New Evaluation Procedure for Multi-Dimensional Mechanical Strains and Tangent Moduli of Breast Implants: IDEAL IMPLANT® Structured Breast Implant Compared to Silicone Gel Implants.

The IDEAL IMPLANT® Structured Breast Implant is a dual lumen saline-filled implant with capsular contracture and deflation/rupture rates much lower than single-lumen silicone gel-filled implants. To better understand the implant's mechanical properties and to provide a potential explanation for these eight-year clinical results, a novel approach to compressive load testing was employed. Multi-dimensional strains and tangent moduli, metrics describing the shape stability of the total implant, were derived from the experimental load and platen spacing data. The IDEAL IMPLANT was found to have projection, diametric, and areal strains that were generally less than silicone gel implants, and tangent moduli that were generally greater than silicone gel implants. Despite having a relatively inviscid saline fill, the IDEAL IMPLANT was found to be more shape stable compared to gel implants, which implies potentially less interaction with the capsule wall when the implant is subjected to compressive loads. Under compressive loads, the shape stability of a higher cross-link density, cohesive gel implant was unexpectedly found to be similar to or the same as a gel implant. In localized diametric compression testing, the IDEAL IMPLANT was found to have a palpability similar to a gel implant, but softer than a cohesive gel implant.

Breast Implants: Protocol for Retrieval and Analysis.

The Center for Implant Retrieval and Analysis has been established at Washington University's Division of Plastic and Reconstructive Surgery for the purpose of studying implantable devices retrieved after surgery or autopsy and assessing their condition after implantation. Since the early 1990s, significant experience has been gained in testing and analyzing silicone gel breast implants and, to a lesser extent, saline-filled devices. However, there has been no systematic method reported for collecting and evaluating these implants in a way that would permit di. erent laboratories to compare their data. This article offers the plastic and reconstructive surgery community a standardized protocol for analyzing explanted silicone gel and saline-filled breast implants. The protocol gives surgeons a clearly defined approach for removing, handling, documenting, and shipping explanted breast implants. At the same time, biomaterials researchers can use the protocol to acquire implant data with reliable and reproducible methods. Because the study of saline implants has lagged behind the study of silicone gel implants, the article concludes with a demonstration of how this protocol can be applied to obtain mechanical properties data and use scanning electron microscopy to illuminate failure mechanisms of saline devices, including three explants removed after 20+ years in vivo.

Microscopy analysis of breast implant rupture caused by surgical instrument damage.

BACKGROUND: The mechanism of breast implant rupture has continued to be an important topic throughout the plastic surgery community and regulatory agencies, such as the US Food and Drug Administration. Retrieved ruptured implants returned to Allergan (Santa Barbara, CA; formerly Inamed Corporation) for analysis exhibit various modes of failure, which can include a small pinhole (approximately 1 to 2 mm in size) in the shell, a ruptured shell, or a severely fragmented shell. OBJECTIVE: The failure mechanisms and associated morphologic features for the modes of implant failure can be quite different. The objective of this study is to analyze and describe the rupture characteristics of silicone gel-filled implants that failed because of surgical instrument damage. METHODS: There are several types of diagnostic techniques available to analyze ruptured implants. Visual inspection, physical examination, and photographic analysis provided an overall description of the implant shape and gross features of the shell failure region. These techniques allowed categorization and documentation of the mode of failure and were quite useful as a supplemental tool in the diagnosis of implant failure mechanisms. Microscopy techniques provided details of the ruptured shell region and could be used to determine the cause of breast implant failure. This study involved the use of optical microscopy and scanning electron microscopy in the analysis of ruptured breast implants. RESULTS: Details of the geometry of ruptured shell regions are described. Illustrations are also presented in which 35-mm photography is used to assist in substantiating the cause of failure. Many of the ruptured regions exhibit striations across the thickness of the shell. Micrographs are presented that clearly show that the striations are due to lines in the cutting surface of the surgical instrument that were formed during the manufacturing process. CONCLUSIONS: This article demonstrates that, with the proper background and experience in analyzing ruptured breast implant shells, the features at the failure site can be correctly interpreted and the corresponding failure mechanisms can be diagnosed. Breast implants are subject to surgical instrument damage during implantation, and this damage can develop into a shell rupture, with the failure mode identifiable via microscopy analysis.

Morphology of breast implant fold flaw failure.

