String (Polypropylene) Breast Implants: Why They Were Banned: String breast implants (polypropylene) caused continuous, uncontrolled growth and were withdrawn globally. Learn what they were, their documented risks, and other banned devices.
Key Takeaways
- String (polypropylene) breast implants were experimental devices made from a braided polypropylene core that caused continuous breast growth by absorbing fluid.
- They were never FDA-approved and were withdrawn from international markets by the early 2000s due to uncontrolled growth, tissue damage, and serious complications.
- Unlike standard silicone or saline implants, string implants caused ongoing enlargement — patients grew larger indefinitely without additional surgery.
- Several other breast implant types have also been withdrawn or banned globally, including soy oil (Trilucent) implants and PIP silicone implants.
- All currently FDA-approved breast implants in the US (Allergan, Mentor, Sientra, Motiva) are silicone shell devices with gel or saline fill — none use polypropylene.
What String Implants Were
String breast implants — also called polypropylene string implants — were an experimental breast implant design developed primarily by Dr. Gerald Johnson in the 1990s. Unlike conventional breast implants, they did not contain a fixed volume of gel or saline.
Instead, they consisted of a braided polypropylene string (a medical suture material) housed in a silicone shell. The polypropylene was deliberately left exposed or semi-exposed to body fluid. The unique and dangerous property of polypropylene is that it is hygroscopic — it continuously absorbs fluid from surrounding tissue.
How Polypropylene Caused Continuous Growth
The mechanism was straightforward and the consequences dramatic. As polypropylene absorbs body fluid over time, the implant volume expands. Unlike a fixed implant that reaches a stable size after settling, polypropylene string implants continued to grow indefinitely as long as they remained in the body.
- Patients who received string implants grew progressively larger over months and years without any additional surgical intervention.
- Some patients reportedly achieved extremely large sizes (multiple kilograms per implant) as the polypropylene absorbed more fluid.
- The rate of growth was unpredictable and could not be controlled or stopped without implant removal.
- Tissue stretch and damage accumulated with ongoing growth, making eventual removal surgery significantly more complex.
String implants have no current FDA-approved equivalent. All claims about "continuously growing" or "self-expanding" breast implants available today should be treated as misinformation or fraud. No approved device works this way.
Why They Were Banned
String implants were never FDA-approved for use in the United States. They were implanted primarily outside the US — in South America, Eastern Europe, and through medical tourism — during the 1990s and early 2000s. They were withdrawn from international markets for several reasons:
- Uncontrolled growth: There was no way to predict or limit how large patients would become.
- Tissue destruction: The continuous expansion caused progressive thinning and damage to breast tissue and skin, with patients eventually developing severe deformities.
- Surgical complexity: Removing string implants after significant growth became extremely difficult, with high rates of surgical complication.
- No clinical benefit over alternatives: Conventional implants provided predictable, stable results without these risks.
- Regulatory action: Regulatory bodies in countries where they were being implanted — including Brazil and the UK — effectively banned them through enforcement actions and physician sanctions.
Documented Complications
Published case reports and series documented the following in string implant patients:
- Massive breast hypertrophy (sometimes reaching 10–20+ kg per breast)
- Severe skin and tissue thinning
- Chronic pain and posture problems from implant weight
- Implant rupture with polypropylene material contaminating surrounding tissue
- Complex removal surgery requiring extensive reconstruction
- Psychological trauma from uncontrolled body change
Other Banned and Withdrawn Implants
String implants are not alone in the history of problematic breast implants. Other notable withdrawals include:
Trilucent (Soy Oil) Implants
Developed in the 1990s, Trilucent implants used a triglyceride (soy oil) fill as an allegedly more natural alternative to silicone. They were withdrawn in the UK in 1999 after studies showed that ruptured implants released oxidized fatty acids into surrounding tissue, causing inflammatory reactions and tissue damage. An estimated 4,000+ women in the UK had to have them removed.
PIP Silicone Implants (Poly Implant Prothèse)
Arguably the largest breast implant scandal in history. French manufacturer PIP used non-medical-grade industrial silicone (not approved for implant use) in approximately 300,000 implants sold across 65 countries between 2001 and 2010. PIP implants had rupture rates approximately twice the industry average. The French founder was later convicted of fraud. Many countries recommended removal and replacement of PIP implants.
Allergan BIOCELL Textured Implants (Recalled 2019)
Not banned, but voluntarily recalled worldwide at FDA request due to disproportionate association with BIA-ALCL. BIOCELL had a macro-textured surface associated with the majority of global BIA-ALCL cases. All currently sold Allergan implants are smooth-surfaced.
What's Used Instead Today
All four FDA-approved breast implant manufacturers (Allergan/Natrelle, Mentor, Sientra, Motiva) produce devices with stable, predictable volumes using silicone elastomer shells and either cohesive silicone gel or saline fill. These devices are subject to rigorous FDA pre-market approval and ongoing post-approval surveillance studies.
For a full comparison of currently approved options, see our silicone implants guide and the FDA safety data page.
Frequently Asked Questions
References & Sources
- A three-year prospective study of polypropylene string implants. Plastic and Reconstructive Surgery (2001) . View source ↗
- Trilucent breast implants: advice for women. MHRA (2000) . View source ↗
- FDA's Analysis of Adverse Event Reports: Breast Implant-Associated Lymphomas. FDA.gov (2022) . View source ↗
This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult with a board-certified plastic surgeon or qualified healthcare provider before making any medical decisions.