Publication:
Surgical Technology International XVI - Hernia Repair
Article title:
Innovations in Ventral Hernia Repair

Contents:

 

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NEW PROSTHETIC

 

Synthetic Meshes
The original three meshes commonly used for hernia repair were polyester, polypropylene (PPM), and polytetrafluoroethylene (PTFE). PTFE was replaced by expanded PTFE (ePTFE) in the 1970s, and during the past 20 to 30 years these three meshes have been the mainstay for repair of VIH. The surgeon should not assume that all meshes within a given category are the same. Each company makes their respective meshes in different ways and, thus, they can act differently depending on the situation. The newer synthetic meshes are all variations and/or combinations of these three meshes. The following is not meant to be an all-inclusive list, but will hopefully cover the basic innovations in mesh.

 

New Polypropylene Meshes (PPM)
PPM comes now in both coated and uncoated forms. The uncoated meshes are for use outside of the peritoneal cavity, whereas the coated meshes are designed for safe use intraperitoneally. The main disadvantage of the original PPM (Marlexâ, Davol, Murray Hill, NJ, USA), is that it is a heavy-weight mesh. This means more foreign body is present than needed for adequate strength of repair and can increase side effects and problems. The intense inflammatory response the mesh incites leads to its incorporation into the host tissues. This response also causes heavy scar formation that can lead to decreased compliance of host tissues as well as shrinkage and contraction of the mesh, which can aggravate the compliance problems and lead to hernia recurrence as the mesh “shrinks.” These heavyweight PPMs such as Marlexâ, Proleneâ (Ethicon, Summerville, NJ, USA), Surgiproâ, (Tyco, Mansfield, MA, USA), Proliteâ(Atrium Medical, Hudson, NH, USA), and others, are over manufactured so that the amount of polypropylene can be reduced without risking recurrence due to inadequate burst strength of the mesh. This has led to the recent introduction of the first lightweight PPM.
Welty and colleagues have been at the forefront in reviewing lightweight PPM.5 They reported a direct correlation with the amount of polypropylene in the mesh and stiffness of the abdominal wall and chronic pain. They compared traditional Marlexâ with a lighter weight mesh made of less polypropylene in combination with absorbable Vicrylâ (Ethicon, Summerville, NJ, USA), Viproâ added to make handling of the mesh easier. The lighter-weight mesh had decreased polypropylene content with much less stiffness of the abdominal wall, increased mobility, and chronic pain (58% vs. 4%). The Vyproâ product is not available in the USA, but similar product, Ultraproâ (Ethicon, Summerville, NJ, USA) is available. It is made up of PPM and Monocrylâ (Ethicon, Summerville, NJ, USA). The Monocrylâ is used to make the mesh easier to use but is absorbable and, thus, all that remains after three months is the less dense PPM. Other companies also are in the process of introducing lighter weight PPM, and soon there should be few reasons to ever use the heavier weight meshes of old because they offer significant side effects without any additional benefit in strength of repair.
The newer PPM can be uncoated or coated with an anti-adhesion barrier. The anti-adhesion barriers vary with the company involved, but what they all have in common is an attempt to limit ingrowth that occurs within that first seven days after implantation. The barrier meshes can be heavy-weight PPM, some are lighter weight, and each should be evaluated for this characteristic. Again, use of the heavier meshes leads to increased side effects, but this may be necessary if an anti-adhesion barrier is required. TiMeshâ (Pfm Medical, Oceanside, CA, USA) is a newer lightweight coated PPM that has been used more in Europe to date than the USA. It is a lightweight (35 g/m2) PPM coated with titanium. Proceedâ (Ethicon, Summerville, NJ, USA) is another lightweight PPM that has Interceedâ (Ethicon, Summerville, NJ, USA) as an anti-adhesion barrier. Some of the barriers are substantial and resist disruption fairly well, whereas others are not so substantial and are more easily torn during both laparoscopic and open use.
To our knowledge, no long-term clinical studies have evaluated the effectiveness of these new-coated meshes. Some isolated Case Reports of second-look operations are available, and some show minimal adhesions, whereas others address significant adhesions. The surgeon must assume that if the barrier is lost, the chance of bowel ingrowth increases. Many studies address adhesion formation when comparing meshes, but what really should be reviewed is true “ingrowth” of the bowel to the mesh, because ingrowth leads to problems, not mere adhesions. Adhesions without ingrowth are not that important with respect to fistula formation and other complications.

 

New Polyester Mesh
Polyester mesh has a long track record, especially in Europe because of the Rives-Stoppa repair. Polyester was used by these surgeons as it is soft, more supple, and does not contract and stiffen like heavy-weight Marlexâ, the only PPM available at the time they developed their technique. A newer type of polyester mesh, Parietexâ (Tyco Healthcare, Norwalk, CT, USA)was recently introduced in the USA after several years of use in Europe. The mesh is available in multiple configurations for inguinal, hiatal, and incisional hernia repair. The fibers are woven in a different way than the older polyester meshes such as Dacronâ and Mersileneâ (Ethicon, Summerville, NJ, USA). In addition, the mesh for VIH repair has a collagen coating to prevent adhesions and can, thus, be placed intraperitoneally. As with the barriers used on PPM, this barrier can be disrupted if treated roughly. Several studies have been done using ultrasound (visceral slide) to evaluate for evidence of post-operative adhesions. Most have shown good results based on ultrasound.6 There have been anecdotal reports of second-look operations, and most show the barrier is effective in preventing ingrowth of the viscera to the mesh. Long-term studies are needed.

