Polypropylene mesh is known to fail, erode, and need to be removed if it is used in hernia mesh procedures. Nevertheless, it continues to be the substance of choice for hernia mesh products, largely because hernia mesh manufacturers can get them approved by the U.S. Food and Drug Administration (FDA) easier. As a result, thousands of hernia mesh lawsuits have been filed to recover compensation for the chronic pain and medical complications that polypropylene mesh products have caused.
- 1. What is polypropylene mesh?
- 2. The defects of polypropylene hernia mesh
- 3. Why is polypropylene mesh still used?
1. What is polypropylene mesh?
Polypropylene mesh is a medical implant made of interwoven threads of polypropylene plastic. The mesh is designed for use in hernia surgeries.
Hernias are eruptions of internal tissue through weakened muscles that contain it. Surgeons can correct a hernia by making an incision near the site of the hernia and pushing the tissue back through the weakened muscle to where it belongs. Then, the surgeon can implant a hernia mesh device on the site of the hernia. This hernia mesh is designed to create scar tissue on the weakened muscle, which grows into the pores of the mesh, creating ingrowth. The scar tissue, together with the mesh implant, strengthens the weakened muscle enough to prevent another hernia in the same spot.
The vast majority of hernia mesh products are made of the plastic polypropylene. Polypropylene is an inexpensive and common type of plastic that is used in everything from chairs to containers. It is popular because it becomes rigid with far less pressure in the manufacturing process, reducing the cost of production.
However, polypropylene oxidizes, or erodes when it comes in contact with oxygen. This trait of polypropylene is at the heart of its problems when it is used as a hernia mesh implant.
2. The defects of polypropylene hernia mesh
When polypropylene is used in hernia mesh implants, those implants are prone to eroding over time. This erosion happens because the chemical nature of polypropylene makes it oxidize. When a polypropylene hernia mesh erodes, it deteriorates and fails, causing chronic pain and other medical problems. However, because hernia mesh products are designed to create scar tissue that grows into the mesh's pores, removing the device is nearly impossible.
Medical device manufacturers have known about polypropylene's tendency to erode inside the human body. In fact, when the chemical company Chevron Phillips learned that its polypropylene was being shaped into hernia mesh products and implanted in human beings by the company Boston Scientific, it refused to keep selling its polypropylene at any price.1 Chevron Phillips wanted no part of the business because it knew that polypropylene would deteriorate inside the body and cause serious problems.
2.1 Polypropylene erosion and failure
Polypropylene slowly erodes when it touches oxygen, a process known as oxidization. While polypropylene can be treated with antioxidants, these additives do not prevent the erosion – they merely slow it down.
The muscles and blood that surround implanted polypropylene mesh are all rich in oxygen, drastically increasing the odds that the polypropylene mesh will erode over time.
When polypropylene erodes, it contracts and shrinks. Because the erosion process takes a long time, and because the polypropylene mesh is designed to quickly create tissue ingrowth to strengthen the weakened muscle that allowed the hernia, the polypropylene is likely to have become encased in the muscle before it begins to shrink. When it does shrink, then, it will pull on the surrounding muscle, creating pain and discomfort. The pain can become intense and chronic if nerves have also become part of the ingrowth.
2.2 Problems removing polypropylene mesh
When polypropylene mesh erodes and fails and causes chronic pain, usually the best thing to do is to remove it. However, precisely because the mesh is designed to create scar tissue and ingrowth, removing a hernia mesh device that was implanted more than a few months ago can be nearly impossible.
Surgeons who perform hernia mesh removals often find that the mesh implant is so buried in the underlying muscle and so covered with scar tissue that it is impossible to remove it all at once. Instead, they have to pull shreds of the implant out, one at a time. The process is extremely traumatizing for the muscles involved, and causes lots of inflammation.
3. Why is polypropylene mesh still used?
In spite of the dangers that it creates, the plastic polypropylene is still used in nearly all of the hernia mesh products that are implanted, today. A big reason for the use of polypropylene is in how the FDA approves medical devices and implants.
The FDA only began regulating medical implants in 1976. Implants that were in use before 1976 were allowed to continue to stay on the market without the FDA's intervention. One of those devices was a hernia mesh product that was based on polypropylene.
Worse, the FDA's regulation of medical implants came with a giant loophole: Medical devices that were “substantially similar” to those in use before 1976 went through an expedited approval process called 510(k) clearance. Medical device manufacturers aimed to have their devices go through the 510(k) clearance process because it did not require them to conduct the costly and lengthy premarket trial on humans that the FDA's normal approval process required.
Because there was already a polypropylene hernia mesh product being used before 1976, medical device companies continued to use polypropylene in their mesh implants so they could claim the new implants were “substantially similar” to a pre-1976 implant. This allowed mesh makers to dodge the FDA's strict approval process and go through its 510(k) clearance process, instead. As a result, polypropylene continues to be used in hernia mesh products so companies can avoid the clinical testing that a different implant would require.
See Scott Pelley, “Gynecological Mesh: The Medical Device that has 100,000 Women Suing,” CBS News (April 17, 2019).