PIP breast implants: Update on TGA testing of PIP breast implants

The TGA has performed and reported on a large number of tests on the chemical properties, physical properties and the biological safety of the gels and shells of PIP breast implants. Reports and updates on these tests were published on the TGA website on 12 January 2012; 2 March 2012; 16 March 2012; and 2 April 2012. The following provides an update on testing conducted on both new and explanted PIP implants since our last report.

On this page: Further tests on new implants | Tests on explanted PIP implants | Results | Conclusions | References

Further tests on new implants

In an effort to try to find whether the gel in PIP implants may be toxic, the TGA and other agencies have conducted tests involving living cells and animals (cytotoxicity, intradermal irritation and mutagenicity tests) on the implants. The results were negative in every case. To provide further assurance of a lack of toxicity, and on a recommendation from the Chief Medical Officer's Clinical Advisory Committee, TGA recently commissioned chemical screening tests from two separate laboratories. The screening tests were conducted on samples from 10 different batches of PIP implants. None of the organic compounds listed in Table 1 were detected in any of the gels from the ten batches tested.

Table 1: Volatile organic compounds not detected in samples of PIP silicone gel breast implants

Limits of detection: Oxygenated compounds and Carbon disulphide, 100 µg/L; m & p-Xylenes, 20 µg/L; all other compounds in Table 1, 10 µg/L.

Tests on explanted PIP implants

Explanted breast implants that have been examined by the TGA are ones that have been removed from a patient either because the implant was ruptured or because a rupture was suspected. Surgeons were asked to forward explanted PIP implants to the TGA, ruptured or not, if the surgeon believed there was something unusual about the explanted prosthesis. Testing on explanted products also allowed the TGA to assess whether or not the tensile properties of the implants change as a result of being implanted.

As of December 2012, 20 clinicians have submitted a total of 107 explanted PIP silicone breast implants for examination by the TGA.

On receipt, the implants were visually examined and the presence and appearance of any implant shell rupture, discoloration, opacity or other unusual features were recorded. The gel filling was separated from the shell and also examined.

Samples of the implant shell were taken from non-ruptured implants to determine tensile properties. Samples of gel were also taken and analysed for the presence of the cyclic silicone compounds D4, D5 and D6.

There is an International Standard (ISO14607:2007 Non-active surgical implants - Mammary implants) that provides a measure for assessing the quality of new, non-implanted silicone breast implants. However, there is no equivalent reference standard that is applicable to silicone breast implants that have been removed from patients. Nevertheless, as a guide, TGA testing was conducted in accordance with Annex B, Section 1.7 of ISO14607:2007 Non-active surgical implants - Mammary implants - Particular Requirements. While the requirements in this standard apply to non-implanted breast implants the test methods can still be used for comparative purposes.

Results

Presence of the cyclosiloxanes, D4, D5 and D6

Consistent with tests reported previously by the TGA and others on unimplanted PIP breast implants, all of the gel specimens from explanted PIP implants were found to contain traces of D4, D5 and/or D6. As previously noted, a toxicological assessment determined that the presence of these compounds at the levels detected does not pose a health threat.

Visual inspection

A summary of the observations made is provided in the tables below.

Key to terms

• Pin hole: a small hole located somewhere on the shell - the word "pin" relates to the size and shape of the hole. There is no intention to imply that the damage was made by a pin or a needle.
• Split: a slit or tear that runs for some length on the surface of the shell.
• Gross damage: very large tears that run right around the implant - in some cases the shell and the gel were totally separated from one another.
• V-shaped split: a split that comes to a sharp "V" shape somewhere along its length. V-shaped splits are usually associated with damage caused by surgical instruments.
• Near mandrel number: the mandrel "moulds" over which implant shells are made have a number. This number becomes imprinted on the inside of the shell during manufacture. It is generally regarded that these sorts of features may be weak points where ruptures can initiate.
• Combination: a combination of two or more of the listed damage types.

Note: The descriptions used in this table are not mutually exclusive in some cases more than one of the terms was used to describe the gel appearance.

Key to terms

• Yellow: a yellow colouration is caused by the absorption of body fluid into the silicone.
• Clear: transparent (see also opaque)
• Opaque: not transparent, cloudy
• Single mass/non-uniform: when the shell is removed, some implants retained the shape of the implant and remained in a cohesive single mass, other gels did not remain in a single cohesive mass but had a non-homogeneous appearance.
• Oily: all silicone gels comprise silicone oil dispersed in a sponge-like cross-linked silicone network. If the oil permeates out of the cross-linked network the gel can take on an "oily" appearance and texture.

Tensile testing of explanted PIP implants

Two tensile properties of samples of explanted PIP breast implants were measured: force at break and elongation at break. Prior to testing, the explanted breast implant shell samples were subjected to a decontamination procedure that involved soaking in alkaline detergent for 30 minutes followed by soaking in a 0.55% solution of o-phthalaldehyde for 5 hours. The disinfection procedure was found not to have a significant effect on the either the force at break or the elongation at break of the shell.

Data for a number of non-implanted untreated samples was compiled from previous testing. This data was used for reference.

Conclusions

The median force at break for shells of textured explanted PIP breast implants was lower than that for ones that have not been in a patient's body. However, for smooth implants the difference in results was not significant.

The median elongation at break for shells of explanted PIP breast implants was approximately 35% lower than that for unimplanted samples for both smooth and textured shells. This observation is expected, having been previously reported for breast implants from other manufacturers. For example, Marotta et al. (1) indicated reductions in the ultimate elongation of 24%, 27%, 30% and 44% and Brandon et al. (2) identified a reduction of 30-35%. The TGA results therefore confirm earlier findings that the mechanical strength properties of silicone breast implants deteriorate as a consequence of being implanted in the human body.

References

1. Marotta JS, Goldberg EP, Habal MB, Amery DP, Martin PJ, Urbaniak DJ, Widenhouse CW. "Silicone gel breast implant failure: evaluation of properties of shells and gels for explanted prostheses and meta-analysis of literature rupture data". Ann Plast Surg 49 (2002) 227
2. Brandon HJ, Young VL, Jerina KL, Wolf CJ, "Analysis of explanted silicone/silica composite breast implants" Advanced Composites Letters 9 (2000) 115