Breast implant rupture

Implant rupture was mentioned as an issue with implants in 1992 [9] and emerged as the most frequently reported problem in adverse event reports to the FDA (see above). Manufacturers opined that the rupture rate for breast implants was 0.2-1.1%, but the American Medical Association taskforce suggested that it could be as high as 4-6% [7]. Manufacturers made the argument, in meetings with the FDA, that when the number of ruptured implants reported to them was used as the numerator and the number of implants ever sold was used as the denominator, implant rupture could be seen to be rare. Their analysis was problematic, since it is well established that adverse events are under-reported at an unknown but significant rate. Neither did this consider that the number of implants sold was not equal to the number of women exposed (or even breasts exposed), since practices with implants included removing and replacing ruptured implants; stacking multiple implants in a surgical pocket; discarding implants that ruptured during surgery or out of the box; and stocking implants, sometimes in large numbers. In order to take these possibilities into account, FDA undertook its own assessment of breast implant rupture, as discussed below.

First, a little background on implant rupture: silicone gel-filled breast implants may rupture without causing any changes, or causing minimal changes, to the implanted breast. This is because the gel may be retained in the implant capsule (scar) that forms around the implant. In other cases, silicone gel-filled breast implant rupture will be recognizedbecause it causes cosmetic changes in the breast, such as changes in the breast shape or the formation of granulomatous tissue (lumps) in the breast that may be visible or detected by palpation. It is not clear whether there is a natural progression from a rupture contained by the fibrous scar (capsule) that forms around the implant to an extracapsular rupture, which is when silicone extrudes outside of the capsule, because little is known of the natural history of rupture.

The phenomenon of 'silent rupture' was first described in a series of 350 women with breast implants undergoing screening mammography [28]. Implant 'leak' was observed in 16 (5%) of the women in this series. Subsequent studies have indicated that mammo-graphy is the least sensitive imaging method for detecting implant rupture (and, as described above, may also contribute to implant rupture) and that magnetic resonance imaging (MRI) in the most sensitive and specific method [29-31]. In contrast to the potential for a silent rupture with silicone gel-filled breast implants, saline breast implants typically quickly deflate when ruptured, with a noticeable change in breast size. In some cases, the deflation may occur over an extended period of time through a pin-hole sized defect, over days to weeks, but it is nonetheless recognized as ruptured as the implant deflates.

Several studies reported rates of silicone gel-filled breast implant rupture confirmed by explantation [32-37]. These series included examination of implants explanted for a variety of reasons, including suspected rupture. The definition of rupture was inconsistent between these reports because there were no agreed standards for defining implant rupture. Further complicating the vague definition of implant rupture was the fact that intact implants may 'bleed' silicone oil. Despite the lack of a definitive definition of rupture, prevalence rates of other than intact implants were found to be consistently high, 23-63% of explanted implants in these series. It was argued that these studies were not representative of implants in general because results came from a population of women who were having problems with their implants - hence their explantation. The range of breast implant rupture estimates (from 0.2% by industry to up to 63% in some studies of explanted implants) was so wide that it was not possible to even give a reasonable range for silicone gel-filled breast implant rupture rate.

Rupture is an important issue for several reasons. First, ruptured implants do not perform as intended. Second, ruptured gel implants may release silicone outside of the shell. Silicone gel may migrate within the breast or outside the breast to the axilla [38-40] or as far as the hands [41]. There have been unusual presentations of migrated gel, such as an abdominal mass [42] and an aggressively expanding silicone granuloma [43]. There are also reports of silicone found in distant organs, such as liver [44].

Third, it is not known whether there are health effects of having silicone gel loose in the breast (including that maintained inside the scar capsule) or whether there may be adverse health effects related to having gel and chemical components of gel migrate to locations outside the breast. A recent study of tissue samples from three women with (explanted) silicone gel-filled breast implants indicated that there were small but measurable amounts of siloxanes in the tissue from the implant capsule (scar) and surrounding fat and muscle, but this was not detected in control women without silicone gel-filled breast implants [45]. There is also concern that, as was seen with Trilucent™ implants, there may be break-down products or changes in the chemical composition of aging silicone [46,47].

