PREVALENCE OF URINARY INCONTINENCE AND PELVIC FLOOR RELAXATION

Interest in women’s health care issues and public awareness of stress urinary incontinence (SUI) and pelvic floor relaxation have increased substantially over the past several years. In 2000, an estimated 17 million community-dwelling individuals had daily urinary incontinence in the United States, and an additional 34 million had symptoms of overactive bladder. The costs of urinary incontinence in the United States were recently estimated at $19.5 billion, with an additional $12.6 billion for overactive bladder.¹

A postal survey regarding urinary incontinence involving 29,500 community-dwelling women aged 18 years or older in France, Germany, Spain, and the United Kingdom was recently reported.² Of the women responding, 35% reported involuntary loss of urine in the proceeding 30 days, with SUI being the most prevalent type. Only 25% of the women had consulted a physician, and fewer than 5% had undergone surgery for their condition.

It is estimated that a woman’s lifetime risk of needing a single prolapse surgery by 80 years of age is 11.1%, and the risk of needing reoperation for recurrent prolapse is 29.2%.³ Undoubtedly, as the population ages, life expectancy increases, and the stigma of incontinence and pelvic prolapse is replaced by education, these numbers and their associated costs will rise.

HISTORY OF THE URINARY SLING WITH AUTOLOGOUS FASCIA

In 1907, Van Girodano introduced the concept of the urinary sling for the treatment of urinary incontinence, when he wrapped a gracilis graft around the urethra.⁴ Credit for the first pubo-vaginal sling (PVS) goes to Goebell, who, in 1910, rotated the pyramidalis muscles beneath the urethra and joined them in the midline.⁵ In 1942, Aldridge described the first fascial sling. He used rectus fascia, without muscle, passed through the retropubic space to support the proximal urethra and bladder neck.⁶ Variations on this procedure over the following decades involved attempts to minimize morbidity and obtain suitable fascia from patients with multiple previous abdominal procedures and/or pelvic radiation. Ridley⁷ described the use of fascia lata in 1955, followed by reports from Williams and Telinde,⁸ Moir,⁹ Morgan,¹⁰ and Stanton and associates¹¹ involving the use of synthetic materials with variations on the approach or on anchoring sutures. Using autologous fascia and synthetic materials, these original investigators showed encouraging results, but the outcomes were plagued with urethral obstruction, erosion, fistula formation, and infections.

McGuire and Lytton revived the PVS in 1978 with their series showing an 80% success rate for intrinsic sphincter deficiency (ISD) using rectus fascia tensioned loosely around the urethra.¹² Blaivas and Jacobs modified the procedure by penetrating the endopelvic fascia, as described by Peyrera,¹³ and completely detaching the rectus fascia from the abdominal wall.¹⁴ They also stressed the importance of minimizing tension on the sling and stated that, “in the majority of patients the sling should be placed under no tension at all.” Subsequent studies showed no difference in histologic or performance characteristics between free and pedicle fascia flaps for sling surgery.¹⁵

As the PVS was gaining acceptance, the first reports of poor long-term results from needle suspension procedures were being published. In a landmark study published in 1995, Trockman and Leach’s group monitored 125 patients for a mean of 10 years after a modified Peyrera needle suspension. By questionnaire data, 51% reported that they had SUI, and only 20% reported no incontinence of any kind.¹⁶ The American Urological Association guidelines panel for the surgical management of SUI was published in 1997 and concluded, based on cure/dry rates, that retropubic suspensions and slings were the most efficacious procedures for long-term success.¹⁷

Since these early reports, many authors have published long-term data that attest to the durability of the autologous fascial sling. Morgan and colleagues observed 247 patients with type II and III SUI for a mean of 51 months after autologous rectus sling placement. They reported an overall continence rate of 88% to 91% for type II and 84% for type III SUI. Among those patients with at least 5 years of follow-up, the continence rate was very durable at 85%.¹⁸ Chaiken and coworkers reported on 251 patients with all types of anatomic incontinence treated with an autologous rectus PVS.¹⁹ At a median follow-up of 3.1 years, 73% of patients were cured and 19% were improved. Among the 20 patients with a minimum of 10 years’ follow-up, the cure rate was 95%. Brown and Govier, using autologous fascia lata, monitored 46 patients for a mean of 44 months; 90% reported overall cure of their anatomic component, and 73% described no or minimal leakage requiring no pads.²⁰

