nipples will be positioned after a proportionate breast augmentation (see preoperative markings below). Knowing ideal implant width the height of different implants can easily be looked up in the manufacturers’ charts. Usually half of the implant height should be positioned above the nipple–areola complex after the augmentation and half below. Thus it is easy to measure above and below the nipple with the arms on top of the head to estimate how the upper and lower poles of the breast will appear with different implant heights.

Fig. 24.8 When using round form stable implants the implant height is obviously equal to the implant width. In spite of this it is advisable to check the upper and lower pole implant position and how this correlates to the thoracic shape and existing inframammary fold. By arm elevation 45° above the horizontal plane, an accurate prediction of the new nipple position is achieved and from this position the amount of implant desired proximally and distally can be calculated (for shaped implants usually 50% above and below and for round implants 45% above and 55% below).

Selection of adequate implant projection

This recommendation of the ideal footprint (height and width) or base plate of the implant obviously has no volume as it is only two-dimensional. The projection, the third dimension of the implant, will provide the final volume of the implant. Implant projection is highly dependent on patient desires, but remember to consider the envelope characteristics as loose envelopes may need more projection or a mastopexy. Also, patients with a contracted lower pole may have less risk for double bubble deformity if more projecting implants, for instance Allergan Style 510, are selected (Fig. 24.7). A good way of selecting implant projection is to communicate this with the patient standing in front of the mirror.

Fig. 24.7 Several different shapes of form stable implants are available, both round and anatomical. Shaped implants are also available with combined cohesivity as used in this case (Allergan style 510 implant with higher and firmer gel cohesivity in the ventral part than in the posterior part of the implant). A Preoperative planning with arms hanging. B Preoperative planning with arms elevated 45° above horizontal plane. C Four hours postoperatively. Note the elevation of the NS line. D Six months postoperatively.

Indications

Form stable breast implants are considered more demanding and difficult to use. An obvious question is then why is there a need for them. The answer to this question is that form stable implants control the shape of the breast in a much better way, especially if we consider long-term effects of a breast augmentation. The high cohesive silicone gel breast implant retains its shape even if it is cut into two pieces and even if it is put under pressure (Fig. 24.9). On the other hand, relatively small forces are needed to deform a responsive low cohesive silicone gel implant. The clinical consequence of this is that a low cohesive silicone gel implant easily is deformed into a spherical shape during capsular contraction (Fig. 24.10). Contrary to this, capsular contraction on high cohesive silicone gel implants deforms implants much less. Clinically, this difference has been observed by the author in a number of cases. A textured shaped form stable implant should also be positioned into a snug fitting implant pocket and one implication of this is that it moves less in the cranial direction during capsular contraction compared to a round smooth implant which usually is massaged to retain a large implant pocket and softness. Thus circumferential shrinkage during capsular contracture moves a smooth walled implant in a large pocket more in the cranial direction (Fig. 24.11). Consequently, these benefits of form stable implants have improved the appearance and the control of the breast shape better and long-term follow up (>10 years) indicates good stability of results (Fig. 24.12). The use of shaped form stable implants constitutes a new era in breast augmentation surgery: The era of breast shaping and long-term customized control of breast shape versus the traditional breast volumetric filling or stuffing era. Obviously a prerequisite for controlled shaping of the breast is not only to have a form stable shaped implant, but also a wide variety of different implant shapes.

Fig. 24.9 A A form stable implant cut in two pieces will still retain its shape and the filling material will be confined to the shell. B The same is true even if the implant is put under pressure.

Fig. 24.10 A The same low cohesive implant on the left and right hand side of the picture, but the right one with its contracted capsule. Note considerable narrowing of the base and increased projection. B Comparison to a form stable high cohesive implant with capsular contraction on the right hand side; note much less narrowing of the base compared to A.

