Surgical mesh

The primary function of surgical mesh is to support prolapsed organs either temporarily or permanently. It is most commonly used in hernia surgery within the abdomen, which is required when an organ protrudes through abdominal muscles. Surgical mesh may also be used for pelvic or vaginal wall reconstructions in women and is implemented to add as a growth guide for damaged tissue. Ideally, these implants should be strong enough to survive mechanical loads and actions of whichever body area they become a part of. Hernia surgery Hernia surgery is one of the most common current applications of surgical mesh, in which case it is often called a hernia mesh. Hernias occur when organs or fatty tissue bulge through openings or debilitated areas of muscle, usually in the abdominal wall. Surgical mesh is implanted to strengthen tissue repair and minimize the rate of recurrence. The surgery can be performed laparoscopically (internally) or open with a variety of materials available for prosthesis. Polypropylene (PP) is the most frequently used type of mesh, although it may be uncomfortable for the patient after implantation. Another type that is less utilized in hernia surgery is polyethylene terephthalate (PET), which faces complications because it easily degrades after some years of implantation, erasing the effects of the surgery. Polytetrafluorethylene (PTFE) is used as well, but is manufactured in the form of a foil and has difficulty integrating into surrounding tissue, therefore it loses stability. In hernia surgery, an implanted mesh may be fixated to the surrounding tissue to prevent it from migrating. This may be performed using a variety of different materials, which include sutures, tacks, tissue adhesives, self-fixating meshes, or a combination of these. Specifically in incisional hernia surgery, there is not sufficient evidence to suggest that any of these should be superior to the others. Pelvic surgery Similar to hernia surgery, synthetic meshes may be used for organ prolapses in the pelvic region as well. Pelvic organ prolapse occurs in 50% of women above the age of 50 with a history of one or more vaginal childbirths throughout her lifetime. Mesh surgery can be performed in various areas of the pelvic region, such as cystocele, rectocele, and vaginal vault or uterus. The most commonly used material, as in hernia surgery, is PP, which is considered to have acceptable biocompatibility within the region. It induces a mild inflammatory response but has a tendency to adhere to the viscera. Additionally, the mesh has enough strength to withstand basic actions and tissue behavior in physiological conditions, particularly during tissue regeneration through the mesh itself. The area is subjected to a variety of loads approaching from abdominal contents, pressure from abdominal/diaphragm muscles, and genital organs, as well as respiratory actions. For the average, reproductive-age woman, the pelvis must withstand loads of 20 N in the supine position, 25–35 N in the standing position, and 90–130 N whilst coughing. Any mesh that is implanted in the pelvic area must be strong enough to withstand these loads. == Regulation ==

In 2018, the United Kingdom temporarily halted vaginal mesh implants for treatment of urinary incontinence pending further investigation into the risks and available safeguards. In the United States, the FDA reclassified transvaginal surgical mesh as "class III" (high risk) in 2016, Then on April 16, 2019, the FDA ordered all makers of transvaginal surgical meshes to immediately stop their sale and distribution. == Biocompatibility ==

Mesh implantation will naturally generate an inflammatory response to the inserted mesh, but biocompatibility ranges from how easily it is integrated to how severe the foreign body reaction is. A minimal response includes the formation of fibrosis around the prosthesis (much like in scar tissue formation); this response is generated with the best form of biocompatibility. A physical response triggers an acute inflammatory reaction, which involves the formation of giant cells and subsequently granulomas, meaning that the tissue is "tolerating" the mesh fairly well. Lastly, a chemical response allows for a severe inflammatory reaction during attempted tissue-mesh integration, including fibroblastic cell proliferation. A significant advantage of using nanofibrous mesh is that it can carry far more stem cells than traditional PP mesh, which could improve cell-based therapy for pelvic organ prolapse and regeneration methods. Another important advantage of PVDF is the formation of capillaries after 12 weeks, which is essential for wound healing. The faster neovascularization occurs, the faster tissue can be repaired and regenerated, which decreases the likelihood of exposure or extrusion of the mesh. == Antimicrobial hernia meshes ==

Alongside mesh erosion, mesh migration, and enterocuteneous fistula, mesh-related surgical site infections (SSI) remain a significant healthcare problem. Approximately 60,000 inguinal and ventral hernia repairs become infected annually, with similar numbers in Europe. The pathogenesis behind mesh-related contaminations is mostly due to the patient's skin or mucosa during primary incision and clinical practices. The insertion of medical devices has been found to increase the susceptibility to the uptake of adherent bacteria by a factor of 10,000 up to 100,000. In the case of hernia operations, one-third to two-thirds of the implanted mesh would be contaminated at the point of insertion, although only a small number of them will cause an infection. Many factors affect the chances of an infection incurring on a mesh material, among which the type of the surgical procedure and the location are of the highest importance. For instance, the chances of an infection incurring are 2–4% for an open inguinal repair, but as high as 10% for incisional hernia repair. Laparoscopy carries the lowest infection rate, which generally ranges below 1% and as low as 0.1%. This will then be assessed by CT or MRI, followed by aspiration of fluid and culturing. Staphylococci species, and more specifically S. aureus and S. epidermidis account for approximately 90% for the incurring infections, with a prevalent presence of methicillin-resistant Staphylococcus aureus (MRSA). Gram-negative species such as Pseudomonas sp., Enterobacteriaceae are also commonly found. With multi-species biofilms also commonly encountered. If an infection settles on a mesh, administration of antibiotics is commonly ineffective, due to the blood-mesh barrier, and removal of the mesh will be required for over 40% of the deep surgical site infections. From a material science perspective, a mesh can play a passive role towards antibacterial protection through its architecture, or an active role by combining therapeutics in the mesh's composition. For instance, monofilament meshes have been found to be twice as unlikely to adhere bacteria than multifilament meshes. As a drug delivery system, a hernia mesh can be used to deliver antibiotics, antiseptics, antimicrobials, or nanoparticles. Different techniques can be used to implement the integration of such substances, including dipping/soaking, physical coating, chemical surface functionalization and electrospinning. FDA Approved Antimicrobial Hernia Meshes • MycroMesh and DualMesh Plus by GORE ==See also==