A hernia is a medical condition where an internal organ or fatty tissue bulges through a weak spot in the surrounding muscle or tissue wall. These defects occur most commonly in the abdomen or groin area, often resulting in a noticeable lump or bulge under the skin. Hernia repair is one of the most frequently performed surgical procedures globally. Surgical mesh has become a standard tool in modern repair techniques, designed to reinforce the weakened abdominal wall and provide a lasting solution.
The Structural Role of Surgical Mesh in Repair
The introduction of mesh fundamentally changed hernia repair by establishing the concept of “tension-free” surgery. Older methods, such as the Bassini or Shouldice repairs, relied on stitching the patient’s native tissue together across the defect. This tension contributed to high recurrence rates, sometimes exceeding 10%.
Mesh acts as a permanent or temporary scaffolding to bridge the gap in the abdominal wall, eliminating the need to forcefully close the defect with sutures. This prosthetic material encourages the body’s own connective tissue, primarily collagen, to grow into its structure, creating a strong, integrated layer of reinforcement. By removing tension, the mesh significantly reduces the chance of the hernia returning, with modern recurrence rates typically falling between 2% and 4%.
Classifications and Materials of Hernia Mesh
Surgical mesh is broadly categorized by its composition and structural properties. Synthetic mesh, made from man-made polymers, is the most common type and is typically non-absorbable, remaining permanently in the body to provide strength. The most frequently used polymers include polypropylene (PP), which promotes tissue ingrowth, and expanded polytetrafluoroethylene (ePTFE), which is more inert and often used for its smooth, anti-adhesive surface.
Pore Size and Composite Mesh
Synthetic meshes are further classified by pore size. Macro-porous meshes have pores larger than 75 micrometers to facilitate robust tissue integration. Conversely, micro-porous meshes, often made of ePTFE, restrict tissue ingrowth, which can lower the risk of adhesion but may reduce the strength of the final repair. Some repairs utilize composite mesh, which combines materials like PP and ePTFE in a layered design, often with an absorbable coating to prevent bowel adhesion immediately following surgery.
Absorbable and Biological Mesh
Absorbable meshes provide temporary support and degrade over time, leaving only the patient’s newly formed tissue behind. Synthetic absorbable materials, such as polyglycolic acid, are used when a permanent material is not desired or when the surgical field is contaminated. Biological mesh is derived from processed animal tissue, like porcine or bovine dermis. These are often selected for repairs in contaminated or infected areas where a permanent synthetic material would carry a high risk of deep infection.
Surgical Approaches for Mesh Placement
The method used to place the mesh depends on the type of hernia and the surgical approach selected: open or minimally invasive.
Open Repair
Open hernia repair involves a single incision made directly over the hernia site, allowing the surgeon direct visualization of the tissue layers. The mesh is secured to reinforce the abdominal wall, often in a position known as Onlay (on top of the outer muscle layer) or Sublay/Preperitoneal (underneath the muscle layer but outside the abdominal cavity).
Minimally Invasive Repair
Minimally invasive techniques, primarily laparoscopic or robotic surgery, utilize several small incisions to insert a camera and specialized instruments. The two main laparoscopic methods for groin hernias are Transabdominal Preperitoneal (TAPP) and Totally Extraperitoneal (TEP) repair. Both TAPP and TEP place the mesh in the preperitoneal space, a layer between the muscle and the inner lining of the abdomen. These procedures are associated with less immediate post-operative pain and a quicker return to normal activities compared to open techniques.
Potential Post-Operative Concerns
While mesh repair is highly effective at preventing recurrence, the introduction of a foreign material carries a risk of specific post-operative issues. Chronic pain, sometimes referred to as post-herniorrhaphy neuralgia, is the most common long-term complaint. It is often caused by nerve entrapment or inflammation in the area where the mesh was placed, and a small percentage of patients experience persistent discomfort lasting months or years.
Infection is a risk with any implant, and contamination of the synthetic mesh can lead to a persistent, difficult-to-treat condition requiring intravenous antibiotics and surgical removal. Other potential issues include the formation of adhesions, which are bands of internal scar tissue that can cause the mesh to stick to nearby organs, sometimes resulting in a blockage. Less frequently, the mesh may contract or shrink after implantation, with some materials like ePTFE having reported shrinkage rates up to 40%, or it may migrate from its original placement site.