Pelvic organ prolapse (POP) and urinary incontinence are common conditions that impose substantial physical, social, and economic burdens on aging women. In a population of ambulatory women presenting for routine gynecologic care, 35% and 2% of patients had stage two and stage three prolapse, respectively.¹ The US National Health and Nutrition Examination Survey (NHANES) of noninstitutionalized women aged 20 years and greater found that 2.9% of women reported seeing or feeling a bulge outside the vagina and that 15.7% of women had at least moderate to severe urinary incontinence.² Further, the NHANES report identified that the proportion of women with at least one pelvic floor disorder such as prolapse or incontinence increased incrementally with age, ranging from 9.7% in women 20 to 29 years to 49.7% in those aged 80 years or older.

While nonsurgical interventions for incontinence and POP including pelvic floor muscle therapy, behavioral changes and pessaries are commonly employed, POP and incontinence are among the most common indications for surgery in postmenopausal women. In a seminal article, Olsen et al. estimated that the lifetime risk of a prolapse or urinary incontinence operation in a US health maintenance cohort was 11.1%.³ Later, in another health maintenance organization cohort, Fialkow et al. similarly identified a lifetime risk for surgery as 11.8%.⁴ Estimate for surgery among a managed-care population in Western Australia was 19%.⁵ Unfortunately, the need for repeat surgical repair is also high with approximately 13% to 29% of women undergoing an additional operation within five years of their primary surgery.^3,6

Surgeries for prolapse treatment may be categorized as obliterative or reconstructive. Obliterative procedures such as a colpocleisis or LeFort partial colpocleisis close off the vaginal canal either completely or partially and elevates the pelvic viscera back into the pelvis; these procedures are usually reserved only for elderly women who are no longer sexually active and who are often medically compromised. An obvious disadvantage to these procedures is the elimination of the future possibility of vaginal intercourse.

For most women with symptomatic POP, reconstructive surgery will be chosen as the means to correct the prolapsed vagina while maintaining—or improving—sexual function and relieving associated pelvic floor symptoms. These reconstructive surgical procedures may be approached vaginally, abdominally, or laparoscopically, and all may utilize graft materials to replace or augment native tissue. National or insurance databases suggest that the preferred route for primary prolapse repair is vaginal, with approximately 80% to 90% of operations performed vaginally.^3,7 Compared with open abdominal procedures, a vaginal approach generally has shorter operating time, shorter length of admission, less patient morbidity, and less cost. On the other hand, traditional vaginal approaches to prolapse repair often have higher rates of recurrent prolapse than an abdominal sacral colpopexy, a mesh repair with an abdominal approach.⁸ Randomized trials of various anterior colporrhaphy techniques with and without use of mesh for repair of anterior vaginal prolapse report only a 40% to 60% success rate in absence of mesh.^9,10 In an attempt to take advantage of the benefits of the vaginal route for prolapse correction while improving the efficacy and longevity of repair to more closely replicate those reported with abdominal routes, transvaginal use of graft materials has become more common in the past decade.

This chapter will review the indications for grafted repairs of prolapse and stress urinary incontinence and will characterize the various types of graft materials used in reconstructive pelvic surgeries. While the efficacy and potential complications related to graft use will be summarized for stress urinary incontinence procedures and abdominal sacral colpopexies, more attention will be focused on the more controversial transvaginal placement of graft materials for prolapse repair.

The quality of evidence supporting graft use in pelvic reconstructive surgery varies with the condition being treated, the specific surgical procedure chosen, and type of graft used. Efficacy of synthetic material in the abdominal repair of vaginal vault prolapse (sacral colpopexy) and anti-incontinence procedures such as full length midurethral slings is robust. Less evidence exists to guide when and in whom biologic or synthetic grafts should be used for transvaginal prolapse repairs. Some authors suggest, based on low quality of evidence, that contraindications to graft use include history of pelvic radiation or other patient conditions that may compromise the pelvic floor vascular supply, poorly controlled diabetes, severe vaginal atrophy, frequent or regular systemic steroid use, active vaginal infection, and heavy smoking. Common indications given in support of use of graft augmentation include patients with weak or suboptimal autologous tissue, history of connective tissue disorders, and history of medical conditions that may increase the risk of a failed repair including chronic obstructive pulmonary disease or chronic straining with bowel movements.

Grafts are also used for reconstruction of a neovagina, which may be indicated from either hereditary conditions or a significantly foreshortened vagina from previous vaginal surgeries. Typically, autologous skin grafts or biologic grafts are used for neovagina procedures. The use of biologic grafts for vesicovaginal and rectovaginal fistula repairs has also been described when repairing fistulas that are recurrent, related to previous radiotherapy or ischemic injury, large, and/or associated with difficult closure, or when the surgeon suspects there is poor tissue quality or vascularization, although most of the data are limited to case series and case reports. Finally, biologic and autologous graft use has also been described in reconstructive cases for bladder exstrophy to allow a tension-free reconstructive closure.

