Full Citation
- Citation (Vancouver style): Jones P, Mempin M, Hu H, Chowdhury D, Foley M, Cooter R, Adams WP Jr, Vickery K, Deva AK. The Functional Influence of Breast Implant Outer Shell Morphology on Bacterial Attachment and Growth. Plast Reconstr Surg. 2018 Oct;142(4):837-849 [1].
- DOI:1097/PRS.0000000000004801 [1].
Authors and Affiliations
- Authors: Phoebe Jones, M.B.B.S., Maria Mempin, B.Med.Sc., M.Res.(Med.), Honghua Hu, Ph.D., Durdana Chowdhury, M.B.B.S., M.Phil., Ph.D., Matthew Foley, Ph.D., Rodney Cooter, M.D., William P. Adams, Jr., M.D., Karen Vickery, B.V.Sc., Ph.D., and Anand K. Deva, B.Sc.(Med.), M.B.B.S., M.S [2].
- Affiliations: Surgical Infection Research Group, Faculty of Medicine and Health Sciences, Macquarie University; Integrated Specialist Healthcare Education and Research Foundation; Monash University; Australian Center for Microscopy and Microanalysis, University of Sydney; and the University of Texas Southwestern [3].
Study Design and Evidence Level
- Study Type: In vitro laboratory study analyzing surface morphology and bacterial attachment [4].
- IRB Approval: Not reported.
- Sample Size: 11 available implant surface types tested for morphology [5], and 9 types subjected to bacterial attachment assays [6].
- Groups: 11 implant types: Silimed polyurethane, Polytech POLYtxt, Mentor Siltex, Mentor Smooth, Motiva SilkSurface, Motiva VelvetSurface, Allergan Biocell, Allergan Natrelle Smooth, Nagor Nagotex, Sientra Smooth, and Eurosilicone textured [5].
- Follow-up: In vitro incubation up to 24 hours (measured at 2, 6, and 24 hours) [7].
- Level of Evidence: Not reported.
Objectives
- To measure the surface area and surface roughness of 11 available breast implants [4].
- To subject these implant shells to an in vitro bacterial attachment assay with four bacterial pathogens (Staphylococcus epidermidis, aureus, Pseudomonas aeruginosa, and Ralstonia pickettii) [4].
- To study the relationship among surface area, surface roughness, and bacterial growth [4].
Background Context
- Introduction of Texturing: First introduced in 1968 with the 'natural Y' implant, which featured a 1.2- to 2-mm polyurethane foam coating to prevent myofibroblast alignment and reduce capsular contracture [8].
- Polyurethane Withdrawal: In 1991, a voluntary withdrawal of polyurethane-coated implants occurred in the US due to an association with the carcinogen 2,4-toluenediamine [8].
- Manufacturing Processes: Four main processes generate surface texture on silicone shells: salt loss, vulcanisation, imprinting, and proprietary 'nano' textures [9].
- Clinical Controversy: The benefits of texturization in reducing capsular contracture remain controversial, with systematic reviews showing reduced early contracture in subglandular augmentation, while smaller studies are evenly divided [10].
- Bacterial and Lymphoma Link: Textured implants support higher rates of bacterial growth in vitro [11]. Bacterial infection is proposed as one of four factors in the genesis of breast implant-associated anaplastic large cell lymphoma (ALCL) [12].
Methods
- Scanning Electron Microscopy (SEM): Samples (up to 1 cm²) were fixed in 3% glutaraldehyde, dehydrated in ethanol, immersed in hexamethyldisilazane for 3 minutes, evaporated overnight, mounted on aluminum stubs, sputter-coated with 20-nm gold film, and visualized using a JEOL 6480LA SEM [13].
- Micro-Computed Tomography (Micro-CT): Specimens were mounted horizontally on a metal pin and scanned in a Zeiss Xradia MicroXCT-400 system at 50 kV and 200 μA. Projections were collected every 0.25 degrees over a 180-degree rotation with a 3-second exposure [14]. Reconstructions yielded 2.2-μm isotropic voxels, analyzed using Avizo 9.3 and Fiji [15].
- Surface Area Determination: Calculated as the three-dimensional-to-two-dimensional surface area ratio ($SA_{3D}/SA_{2D}$) [16].
- Surface Roughness ($S_a$): Measured by dropping a virtual thin probe toward the surface to calculate the arithmetic mean deviation of the assessed profile [17].
- In Vitro Bacterial Attachment Assay: 5-mm punch biopsy sections of 9 implant types were sterilized under dry heat at 115°C for 39 hours [6]. Sections were incubated at 37°C in 10% tryptone soy broth containing $10^5$ cells/ml of epidermidis, S. aureus, and R. pickettii, or $10^4$ cells/ml of P. aeruginosa [18]. Samples were removed at 2, 6, and 24 hours, washed in PBS, sonicated for 20 minutes, and vortexed for 1 minute before serial dilution and plate culture [7].
- Statistical Analysis: Conducted using Sigma Plot 13. One-way repeated measures ANOVA with Holm-Sidak pairwise comparisons was used for normal data; Kruskal-Wallis with Dunn's method was used for non-normal data. Pearson or Spearman correlation was used to test relationships. Significance was set at $p < 0.05$ [19].
