Update on suburethral slings for stress urinary incontinence

By Peter L. Rosenblatt, MD, and Samantha J. Pulliam, MD

Two experts review the tension-free vaginal tape procedure that revolutionized SUI treatment, the wide choice of pubovaginal sling types now available, and the latest approach: transobturator slings.

Agrowing number of gynecologic surgeons are using suburethral slings to treat stress urinary incontinence (SUI) in women. In fact, these slings account for one third of the 300,000 procedures performed annually for this indication in the United States. The sling approach has been around since 1907 and has consistently had high success rates, with cure rates of up to 91%.¹ The downside until recently, however, had been that suburethral slings for SUI caused more postoperative complications, including voiding dysfunction, urinary retention, and sling erosion.

These shortcomings prompted many surgeons to reserve them for more complicated cases, such as recurrent SUI and intrinsic sphincter deficiency (ISD). However, the 1996 introduction of the tension-free vaginal tape (TVT) procedure revolutionized the treatment of SUI, opening up a variety of pubovaginal sling options. Our goal is to discuss these options, including synthetic and natural graft materials, as well as the newest development: the transobturator sling approach.

Association guidelines and TVT

In its 1997 clinical guidelines for the surgical management of female SUI, the American Urologic Association (AUA) found that retropubic urethropexies and suburethral slings were the most effective surgical treatments for SUI. They also pointed out that, in contrast, procedures such as needle suspensions and anterior repairs were significantly less successful. The AUA further concluded that surgery can be a first-line treatment for some women with SUI.

Certainly, autologous fascia pubovaginal slings are considered a benchmark for SUI. However, this procedure requires not only additional time for harvesting the fascia, but also large enough suprapubic incisions to suture the sling to the rectus fascia. In introducing the TVT procedure in Europe, Ulmsten developed a new approach to the synthetic sling. The TVT procedure involved synthetic material that did not require suturing—and that wasn't anchored to any tissue by traditional means, such as sutures or bone anchors. The unique nature of the polypropylene mesh enables it to adhere to surrounding tissues with a "Velcro-like" effect, once the surgeon removes the plastic sheaths that cover the mesh. The chief advantage of this property of the material is that it permits the surgeon to make extremely small incisions for insertion of the sling, which is placed without tension at the midurethra, rather than at the bladder neck. For the first time, surgeons had a reproducible, highly-effective, minimally-invasive sling procedure.

Steps in the TVT procedure

To perform a TVT procedure, which may be done under local anesthesia with conscious sedation, make two 5-mm incisions suprapubically and a 2-cm vaginal incision under the mid-portion of the urethra. After minimal lateral dissection, insert the TVT needle paraurethrally and perforate the endopelvic fascia. Next, bring the needle into the retropubic space (maintaining contact with the posterior surface of the pubic bone), and then bring it up through the ipsilateral suprapubic incision. After performing cystoscopy to rule out inadvertent bladder perforation, repeat the procedure on the contralateral side. You then position the sling under the urethra and can adjust it while the patient coughs with a full bladder (Figure 1, bottom).

Once the sling is correctly positioned, remove the plastic sheaths covering the sling, trim the sling arms just beneath the abdominal incisions, and close the vaginal incision. With the introduction of TVT-abdominal guides, the surgeon has the option of passing needles with a "top-down" or "abdominal" approach. After passage to the vaginal incisions, the sling is attached to the abdominal guides and brought up through the suprapubic sites. The remainder of the procedure is identical to the original TVT technique.

TVT's track record

As of the beginning of 2003, with more than 500,000 TVT procedures performed worldwide, study after study has consistently demonstrated the procedure's safety and effectiveness. Recently published 7-year follow-up shows a cure rate of 81.3% with an additional improvement rate of 16.3%.² These results are quite similar to the findings from the same group of patients who've been followed at various intervals since their procedures. The objective cure rates at 1, 3, and 5 years were 91%, 86%, and 84.7%, respectively.^3-5 These consistent results strongly suggest that the TVT procedure is not only effective but durable.

Complications. According to Gynecare, the frequency of complications from the TVT procedure has been extremely low, although there have been reports of serious complications such as bowel and major vascular injury—which fortunately are extremely rare. Earlier manufacturer-reported rates of complications, based on 500,000 patients treated worldwide, were 28 bowel perforations (0.006%), 55 vascular injuries (0.009%), 93 cases of urinary retention, 60 vaginal mesh exposures, 20 urethral erosions, 20 hematomas, and four nerve injuries (Data on file, Gynecare, Johnson & Johnson).