The two greatest advantages of the autologous PVS were that all types of anatomic incontinence could be addressed and, if a good result were achieved at 1 year, the result would be durable. Because of these attributes, by the late 1990s most authorities agreed that the PVS using autologous fascia was the gold standard for the surgical management of anatomic incontinence. Unfortunately, harvesting this fascia from the abdominal wall or thigh adds operative time and incurs a risk of hematoma formation, wound infection, and/or hernia formation. Only relatively narrow strips of fascia can be harvested, and even then the patient requires several weeks of recovery time to achieve a normal activity level. In an effort to minimize patient morbidity and yet further improve surgical results, a variety of biomaterials (allografts, xenografts) and synthetic products (absorbable and permanent) have been introduced and are currently being used for the construction of urinary slings and vaginal reconstructions.

HISTORY AND CHARACTERISTICS OF BIOMATERIALS IN PELVIC RECONSTRUCTION

Allografts

Allografts are harvested from a human donor, usually a cadaver, and transplanted into a human recipient. The most common tissues used for pelvic floor reconstruction are fascia lata, dermis, and dura matter. Table 59-1 lists some of the companies supplying these components and their trade names. There are many advantages to the use of allografts or xenografts for pelvic floor reconstruction. Several studies have documented decreased recovery time, length of hospitalization, and postoperative pain using these materials.²¹^–²³ Compared with permanent synthetic materials, allografts carry a lower risk of vaginal extrusion, and, if extrusion does occur, in general the graft does not require removal. Finally, larger-sized grafts for pelvic reconstructive procedures can be obtained easily without incurring additional patient morbidity.

Table 59-1 Allografts and Xenografts

Type	Component	Trade Name (Manufacturer)
Autologous	Rectus fascia
	Fascia lata
	Vaginal wall
Allograft	Fascia lata	Tutoplast (Mentor, Santa Barbara, CA)
		Faslata (Bard, Covington, GA)
	Dermis	Repliform (LifeCell Corporation, The Woodlands, TX)
		Duraderm (CR Bard, Inc., Murray Hill, NJ)
	Dura mater (no longer used)
Xenograft	Porcine small intestine submucosa	Stratasis (Cook, West Lafayette, IN)
	Porcine dermis	Pelvicol (Bard, Covington, GA)
		IneXen (American Medical Systems, Minnetonka, MN)
	Bovine pericardium	(Braile Biomedical Industria, Brazil)

All cadaveric donor materials in the United States are processed by licensed tissue banks regulated by the Food and Drug Administration.²⁴ Cadaveric donors are carefully screened by review of their medical and social history with the family, partners, and friends. Donors are excluded if the cause of death is unknown or the medical history suggests any of the following: hepatitis, bacterial sepsis, syphilis, intravenous drug abuse, cancer, collagen vascular disease, rabies, Creutzfeld-Jakob’s disease (CJD), or significant risk factors for human immuno-deficiency virus (HIV) infection.²⁵ Serologic testing is performed for HIV-1 and HIV-2 antibodies, hepatitis B surface antigen, and hepatitis C antibodies. One of the most significant problems with serologic testing is that false-negative results can occur, because it takes time after the initial infection before the immunologic response is sufficient for serologic detection. The delay can be up to 6 weeks in the case of hepatitis B, and up to 6 months for HIV.^26,²⁷

Tissue processing allows for the removal of most of the cellular content, along with the associated antigens, making donor and recipient tissue matching unnecessary. Additionally, tissue sterilization, while preserving the inherent collagen matrix, is required to eliminate infectious complications and ensure satisfactory graft assimilation. Although the American Association of Tissue Banks has made recommendations, no federally mandated processing techniques for all tissue banks exist. Currently, allografts are prepared using a variety of proprietary processing techniques that vary depending on the vendor.

