A study conducted by MIT in partnership with plastic surgeons around the world, one of them from the Hospital Sírio-Libanês, evaluated how the texture of the silicone implant affects the immune system. Researchers have found that certain textures elicit less of an inflammatory response than others and therefore have better compatibility with the body.
The discovery should help in choosing the most suitable silicone prostheses for cosmetic and reconstructive plastic surgery, which can prevent the so-called “Silicone Disease”. The term is used to describe health problems linked to the use of implants, such as contractures, fibrosis and inflammation.
As they are synthetic materials, silicone implants trigger an immune system response. The difference is in the type of response and the degree of balance with our organism. This is a common phenomenon in any implant, such as pacemakers, heart valves, catheters and even dental implants, says Alexandre Mendonça Munhoz, a plastic surgeon at Hospital Sírio-Libanês, a member of the group that conducted the study at MIT in Boston, in U.S.
“While the rougher surface silicone implants provoked a greater inflammatory response, those with less rough surfaces caused a reaction whose objective was to inhibit inflammation in the tissue around the implant”, explains Munhoz.
Among the more than ten items analyzed in the study, published in Nature Biomedical Engineering, are the increase in the production of antibodies, the activation of T cells and the thickness of the capsule created around the prosthesis.
In all, five types of breast implants were considered, whose surface characteristics vary in roughness and are used in cosmetic and reconstructive breast surgery worldwide, from the most textured (rough) to the smoothest.
Choice beyond aesthetics
The expert emphasizes that the new evidence will be important in choosing the prosthesis in cosmetic breast surgery, but also in reconstructive surgery, after cancer treatment, for example.
Avoiding biocompatibility problems in convalescent patients can be considered an advance, because the need to redo the implants due to rejection problems in these patients is not uncommon.
Munhoz stated that research carried out in the Postgraduate Program at the Hospital Sírio-Libanês showed that one third of women underwent new surgery five years after the completion of breast reconstruction.
According to the plastic surgeon, hyperstimulation of the immune system can cause fibrosis, capsular contracture and even rupture of the implant, which are among the main reasons for reoperations.
“New technologies, involving implants with less roughness, favor the rehabilitation process of these women with breast cancer, thus reducing the number of long-term surgeries. These aspects have a direct impact on the quality of life and also on the costs of the entire surgical process”, he stated.
The study started in 2016 and ended in 2020 had the participation of plastic surgeons from the United States, England and Brazil and included two stages with an animal model and a third, which analyzed samples of oncological tissue and prostheses from explanted patients. This model allowed researchers to observe the same results in humans and animals.
Prostheses vs. adverse effects
Silicone implants are classified using the micrometer (µm) measurement unit, which is obtained after an evaluation of the surface using an electronic device and allows the classification of surface roughness (Ra or roughness, in English). The implants best evaluated by the study have an Ra of approximately 3.2 µm.
It was in the 1960s that the first silicone implants appeared. Smooth, they had an Ra of 0.27 µm, which caused capsular contracture, material fatigue and subsequent rupture.
Munhoz explains that contracture happens when the body forms scar tissue around the prosthesis, which starts to tighten the implant and cause pain, discomfort and deformation, modifying the position of the implant and leading to the need for further surgery. Incidence that may be higher in women who underwent breast reconstruction in cases of cancer, due to the characteristics of surgical treatment and radiotherapy.
In the 1980s, the industry developed implants with a macrotextured surface, with Ra greater than 50 µm, and microtexturized, with a Ra between 10 and 50 µm, to better adhere to human tissue and avoid encapsulation.
Years passed, and in mid 2019, some highly textured implants were linked to the development of a rare type of lymphoma, which led to the product being withdrawn from the market.
According to the FDA, an American regulatory body, the cause would be the hyperstimulation of T lymphocytes (the body’s defense cells) resulting from the greater degree of roughness, as well as the release of silicone microparticles in genetically susceptible women. Furthermore, studies have shown that prostheses with higher Ra favor bacterial colonization on the implant surface (biofilm), which would also lead to chronic stimulation of the immune system and the development of lymphoma.
There are several options for dentures on the market, which are evaluated by the surgeon prior to placement. What can change are the selection criteria, which are no longer just aesthetic, that is, the focus is now no longer just the anatomy, the shape of the breast and the prosthesis, and also takes into account the health history of those who intend to to place prostheses, says the surgeon.
“With this new information, we will have another factor for decision. It doesn’t make sense for me to opt for models that will cause a greater autoimmune response in a woman with autoimmune disease. I will look for more biocompatible materials”.
However, Munhoz is emphatic in saying that the prostheses available on the market are biocompatible, otherwise they could not be commercialized. “What we have today is that a certain surface generates a lower autoimmune response that can lead to these three aspects: contracture, lymphoma and silicone disease. Since the immune response is smaller, it has better biocompatibility than the others, which are still biocompatible”, he says.
Over the years, with the popularization of silicone implants, reports of chronic fatigue, intestinal problems, joint pain and depression, among other symptoms, after the implants also increased. Studies found that they were not isolated situations and named the set of symptoms as “Silicone Disease”.
According to rheumatologist Ricardo Krieger, from Hospital Sírio-Libanês, Silicone Disease is one of the manifestations of Asia Syndrome, which means Adjuvant-Induced Autoinflammatory Syndrome, a term that refers to a wide range of substances, such as silicone, which can induce an immune response and, in turn, some clinical manifestation.
“In general terms, it is postulated that adjuvants, such as silicone, chronically stimulate the immune system. That’s why it is considered an inflammation, a response against the body’s own antigens in susceptible people”, he says.
The problem can be triggered by the roughness of the implant or even by the surgery itself, since the prosthesis is a foreign body, which when implanted can carry bacteria into the body, inducing a response from the immune system.
Krieger explains that Asia Syndrome is not easy to diagnose, as it has symptoms that can be confused separately. In the latest criteria, proposed in 2019, it is recommended that the diagnosis related to silicone implants take place one month after the procedure. If the patient has symptoms before, it is not considered Asia’s Syndrome, because it does not manifest quickly and may take years.
“There are varied symptoms. It is not a disease in itself, it is a syndrome and involves the involvement of several systems. The person may have muscle pain, tiredness, fatigue, joint pain, tendon and joint or muscle inflammation and affect the nervous system. You can also have complaints such as tingling or changes in sensitivity, especially in the extremities”, he said.