TVT versus Burch. In comparing TVT to open Burch colposuspension in a multicenter randomized trial, researchers recently found that TVT was less costly and more cost effective than open Burch over the 6 months after surgery.⁶ Other investigators reported on an RCT that compared TVT with laparoscopic Burch colposuspension in 72 women with SUI.⁷ Multichannel urodynamic studies showed a significantly higher objective cure rate in the TVT group compared with the open Burch group (96% vs. 77%, respectively) at 1 year. Subjective cure rates were also higher in the TVT group (P<0.03).

Variety of pubovaginal slings

While gynecologists and urogynecologists now have several commercially-available sling procedures to choose from—as reflected in the size of Table 1—most surgeons favor the self-adherent sling material properties that originated with the TVT procedure. The three key differences among the sling kits are the physical properties of the sling material, the direction of needle placement (vaginal or abdominal), and the anatomic path of the sling arms. With so many diverse sling kits out there, the obvious question is: Are there any differences among products that could affect either complications or success rates? The most apparent difference between slings are the physical properties of the synthetic meshes.

TABLE 1
Characteristics of pubovaginal and transobturator slings

Synthetic slings

Most synthetic sling kits use a knitted polypropylene material, although the pore size, microscopic architecture, and elasticity vary, which may influence tissue in-growth, erosion, and infection rates. And the SPARC procedure (American Medical Systems, Minnetonka, Minn.) is no exception. It also employs a polypropylene mesh covered by a plastic passing sheath to support the midurethra, in a manner similar to the TVT procedure. But the SPARC procedure differs from the original TVT in that the needle enters through the abdomen and exits from the vaginal incision, not unlike the approach once used for needle urethropexies. In addition, the SPARC system includes a tensioning suture threaded along the length of the mesh, which helps in adjusting sling tension.

Two other polypropylene mesh sling systems are Uretex (C.R. Bard, Covington, Ga.), which features an introduction needle that can be used with a vaginal, abdominal, or combined approach, and the Advantage system (Boston Scientific Corp, Natick, Mass.), whose unique features include a centering tab for intraoperative manipulation, and a "detanged" mesh (fused bristled mesh edges) at the suburethral portion that's designed to resist deformation of the material.

Recent small head-to-head comparisons of various midurethral slings include a retrospective study of 85 patients. Gandhi and colleagues found that at 14 weeks after surgery, 95.7% of the women treated with TVT were cured, compared with 76.2% of those who'd undergone the SPARC procedure (P=0.062), and the SPARC group also had more bladder injuries.⁸ The authors could identify no intraoperative or postoperative factors to account for these differences. Other investigators, in randomizing 164 women with SUI to either TVT or IVS (Tyco Healthcare Group, Norwalk, Conn.), found that the postoperative objective cure rate was 87% for TVT and 78% for IVS (P=0.76). ⁹ In addition, 6% of the women in the IVS group required intervention for a vaginal foreign body reaction.

Natural slings to thwart erosion

Sling erosion or extrusion is still a concern for many surgeons, even though the current generation of midurethral synthetic slings apparently cause fewer complications than their predecessors. An alternative to synthetic material is the Stratasis TF sling kit (Cook Ob/Gyn, Spencer, Ind.), which uses porcine small intestinal submucosa (SIS) as a suburethral sling. The serrated design of the sling arms enables this natural material to adhere to the patient's tissues without the aid of sutures or other fixation devices, in a manner similar to the self-adherent properties of the synthetic meshes.

After implantation, the SIS material undergoes a remodeling process, whereby host tissues populate and eventually replace the sling's collagen scaffold, resulting in strong and natural support under the urethra. Jones recently reported on 34 women who underwent a Stratasis TF sling for genuine SUI.¹⁰ At 1-year follow-up, 76% were completely continent, while another 17% were improved. Three women had a mild, transient cellulitis, while another suffered urethral injury intraoperatively. There were no erosions and no prolonged retention in the group.

Hybrid slings to retain adherent properties

Two "hybrid" slings may appeal to those surgeons who are concerned about potential erosion of permanent material under the urethra, but who still want the adherent properties of permanent polypropylene mesh to fix the sling in position suprapubically. The T-Sling with Centrasorb (Caldera Medical, Thousand Oaks, Calif.) has two polypropylene sections connected by a monofilament, polydioxanone center, which is positioned under the urethra, and is completely absorbed in 100 days via hydrolysis.

The second, the BioArc sling (American Medical Systems) combines a self-fixating polypropylene sling and the surgeon's choice of suburethral biologic graft, which are sutured together at the start of the procedure. There are no clinical data available on this sling kit.

