The lure to the development of a second generation of midurethral slings lay in the small but still significant number of reported complications with the TVT procedure, in which a polypropylene mesh is placed through a vaginal-to-suprapubic route. The question loomed: Could reports of vascular injury, bowel and bladder perforations, and nerve injury with TVT be eliminated?
Dr. Emmanuel Delorme addressed the issue in 2001 by describing the first transobturator tape (TOT) procedure. In this approach, the sling is placed transperineally beneath the ischiopubic rami, rather than retropubically. It mimics the shape and function of the pubocervical fascia, forming a suburethral hammock of support.
Dr. Delorme's idea was that if we could avoid passing needles through the retropubic space and instead insert the tape through a transobturator approach, we would have little or no chance of hitting the bladder or urethra—bladder perforations have occurred in approximately 3% of TVT procedures, according to reports—and we would alleviate the risk of bowel injury. Nor would we go near the abdominal vessels. Routine cystoscopy, moreover, might be unnecessary.
Today, transobturator tape (TOT) procedures are fast proving to be a safer—and at least equally effective—alternative to the original TVT procedure described by Dr. Ulf Ulmsten in 1996.
In the first randomized, prospective trial comparing TVT and TOT in approximately 60 patients, Dr. Renaud de Tayrac demonstrated that at 1 year, similar numbers of patients were cured and significantly improved (over 90%). Patients undergoing TOT, interestingly, had significantly lower postoperative rates of retention. They also had shorter operation times. And whereas bladder perforation occurred in almost 10% of the TVT patients, that complication affected none of the TOT patients.
(The de Tayrac paper was published in 2004 in the American Journal of Obstetrics and Gynecology, but it was later retracted, unfortunately, for lack of Institutional Review Board approval.)
Although longer-term data from prospective randomized studies are still forthcoming, additional studies of increasingly larger numbers of patients are clearly demonstrating that TOT offers comparable results to retropubic slings, with the benefit of lower complication rates and shorter operating times.
Some data suggest, just as Dr. de Tayrac's work did, that TOT is also more forgiving with respect to voiding, and may be particularly preferable for patients with mixed incontinence or any symptoms of urge incontinence. It appears that TOT is less likely to impair bladder emptying, which, ironically, can be more problematic to patients than their original stress incontinence. The last thing we want to do is to alleviate the stress urinary incontinence only to induce or exacerbate any urge urinary incontinence.
There's still a place for retropubic slings, however. Small trials have also shown that patients with intrinsic sphincter deficiency (ISD) have a higher success rate with the TVT procedure than with TOT, which makes sense when we consider the configurations of the two midurethral slings: the original retropubic sling's U-shaped fit around the urethra, and the gentler hammocklike configuration of the transobturator sling. All told, TVT is significantly more effective than TOT when the urethral closure pressure while sitting with a full bladder is less than 43 cm H2O.
For most patients other than those with ISD, though, TOT now seems to be the preferable minimally invasive treatment. In addition to being safe and effective, it is easier to learn than the original TVT approach, especially for physicians who are not yet comfortable or experienced with the retropubic space.
Work on yet another generation of midurethral slings is advancing quickly, but physicians today are utilizing two TOT techniques: In the original technique—coined the “outside-in” or “out-to-in” procedure (the technique described by Dr. Delorme)—the transobturator sling is placed inward through the obturator foramens from the labiocrural folds. The second technique—the newer version of TOT—involves placing the sling outward from the vaginal side toward labiocrural folds and, accordingly, is referred to as the “inside-out” or “in-to-out” TOT procedure.
The two techniques are quite different, and most physicians now favor one approach more than the other when they decide to perform TOT.
Peter Sand, M.D.: The Outside-In Approach to TOT
For me, the outside-in approach, which uses a transobturator-to-vagina approach to mesh placement, is a logical choice. The TOT procedure was first described this way, and I have seen no need to deviate from it. It is simpler than the inside-out approach, and I see no logic to performing it the other way.
First of all, we know we're improving outcomes with TOT in many women. In a retrospective cohort study comparing the TOT sling procedure (107 patients) with TVT (91 patients) at the Evanston Continence Center, we found that TOT resulted in significantly less postoperative retention and lower rates of de novo urge urinary incontinence.