SUFU WM 2014 - Mechanism of action of the midurethral sling: A critical appraisal - Session Highlights

MIAMI, FL USA ( - Moderator, Dr. Craig Comiter, began the debate by noting the many surgical options for SUI which are efficacious in properly selected patients. However, because there are multiple etiologies of SUI, there must be multiple mechanisms of action. He provided an historical list of the many surgical options for SUI:

  1. Kelly plication (anatomic) - pubocervical fascia plicated at level of bladder neck (BN)
  2. Transabdominal approach (anatomic) of which there are:
    • MMK: periurethral tissue anterolateral to urethra sutured to symphysis
      • From midurethral to BN
    • Burch: paravaginal tissue near BN sutured to Cooper’s ligament
      • More proximal and lateral than MMK sutures
    • Paravaginal repair: paravaginal tissue proximal to BN to pelvic sidewall
      • Needle suspension (anatomic) - periurethral tissue lifted up
      • Periurethral bulking (intrinsic or anatomic) to improve urethral seal
  3. Sling (anatomic or intrinsic)
    • Bladder neck
    • Mid-urethra
      • Retropubic or transobturator (TOT)
    • Slings provide a “backboard” of support for the vesico-urethral junction and with appropriate tension, can also create some degree of urethral coaptation

The mid-urethral sling (MUS) is now the most common surgery performed for SUI.

sufu xDr. Howard Goldman began his presentation by quoting the AUGS/SUFU position statement on MUSs as the world-wide standard of care for the surgical treatment of SUI. This is because the procedure is safe, effective, and has improved quality of life for millions of women. Complications occur but are a distinct minority. He presented the serious adverse events from the TOMUS (Richter, 2010) trial which compared the retropubic sling (n=298) to the TOT sling (n=299), noting the low mesh erosion (RP= 0.3% v TOT=0.3%) and mesh exposure (RP=2.7% v TOT=0.3). Dr. Goldman noted the preponderance of the evidence in high-quality studies detailed in the Society of Gynecologic Surgeons (SGS) systematic review. (Schimpf, et al., Sling surgery for stress urinary incontinence in women: A systematic review and meta-analysis. Am J Obstet Gynecol. 2014 Jan 29. pii: S0002-9378(14)00059-3. doi: 10.1016/j.ajog.2014.01.030). The SGS clinical practice guidelines state that for “women considering a pubovaginal or midurethral sling for treatment of SUI, we recommend the MUS for better subjective cure outcomes.” Dr. Goldberg went on to say that all agree that the synthetic MUS is the “gold standard” sling as it has better outcomes and less obstruction than the BN fascial pubovaginal sling. The MUS is based on the integral theory: intact pubourethral ligament (PUL) and muscles contract and relax appropriately, allowing for voiding and continence. A basic tenet of the integral theory is that a structure is created by muscle forces stretching the organs and vaginal wall against suspensory ligaments, like a suspension bridge. But when the PUL is damaged, the ability to have dynamic kinking of the urethra is lost. The MUS replaces and reinforces the PUL, allowing a return of normal function, a dynamic kinking. So, depending on the tension of the MUS, continence is maintained during valsalva, because the proximal urethra remains closed and there is dynamic kinking of mid/distal urethra around the PUL. When voiding, the BN and proximal urethra open to reduce resistance and allow good flow. Thus, the mechanism of action of a sling is that it reinforces the PUL allowing a return of normal function – a dynamic kinking. He also felt that an outside-in approach may be better. 

Dr. Philippe Zimmern presented an opposing view and was very strong in his views on the synthetic MUS. He has never placed a synthetic MUS and never will. Since 2000, he has been vocal in alerting his colleagues about his concerns with the MUS. He asked the audience members, “who had removed, on average, a MUS 1/month, 2/ month, 1/week or 2 or more each week?” It was evident by the show of hands that removing a MUS was a very frequent occurrence in practice. He cannot defend the mechanism of action of a MUS as SUI is a vaginal disease; the urethra and anterior wall are connected and move together. The MMK procedure, a very popular technique in the past, caused obstruction of the urethra. He feels that the sling is the ‘last resort” procedure because the adjustment of the tension of the sling is an “art,” not a science, and there is a lifetime risk of retention which can lead to bladder changes from obstruction. He presented UDS data (Kraus, 2011), comparing Burch or sling 2 years after the procedure, showing that PdetQmax significantly increased when compared to the Burch (Pre: Burch 20.5, Sling 16; Post: Burch 22, Sling 27). Dr. Zimmern noted that the MUS was a sub-urethral tape that is described as “tension-free," which may be the case when placed in the OR, but with retraction, scarring, and misplacement, the end result may not be “tension-free,” even with the most expert surgeon. There is no long- term data and his concern is that with the sub-urethral kink during stress efforts, the proximal urethra, BN, and bladder base have no support, and over time, this may lead to outlet obstruction, urgency, and possibly a cystocele. Further, if the MUS needs to be removed, this is a difficult surgery that can cause residual pain, dyspareunia, lower urinary tract symptoms, risk of urethro-vaginal fistula, etc. Dr. Zimmern presented his case more extensively in a write-up in the SUFU program book. He noted that he felt the title of his talk should not have been “Not Ideal” but “Frankly Bad.” He notes that the scientific community is under scrutiny by the media, lawyers, and patients. This was further reinforced by a lawyer, Brian Hoffman, who presented his opinion on ongoing mesh litigation. Mr. Hoffman noted that the numbers of filed mesh-injury claims are rapidly increasing and that they are being handled by the individual state courts, not federal courts. His strongest recommendation was to ensure informed consent occurred when counseling women on a mesh procedure. He felt that the physician should go over each page of the consent, and, as an audience member suggested, perhaps the consent process should be videotaped. He thought that would be a good idea!

Moderated by Craig V. Comiter, MD at the Society of Urodynamics, Female Pelvic Medicine and Urogenital Reconstruction (SUFU) Winter Meeting - February 25 - March 1, 2014 - Doral Golf Resort and Spa - Miami, Florida USA

Ideal MOA: Howard B. Goldman, MD
Not Ideal: Philippe E. Zimmern, MD

Reported for by Diane K. Newman, DNP, FAAN, BCB-PMD