The older generation of silicone gel implants certainly did have gel leakage when rupture occurred. Typically the gel would mostly stay within the implant pocket which is the normal sac-like scar that forms around any implant. It did occasionally leak even beyond the capsule however.
The newer generation of silicone gel in breast implants is firmer and more thick such that even if shell rupture does occur, the gel stays put inside. A good way to explain it is that the breast implant is like a jello mold—when you cut jello it keeps it shape and doesn’t leak all.
Additionally, despite the FDA moratorium on use of silicone gel breast implants from 1992 – 2006 their safety has been proven in clinical studies. There is no known association between silicone breast implant use and health issues such as connective tissue disorders, breast cancer, and reproductive problems. These implants (as well as all other implants) are always in the process of study, tracking, and evaluation by the FDA and plastic surgeons to ensure their continued safe and appropriate use.