A wide variety of grafts and meshes are available to clinicians for use in pelvic reconstructive surgery, although the majority has not been evaluated with rigorous randomized surgical trials. Both biologic (“natural”) and synthetic grafts have been used successfully for abdominal hernia repairs, and mesh-augmented repairs have become the “standard of care” for inguinal hernia repairs with good evidence of superior success rates compared with suture repair alone. Although there is much information involving grafts in the surgical repair of abdominal wall hernias, there is little information supporting its use in pelvic reconstructive surgery. In addition, there is very limited quantitative or comparative data to guide the selection of a specific graft material for pelvic reconstructive repairs, especially for POP. Table 22-1 presents marketed grafts and characteristics.

Graft materials can be classified as either biologic or synthetic. The “ideal” graft should be inert, noncarcinogenic, nonallergenic, noninflammatory, able to be sterilized, convenient, affordable, and safe as well as effective for improving outcomes.¹¹ It should persist long enough for incorporation of the surrounding native tissue and resist mechanical stress or retraction. Specifically for POP surgery, the ideal graft would help restore normal anatomy and vaginal function and improve the durability of the repair while still allowing important properties of the vagina for function, including dispensability and flexibility. Unfortunately, no graft material yet devised meets all these criteria.

Biologic Grafts

Biologic grafts may be of human or animal origin. Theoretical advantages of biologic grafts over synthetic meshes may include in vivo tissue remodeling, which in turn is thought to lead to reduced erosion rates. This occurs because the biologic grafts are of histologic similarity to the native tissues in which they are placed. Potential limitations include limited supply, cost, inconsistent tissue strength, and potential concern of transmission of infectious diseases from the host/donor to recipient. In addition, tissue processing of the graft may impact the tensile strength and ultimate efficacy. Biologic grafts may be preferred over synthetic grafts in women at higher risk for erosion including those with severe vaginal atrophy, history of local radiation, immunosuppression, or history of prior synthetic graft erosion.

Biologic grafts are classified into three subgroups: autografts, allografts, and xenografts. Autografts, or grafts derived from another site in the body from the same individual, include fascia lata, rectus fascia, or skin grafts. Autografts require intraoperative harvesting that increases operative time and perioperative morbidity. They can also be associated with incisional hernia and poor cosmesis at the harvesting site. Typically, no processing is required. Because the graft is well incorporated into the native tissues, foreign body reaction is less likely, but the durability and long-term efficacy may be limited because the graft is eventually replaced with the patient’s own connective tissue.

Allografts are tissues transplanted from one individual to another of the same species with a different genotype. They are designed to provide a scaffold of acellular material consisting mainly of proteins, collagen, elastin, and other growth factors to facilitate the infiltration and subsequent replacement of the graft tissue with regenerated functional host tissue. Examples of allografts include dura matter, cadaveric rectus sheath, or fascia lata. Donors are serologically screened for transmissible infectious organisms prior to allograft harvest, and graft specimens require preparation to decrease graft antigenicity and potential disease transmission. The risk of HIV transmission from allografts has been estimated at one in 1.67 million and there have been no reported cases of transmission in the literature.¹² Preparation techniques include ethanol extraction, high-pressure agitation, freeze-drying (lyophilization), and gamma irradiation. When processed by ethanol extraction, dermis and cadaveric fascia have shown similar tensile properties to fresh, unprocessed tissue.¹³ Studies suggest that freeze-drying is associated with weakened graft materials and higher failures than solvent-dehydrated fascia. Cross-linking is another preparation technique but may be associated with encapsulation.

Xenografts are tissues harvested from one species and transplanted into a different species. Similar to allografts, they are designed to provide a scaffold to facilitate host tissue regeneration and require tissue processing using similar methods. Examples include porcine dermis, porcine small intestine submucosa, bovine pericardium, and bovine dermis. Xenografts are commonly cross-linked to delay reabsorption after implantation. Cross-linking is thought to increase the success of graft augmentation procedures, although data are lacking to support this. In summary, there is wide variation in the nature of biologic graft materials and their processing; the clinical impact of this variability is unclear.

Synthetic Meshes

Similar to biologic grafts, there are a variety of synthetic mesh materials with different characteristics, including composition (monofilament vs multifilament), flexibility, pore size, surface properties (coated vs noncoated), and architecture (knit vs woven). Theoretical advantages of synthetic meshes over biologic grafts include the lack of potential infectious disease transmission, higher tensile strength, and availability. Synthetic meshes do not require harvesting, decreasing operative risks.

Synthetic meshes can be absorbable or nonabsorbable. Absorbable implants promote fibroblast activity and have a lower risk of erosion or infection compared with nonabsorbable meshes. Examples of these include polyglycolic acid and polyglactin 910. Once implanted, mesh absorption begins with macrophage activation and recycling of by-products into new collagen fibers.¹⁴ Similar to biologics, a theoretical disadvantage of absorbable meshes is that there is loss in tensile strength over time, potentially leading to a less durable repair.

