Surgical mesh is a medical device engineered to provide structural support and reinforce weakened tissue, particularly during hernia repair. The mesh acts as a scaffold to bridge the defect in the muscle wall, which significantly reduces the likelihood of the hernia returning after surgery. This reinforcement allows the body’s own healing mechanisms to create a stronger, more stable abdominal barrier. Selecting the appropriate mesh is a complex clinical decision, as various materials and physical constructions offer different performance characteristics for the patient’s long-term outcome.
The Primary Categories of Surgical Mesh
Hernia repair devices are primarily classified as synthetic or biological, based on their origin and fate within the body. Synthetic mesh, which represents the majority of devices used today, is engineered from man-made polymers. It provides permanent, long-term reinforcement to the abdominal wall and is designed to remain in place indefinitely to prevent hernia recurrence.
Biological mesh, also known as bioscaffolds, offers an alternative approach that avoids permanent foreign material. These devices are derived from human cadaveric tissue or animal sources, such as porcine or bovine dermis. Unlike synthetic meshes, biological meshes are designed to be gradually absorbed and remodeled by the body, leaving behind the patient’s own newly grown tissue structure.
Surgeons reserve biological scaffolds for complex cases, such as repairs involving contaminated or infected surgical fields where permanent foreign material is inappropriate. The temporary support allows the body to remodel the area without the long-term presence of synthetic material. This distinction guides the initial selection process before considering specific material compositions.
Common Synthetic Mesh Materials
The most common material in synthetic hernia repair devices is Polypropylene (PP), an inert synthetic polymer. PP is favored due to its flexibility, durability, and robust mechanical strength, providing reliable support. Its chemical inertness provokes a manageable foreign body reaction, which is necessary for the surrounding tissue to successfully integrate with the mesh.
Polyester (PET), or Polyethylene Terephthalate, is another frequently employed material. PET meshes sometimes elicit a slightly more pronounced inflammatory response compared to PP. Despite this, surgeons may prefer PET for specific repairs where its handling characteristics or structural properties are beneficial.
Expanded Polytetrafluoroethylene (ePTFE) offers a unique set of properties, particularly its smooth surface texture. This surface is engineered to be non-adhesive, which is desirable when the mesh must be placed directly adjacent to internal organs like the bowel. By minimizing contact, ePTFE helps reduce the risk of tissue adhesion.
To balance the need for permanent support and reduced adhesion, manufacturers developed composite meshes. These products combine two or more distinct materials, often featuring a permanent structural layer (e.g., PP) and a separate absorbable layer. The absorbable layer typically faces the viscera (internal organs) and acts as a temporary barrier to prevent immediate adhesion, dissolving once the surrounding tissue has healed.
This multi-layered approach allows the permanent polymer to reinforce the abdominal wall while the temporary layer mitigates complications associated with direct contact with the intestines. The composite design optimizes the repair by leveraging the properties of different chemical compositions simultaneously.
How Mesh Structure Varies
Beyond chemical composition, the physical architecture significantly influences how the device performs within the body. One primary structural variation is mesh weight, quantified by the amount of material present per square unit of area. Heavyweight meshes use more polymer, providing maximum mechanical strength, but they can sometimes lead to a noticeable foreign body sensation after implantation.
Lightweight meshes are manufactured with less polymer, making them more flexible and conforming better to the body’s natural movements. This reduced material load minimizes discomfort and chronic pain while still providing adequate structural support for many common repairs. The choice balances the need for maximum strength against improved patient comfort.
Mesh porosity, defined by the size of the openings between the fibers, is another structural characteristic governing the body’s reaction. Macroporous meshes possess large pore sizes, allowing for the rapid infiltration of connective tissue and immune cells. This open structure promotes better tissue integration and may reduce the risk of infection by allowing bacteria to be cleared more effectively.
Microporous structures contain very small openings, which prevent the ingrowth of larger cells and tissue elements. While this creates a more solid barrier, the small pore size can lead to the encapsulation of bacteria, potentially increasing the risk of chronic infection if contamination occurs. Surgeons often prefer macroporous designs to encourage an integrated healing response.
The specific manufacturing technique used to assemble the fibers, known as the knit pattern, also dictates performance. Whether the fibers are knitted, woven, or constructed as a non-woven sheet impacts the mesh’s overall flexibility and bi-directional mechanical strength. A more elastic knit allows the mesh to stretch and move with the abdominal wall, contributing to a more dynamic and comfortable repair.