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Information regarding tests that have been conducted on silicone gel filled breast implants manufactured by Poly-Implant Prothese (PIP)
- In 2010, the Therapeutic Goods Administration (TGA) conducted a range of laboratory tests on gel-filled breast implants manufactured by Poly-Implant Prothèse (PIP).
- To date, the results of the testing on shell integrity (tensile set, tensile elongation) and gel cohesion of the implants complied with the requirements of ISO 14607:2007 Non-active surgical implants - Mammary implants - Particular requirements (ISO 14607:2007).
- Similar findings have been reported by the regulatory authority in France (AFSSAPS), although they reported that the results of the tensile elongation of the shells did not comply with the requirement in ISO 14607:2007.
- Tests conducted by the TGA in accordance with an international standard for cytotoxicity indicated that the gel was not cytotoxic. Similar findings have been reported by AFSSAPS, as well as the regulatory authority in the UK (MHRA). Both those Authorities also reported that tests for genotoxicity indicted that the gel was not genotoxic.
- AFSSAPS have reported that intra-dermal irritation tests show "an irritant potential of the PIP gel not found with the silicone gels from other prosthesis". The TGA is not aware of any other study that verifies this finding.
- The TGA is developing follow-up laboratory testing and liaising with other international regulatory authorities about their testing programs.
Following the recall from the Australian Market in 2010, and subsequent reports about the quality and safety of the silicone gel filled breast implants made by Poly Implants Prothèse (PIP), the TGA conducted a range of laboratory tests on PIP breast implants. The regulatory authorities in the UK (Medicines and Healthcare products Regulatory Agency - MHRA) and France (Agence Francaise de Securite Sanitaire des Produits de Sante - AFSSAPS) have also either commissioned or conducted tests on these implants.
What is a silicone gel filled breast implant?
A silicone gel filled breast implant is a silicone elastomer shell (sac) that's been filled with a cohesive silicone gel. The thickness of the shell varies around the implant but is typically between 0.5 and 1.0 mm thick. There is a hole at the back of the shell through which the silicones which make up the gel material are introduced. The hole is covered by a welded patch after the shell has been filled with the silicones that make up the gel.
The gel is produced by curing the silicones inside the sealed (patched) shell. Prior to curing, the silicones that make up the gel are viscous liquids. During the curing process these silicones react together to form a cross-linked cohesive network, which is gelatine-like. Thus if the shell was to split or rupture, the gel inside a properly made silicone gel filled breast implant will not "ooze out", but rather remain as a gelatine-like mass inside the breast.
Tests performed by the TGA
The laboratory tests carried out by the TGA measured:
- the capacity of the implant shell to remain intact (shell integrity);
- the extent that the silicone gel sticks together (cohesion); and
- the toxicity of the implant.
The shell integrity and gel cohesion tests were all conducted in accordance with ISO 14607:2007.
The cytotoxicity tests of the shells and the gels were conducted in accordance with ISO 10993 -5:2009 Biological evaluation of medical devices - Part 5: Tests for in vitro cytotoxicity.
The TGA tested 8 implants (see Table 1)of various profiles, sizes and dates of manufacture provided by Medical Visions Australia (the supplier of PIP implants in Australia).
The model name indicates the surface finish (LS - smooth / TX - textured) the profile (S - standard / H - high) and the number at the end is the volume of the implant.
*Models used in cytotoxicity studies.
Limitations to the testing
Testing provides a measure of the compliance of a particular sample with specified quality criteria. The quality of the sample is taken to be reflective of the batch from which the sample is drawn. However, the samples tested may not be representative of other batches of the product. Nevertheless, it does provide a very useful support to other measures by providing an immediate assessment of quality of the portion or the sample of the batch tested.
The testing protocol was based on 8 implants of various profiles, sizes and dates of manufacture. While this information provided evidence that the tested samples were compliant with the requirements of the standards used in the testing program, the testing numbers were relatively low and may not be sufficient to represent the overall quality of the product that has been produced over the years.
The tests, requirements and results performed by the TGA are shown in Table 2, below:
|Tests Performed||Test Requirement||Test Result|
(ISO 14607:2007 Annex B Section 1.2)
|The specimen is stretched to breaking point. The elongation at break of the shell specimen must exceed 450% compared to the original length of the specimen.||The minimum elongation recorded by testing several specimens from each of the 8 implants tested was 580%. The tensile elongation obtained by the TGA met the requirements of the standard and was generally higher than the specification submitted by the manufacturer for approval. Further details of the test results are provided in Table 3.|
(ISO 14607:2007 Annex B Section 1.3)
|The tensile set is the change in length that occurs after a specimen is stretched to 300% of its original length for 3 minutes. The tensile set must be lower than 10%.||The length of all of the specimens tested before and after extension to 300% was 75.0+/-0.5 mm, indicating that the samples exhibited negligible, if any, tensile set and thus met the requirements of the standard.|
(ISO 14607:2007 Annex B Section 1.4)
|The standard only requires for the tests to be carried out and the results recorded.||The TGA carried out tear resistance tests using different test geometry than that specified in the standard, but which is regarded to be more sensitive to tear initiation. The tear resistance results for the tests carried out on PIP shells were similar to those of comparable materials.|
|Strength of joints, seams and seals
(ISO 14607:2007 Annex B Section 2)
|When a specimen containing the seam is stretched to 300% of its original length for 10 seconds, the area of the shell adjacent to the bonded area must not break.||None of the specimens tested showed any signs of failure or tearing and they all returned to their original dimensions when the stress was released. The results met the requirements of the standard.|
|Silicone Gel Cohesion
(ISO 14607:2007 Annex D Section 4&5)
|When allowed to flow through a funnel of specified dimensions for 30 minutes, there must be no separation of the gel and the projecting length from the end of the funnel must be less than or equal to 30mm.||The gels recovered from the PIP implants were strongly cohesive with no detachment and minimal (<3mm) projection through the end of the funnel during the test period. None of the gel materials detached from the cone geometry. The results met the requirements of the standard.|
(ISO 10993:2009 Part 5)
|There are no specific requirements, but this standard allows the grading of the cytotoxic effect of the material. A toxic effect would warrant further investigation.||None of the materials taken from any of the PIP shells or gels displayed a cytotoxic effect.|
|Model||Thickness (mm)||Force (N)||Elongation (%)|
Please note that the information in Table 3 has been updated. See: Update to testing results of PIP breast implants
Tests conducted by the MHRA
In a number of circular published since September 2010, the MHRA has indicated that they had tested PIP implants. The MHRA tests found no evidence of genotoxicity (potential for cancer) or chemical toxicity. No other test results were reported. The latest information from the MHRA can be found at: Press statement: PIP breast implants - UK medical devices regulator says no evidence to support routine removal.
Tests conducted by AFSSAPS
In a topical report dated June 2011 the AFSSAPS provided a summary of the tests that they had performed and sponsored.
The results of the tensile set and fatigue resistance tests carried out on PIP implants in France complied with the requirements in ISO 14607:2007. The tensile elongation of the implants tested in France did not comply.
AFFSAPS also commissioned cytotoxicity tests, a variety of genotoxicity tests and an intradermal irritation test. The tests concluded that the materials used in PIP implants are not cytotoxic or genotoxic, but the intradermal irritation test showed "an irritant potential in the PIP gel not found with the silicones from other prostheses nor on the gel declared in the manufacturer' dossier". The TGA is seeking further details about the intradermal irritation test.
An English version of the AFFSAPS Topical Report on PIP Implants can be found at: