Hernia meshes come in an ever-widening array of materials, coatings, sizes, shapes and styles designed to prevent adhesion, ward off infection and give patients a more natural, comfortable feel. While no one has succeeded in creating the "perfect" mesh, the options available to your general surgeons today are head and shoulders above the bulky, heavyweight meshes of yesteryear. Let's explore how the different prosthetic mesh materials, coatings and weaves contribute to improved hernia repair outcomes.

Permanent mesh materials
There are 3 types of synthetic, permanent hernia mesh materials:

• Polypropylene. Perhaps the most common material used in prosthetic hernia mesh, polypropylene has many advantages and one major disadvantage. On the plus side, the monofilament fibers help prevent bacteria from getting into the mesh, while the increasingly lightweight, open-pore designs of these meshes let blood vessels grow between the fibers, enhancing the rate of healing. Because of these properties, if polypropylene mesh does become contaminated with bacteria, the infection can often be treated with antibiotics instead of additional surgery to remove the mesh.

On the negative side, polypropylene tends to cause a strong inflammatory response, which can lead to scarring, adhesion and loss of tissue flexibility. Manufacturers have tried to counteract this inflammatory response by coating polypropylene meshes with various types of inert materials. We'll get to those in a moment.

• Expanded PTFE. Also known by the brand name Gore-Tex, expanded polytetrafluoroethylene (PTFE) is a solid, impermeable membrane that is not incorporated into the body, as polypropylene is, but encapsulated by it. The non-porous, non-stick, impervious material has a very low adhesion rate. However, because the body encapsulates the material, it tends to make a bigger scar that the patient can feel. Also, if PTFE mesh becomes contaminated with bacteria, white blood cells can't penetrate the material to fight the infection. So when PTFE becomes contaminated, it almost certainly has to be removed.
• Polyester. This braided, multi-filament material is hydrophilic and therefore designed to be well accepted by and better incorporated into the body than polypropylene, with less scarring. As with PTFE, however, it's more difficult to treat infections associated with polyester mesh. If bacteria get into the braiding of the material, white blood cells can't penetrate it and it's almost impossible to sterilize. Most of the time, the contaminated mesh will have to be removed.

Protective coatings
As you can see, there are pros and cons to all 3 types of prosthetic mesh, meaning none of them are completely immune to the risk of inflammation, adhesion and infection. To further prevent these complications and enhance the beneficial properties of the mesh materials, manufacturers offer a variety of coatings, such as titanium and absorbable biological materials, designed to better incorporate the mesh into the body while minimizing adverse reactions.

• Omega-3 fatty acid. A substance that occurs naturally in the body, omega-3 fatty acid is supposed to blunt the potential inflammatory response of polypropylene mesh. The substance also has bacteriostatic properties, which help ward off infection.
• Molecular titanium. Manufacturers have found a way to gasify titanium and use it as a coating for mesh. This is good news because titanium is completely inert, so the body doesn't recognize it as foreign. Titanium-coated prostheses are incorporated well into the body, prevent bowel adhesion and result in less scarring.
• Cellulose. Prevents tissue attachment by creating a protective barrier between the mesh and the abdominal wall.
• Anti-bacterial agents. This is a growing area of development in hernia mesh technology, as manufacturers are beginning to coat or impregnate mesh materials with antibacterial agents. For the more solid meshes, which make it difficult for the body to fight off bacteria naturally, this solution is designed to kill any bacteria that come into contact with the prosthetic, thereby preventing infection and the need to remove the contaminated mesh.

Different weaves and weights
Prosthetic hernia mesh will always be fraught with the risk of infection and adhesion because it's essentially a foreign body that's implanted into the abdomen. One way to reduce these risks is to limit the amount of foreign body that's implanted by using thinner, lighter, more porous mesh.

In the old days, the mesh we used was what we now consider "heavyweight": about 100 grams per square meter. These meshes were constructed with a very dense, thick thread in a very tight weave, which created a stiff piece of material that didn't handle well, didn't incorporate well and didn't feel very comfortable once implanted. But back then the medical community believed that a thick mesh was necessary to survive pressure on the abdominal wall caused by coughing, laughing, sneezing and other factors. Studies have since given us a better understanding of the biomechanical properties of the abdominal wall and shown that lighter meshes can hold up to the pressure.

Today's mid-weight meshes are about 30 grams per square meter with a more open weave — pores greater than 1mm in diameter. With a mesh of this structure, you're implanting much less foreign body, which is safer for the patient because it causes less reaction. Lightweight meshes, at about 16 grams per square meter, are an even better material, but are limited in their tensile strength. So although these lightweight options can be used for the more common inguinal hernia, they aren't ideal for ventral hernia repair.

Absorbable options
To make up for the loss of strength associated with lightweight meshes, some manufacturers will weave absorbable materials with polypropylene or polyester to create a composite mesh that, over time, is partially absorbed by the body. The absorbable material, typically poligleacaprone 25, polylactic acid or a co-polymer of glycolide and lactide, helps to reinforce the strength of the mesh when it's initially implanted. Ideally, by the time the absorbable material disappears, the mesh should be incorporated and healed enough in the body to provide sufficient strength with the permanent material alone. Meanwhile, you've decreased the amount of long-term foreign materials implanted in the body, which helps to reduce the risk of adverse reactions such as adhesions, stiffness and infection.

There are 2 types of mesh that are made up of 100% completely absorbable material: a co-polymer of glycolide and lactide, or polyglycolic acid trimethylene carbonate. These absorbable meshes are designed to be a temporary fix in contaminated surgical fields. When implanted, they allow the abdominal wall to heal, then they are absorbed by the body so as not to become a source of adhesions or infection.

What's the best choice?
One of the ongoing challenges in abdominal hernia repair is the unfortunate fact that the materials we use to treat the condition — primarily prosthetic meshes —have the potential to cause damage themselves by stimulating foreign body reactions that cause adhesions or by becoming a nidus of infection.

The good news is, with their improved designs and innovative materials and coatings, many of today's hernia meshes perform quite well (some better than others) and have a lower risk of adhesion and infection than their heavyweight, unwieldy predecessors. The bad news? If you tried to have an objective, scientific contest to determine the "World's Safest Hernia Mesh," there'd be no clear winner. Most of the research we have is based on animal studies and retrospective analyses. Pretty much every manufacturer is going to claim that their mesh has the lowest risk of complications. Until the undisputed perfect mesh emerges on the scene and blows all the competition away, you and your surgeons are going to have to face the daunting task of assessing the options, understanding their unique characteristics and deciding which solutions would be best for the types of procedures and patients your facility hosts.