Nonabsorbable synthetic meshes have the theoretical advantage of permanency at the expense of increased risks of infection, erosion into surrounding viscera, vaginal exposure, and pain. They are commonly classified based on pore size and filamentous nature. Meshes of pore size greater than 75 μm are considered macroporous, whereas those less than 10 μm are considered microporous. Pore size is important because it determines which cells can enter the mesh and thus determines the risk of mesh infection and fibrous ingrowth. For example, most bacteria are less than 1 μm in diameter, whereas macrophage and granulocytes are greater than 10 μm in diameter. Studies suggest that in order to allow entry of important fibroblasts, macrophages, blood vessels, and collagen fibers, pore size needs to be 75 μm or greater.

The filamentous nature of the mesh is also important. Synthetic meshes are composed of monofilament or multifilament materials. Multifilament materials have interstices within the filamentous fibers that are less than 10 μm. In theory, these spaces are large enough for bacteria to traverse, but would prevent host immune cells to penetrate, forming a favorable environment for bacterial colonization and possible infection.

Based on pore size and filamentous nature, nonabsorbable synthetic meshes are classified as types I to IV (Figure 22-1)¹⁵ as follows:

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  Type I: macroporous and monofilamentous (eg, polypropylene):

  
  
  
  
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    – Theoretically, the best type of implant for reconstructive pelvic surgery as it allows infiltration of host immune cells

  
  
  
  
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  Type II: microporous in at least one of three dimensions and multifilament (eg, expanded polytetrafluoroethylene):

  
  
  
  
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    – Greater foreign body reaction and erosion due to smaller pore size

  
  
  
  
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  Type III: macroporous with microporous and multifilamentous components (eg, polyester):

  
  
  
  
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    – Greater foreign body reaction and erosion due to smaller pore size

  
  
  
  
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  Type IV: submicronic (pore size <1 μm):

  
  
  
  
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    – Not currently used for reconstructive pelvic surgery

  
  

Many varieties of meshes are available, all with purported advantages of decreased mesh burden by manufacturers, although in vivo and ex vivo scientific evidence is scarce. One study compared tensile testing of five currently available full-length synthetic nonabsorbable meshes marketed for prolapse repair and reported that newer generation meshes were less stiff but had irreversible deformation at significantly lower loads.¹⁶ The impact of ex vivo tensile strength and mesh properties on clinical outcomes remains unclear.

Composite Meshes

Composite meshes are meshes that have two distinct surfaces, which can include synthetic and biologic components, or two different synthetic components. There is even less evidence regarding the utility of composite meshes in pelvic reconstructive procedures.

Approval and Clearance Process for Grafts in Pelvic Reconstructive Surgery

An understanding of the availability, usefulness, and utility of grafts in pelvic reconstructive surgery would not be complete without a discussion about the approval and clearance process required for new medical devices. In the United States, the Food and Drug Administration (FDA) oversees drugs and medical devices as well as foods, vaccines, biologic products, cosmetics, radiation-emitting products, tobacco products, and animal and veterinary products. The FDA’s Center for Devices and Radiologic Health (CDRH) is responsible for regulating firms that manufacture, repackage, relabel, and/or import medical devices sold in the United States.

The majority of medical devices are not “FDA approved”; rather they are “FDA cleared” through the 510(k) clearance process, also known as premarket notification process. Through this process the device is found to be equivalent to a predicate device, and premarket testing is not required. Thus, many of the grafts available on the market for the treatment of prolapse and incontinence were cleared for use in this manner and were not tested in humans prior to marketing. This clearance process was created to support innovation and is much less costly than the approval process for devices.^17,18

Specifically for grafts in pelvic reconstructive surgery, the majority of currently available grafts can be linked back through the 510(k) clearance process to the predicate device, the ProteGen^® sling. The ProteGen^® sling was cleared through the 510(k) in 1997, claiming substantial equivalence to three marketed grafts previously cleared for abdominal hernia repairs. There were no independent animal or human testing or efficacy data for the ProteGen^® sling and the material had not previously been used for urologic procedures. Over 300 adverse events were reported after the first year and in January 1999, and the product was recalled and removed from the market. However, the subsequent grafts that were cleared based on this predicate device were not impacted based on this recall and remain on the market.

In 2011, secondary to increased voluntary reporting to the FDA regarding adverse events associated with the use of graft materials in the treatment of POP and urinary incontinence, the FDA held an advisory panel meeting. The outcome of the meeting resulted in the reclassification of grafts used for vaginal treatment of prolapse so that they require clinical data regarding their safety and efficacy, and currently marketed products have a limited time period to provide postmarket data regarding the safety and efficacy. For first-generation full length midurethral slings, the panel felt that there were adequate data supporting their use and that these devices need not be reclassified, and that future devices can use them as a predicate. This represents a radical change in the way new products will be introduced to the market for the care of patients and will hopefully lead to fewer complications and better data regarding their use without stifling innovation.