The percent of modern silicone gel breast implants that fail due to shell rupture is quite low, amounting to less than 1% per year. Nonetheless, extensive retrieval and analysis studies are being conducted on failed devices returned to Allergan Medical (formerly Inamed Corporation) in order to determine the modes and causes of failure. With the modes and causes known, solutions can be implemented to eliminate the failure mechanisms. Analyses conducted thus far have demonstrated that there are several causes of breast implant failure. The focus of this paper is on one type of silicone gel breast implant failure, i.e., a failure associated with a fold or wrinkle, which is termed "fold flaw failure." Although fold flaw failure is not a dominant mode of failure for silicone gel breast implants, its failure characteristics must be understood in order for this type of shell rupture to be detected and eventually eliminated. In this study, optical microscopy and scanning electron microscopy are used to describe the morphology of fold flaw failure for explanted silicone gel breast implants with smooth shells. The microscopy analysis demonstrates that there are several different types of shell failure patterns that can be produced by a fold or wrinkle in a silicone gel breast implant.

The physics of suction-assisted lipoplasty.

BACKGROUND: Some medical equipment manufacturers and surgeons have asserted that certain types of cannulas and other components of liposuction systems enhance the efficiency of fat aspiration. OBJECTIVE: A laboratory experiment was designed to evaluate the effect of each component of a standard liposuction system on the rate of fat aspiration. A clinical investigation of the effectiveness of a vented (Turbo) cannula versus that of a standard cannula was also undertaken. METHODS: The equipment used for the experiment included cannulas of varying lengths and diameters, provided with different tip geometries, suction tubes of 2 diameters, graduated canisters, and a vacuum pump. Applesauce was used as a simulated aspirant because its consistency appears similar to that of a mixture of fat and infiltrate. The time required to aspirate 1500 mL of material, with the pump set at maximum vacuum and the temperature and barometric pressure held constant, was measured. RESULTS: Aspiration rates for the laboratory experiment with Becker, Keel Cobra Accelerator III, and Mercedes tip geometries were similar. In general, clinical aspiration rates were significantly lower than the laboratory rates. A higher aspiration rate was obtained with the vented Turbo cannula than with the conventional cannula. CONCLUSIONS: Cannula-tip geometry has a minimal effect on the rate of aspiration; however, use of a tip less than 4 mm in diameter can cause clogging with fibrous tissue and significantly decrease the rate of aspiration. Aspiration is directly proportional to cannula and suction-tubing diameter and inversely proportional to cannula and suction-tubing length. Vented cannulas can enhance aspirate flow and efficiency. Further research is needed to investigate the significance of the fat fragmentation process and the development of fluids to simulate infiltrate/fat solutions in laboratory experiments.

Protocol for retrieval and analysis of breast implants.

The Center for Implant Retrieval and Analysis has been established at Washington University's Division of Plastic and Reconstructive Surgery for the purpose of studying implantable devices retrieved after surgery or autopsy and assessing their condition after implantation. Since the early 1990s, significant experience has been gained in testing and analyzing silicone gel breast implants and, to a lesser extent, saline-filled devices. However, there has been no systematic method reported for collecting and evaluating these implants in a way that would permit different laboratories to compare their data. This article offers the plastic and reconstructive surgery community a standardized protocol for analyzing explanted silicone gel and saline-filled breast implants. The protocol gives surgeons a clearly defined approach for removing, handling, documenting, and shipping explanted breast implants. At the same time, biomaterials researchers can use the protocol to acquire implant data with reliable and reproducible methods. Because the study of saline implants has lagged behind the study of silicone gel implants, the article concludes with a demonstration of how this protocol can be applied to obtain mechanical properties data and use scanning electron microscopy to illuminate failure mechanisms of saline devices, including three explants removed after 20+ years in vivo.

Biodurability of retrieved silicone gel breast implants.

This study analyzed the shells of single-lumen silicone gel breast implants within the general context of device durability in vivo. The investigation included the major types of gel-filled implants that were manufactured in the United States in a 30-year period. The implants analyzed were Cronin seamed (two explants and one control), Silastic 0 and Silastic I (18 explants and seven controls), and Silastic II (22 explants and 43 controls). The biodurability of the explants was investigated with measurements of the mechanical and chemical properties of the various types of silicone gel control and explanted shells, with implantation times ranging from 3 months to 32 years. The shell properties measured for the controls and explants included the stress-strain relationships, tensile strength, elongation, tear resistance, moduli, cross-link density, and amount of extractable material in the shell. In addition, the mechanical properties of shells that had been extracted with hexane were analyzed for both explants and control implants. The silicone gel explants investigated in this study included some of the oldest explants of the various major types that have been tested to date. For assessment of long-term implantation effects, the data obtained in this study were combined with all known data from other institutions on the various major types of gel implants. The study also addressed the failure mechanisms associated with silicone gel breast implants. The results of the study demonstrated that silicone gel implants have remained intact for 32 years in vivo and that degradation of the shell mechanical and chemical properties is not a primary mechanism for silicone gel breast implant failure.