Various mechanisms are used for cellular destruction and include hypertonic solutions that osmotically rupture cells and destroy bacteria and viruses; oxidative destruction with hydrogen peroxide, which oxidatively destroys most proteins; and isopropyl alcohol to destroy cells, bacteria, and viruses by dissolving the lipids in their cell walls.^28,²⁹ An additional method used for tissue sterilization is gamma irradiation, which kills bacteria by disrupting nucleic acids but does not guarantee sterilization of viruses or prions, even at the American Association of Tissue Banks recommended level of 1500 Gy (1.5 megarads).^27,³⁰

Options for long-term preservation include cryopreservation, freeze-drying (lyophilization), and solvent dehydration. Controversy exists with regards to tissue processing and how it affects tissue strength. Most of the concern regarding processing and storage revolves around two issues. The first is irradiation and how it affects the tensile strength of collagen, and the second is the ice crystal formation that occurs with cryopreservation and the freeze-drying processes and whether they adversely affect the collagen microstructure.^28,^31,³²

Thomas and Gresham found no significant difference in tensile strength among fresh, frozen and freeze-dried fascia lata specimens.³³ Sutaria and Staskin found no significant difference in the tensile strength of fascias that were freeze-dried and gamma-irradiated, freeze-dried alone, or solvent-dehydrated and gamma-irradiated.³⁴ In contrast, Hinton and colleagues found solvent-dehydrated, irradiated fascia lata to be significantly stiffer, with a higher tensile strength than freeze-dried fascia.³² Two studies reported that tissue irradiated after dehydration resulted in significant loss of tensile strength, and the investigators recommended that irradiation be performed before dehydration.^28,³⁵ In an excellent review, Gallentine and Cespedes concluded that “a number of processing techniques are available that may have different adverse affects on the mechanical properties of allografts, but currently no definitive evidence is available that one technique is superior to another.”²⁵

With current federal regulations in place to obtain, process, and store cadaveric materials, the risk of infectious disease transmission is extremely small. As of 1995, approximately 220,000 soft tissue transplants were being performed annually in the United States, and no cases of a transmitted infectious disease had been reported for processed cadaveric fascia lata (CFL) or dermal grafts.²⁴

The risk of acquiring HIV-infected tissue from a properly screened donor is reported to be between 1 in 1,667,600 and 1 in 8 million from banked cadaveric fascia.³⁶^–³⁸ Seroconversion was reported in recipients of solid organs (4 of 4) and unprocessed fresh-frozen bone (3 of 3); however, 0 of 34 patients receiving other tissues, including 3 who received lyophilized tissue, became infected with HIV.²⁶ Still, it is alarming that intact genetic material (DNA segments) was isolated from four commercial sources of processed human cadaveric allografts.³⁹

Prion transmission has gained increasing attention because of the neurodegenerative symptoms that occur in the recipient but not in the host. Prions are proteinaceous pathogens that use a novel mechanism of amino acid transposition to change the protein configuration to a that of a neurotoxic prion protein peptide, leading to cases of neurodegenerative Creutz feld–Jakob Disease. Iatrogenic cases have been reported after many types of procedures, including corneal transplants and dura mater grafting.⁴⁰ It has been described in 43 patients receiving cadaveric dural grafts after neurosurgical or orthopedic procedures, and, for this reason, dura mater is no longer being used as a biomaterial.⁴¹ However, prion transmission has not been described with the use of cadaveric fascia or dermis for anti-incontinence or prolapse procedures. Even though no transmission has been documented in our field, the potential for infectious transmission with these allografts does exist, and all patients need to be informed of the risk before their use.

Xenografts

The most popular xenograft materials used for sling surgery are derived from porcine and bovine sources (see Table 59-1). Being from an animal source, xenografts are readily available and are devoid of the potential ethical issues associated with use of human tissue. The types most frequently used for pelvic reconstruction are porcine dermis and small intestinal sub-mucosa (SIS) or bovine pericardium. The Food and Drug Administration has strict guidelines controlling all phases of their production.⁴²

Fate of Autologous Tissue and Biomaterials

The most significant controversy involving biomaterials is the ultimate fate of the graft material itself, within the host. When autologous rectus fascia or fascia lata is used to construct a urinary sling, the results of these procedures in terms of durability are uniformly excellent.¹⁷^–²⁰ Three studies in the literature examined the fate of autologous fascia in the host. In 1969, Crawford evaluated autologous and frozen fascia lata in rabbits by attaching strips of each from the flank to the posterior abdominal wall.⁴³ After killing the animals and examining the tissue, he concluded that “fresh fascia is living sutures and cadaveric tissue merely provides a bridge for host fibroblasts.” A more recent paper, in 1997, looked at free versus pedicled fascial flaps again in rabbits.⁴⁴ Strips of 7 and 15 mm of each were obtained from the abdominal wall and used to create a urethral sling. The rabbits were killed at 3 months, and all slings were found to be viable with the original histology preserved. The authors surmised that the fascia survives in the early postoperative period by diffusion. Later, neovascularization from the loose connective tissue around the flaps provides long-term vascularity. FitzGerald and colleagues evaluated the histologic appearance of autologous rectus fascial slings that were examined at revision at 3, 5, and 8 weeks for urinary retention and at 17 and 208 weeks for persistent SUI.⁴⁵ They concluded that autologous fascial slings remain viable after implantation. They did note fibroblast proliferation, neovascularization, and some remodeling of the graft, but no evidence of graft degeneration was detected. A linear orientation of the connective tissue and fibroblasts was seen in some areas, whereas other areas had remodeled to form tissue similar to noninflammatory scar.

