the third technological development was the double lumen breast implant device, a double-cavity prosthesis composed of a silicone breast implant contained within a saline breast implant. The two-fold, technical goal was: (i) the cosmetic benefits of silicone-gel (the inner lumen) enclosed in saline solution (the outer lumen); (ii) a breast implant device the volume of which is post-operatively adjustable. Nevertheless, the more complex design of the double-lumen breast implant suffered a device-failure rate greater than that of single-lumen breast implants. The contemporary versions of second-generation breast implant devices (presented in 1984) are the "Becker Expandable" models of breast implant, which are primarily used for breast reconstruction.
Since experienced surgeons are aware of these issues with saline breast implants and their need for eventual replacement, they opt to place them under the chest muscle. The chest muscle works as an extra layer of tissue over the implant, which makes for a smoother transition from the chest wall to the implant. The finished product is a more seamless transition versus a more visible and abrupt change when the implant is not placed below the pectoral muscle. As for gel breast implants, they can also be safely placed below the pretorial muscle if that is a viable option for the patient since replacement and wrinkling is less common with this type of implant.