The effect of cyclic swelling (octamethylcyclotetrasiloxane) on the physical properties of silicone breast implant shells.

Changes in the physical and mechanical properties of silica filled silicone elastomeric films were studied as a function of repeated sorption extraction cycling. The sorption of octamethylcyclotetrasiloxane (D4) on the properties of three silicone filled elastomeric films was analyzed. Two of the films, SILASTIC I and SILASTIC II, were shells of explanted breast implants and the third, a calendered film, prepared with similar composition to the elastomer used for the breast prosthesis were studied. The as-received (AR) SILASTIC I and II films contained 20 and 26.5 wt% non-cross-linked material that was removed by extraction with hexane. The failure properties of the extracted films are significantly higher than those of the AR films. The amount of swelling, weight gain, volumetric change, and the stress- and strain-to-fail of the films were measured in the as-received condition, and after a series of extractions and swellings. Repeated cycling (up to 5 cycles) of extraction-swelling had essentially no effect on the failure properties of films when all the diluent was removed. The effect of diluent on the failure properties of all three films was quite large. The stress-to fail of the swollen film was reduced a factor of 6 compared to baseline extracted samples while the corresponding strain values were reduced a factor of 5. The energy to fail of the swollen compared to baseline films was reduced almost a factor of 50. However, the overall mechanical properties of the films are restored when the diluent was removed. The mechanical forces involved in the swelling process do not degrade the polymer even when cycled through five swell-extract cycles.

In vivo aging characteristics of silicone gel breast implants compared to lot-matched controls.

A study was conducted to investigate the effect of in vivo aging on the physical, mechanical, and chemical properties of Silastic II gel-filled breast implants. In the study, the properties of 16 Silastic II gel-filled explants (retrieved from eight patients), with in vivo duration times ranging from 4 months to 13 years, were compared with lot-matched control (unimplanted) samples. Tensile and tear strength properties were measured for both explant and control shells by using identical testing protocols. The tensile strength properties of shells, which were extracted with hexane to remove non-cross-linked silicones, were also measured. Swelling measurements were used to determine the average molecular weight between cross-links (or entanglements). In addition, scanning electron microscopy was applied in the comparison of the morphological features of the explants and their lot-matched controls. The results of the study suggest that the silicone polymer used to fabricate the shells does not undergo appreciable degradation for up to 13 years in vivo. The study represents an investigation of the world's largest known inventory of explanted breast implants with lot-matched controls.

Mechanical analysis of explanted saline-filled breast implants exposed to betadine pocket irrigation.

BACKGROUND: Because of concerns that exposure to povidone-iodine (Betadine) may lead to early breast implant failure, the Food and Drug Administration announced in 2000 that any contact between implants and Betadine is contraindicated. The evidence cited by the Food and Drug Administration primarily referred to Betadine added to saline implant filler solution and not to povidone-iodine used for pocket irrigation. OBJECTIVE: Thirteen explanted Mentor saline solution-filled devices that had been exposed to Betadine pocket irrigation during implantation were studied for any loss of implant shell integrity. METHODS: The 13 explants had been in place 1 week to 55 months, and none had intraluminal Betadine exposure. Twelve of the 13 explants were intact when removed, and one had leaked through the anterior valve. All were examined for any signs of patch-shell delamination. The mechanical properties of tensile strength, percent elongation, force-to-break, tear resistance, and patch bond strength were also measured. RESULTS: No shell delamination or disruption of the sealing patch bond was found in any of the 13 explants placed in Betadine-irrigated pockets. In addition, the measured mechanical properties of the explants exceeded American Society for Testing and Materials requirements, with the exception of the textured explants (n = 2), which failed to meet the minimum elongation standards. CONCLUSIONS: We found no evidence of patch or shell delamination in Mentor implants that had extraluminal contact with Betadine irrigation and were later explanted. We believe that the lower mechanical properties of the two textured implants are probably related to the texturing process rather than to Betadine pocket irritation. (Aesthetic Surg J 2002;22:438-445.).