Demystifying breast implants part 2: Fill volumes

Allergan’s new Inspira breast implants and Sientra’s 106/206 series have a higher fill volume percentage than previous designs such as Allergan’s Natrelle  styles 10 (low profile), 15 (moderate), and 20 (high.) How does this affect your choice of implant? Higher fill ratio implants will tend to have less rippling, which is a good thing especially in thinner patients, and when implants are placed above the muscle (subglandular or subfascial.) One trade-off is that they will have more upper pole fullness, which may or may not be desirable as it can look more “fake.” The lower fill implants will fall into more of a teardrop profile when upright, and round out when lying down, like a natural breast does. And some people prefer the softer feel of lower fill volume s (I am thinking New England Patriots quarterback Tom Brady here  . . .)

Because saline implants are filled by the surgeon when they are placed, the fill volume can be determined based on a number of factors, but there is an acceptable range of fill volumes for each size. Silicone gel implants are pre-filled, because the gel is a semi-solid. In order to understand why implants are not made with 100% fill volume, it is helpful to know how implants are manufactured: The shell is made over a form called a mandrel, which has a specific shape and size. The mandrel is dipped into a liquefied silicone, then there is a curing process that converts the silicone into a rubbery material. This shell is peeled off of the mandrel, and then filled. If the volume of the fill is equal to the volume of the mandrel, it would be too firm and artificially round, so the actual fill is less. The Natrelle series of implants were designed to balance a soft and natural feel of a lower fill ratio against a greater tendency for underfilled implants to ripple.

Sientra beat Allergan to the punch by introducing the 106 (smooth) and 206 (textured) high fill ratio implants first, but now both companies have a high fill implant and early signs are that these will be very popular. It will take some adjustment in how we think about implant sizing, because instead of 3 profiles (low, moderate, high) there are now 5. I don’t see it as being particularly helpful to describe implants as low, moderate, “low plus,” full, and “extra full.” It still comes down to measuring base diameter and determining the desired volume. Having a greater range of options is great, the terminology not so much.

Next time: Cohesive gel implants