Breast implants

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Plant oil and microchips improve safety

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New breast implants filled with a natural vegetable oil promise greater safety for women. They are available throughout the European Union but are still undergoing clinical trials in the US and Canada. Unlike silicone and saline implants, X-rays can pass through the new implant, says Terry Knapp, chief executive of Lipomatrix, the implant's developer. An implant can conceal 22-85% of breast tissue, seriously hampering the effectiveness of a mammogram.

Although there are no data to suggest that silicone implants cause cancer or auto-immune diseases, there are over 100 peer-reviewed articles that show they are not safe in the female breast, explains Knapp, a cosmetic surgeon. For example, leaks can produce chronic inflammation and lead to false diagnoses of breast cancer.

The new implant, called Trilucent, contains triglyceride, an oil that has been used for 40 years as a nutrient in intravenous feeding and as a drug carrier in injections. Like saline, it can be metabolised and excreted by the body, but it is also resistant to bacterial and fungal contamination whereas saline is not. Its lubricating properties means that it should not rub the inside surface of the implant; this has been linked to leakages in conventional implants.

Each implant has its own code number, which is held inside the implant on a microchip not much bigger than a grain of rice. Such a system has not been used before in medicine, says Knapp. It provides an 'audit trail' of information about the implant for doctors, patients and manufacturers.

Lipomatrix has patented the whole system of the chip, the hand-held reader and the database. Knapp anticipates that manufacturers of many other devices, such as heart valves and orthopaedic implants, will want to use the technology.

In 1994, about 250,000-300,000 breast implants were sold around the world, 60% of them in the US. Of the world total, about 70% were used for cosmetic purposes and 30% for reconstructive surgery after breast cancer.

Implant sales are beginning to rise again after a four year slump, says Knapp. He expects Trilucent to sell for 10-30% more than silicone and saline implants.

Silicone-filled implants were introduced in the US in the 1960s. Saline-filled versions soon followed.

Silicone implants have caused much controversy because of their alleged health effects, and have cost chemical manufacturers millions of dollars in lawsuits and compensation funds. In 1992, the

US Food and Drug Administration banned silicone gel implants in the US and ordered their withdrawal from the market. Many countries still allow silicone implants, including the UK.

In 1993, breast implant manufacturers established a $4bn compensation fund. Women can gain compensation without needing to prove direct injury. However, the settlement was in danger of collapse this month after lawyers for plaintiffs and manufacturers failed to meet a judge's deadline on a deal to increase the fund. The companies include Bristol-Myers Squibb, Baxter International, Union Carbide and Dow Corning.