The technology, used in VeraFil, uniquely combines saline with biocompatible materials long used in the human body. The overall goal of VeraFil's design was to closely match the visco-elastic properties of the tissue into which the implant is placed. By matching visco-elastic properties, micro-motion between the implant and the tissue is minimized, which should reduce the chance of complications such as erosion, migration and infection.

A small volume of saline is contained within a thin-walled silicone shell that is coated with a membrane, only four thousandths of an inch in thickness, of expanded polytetrafluoroethylene (ePTFE). This thin layer of ePTFE permits only limited in-growth, adequate for tissue anchoring, but without the prolific fibrosis that could eventually harden the implant. Limited tissue in-growth also means that removal of the implant does not require extensive dissection.

A slip plane between the ePTFE membrane and the silicone shell allows independent movement between the materials. This enhances the compliance of the tissue-implant interface, so that full movement of the tissue surrounding the implant is maintained without restricting animation.

At the time of implantation, the volume of saline fill may be adjusted up and down during the procedure to obtain the desired degree of augmentation. Finally, removing the fill tube engages a self-sealing internal micro-valve that keeps the implant from leaking.

VeraFil has undergone extensive bench testing and is capable of withstanding forces, far in excess of what a patient is likely to experience without rupture or loss of integrity.

Schematic of the VeraFil implant in longitudinal (center) and axial (inset, upper right) cross-sections. A: Outer coating composed of micro-porous ePTFE, approximately 0.004 in. thick; B: Silicone elastomer inner membrane, adjustably filled with saline; C: Slip plane between layers; D: Fill tube connected to syringe, and passing through E: Internal micro-valve; F: Distal tether and positioning handle.