Transobturator slings may lessen risk of injury

More recently, a transobturator approach has become popular as an alternative to the sling's more traditional suprapubic fixation point. Rather than the classic suprapubic attachment of sling arms, which creates a "swing" configuration of the sling, this novel approach leaves the sling in a more horizontal or "hammock-like" position (Figure 1, top). Potential advantages of the transobturator approach include fewer bladder and bowel injuries and less voiding dysfunction and urinary retention than with traditional sling procedures. A key controversy surrounding the transobturator approach, however, is whether cystoscopy is needed to rule out bladder injury. Some surgeons argue that routine cystoscopy is not necessary, because the needle approach should avoid the space of Retzius and thus the risk of bladder injury is essentially zero. This could potentially make the transobturator sling procedure available to gynecologists who lack cystoscopy privileges at their institutions. On the other hand, there's bound to be some variation in the precise needle path, and some bladder injuries have resulted from transobturator slings.¹¹ Until we know the true incidence of bladder injury with the transobturator approach, many surgeons recommend performing cystoscopy for all transobturator and traditional sling procedures.

Will success rates be comparable? Another important question is whether the success rates with the transobturator slings will be comparable to those we've come to expect with the pubovaginal midurethral slings. As previously mentioned, the transobturator slings maintain urethral support in a more horizontal position compared with the suprapubic slings, which may influence the sling's effect on continence. Even if the success rates are similar for genuine SUI, long-term clinical results are needed among different subgroups of patients, such as those with ISD, women without urethral hypermobility, or both. Delorme reported his experience with 40 transobturator slings, using a non-woven polypropylene mesh coated with silicone on the urethral surface (UraTape, Mentor Corporation, Santa Barbara, Calif.).¹² Early results, from 3 to 12 months, revealed a 97% cure rate, with one case of sepsis and four cases of transient postoperative dysuria. In a French study of 165 consecutive patients at seven centers who underwent placement of the UraTape, Costa and colleagues reported a cure rate of 82% at 6 months, with another 7% significantly improved. Complications included two urethral perforations, one bladder perforation, six vaginal erosions, and one urethral erosion.¹³

Three choices. Three transobturator slings are currently available in the US. The ObTape (Mentor, Santa Barbara, Calif.) is made from pressed polypropylene fibers, which gives the sling reduced elasticity. A helical or curved needle is placed though an incision just lateral to the labia majora and then passes through the adductor muscles of the thigh, through the obturator membrane covering the obturator foramen, and eventually through an incision in the vagina. The surgeon places his or her finger in the paraurethral incision to guide the needle into the paraurethral space, then brings the sling up through the tissue as the needle is withdrawn. The procedure is then repeated on the opposite side.

The Monarc sling (American Medical Systems) uses a similar method of placing the transobturator sling but involves a knitted monofilament polypropylene mesh. The most recent US choice, TVT-Obturator System (Gynecare, Somerville, N.J.) takes an "inside-out" approach. The surgeon introduces a helical needle through the vaginal incision, passes through the medial portion of the obturator membrane and muscles, and exits through an incision in the medial thigh, in a direction opposite to the other two transobturator slings. This approach may lower the risk of urethral injury, since the surgeon can precisely place the needle in the paraurethral space.

Dargent and colleagues reported on 71 patients who underwent transobturator polypropylene sling surgery (Ethicon, Somerville, N.J.), 21 of whom had had previous surgery for SUI.¹⁴ They had a 94% cure rate, although their follow-up was limited to 6 to 12 weeks postoperatively. Because the first 38 patients they examined with cystoscopy had no bladder injuries, the investigators decided to abandon routine cystoscopy with the procedure. They noted one urethral injury and one episode of "copious" bleeding that spontaneously resolved and found no difference in postoperative urinary retention compared with the standard TVT procedure.

Although long-term comparative studies are needed to determine whether transobturator slings are as safe and effective as midurethral suprapubic slings, the transobturator approach may be especially helpful for certain patients. For women with previous anti-incontinence surgery, including retropubic urethropexies and suburethral slings, a transobturator approach should significantly decrease the risk of bladder injury by avoiding the space of Retzius altogether. Other patients who may benefit from this approach are obese women and those with voiding dysfunction, including Valsalva voiding and women with poor detrusor contractility.

Suburethral slings have become a popular, effective, and safe minimally-invasive choice for the treatment of SUI in women. The gynecologic surgeon currently can choose from a variety of pubovaginal sling types, including both synthetic and natural graft materials. In addition, transobturator slings are gaining in popularity, and may become the procedures of choice for some patients. Although long-term studies are needed to determine the durability of these various sling systems, the devices are clearly a revolutionary advance in the management of women with SUI.

