The US Food and Drug Administration (FDA) study could reawaken the debate over the safety of breast implants.
Many women claim that leaking silicone-gel has sparked serious illness, including chronic autoimmune disease.
The FDA team used MRI scans too look at 344 women with implants.
They found that 69% had a least one ruptured implant.
And in 21%, the silicone gel contained within the implant had leaked beyond the breast into other parts of the body.
In another part of the study, 907 women who had undergone breast enhancement surgery were interviewed.
Removed implants
One-third of these had felt it necessary to have at least one operation to either remove or replace an implant.
Breast enhancement is one of the more common operations carried out by cosmetic surgeons.
Hundreds of thousands of women in the UK have silicone implants.
The alternatives to silicone include saline -salt water - filled pads, or soya-based implants.
The FDA restricted the use of silicone-gel implants in 1992 - only women participating in clinical trials are allowed to have them.
However, doctors studying the health effects of silicone maintain that that there is no evidence of any link between the implants and the diseases reported by the women.
They say that silicone is inert - it does not produce any chemical reactions in the body.
However, they did find that women undergoing breast enhancement surgery were running extra risks - but mainly associated with the operation itself.
Dow Corning, once the world's biggest makers of silicone gel implants, filed for protection from creditors in May 1995 after lawsuits from thousands of women were filed alleging health problems caused by the implants.