CPG

CPG IMPLANTS

The Mentor CPG silicone gel breast implant was approved by the FDA in June 2013. 


The Contour Profile Gel (CPG) breast implant is the teardrop shaped gummy bear implant made by Mentor (a part of Johnson & Johnson.) It was designed after the Style 410, so some would call it a copycat implant while others would say it is an updated design that improved upon perceived shortcomings of the 410.

One complaint about the 410 was that it was too firm, so the CPG was designed with a softer gel. Does it feel meaningfully softer in the body? Is it so soft that it is inadequately form stable, allowing its shape to deform and even create ripples? There is no question that when comparing a CPG to a 410 in your hand that the CPG feels softer and the 410 seems a bit more form stable. But it is not obvious how different they actually look and feel inside of the body.

Both implants are clearly excellent. There is just a different balance of form stability and softness. Allergan had paid attention to complaints about the Style 410 breast implant feeling firm, so they made a second version of the Style 410 breast implant called the 410 Soft Touch®. In Europe the 410 Soft Touch® is now more popular than the regular 410. The CPG seems to be in the middle between the 410 and the 410 Soft Touch. The 410 Soft Touch is available only outside the US and has not even undergone any US clinical trials. There is no expectation that it will be available in the United States in the foreseeable future.

The CPG breast implant shapes were designed with a different overall style than the 410. The 410s have an exaggerated teardrop shape, with more fill in the lower part of the implant. The CPG has a slightly greater similarity to a round breast implant. The CPG edges have a slightly wider radius while the 410 edges taper more. Most CPG shapes project more towards the middle, while 410s tend to project more in the lower third of the implant. But these are extremely subtle and subjective distinctions. Even the smallest differences in patient breast tissue, surgical technique, or implant size selection will have a greater effect on the final breast shape.

Shapes and sizes of Mentor CPG silicone gel breast implants

Allergan’s initial clinical trial focused on four shapes: the MM, MF, FM, and FF. Mentor’s CPG trial had a single size called the “321”. It is most similar to the Natrelle® 410 MM. At moderate heights and projections, the CPG 321 and the 410 MM are the most popular shapes because they are ideal for the widest range of breast types.

click for larger view Since the 321, Mentor has released five other CPG shapes. They refer to them as The CPG Family of Implants, while Allergan refers to the various 410s as The 410 Matrix System.

All of the shapes are named with numbers. The 3 indicates it is the most cohesive of the three types of silicone used in Mentor implants (all CPGs are Cohesive 3; Cohesive 1 and Cohesive 2 gels are used for round breast implants, though only cohesive 1 gel is available in the USA.) The second number indicates the height, with 1 being low, 2 moderate, and 3 tall. The final number is for projection, with 1 being moderate, 2 being moderate-plus, and 3 being high.

In the 2 height (moderate), all three projections are made, a 321, 322, and 323.

In the 1 height (low), only a 2 (moderate plus projection) is made, the 312.

In the 3 height (tall), only a 2 (moderate plus projection) and a 3 (high projection) are made, the 332, and the 333.

By the way, if you know this, you’ll know more than nearly any plastic surgeon about CPG sizing.

So how do you choose the right size?

There is no formula to select the exact CPG style for a given patient, nor is there a single right answer. In general, the lower the height and the greater the projection, the more the breast will look round. The greatest distinction of any gummy bear implant from a standard round silicone implant is when the tallest of the gummy bear implants, because the height creates a more graduated taper in the upper breast. The final selection should always be left to the surgeon, as he or she will know the shape with which they could most enhance a breast.

click for larger view Mentor calls the silicone gel it uses in its standard round silicone gel implants MemoryGel®. It calls the silicone gel in its gummy bear implants MemoryShape®. What’s interesting is that if the MemoryGel® really had memory, then what would be different about MemoryShape®? What could be “remembered” other than shape? In reality, MemoryGel® has no memory at all; the implant has an amorphous shape and it readily changes it shape based upon gravity and pressure. However the MemoryGel® used in the CPG breast implant does have significant shape memory. It is hard for surgeons, and it must be impossible for patients to make sense out of these meaningless marketing terms.