In contrast, cadaveric fascial allografts have been extensively studied in multiple human models in the orthopedic literature as well as animal models.^43,^46,⁴⁷ With the use of serial biopsies, it was found that there is an initial donor fibrocyte death, which is followed by neovascularization of the graft. Fibroblast migration into the implant is then followed by remodeling and eventually by maturation of the graft.^48,⁴⁹

The maturation of xenografts is similar to that described for allografts. The processed material serves as an acellular mesh or scaffolding, which requires remodeling by the host to end up as a viable graft.

It is this need to “remodel” the graft that appears to be the Achilles heel for many or all of the allograft and xenograft products on the market today. As one examines the surgical results with these materials, it is evident that some patients quickly remodel this material to a strong durable structure. In others, it appears that the scaffolding entirely disappears. Authors have theorized that increasing age, poor vascularity, excessive scarring, diabetes, or the use of steroids can adversely affect the remodeling process; however, studies are lacking, and at this time the discrepancies in outcome are largely unexplained.

SURGICAL RESULTS OF BIOMATERIALS FOR URINARY SLINGS

Allografts

Hanada and associates,⁵⁰ in 1996, and Labasky and Soper,⁵¹ in 1997, were the first to report on the use of cadaveric products for urinary slings. In 1998, Wright and colleagues published the first paper comparing cadaveric allograft fascia lata to autologous rectus fascia.⁵² This series reported on a group of 92 patients undergoing sling procedures over a 28-month period. Fifty-nine patients received a 13 × 2 cm portion of freeze-dried allograft fascia lata, and 33 patients received autologous rectus fascia. With a mean follow-up of 9.6 months for the allograft and 16 months for the autologous fascia, no differences in surgical outcome were found. Chaikin and Blaivas described an early failure of a freeze-dried cadaveric fascia sling in which the holding sutures pulled through.⁵³ In 1999, FitzGerald and associates reported 35 patients who underwent PVS placement using freeze-dried irradiated CFL.⁵⁴ At the time of re-exploration in seven of the failures, “histopathologic analysis revealed areas of disorganized remodeling and graft degeneration, as well as complete absence of the graft in some patients.”

In 2000, Brown and Govier compared 121 consecutive patients undergoing slings constructed with fresh-frozen CFL with 46 earlier patients undergoing the same surgical procedure with autologous fascia lata.²⁰ Although the mean follow-up was longer in the autologous group (44 versus 12 months), questionnaire data demonstrated no significant difference in surgical outcomes. Elliott and Boone, in 2001, reported 12-month follow-up using solvent-dehydrated CFL in 26 patients. Ninety-six percent of patients reported improvement.⁵⁵

In 2001, Carbone and Raz’s group reported on a series of irradiated freeze-dried cadaveric fascial sling procedures with a 40% failure rate and a reoperation rate of 16.9%. At the time of reoperation in 26 patients, they found the allografts to be “fragmented, attenuated or simply absent.”⁵⁶ On the basis of these findings, they abandoned the use of allografts for sling construction. In 2002, O’Reilly and Govier re-examined a group of 121 patients who had slings constructed with fresh-frozen CFL; these patients had been reported earlier to have similar results to those treated with autologous slings.⁵⁷ They identified 8 patients who experienced intermediate-term failure at 4 to 13 months after they had initially been dry. This development was not noted in the autologous sling group, and, on the basis of these findings, they too abandoned the use of fresh-frozen CFL for slings.

