Hernia mesh is a surgical device used to reinforce weakened tissue in the abdominal wall or other areas where a hernia has occurred. This prosthetic material provides a scaffold to support the repair and reduce the risk of the hernia returning. The mesh itself is not a single product but a diverse category of materials, each selected for its specific chemical and physical properties to suit different surgical needs and patient conditions. The choice of mesh determines the body’s long-term reaction and the durability of the repair.
Permanent Synthetic Materials
The majority of hernia repairs use synthetic materials designed to remain in the body indefinitely. These materials are polymers chosen for their high strength, durability, and biological inertness. They form a permanent scaffold, allowing the patient’s tissue to grow into and around the mesh.
Polypropylene (PP) is the most common material used in permanent mesh, recognized for its chemical stability and resistance to biological degradation. This non-absorbable polymer provides excellent tensile strength. While highly durable, the body’s reaction to the material can sometimes lead to scar tissue formation and mesh shrinkage over time.
Polyester (Polyethylene terephthalate or PET) is another synthetic option known for its flexibility and strength. However, polyester mesh can trigger a stronger inflammatory response in the body compared to polypropylene. This increased inflammation leads to significant fibrosis.
Expanded Polytetrafluoroethylene (ePTFE) is a soft, non-woven polymer that resists tissue ingrowth. The material is often used as a barrier layer in composite meshes to prevent the mesh from adhering to internal organs like the bowel. Unlike PP and polyester, ePTFE primarily induces a reaction of encapsulation by the body rather than tissue integration.
Biologic and Temporary Materials
This category of materials is designed to be temporary or derived from natural sources. They are often reserved for specialized cases, such as repairs in contaminated or infected surgical fields. Their goal is to provide a temporary scaffold that the body can use to regenerate its own tissue.
Biologic meshes are derived from human or animal tissue, commonly dermis. To make them compatible with humans, the material undergoes decellularization. This collagen scaffold acts as a framework that is gradually remodeled and replaced by the patient’s own native tissue over time.
Absorbable synthetic meshes are man-made polymers that are designed to disintegrate and be absorbed by the body over a period of months. These meshes provide initial support, allowing the body to heal and form a strong layer of scar tissue before the material dissolves. They are beneficial in high-risk procedures, such as contaminated surgery, where a permanent foreign body is undesirable.
Material Structure and Design
The performance and biocompatibility of a hernia mesh depend on its physical structure and manufacturing design. These structural variables determine how the mesh interacts with the body’s tissues and its mechanical properties. By adjusting the physical architecture, manufacturers can optimize the mesh for flexibility, tissue integration, and the body’s foreign body response.
The filament type refers to how the polymer strands are constructed into the mesh fabric. Monofilament meshes are made from single, continuous strands of material, which are thought to offer a lower risk of harboring bacteria. Multifilament meshes, conversely, are made from braided or woven strands, which may be stronger but have tiny spaces between the fibers that could potentially increase the risk of infection.
Mesh weight is a measure of the material’s density. Heavyweight meshes use more material and are generally stiffer, providing a strong repair but potentially causing more discomfort and a greater inflammatory response. Lightweight meshes use significantly less material, offering more flexibility and compliance with the abdominal wall movements, which is thought to reduce chronic pain.
Pore size is a design element that dictates the mesh’s ability to integrate with host tissue. Macroporous meshes have large openings, which allow large cells like macrophages and fibroblasts to infiltrate and promote healthy tissue growth into the mesh. Microporous meshes have small pores that prevent this cellular infiltration, which can lead to a more intense foreign body reaction and encapsulation. The design choices regarding filament, weight, and pore size are often combined to create composite meshes that balance the need for strength and durability with the body’s tolerance for the material.