A hernia mesh is a specialized medical device used during hernia repair surgery to provide internal support to weakened or damaged tissue. A hernia occurs when an organ, such as the intestine, pushes through the muscle wall meant to contain it, and the mesh is implanted to reinforce that defect. This reinforcement helps reduce the likelihood of the hernia recurring, which is a common problem when surgical repair relies only on stitching the patient’s native tissue back together. The materials are selected for their mechanical strength and ability to be accepted by the body, impacting how the mesh integrates and whether the support is temporary or permanent.
Permanent Synthetic Mesh Materials
The most frequently used materials for long-term hernia repair are non-absorbable polymers designed to remain in the body indefinitely. These synthetic materials must be stable and inert, meaning they resist degradation by the body’s biological processes over time. The industry standard for permanent support is Polypropylene (PP), a durable, flexible plastic polymer known for its high tensile strength. When implanted, polypropylene provokes a localized, controlled inflammatory response that encourages the patient’s tissue to grow into the mesh structure, securing it firmly in place for a lasting repair.
Polytetrafluoroethylene (PTFE), often used in its expanded form (ePTFE), is another common permanent material. This polymer is extremely inert, leading to a minimal inflammatory reaction and less scar tissue formation compared to polypropylene. ePTFE is often manufactured with a smooth, microporous structure that encourages the body to form a capsule around it rather than growing extensively into the material itself. While this characteristic can reduce the risk of tissue adhesion to surrounding organs, it can also result in a weaker bond to the abdominal wall if not properly secured.
Polyester (PET), also known as polyethylene terephthalate, is a third non-absorbable option. These materials are generally pliable and offer good handling properties for the surgeon during implantation. However, polyester can be susceptible to oxidation and gradual hydrolytic degradation after long periods in the body, potentially leading to a reduction in mechanical strength over a decade or more.
Biological and Absorbable Mesh Materials
In contrast to permanent synthetic meshes, other materials are designed to provide temporary reinforcement and then safely disappear from the body. These temporary options include both synthetic polymers and biological matrices derived from animal tissue. The goal is to allow the patient’s own tissue to heal and assume the full mechanical load of the repair over time.
Absorbable synthetic meshes are typically made from polymers such as Polyglycolic Acid (PGA) or Polylactic Acid (PLA), or a copolymer like polyglactin. These materials break down through hydrolysis, a process where water molecules slowly separate the polymer chains until the material is completely dissolved and safely metabolized by the body. The time for full absorption varies, but these meshes generally maintain their strength for a few weeks to months before beginning to degrade. They are often used in contaminated surgical fields where a permanent foreign body could increase the risk of chronic infection.
Biological meshes are derived from the dermis or submucosa of animals, such as porcine (pig) or bovine (cow) tissue. These tissues undergo extensive processing to remove all cellular components, leaving behind an acellular collagen framework. This structure acts as a bio-scaffold, which the patient’s cells colonize and gradually replace with new, native tissue. Biological meshes are typically reserved for complex repairs, particularly those involving active infection, because the body’s immune system tends to accept and remodel the collagen matrix more readily than a synthetic foreign body.
Material Design and Structural Variations
The effectiveness of a hernia mesh is determined not only by its chemical composition but also by its physical architecture and design. The construction of the mesh fibers is a primary factor, classified as either monofilament or multifilament. Monofilament meshes consist of single, smooth strands woven together, providing large interstitial spaces less likely to harbor bacteria. Multifilament meshes use braided or woven fibers, increasing flexibility and strength but creating tiny crevices where bacteria can hide, making them more susceptible to infection.
Porosity, or the size of the holes in the mesh, is a significant structural consideration that influences tissue integration and flexibility. Meshes are categorized by weight, which is often a proxy for pore size. Heavyweight meshes typically have smaller pores and a higher material density, leading to a more intense inflammatory reaction and stiffness. Conversely, lightweight meshes feature larger pores (generally greater than one millimeter), promoting better tissue ingrowth, reducing foreign material, and resulting in a more pliable repair that better matches the natural elasticity of the abdominal wall.
For meshes placed directly against internal organs, especially the bowel, a barrier layer is often incorporated to create a composite mesh. This coating prevents the raw mesh material from coming into contact with the intestines, reducing the risk of adhesions (internal scar tissues that can lead to complications like bowel obstruction). Common barrier materials include films made of absorbable polymers, such as oxidized regenerated cellulose or specialized collagen layers, which dissolve after the initial healing period while the permanent support layer remains in place.