Dr. Rosenblatt is a paid consultant and speaker for Gynecare and a paid consultant for Cook Ob/Gyn, from which he receives royalties from the Stratasis TF sling.

REFERENCES

1. Leach GE, Dmochowski RR, Appell RA, et al. Female Stress Urinary Incontinence Clinical Guidelines Panel summary report on surgical management of female stress urinary incontinence. The American Urological Association. J Urol. 1997;158:875-880.

2. Nilsson CG, Rezapour M, Falconer C. Seven years follow-up of the tension free vaginal (TVT) procedure. International Urogynecologic Association, 2003.

3. Ulmsten U, Falconer C, Johnson P, et al. A multicenter study of tension-free vaginal tape (TVT) for surgical treatment of stress urinary incontinence. Int Urogynecol J Pelvic Floor Dysfunct. 1998;9:210-213.

4. Ulmsten U, Johnson P, Rezapour M. A three-year follow up of tension free vaginal tape for surgical treatment of female stress urinary incontinence. Br J Obstet Gynaecol. 1999;106:345-350.

5. Nilsson CG, Kuuva N, Falconer C, et al. Long-term results of the tension-free vaginal tape (TVT) procedure for surgical treatment of female stress urinary incontinence. Int Urogynecol J Pelvic Floor Dysfunct. 2001;(12 Suppl 2):S5-S8.

6. Manca A, Sculpher MJ, Ward K, et al. A cost-utility analysis of tension-free vaginal tape versus colposuspension for primary urodynamic stress incontinence. BJOG. 2003;110:255-262.

7. Paraiso MF, Walters M, Karram M, et al. Laparoscopic Burch colposuspension versus the tension-free vaginal tape procedure: a randomized clinical trial. American Urogynecology Society Annual Meeting, 2003. Abstract 87.

8. Gandhi S, Kwon C, Abramov Y, et al. Midurethral tape procedures: are they all the same? International Continence Society Conference Report, 2003. Abstract 360.

9. Meschia M, Pifarotti P, Bernasconi F, et al. Multicenter randomized trial of TVT and IVS for the treatment of stress urinary incontinence in women. International Continence Society, 2003. Abstract 385.

10. Jones S, Berglund R, Rachley R, et al. AUA North Central Section Annual Meeting, Vancouver, Canada, September 2003.

11. Hermieu JF, Messas A, Delmas V, et al. [Bladder injury after TVT transobturator.] Prog Urol. 2003;13:115-117.

12. Delorme E. [Transobturator urethral suspension: mini-invasive procedure in the treatment of stress urinary incontinence in women]. Prog Urol. 2001;11:1306-1313.

13. Costa P, Ballanger P, Grise P, et al. Trans-obturator tape (T.O.T) for female stress urinary incontinence preliminary results of a prospective multicenter register. International Continence Society, 2003. Abstract 379.

14. Dargent D, Bretones S, George P, et al. [Insertion of a sub-urethral sling through the obturating membrane for treatment of female urinary incontinence]. Gynecol Obstet Fertil. 2002;30:576-582.

DR. ROSENBLATT is Director of Urogynecology, Mount Auburn Hospital, Beth Israel Deaconess Medical Center, and Assistant Professor, Harvard Medical School, Cambridge, Mass.

DR. PULLIAM is a Clinical Fellow, Urogynecology and Reconstructive Pelvic Surgery, Mount Auburn Hospital, and Clinical Instructor, Harvard Medical School.

Key points

• The various sling systems now available result in fewer postop complications than when first introduced, and although long-term studies are needed to determine their safety and durability, these systems are a revolutionary advance in managing female SUI.

• Differences between sling kits for SUI include (1) the direction of needle placement (vaginal or abdominal), (2) the anatomic path of the sling arms, and (3) the physical properties of the sling material.

• A transobturator approach, which leaves the sling in a more horizontal or "hammock-like" position, is a growing alternative to the more traditional suprapubic fixation point of the sling. Potential advantages include fewer bladder and bowel injuries, and less voiding dysfunction and urinary retention.

• Until we know the true incidence of bladder injury with the transobturator approach, many surgeons recommend performing cystoscopy during all transobturator and traditional sling procedures.

 

Peter Rosenblatt. An update on suburethral slings for stress urinary incontinence. Contemporary Ob/Gyn Apr. 15, 2004;49:33-43.