Because of these concerns and the lack of a definitive estimates of either for the incidence rate or prevalence of silicone gel-filled breast implant rupture, FDA worked with an epidemiologist at the US National Cancer Institute (NCI), on a cohort from its ongoing study on breast implants and cancer risks, to examine breast implant rupture. The FDA contracted for an MRI study at two of the sites in this NCI study on women who still had their silicone gel-filled breast implants. We selected two plastic surgery study sites in Birmingham, Alabama, because of the high response rate there to a previous patient questionnaire. Women who still resided in the Birmingham area were called and asked to respond to a questionnaire on their current health status and surgeries related to their breast implants. Women from both Birmingham sites who still had silicone gel-filled breast implants were invited to undergo an MRI examination at the Kirklin Clinic at the University of Alabama at Birmingham, to determine the status of their breast implants with respect to rupture. Three experienced radiologists independently examined and rated all MR images for signs of implant rupture and extracapsular silicone. A consensus reading, based on the majority opinion of these radiologists, was developed for each implant as to whether it was ruptured, indeterminate, or had no evidence of of rupture (intact). There were 344 women with silicone gel-filled breast implants in this study who underwent an MRI evaluation [48]. The average age of women in the study was 51.4 ± 8.4 years and the average age of their implants was 16.5 ± 3.4 years at the time of the evaluation. The findings indicated that of the 687 implants in the study, 378 (55%) were rated as ruptured. Another 50 implants (7.2%) were rated as indeterminate, indicating that there was uncertainty as to their status but reason to be suspicious of rupture. Overall, 265 (77%) women had at least one implant that was rated as ruptured or indeterminate. The radiologists' agreement on implant status, measured with a weighted kappa statistic for agreement, indicated that agreement among these experienced radiologists was almost perfect. Risk factors for implant rupture included implant age, implant location (with submuscular implants being more likely to rupture than subglandular placement), and implant manufacturer.

Radiologists also evaluated whether there was silicone outside of the scar capsule (extracapsular silicone). Extracapsular silicone was observed around 85 of the 687 implants, affecting 73 (21%) of women in the study. The radiologists' agreement on this was not as high as it had been for implant rupture status [49].

This study was unique in that it was the first study in which an unselected and presumably unbiased population of women with silicone breast implants underwent an MRI examination. This contrasted with other studies, in which implants were evaluated in women who had problems or complaints about their implants. The study had shortcomings, including the fact that it was limited to two study sites in the same state and one particular brand of implants predominated.

A similar subsequent study, funded by implant manufacturers, examined 271 women with 533 silicone gel-filledbreast implants [50]. In their study, 26% of implants in 36% of women examined were ruptured, and an additional 6% of implants were probably ruptured. In this study, in contrast to the FDA study, there were three facilities at which MRI examinations were performed, and equipment in one of the facilities, which examined 116 (43%) of the 271 women, was subsequently found to not be working properly, so that silicone-excited sequences could not be generated. Some, but not all, of these cases were subsequently imaged at another site, with a change in diagnosis from no rupture to possible rupture or from possible rupture to ruptured for 9 of 28 evaluations. This indicates that their finding of 36% of women with ruptured implants likely represents a minimum estimate, since more ruptures might have been diagnosed with properly functioning equipment. In this study, 22% of ruptured implants had signs of extracapsular silicone.

In the decade after 1992, the prevailing thought on silicone gel-filled breast implant rupture had moved from believing that rupture was rare (0.2-1.1%) to recognizing that rupture was very common, particularly as implants age. A meta-analysis of 35 studies reporting on rupture status of over 8000 breast implants reported that implant failure was 30% at 5 years, 50% at 10 years, and 70% at 17 years [51].

There is still no consensus on how the rupture of silicone breast implants should be managed or even whether intermittent screening for rupture after implantation should be recommended. Clinical (physical) examination for implant rupture is inadequate, and expensive imaging methods would be required for a sensitive and specific method of screening and detection [52,53]. Despite the current recognition that breast implants are not typically intact years after implantation, there remains little information on the potential health effects of ruptured vs. intact implants or of the prudent course for detecting and managing silicone gel-filled breast implant rupture.

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