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Synthetic Midurethral Slings: TVT and TOT


 

Today, there are more published studies on the use of tension-free vaginal tape in the treatment of stress urinary incontinence than on any other procedure that has ever been performed for stress incontinence.

When compared with traditional suspensions and slings, TVT has been shown to be at least as—if not more—efficacious for all types of stress urinary incontinence, from incontinence due to anatomical abnormalities to incontinence resulting from intrinsic sphincter deficiency and mixed incontinence.

Added to TVT's efficacy is the fact that the TVT procedure is simpler, shorter in duration (approximately 20 minutes), and less invasive than other procedures, with extremely low complication rates when the appropriate technique is utilized and retropublic anatomy is appreciated.

Clearly, the TVT procedure is a good treatment of choice.

TVT's Origins

The TVT procedure, which was the first use of the synthetic midurethral sling, was first done in this country in 1998.

The history of TVT is interesting because the procedure went against everything we always thought we understood about surgery for SUI: mainly, that the mechanism for continence was at the proximal urethra and bladder neck, and that surgeries for incontinence needed to either elevate or support this area. TVT, on the other hand, uses a midurethral placement. It provides a backboard under a portion of the urethra that has very little mobility.

In addition to processing this major change in thinking, many of us also thought at the time that synthetic materials should be avoided for sling procedures, and few of us could easily grasp the notion of placing a sling without fixing it to anything.

The TVT procedure was first described by Dr. Ulf Ulmsten in 1996. In the mid-1980s, he and his fellow, Dr. Peter Petros, set out to identify and describe a new minimally invasive outpatient procedure for stress incontinence.

They described a series of small studies, exploring what they called the “integral theory,” in which they looked at different slings or meshes placed at different anatomical sites underneath the urethra.

In the end, they determined that a certain type of polypropylene mesh, placed through a vaginal-to-suprapubic route using specially designed, long stainless steel needles that can be passed under local anesthesia, was the best approach.

According to Dr. Ulmsten's theory, the procedure works by reinforcing the pubourethral ligaments and levator ani muscles, as well as increasing the support of the vaginal hammock.

The Entry of Transobturator Slings

The TVT procedure required blind passage of needles through the retropubic space, a process that potentially brings the needle into close proximity with vascular structures as well as bowel and the bladder.

And indeed, there were rare reports of very serious complications related to vascular and bowel injuries.

These complications led a Frenchman, Dr. Emmanuel Delorme, to describe the first transobturator tape (TOT) procedure. The theory behind this technique, which represented a second generation of midurethral slings, was that it avoided the retropubic space and thus avoided these potential vascular, bowel, and bladder injuries.

The procedure became quite popular, and techniques to place the transobturator sling from the vaginal side or from the inner thigh were described. Experience with these modifications has grown over the last few years.

Complication rates with TOT have been low, but some complications, particularly those related to the inner thigh, have been described.

The next generation of synthetic midurethral slings, which will be available in the next year, will be even less invasive than TOT, as the sling will not have an exit site.

To date, we lack data from any long-term, randomized comparison of the two procedures, and we should not draw any conclusions until we have such long-term data. I believe we need to see a minimum follow-up of 2 years.

The data should accumulate quickly, however. In fact, a prospective, randomized comparison of TVT versus TOT has just been completed, so data should be forthcoming.

Regarding TVT specifically, we have long-term data (up to 7 years) showing that TVT maintains its high cure rate of greater than 80%.

I sometimes use TOT in my practice; at this time, it seems especially reasonable in patients at high risk for pelvic adhesions and in patients who have milder degrees of incontinence or SUI that is felt to be occult.

Performing TVT

The TVT procedure begins with the administration of a hemostatic agent and an anesthetic. (We prefer lidocaine with epinephrine.) The anterior vaginal wall is injected at the level of the distal- to midurethra.

It is important to appreciate that this portion of the anterior vaginal wall is fused to the posterior urethra. No clear plane of dissection exists between these two structures.

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