Fig. 24.11 A Frontal view of a patient with a smooth round responsive silicone gel implant with capsular contraction Baker grade III. As ‘smooth’ implant pockets frequently are made larger than the implant and implants are massaged to maintain softness, implants shift cranially during circumferential shrinkage of the capsule. B Same patient, side view. C After exchange to form stable textured implant positioned in a new submuscular pocket which is much more snug fitting than the excessively large pocket made for the non-form stable implants. Frontal view after implant exchange. D Same patient, side view after implant exchange. Note that capsular contraction has redeveloped in this case, but as the implant pocket is snug fitting and the implant textured, there is much less cranial displacement of the implant and less deformation compared to smooth walled implants. The degree of capsular firmness is similar before and after implant exchange but the shape is much better.

Fig. 24.12 A Before breast augmentation with form stable implants, oblique view. B Frontal view. C Six months after breast augmentation (Allergan style 410 FM model 350 g subglandular), oblique view. D Frontal view. E Oblique view of the same patient ten years later. F Frontal view of the same patient ten years later.

Other advantages relating to these devices have been reviewed elsewhere.⁹ Among these are that breast augmentation can be more customized than ever before and that the great variability of different implant shapes makes it possible to compensate for breast asymmetries. This is also a great advantage when it comes to breast reconstructive procedures where bilateral treatment with different sized implants (Fig. 24.13) and different shaped implants can provide a long-term stability of the results compared to unilateral implantation of a round, non-form stable device.¹⁰ High cohesive silicone gel also minimizes gel bleeding and leakage after a shell rupture and as the filler is form stable, irregularities such as fold and rippling are significantly less common.¹¹ Capsular contracture rates have also been lower for form stable implants compared to implants filled with saline or regular low cohesive silicone gel.¹² It is also likely that the form stable filler minimizes the envelope movements, and thus the wear of the envelope, giving better chances of low long-term risk for ruptures. This has also been clinically proven in long-term magnetic resonance imaging (MRI) evaluation of these devices.¹³ The rupture frequency has been as low as 0.3% after up to 9 years of implantation, and comparing this to other similar MRI studies on non-form stable breast implants these have shown that the risk for rupture has been considerably (3.5–17%) higher.^14–17 Others have also confirmed the low rupture of Allergan form stable implants whereas other manufacturers’ form stable implants have not been confirmed to have this low incidence of ruptures.^18,19

Fig. 24.13 The large variability in different breast implant shapes is also suitable for breast reconstructive surgery. A Preoperative situation after a previous reduction mammaplasty on the patient’s right side and secondary mastectomy. B After bilateral breast implants, on the right side (Allergan style 410 FX model) extra projecting and a latissimus dorsi flap and on the left side augmentation with low projecting implant (FL) to create long term symmetry.

In spite of all these advantages several surgeons refrain from use of form stable implants. A common argument against is that patients are happy with the non-form stable devices provided. This is true as patients usually are happy even with inferior result, but this is no reason why we should refrain from doing our best to improve results. It is also claimed that non-form stable implants deform into an ‘anatomical’ shape when a patient is standing,²⁰ which also is true if the device is underfilled with a low cohesive filler and if there is no capsular contraction (Fig. 24.14). However, during capsular contraction the implants become more round and artificial in their appearance (Fig. 24.10) and also the shaped ‘deformity’ of a round implant increase rippling and irregularities in the upper pole which is likely to increase the wear of the envelope. It is sometimes also claimed that form stable implants behave unnaturally on the chest wall giving unnatural appearance when the patient is lying on their back. This has not been our clinical experience as even these implants move laterally when the patient is lying on her back. The firmness and movement of the implant is more related to common and small degrees of capsular contraction not regarded as true Baker II deformities. These small degrees of capsular activity usually regarded as natural softness are relatively common and by the author regarded to be more important for the movement and firmness of the breast than the firmness of the implant itself.

Fig. 24.14 Low cohesive non-form stable or responsive gel implants (here, Allergan style 110) held in vertical position deforms from round to ‘anatomical’ shape.

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