Suburethral slings were initially developed as a treatment for recurrent, urodynamically confirmed SUI, particularly SUI caused by intrinsic sphincter deficiency (ISD). Pubovaginal slings, usually consisting of autologous fascia, were placed at the bladder neck to both support and slightly compress the proximal urethra. Compared with synthetic slings, fascial slings are effective but take longer to place and have a higher rate of surgical morbidity and more postoperative voiding dysfunction. They are now mostly indicated for complex recurrent SUI, usually managed by specialists in female pelvic medicine and reconstructive surgery.
Current slings are lightweight polypropylene mesh
Most slings today are tension-free midurethral slings consisting of synthetic, large-pore polypropylene mesh; they are sold in kits available from several different companies. Sling procedures can also be performed using hand-cut polypropylene mesh and a reusable needle passer.
These slings are placed at the midurethra and work by mechanical kinking or folding of the urethra over the sling, with an increase in intra-abdominal pressure. Ideally, the midurethral sling will not compress the urethra at rest and have no effect on the normal voiding mechanism.
Three main techniques are used to place synthetic midurethral slings:
- the retropubic approach
- the TOT approach
- variations of single-incision “mini-sling” procedures.
Early studies of mini-slings showed few complications but lower effectiveness, compared with retropubic and TOT midurethral slings, according to short-term follow-up data.2-4 A mini-sling might be an option for some patients in whom surgical complications must be kept to a minimum; otherwise, they will not be discussed further.
Retropubic midurethral slings
The tension-free vaginal tape (TVT) procedure described by Petros and Ulmsten was the first synthetic midurethral sling.5 This ambulatory procedure aims to restore the pubourethral ligament and suburethral vaginal hammock by using specially designed needles attached to synthetic sling material.
The synthetic sling consists of polypropylene, approximately 1 cm wide and 40 cm long. The sling material is attached to two stainless steel needles that are passed from a vaginal incision made at the level of the midurethra, through the retropubic space, and exiting at a previously created mark or stab incision in the suprapubic area (FIGURE 1).
Variations of the retropubic midurethral sling have been developed, with sling passers going from the vagina upward (“bottom to top”) and also from the suprapubic area downward (“top to bottom”). A recent Cochrane review reported that the bottom-to-top variation is slightly more effective.6
FIGURE 1 Retropubic sling
Placement of the tension-free vaginal tape trocar into the retropubic space.
Illustration: Craig Zuckerman for OBG Management
Transobturator midurethral slings
The TOT sling has become one of the most popular and effective surgical treatments for female SUI worldwide (Video 1 and Video 2). It is a relatively rapid and low-risk surgery that is comparable to other surgical options in effectiveness while avoiding an abdominal incision and the passage of a needle or trocar through the space of Retzius.
The TOT sling lies flatter under the urethra and carries a lower risk of urethral obstruction, urinary retention, and subsequent need for sling release, compared with retropubic slings.7-9 Compared with the retropubic TVT, the TOT sling produces similar rates of cure, with fewer bladder perforations and less postoperative irritative voiding symptoms.6,10-12 It nearly eliminates the rare but catastrophic risk of bowel or major vessel perforation. The trade-off is that patients experience more complications referable to the groin (pain and leg weakness or numbness) with the TOT approach.9,13
All TOT slings on the market consist of a large-pore, lightweight, polypropylene mesh strip, usually covered with a plastic sheath. Various devices are used to place the sling, but most of them involve a helical trocar that curves around the ischiopubic ramus, passing through the inner thigh and obturator membrane to a space created in the ipsilateral peri-urethral tissues.
TOT slings can be placed outside-to-inside or inside-to-outside (FIGURE 2), and the indications, effectiveness, and frequency of complications seem to be similar between these two approaches.12 One study found a higher frequency of new sexual dysfunction (tender, palpable sling; penile pain in male partner) in women after the “outside-in” approach,14 but this clinical issue has not been observed in all studies.15,16
FIGURE 2 TOT sling variations
Placement of the transobturator (TOT) sling helical trocar using the (A) “outside-in” variation and (B) “inside-out” variation.
Illustration: Craig Zuckerman for OBG Management
Reprinted with permission, Cleveland Clinic Center for Medical Art & Photography
© 2005-2012. All Rights Reserved.
Success rates are similar for retropubic and TOT slings
Despite differences in technique and brand of mesh used, treatment success rates for uncomplicated primary SUI are similar for the retropubic (Video 3) and TOT tension-free slings.6-8,10-12,17 The percentage of patients treated successfully depends on the definition used, ranging from a high of 96% to a low of 60%. When the definition of success is restricted to stress incontinence symptoms, especially over a short period of time, the reported effectiveness is high.