CAPSULAR CALCIFICATION ASSOCIATED WITH SILICONE BREAST IMPLANTS - INCIDENCE, DETERMINANTS, AND CHARACTERIZATION

Capsular calcification was present clinically in 64 of 404 silicone ge l breast implant capsules (15.8%) analyzed from 1981 to 1996. It prese nted as white-gray plaques on the inner surface of capsules in 62 of 6 4 capsules, and as massive heterotopic ossification in 2 capsules. Chi -squared analysis confirmed that calcification was related to the gene ration of the implant (i.e., year of manufacture; p<0.001). All 28 fir st-generation implants (1963-1972, with Dacron patches) were clinicall y intact and all demonstrated extensive calcification. Their mean dura tion in situ was 17.6 years (range, 14-28 years). Thirty-four of the 3 48 second-generation implants (9.8%; 1973-1987) were associated with c apsular calcification. Their mean duration in situ was 16.0 years (ran ge, 13-22 years). Because all first-generation implants demonstrated c alcification, they were compared with the second-generation implants t hat had been in place for the same duration (>14 years). Only 42% of t hese 81 second-generation implants demonstrated calcification, compare d with 100% of the first-generation implants (p<0.001). Thus, thicker first-generation implants with Dacron patches are more likely to calci fy and the effect is not entirely due to their longevity. None of the 28 third-generation implants (1987-1991) demonstrated calcification. T heir mean duration in situ was 4.2 years (range, 2-7 years). For secon d-generation implants, calcification was related to duration in situ ( p<0.001). None of the 294 implants in place for less than 11 years wer e associated with significant clinical calcification. The percentages of capsules with calcification were 13 to 14 years, 33%; 15 to 16 year s, 45%; and 17 to 22 years, 57%. Calcification with second-generation implants was not associated with patches on the envelopes. Of the 348 second-generation implants with calcification, only two had patches (c omposed of silicone, not Dacron). Among second-generation implants, ca lcification was related to implant integrity. Of implants in place for more than 12 years, 52.5% of those implants that were ruptured showed calcification, but only 10.0% of intact implants demonstrated calcifi cation (p<0.001). Seventeen of the 64 calcified capsules were examined histologically. In all of these specimens, calcification existed in t wo forms: globular aggregates on the surface of the capsule (adjacent to the implant) and actual bone formation within the fibrous tissue of the capsule. All calcified capsules demonstrated both globular aggreg ates and true bone formation regardless of the implant generation, dur ation in situ, or integrity. Ultrastructural analysis was performed on four capsules from 2 women who had received first-generation Dow Corn ing gel implants 24 and 28 years previously, and on 2 capsules from on e woman who had received Heyer-Schulte gel implants 21 years previousl y. These capsules were analyzed according to distribution, density, mi neral nature, crystal phases, and elements within crystals by electron microscopy, energy-dispersive x-ray spectrometry, and electron diffra ction. These analyses confirmed two types of calcification, each with hydroxyapatite crystals. In areas of heterotopic bone, crystals 40 x 1 0 nm were deposited in an orderly fashion on collagen fibers. In contr ast, in areas of globular aggregates, spherulitic aggregates of much l arger crystals were present, without any relationship to the collagen. Titanium was demonstrated in capsules of first-generation implants at areas of attachment of the Dacron patches. The calcification associat ed with saline implants revealed only one form of crystal: agglomerate s, which were adherent to the elastomeric shell of the implants. A hyp othesis is presented to explain the differences in calcification depos ition properties between silicone gel-filled and saline-filled breast implants.