Results
Surface Area and Roughness Groupings
- Surface Area Ratio ($SA_{3D}/SA_{2D}$): Grouped into high (>5), intermediate (3 to 5), low (2 to 3), and minimal (<2) [20]. Raw ratios included Silimed polyurethane (20.8), Eurosilicone textured (3.9), Allergan Biocell (3.2), Polytech POLYtxt (3.2), Nagor Nagotex (2.8), Mentor Siltex (2.2), Motiva VelvetSurface (1.2), Sientra Smooth (1.1), Motiva SilkSurface (1.1), Allergan Smooth (1.0), and Mentor Smooth (1.0) [21].
- Surface Roughness ($S_a$ in μm): Grouped into high (>150), intermediate (75 to 150), low (25 to 75), and minimal (<25) [22]. Values included Silimed polyurethane (277.6), Eurosilicone textured (111.7), Allergan Biocell (91.7), Nagor Nagotex (60.9), Polytech POLYtxt (58.8), Mentor Siltex (51.4), Motiva SilkSurface (20.1), Motiva VelvetSurface (12.9), Allergan Smooth (8.5), Sientra Smooth (8.1), and Mentor Smooth (2.1) [23].
Bacterial Attachment Findings
- epidermidis: At 2 hours, Silimed polyurethane had significantly more bacteria than less textured implants ($p < 0.001$) [24]. At 24 hours, high/intermediate surface area implants grew significantly more bacteria than low/minimal ones ($p < 0.001$) [25]. Smooth implants grew significantly fewer bacteria than intermediate/high profiles ($p < 0.001$) [26]. Growth positively correlated with surface area ratio ($R = 0.64$; $p < 0.001$) [27].
- aureus: Silimed polyurethane grew significantly more bacteria than any other implant ($p < 0.05$) [28]. Smooth implants grew significantly fewer bacteria than all others ($p < 0.001$) except Mentor Siltex ($p = 0.4$) [28]. Growth positively correlated with surface area ratio ($R = 0.75$; $p < 0.001$) [29].
- aeruginosa: Maximum growth occurred on Silimed polyurethane, followed by Polytech POLYtxt and Allergan Biocell [30]. Smooth implants grew significantly fewer bacteria than all others ($p < 0.001$) [31]. Motiva VelvetSurface grew significantly fewer bacteria than Motiva SilkSurface ($p = 0.008$) [32]. Growth positively correlated with surface area ratio ($R = 0.81$; $p < 0.001$) [33].
- pickettii: Only Silimed polyurethane, Biocell, and Nagor Nagotex grew significantly more bacteria than smooth implants ($p < 0.001$) [34] [35]. Growth positively correlated with surface area ratio ($R = 0.87$; $p < 0.001$) [35].
Conclusions
- Breast implant shells should be reclassified into four objective categories (high, intermediate, low, and minimal) based on surface area and roughness [36].
- This objective classification is superior to descriptive terms (macrotexture, microtexture, nanotexture) which do not correlate well with functional outcomes [36].
- High- and intermediate-surface-area textured implants have a 10-fold higher propensity to cause breast implant-associated ALCL compared to low-surface-area textures [37].
- Bacterial contamination on implant surfaces is a significant potentiator for capsular contracture [38].
Key Terminology and Definitions
- Surface Area Ratio ($SA_{3D}/SA_{2D}$): The ratio of the three-dimensional surface area of the interface between the binarized sample and air to the two-dimensional x-y dimensions of the sample [16].
- Surface Roughness ($S_a$): The arithmetic mean deviation of the assessed profile over an approximated surface [17].
- Generic Breast Implant Classification: A proposed nomenclature system defining Fill (GF = Gel filled, S = Saline filled, A = Part air filled), Surface area (4 = High, 3 = Intermediate, 2 = Low, 1 = Minimal), Shape (A = Anatomical, R = Round), and Size (in cc) [39].
Limitations
- Confocal and light microscopy have resolution limits in deeper zones of thick textures, necessitating micro-CT for accurate morphologic assessment [40].
- Certain complex textures (e.g., Polytech POLYtxt) contain hidden 'caves' that do not communicate directly with the outer surface, requiring subtractive analysis and assumptions (such as a mean choke size of 5 μm) [41].
- The functional significance of these in vitro findings must be further validated by clinical studies [40].
Funding and Conflicts of Interest
- Funding: Not reported.
- Conflicts of Interest: Professor Deva is a research coordinator and consultant to Allergan, Mentor (Johnson & Johnson), Sientra, Motiva, and Acelity. Associate Professor Vickery is a research coordinator and consultant to Allergan, Mentor (Johnson & Johnson), and Acelity [42].
Plain-Language Patient Summary
This study investigated how the surface texture of different breast implants affects the attachment and growth of bacteria, which are linked to complications like capsular contracture and a rare cancer called breast implant-associated ALCL. The researchers found that implants with higher surface area and roughness support significantly more bacterial growth compared to smoother or minimally textured implants. Based on these findings, they propose a new, objective classification system to help surgeons select implants with lower bacterial risks to improve patient safety.
References
[1]“File: 11. The Functional Influence of Breast Implant Outer Shell - Deva et al OCT 2018 (1).pdf,” File.