 

All New ePTFE Meshes
The original ePTFE was introduced for repair of soft-tissue defects in 1983. Just as with PPM, not all ePTFE is the same, and important for the surgeon to know is the subtle differences between the various products. In 1994, a unique dual-sided mesh was introduced in response to the then new technique of laparoscopic VIH repair. This mesh has one side with large pores that allow fibroblastic ingrowth and the other side that faces the viscera prohibits ingrowth due to a smaller pore size. This type of mesh does not depend on a coating or barrier (that can be disrupted) as with the PPM or polyester meshes. The WL Gore & Associates, Inc., who developed this mesh, was then able to bond chlorhexadine and silver salts to the Dual-Meshâ (WL Gore & Associates, Inc., Flagstaff, AZ, USA), and it became the first and only antimicrobial impregnated mesh (Dual Mesh Plusâ, (WL Gore & Associates, Inc., Flagstaff, AZ, USA) and remains so to this day. Davol has a dual-sided ePTFE mesh (Dulexâ, Davol, Murray Hill, NJ, USA) without antibiotic different in make-up but used in similar situations to the Gore product.

 

Combined PPM/ePTFE Meshes
Davol has taken two of the meshes used most commonly, PPM and ePTFE, and recently combined them in an attempt to take advantage of the best traits of both. The Composixâ (Davol, Murray Hill, NJ, USA), Composix Kugelâ (Davol, Murray Hill, NJ, USA), Composix EXâ (Davol, Murray Hill, NJ, USA), and the Ventralexâ (Davol, Murray Hill, NJ, USA) patches combine various amounts of a heavy-weight PPM on one side for ingrowth with ePTFE on the other side to prevent ingrowth. The Composix Kugelâ (Davol, Murray Hill, NJ, USA) has a memory ring that allows it to spring open readily for easier placement. The smaller patches have less heavy-weight PPM, but the Kugel and large Composix patches have a lot of heavy-weight PPM, and thus, shrinkage, contracture, stiffening, and pain are certainly an issue.

 

Biologic Meshes
During the past five or six years, a number of biologically derived meshes have become available for use of VIH repair. These all have in common taking human or animal tissue, removing the cellular components, and stabilizing the resultant extracellular protein structure to act as a collagen scaffold for fibroblastic ingrowth and collagen depostition. All of these meshes have been brought to the clinical arena of hernia repair without ANY clinical long-term data in hernia repair. The companies are marketing them as long-term solutions in hernia repair, which is not supported as of yet. Franklin and colleagues recently reported good short-term outcomes with Surgisisâ, brand of mesh used laparoscopically in contaminated cases where permanent synthetic meshes are contraindicated.7 Helton and colleagues, in 2005, reported poor results with Surgisisâ (Cook, West Lafayette, IN, USA) in dirty wounds, but satisfactory results in the short term in clean contaminated wounds when used in open VIH repair.8 These meshes rely on native host collagen for long-term success, which may be a mistake when most of these hernia-forming patients have a defect in collagen synthesis that causes their hernia. Allodermâ (Lifecell, Central, NJ, USA) is cadaver dermis and has been used extensively in burn wounds. To our knowledge, no long-term reports in humans are available, and the disadvantage of this biologic mesh is cost and small size such that many pieces have to be sutured together for large hernia coverage. Permacolâ (Tissue Cell Science Labs, Covington, GA, USA) has been used in Europe in plastic, orthopedic, and urologic surgery for some time. It has been introduced recently in the USA. At present, all of these meshes should not be considered as the first choice over a synthetic when a synthetic can be used safely. Longer-term data are essential to better define the role of biologic meshes in hernia repair.

 

 

INNOVATIONS IN UMBILICAL AND EPIGASTRIC HERNIA REPAIR

 

Autogenous repair for these hernias have a recurrence rate of up to 40%. For this reason, only the smallest of defects in the non-overweight patient should be repaired without mesh.9 Many of these patients, especially with the obesity epidemic, are large, and have large hernias, and are best served with a mesh-based repair. As with all ventral hernias, it is most important to have a large piece of mesh behind the defect for long-term success. This is difficult to do with these hernias with the older traditional meshes, because they require a large incision—much larger than the hernia itself—to place them behind the defect.
Until recently, the best way to get a large mesh behind the defect was by doing a laparoscopic repair, and this remains the best option for large defects. However, in the last two to three years, a good option for the majority of these hernias is the new Ventralexâ patch described in the previous section on combination meshes. This mesh is available in a small (4.3 cm) and medium (6.4 cm) size well-suited for the vast majority of epigastric and umbilical hernias. The mesh can be placed intraperitoneally through a small incision, and results in the mesh being behind the defect with a good amount of mesh overlap beyond the hernia borders.
Our technique differs from the one suggested by the company in that the fat is dissected off the fascia to get back into good healthy fascia 3 cm-5 cm from the edge of the defect 360°. Polypropylene “U” stitches are placed at the 12, 3, 6, and 9 o’clock positions to anchor the mesh. The fascial edges are closed over the mesh to protect it from wound problems. The postoperative pain is less than the laparoscopic approach and in more than 130 repairs to date, the only complications the authors have seen are two infections that required mesh removal. The one disadvantage to the repair is that the PPM in the patch is heavy-weight PP, but it is only a small amount and we have not seen any chronic pain problems to date.