In 2005, the debate over biografts continues, but the pendulum clearly appears to be heading away from the use of biografts for construction of urinary slings. Crivellaro and colleagues published a prospective series of 253 patients with 18-month follow-up using human dermal allografts for slings.⁵⁸ They found that 78% of the patients were improved or cured of their incontinence and were happy with their experience. Owens and Winters also looked at human dermal allografts in slings in 25 patients.⁵⁹ At a mean follow-up of 6 months, 68% of the patients were dry, but this rate fell to 32% at a mean follow-up of 14.8 months. They concluded that graft degeneration was the most likely cause of the failures. FitzGerald and coworkers looked at a longer-term follow-up in patients from a previously reported group who had undergone abdominal sacrocolpopexies (67) and/or urinary slings (35) with freeze-dried, irradiated fascia lata. They found that 83% of the sacrocolpopexy patients experienced failure at a mean follow-up of 12 months, and, at the time of reoperation in 16 patients, the graft was still present in only 3 patients.⁶⁰ In 2005, Frederick and Leach reported on 251 patients who had undergone a combined anterior repair/sling procedure for SUI using solvent-dehydrated fascia lata. They found a cure/dry rate of 56% with a cure/improved rate of 76% at a mean follow-up of 24 months. They did note that, of the failures, 56% occurred after 12 months. They concluded the late failures were of concern and are continuing to monitor this group.⁶¹

Xenografts

The two most commonly used xenografts in reconstructive urology are porcine dermis and porcine small intestinal sub-mucosa (SIS). As with allografts, the results for urinary slings are controversial, and there are even fewer published reports, or fewer publications with shorter follow-up.

Porcine SIS gained increased attention after being successfully implanted in a canine model for bladder augmentation without evidence of rejection or shrinkage.⁶² Histologically, the SIS-regenerated bladders demonstrated three separate layers, indicating that a regenerative healing process was occurring rather than a simple replacement with fibroblasts. During the manufacturing process, the serosa, tunica muscularis, and mucosa are removed mechanically from porcine jejunum. Intestinal submucosa is transferred into an acellular collagen matrix which, once implanted, induces local host tissue cell infiltration and is subsequently remodeled within 90 to 120 days. The biomatrix in SIS lacks cellular elements; however, collagen and other growth factors with activities similar to those of transforming growth factor-β and fibroblast growth factor 2 are present. These growth factors may act as signals for local epithelial cells to proliferate, thereby colonizing the graft and leading to tissue healing without scarring.⁶³

Several groups have employed porcine SIS with good short-term results. Palma and colleagues reported that 92% of 50 patients were cured of SUI at a mean follow-up of 13 months without any serious postoperative complications.⁶⁴ Rutner and associates reported on a series of 152 patients undergoing placement of an SIS sling fixed to the pubic bone without bone anchors. Of those patients, 142 (93.4%) remained dry at a median follow-up of 2.3 years.⁶⁵ Intermediate-term failures at 9 and 11 months occurred in 2 patients.

Histopathologic studies in which porcine SIS grafts were biopsied and removed have suggested variable levels of biocompatibility. Implant site biopsies under the vaginal mucosa were taken in three cases of recurrent SUI after PVS using SIS. In all three cases, exceptional biocompatibility was demonstrated, with minimal foreign body or inflammatory reaction.⁶⁶ Ho and colleagues were less enthusiastic about the biocompatibility of porcine SIS.⁶⁷ They noted postoperative inflammatory reactions consisting of erythema and pain in 6 of 10 patients undergoing eight-ply SIS tension-free sling placement. SIS is an attractive material because of its theoretical ability to stimulate local tissue in-growth. Whether this will translate into long-term efficacy and durability remains to be seen.

As for porcine dermis, Arunkalaivanan and Barrington reported a prospective randomized trial of tension-free vaginal tape (n = 74) versus porcine dermis (n = 68).⁶⁸ With a mean follow-up of 12 months (range, 6 to 24 months), they found no difference in success for correcting SUI. In another prospective randomized trial of porcine dermis (n = 34) versus autologous rectus fascia (n = 31), Giri and colleagues demonstrated similar rates of cure and improvement between the two groups but noted significantly less morbidity for the xenograft group.⁶⁹

In contrast, Gandhi and colleagues performed histopathologic analysis of porcine dermis sling specimens in eight patients with urinary retention and two failures.⁷⁰ Variable tissue reactions were seen, suggestive of a vigorous foreign body reaction. In cases of retention, the original graft was mostly intact, with minimal remodeling and tissue in-growth. However, surgical failures revealed minimal graft remnants left within the resected suburethral tissue.

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