Texture of Mentor CPG silicone gel breast implants

Another important identifying characteristic of a breast implant is its surface texturing. The surface on all textured Mentor implants is called Siltex®. When the implant surface is still sticky during the curing process, a special sponge is pressed against it under high pressure. When it is removed, it leaves a roughened impression. In order to create enough friction to hold the teardrop shaped CPG in place they made a more aggressive Siltex® texturing just for that implant. Their data shows that it has been effective in preventing rotation.

Mentor breast implants are made in America

Mentor is distinguished from Allergan and Sientra by being the only company to manufacturer its implants in the United States. It is true that the Sientra factory in Brazil and the Allergan factory in Costa Rica are held to exactly the same standards by the FDA. But for many there is no substitute for “American made.”

 

This list shows Mentor’s suggestions for selecting amongst their different CPG shapes. These are just promotional guidelines, but it is interesting to note the situations in which they envision the use of each of their CPG shapes.


The CPG is very soft to squeeze. Even with a large piece cut out of the implant, the gel still stays together even under pressure.
With the pressure relieved, the gel returns to its place within the shell. This is interesting to see, but one should not extrapolate this to imagine what occurs in the body with a broken implant. There is a perception by both the general public and plastic surgeons that gummy bear implants cannot break, and that if they do, the gel cannot go anywhere. While the rupture rate is low, indeed they can break. And while there are cases in which the gel did stay within the shell of a broken gummy bear implant, there are also cases in which the gel migrated out of the shell. They certainly are more resilient to such problems than standard silicone gel, but no one should think that they are impervious to breakage and leakage.
Note how the CPG is soft enough to conform to the irregularities of the fingers, yet still maintains its overall shape. When as standard round implant is tipped like this, some of the shell shifts to the lower part of the bag, creating a quasi-tear drop shape. However, for that to occur, some degree of folding in the shell must occur (see other photos in this series for an example.) And when it does adopt this teardrop shape, it will not hold the shape either as predictable nor as smoothly as does the CPG shown in this photograph.
When the CPG is turned upside down, it still maintains its shape. This illustrates what it means for a breast implant to be form stable. It also suggests how there can be a deformity if the implant were to turn in the body. With a properly sized implant and careful surgical technique, this is a very uncommon event, but it still can occur. For some patients the rotation is rare and they can easily flip it back; for some it occurs frequently and they can’t always rotate it back. In either case, the only treatment is to remove the shaped implant and either reposition it (with a chance of it happening again) or to switch both implants to a round implant. Rotation is a tradeoff of shaped implants that every patient must accept. If properly sized and if the operation is carefully done, then it is a rare event, but it is not a never event.


This MRI of a cohesive implant in a breast shows how its shape in the body is very similar to what is shown in the photos above. Note how the back of the implant conforms to the rib cage. While this MRI shows the implant totally free of any folds and a nice teardrop taper, gummy bear implants can form surface irregularities in certain situations.


On the left is a CPG and on the right is a standard round silicone gel implant. One can see undulations on the top surface of the round implant. This is not visible in the CPG because the CPG breast implant is filled with more cohesive silicone gel.


When turned upright, the differences between the CPG and a standard round MemoryGel® implant are quite obvious. The CPG preserves its shape with no conspicuous folds, whereas the standard round implant has significant shell folding. Part of the reason for this is that the gel in the standard implant is less cohesive. Another reason is that the bag of the standard round gel implant is not filled as fully as the bag of the CPG implant. It also begs the question of what it means to say that the implant on the right is a MemoryGel® implant. If it had memory, why would it look so different standing up than lying down? In fact, the gel in all standard round silicone implants has no memory or shape retention whatsoever. The gel may be cohesive to some extent, but that is not the same thing as being form stable. MemoryGel® is a great product, but the term is a misleading marketing term.


The front view shows the collapse of a standard round MemoryGel® implant. Of course with pressure from the breast against it, it would not be collapse and fold this much. The final shape of a standard silicone breast implant is very dependent on the pressure put against it in the body, whereas gummy bear implants ideally maintain their shape. It is said that a standard silicone implant is shaped by the breast and that a highly cohesive implant shapes the breast. Note how the CPG on the left has just a slight amount of buckling about halfway up. A stiffer implant such as the 410 would be less likely to do this. But Mentor intentionally softened the CPG gel to create what they thought was the ideal balance of form stability and softness.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>