Midurethral Slings

Midurethral Slings

Emily L. Whitcomb

Emily Helena Frisch


Since its introduction in 1996 by Ulmsten et al., the tension-free vaginal tape (TVT) has become the most commonly performed and “gold standard” surgery for stress urinary incontinence (SUI).1 The TVT gained popularity due to its minimally invasive approach without the voiding dysfunction, de novo urgency urinary incontinence, and longer recovery seen in other procedures. Cure rates for the TVT are higher than those of the Burch colposuspension and at least equivalent to traditional sling procedures.2,3,4,5 Although based on the traditional sling technique, TVT has several characteristics that distinguish it, including placement of the sling at the midurethra, sling arms that are “self-fixing” and do not require suturing to the rectus fascia, the use of trocars that pass the sling from the urethra to the abdomen (“bottom-up” trocar passage), the use of loosely knitted polypropylene mesh for the sling material, and “tension-free” placement (Table 29.1). TVT is indicated for the primary treatment of SUI, or stress-predominant mixed urinary incontinence (MUI), with urethral hypermobility and is also commonly used with modified success in women with intrinsic sphincter deficiency (ISD).6 In addition, it has a role as a salvage operation in subjects who have failed previous SUI surgery.7


Petros and Ulmsten developed the TVT based on the integral theory wherein SUI results from impairment in the pubourethral ligaments that connect the anterior wall of the bladder and the proximal urethra to the posterior surface of the pubic bone.8,9,10 The proposed goal of the TVT was to correct “inadequate urethral support from the pubourethral vesical ligaments.”9,11 As such, the TVT is placed under the midurethra where, based on urethral pressure profilometry, the pubourethral ligaments were assumed to have their functional attachment.

Although the most important anatomic landmark of the integral theory, the role of the pubourethral ligaments in maintaining continence has been called into question by some anatomic and radiologic studies. An anatomic study by Fritsch et al.12 concluded that the female urethra has no direct ligamentous fixation to the pubic bone. They identified “delicate cords” of smooth muscle running form the pubic bone to the bladder neck, which they proposed should be called the “pubovesical muscles” rather than pubourethral ligaments. They concluded that because of the low content of connective tissue and small dimensions of these structures, they cannot be considered a supportive structure of the urethra.12 In contrast, anatomic and histologic study by Petros13 found the pubourethral ligaments to be “strong finite structures” consisting of smooth muscle, elastin, collagen, nerves, and blood vessels. Magnetic resonance imaging and sonographic data also demonstrate the urethra is a mobile structure that moves up and down and is not fixed to the pubic bone.14,15 These findings suggest the integral theory may not provide the best explanation for the effectiveness of the TVT.

A more plausible mechanism of action for the TVT is that of transient urethral kinking during stress.16,17 Unlike traditional sling procedures or retropubic colposuspensions, the effectiveness of the TVT does not appear to be related to correction of urethral hypermobility. Most patients with urethral hypermobility preoperatively continue to have urethral hypermobility postoperatively while still achieving high cure rates.18 Ultrasound studies demonstrate that during Valsalva or a cough, dynamic urethral kinking occurs in the presence of the TVT, with the suburethral portion of the sling serving as the fulcrum.19,20 At rest, there is no compression or kinking of the urethra. This suggests that urethral mobility may be important in the mechanism of action of the TVT.

There is debate regarding the appropriate position of the urethral tape along the urethra. Urodynamic studies demonstrate an increase in pressure transmission ratios after a TVT with no change in maximum urethral closure pressure.21 Although midurethral placement is often emphasized, postoperative ultrasonography demonstrates marked variation of sling placement relative to the urethra, with little apparent effect on symptoms or continence rates.22,23 In contrast, other studies have shown a greater risk of treatment failure when the tape was located under the
proximal urethra.24,25 In a prospective study investigating whether the location of the tape may influence outside-in transobturator sling outcome, the highest failure rate was associated with the tape under the proximal third of the urethra.26 As such, the authors concluded that both the middle and distal sections of the urethra may be regarded as targets for transobturator tape (TOT) placement.23 Proximal midurethral sling (MUS) placement has also been shown to have a weak association with irritative voiding symptoms.22


Although in their original description of the TVT technique, Ulmsten et al.11 used local anesthesia with intravenous sedation, general or regional anesthesia is also acceptable. The patient is placed in the dorsal lithotomy position in high stirrups and the vagina and lower abdomen are prepped and draped. A Foley catheter is placed to dependent drainage. Using a pen, the suprapubic sites for the two stab incisions are marked just superior to the pubic symphysis 2 fingerbreadths (2 cm) lateral to the midline on each side. Local anesthetic such as 1% lidocaine is often injected at the two suprapubic sites, 10 mL on each side. Using a spinal needle, the injection is carried down behind the pubic bone and should include the rectus muscle, fascia, and skin. In a randomized, double-blind trial of 42 women undergoing MUS, retropubic injection of 0.125% bupivacaine decreased short-term postoperative pain as measured by VAS scores up to 24 hours compared to no injection.27

Attention is turned to the vagina, where a weighted speculum is placed for exposure. The midurethra is identified with traction on the Foley catheter, allowing identification of the urethrovesical junction and the distal urethra. The vaginal epithelium at this level is often grasped with Allis clamps. Local anesthetic (10 mL) with dilute epinephrine or vasopressin is infiltrated in the anterior vaginal wall at the location of the midurethra and laterally to the inferior pubic rami for hydrodissection and hemostasis. A 1.5-cm midurethral incision is made vertically at least 1 cm from the external urethral meatus and the dissection is carried laterally with Metzenbaum scissors to create a tunnel to the inferior pubic ramus bilaterally. The TVT kit (Gynecare Worldwide, a division of Ethicon, Somerville, New Jersey) includes two curved stainless-steel trocars connected by a 1 cm × 40 cm piece of polypropylene mesh encased in a plastic sheath and a nondisposable handle that attaches to the trocars. The plastic sheath covering the mesh consists of two pieces that overlap in the midline, allowing for easy removal after the sling is placed. A hemostat placed in the middle of the sling in the area of overlap can be useful for marking the midline and preventing sheath slippage during placement. One of the two trocars is attached to the trocar handle. Prior to each trocar passage, the bladder is drained, and a rigid catheter guide is placed in the Foley catheter and directed to the ipsilateral side of trocar placement to displace the urethrovesical junction away from the path of the trocar. Of note, in two retrospective cohort studies, Foley catheter guide use did not decrease the risk of lower urinary tract injury during retropubic MUS placement.28,29

The trocar handle is held in the hand contralateral to the side of trocar placement while the thumb of the ipsilateral hand stabilizes the trocar as it curves into the vagina and the index finger maintains proper alignment of the tip. The tip of the trocar is placed in the periurethral tunnel and directed toward the patient’s ipsilateral
shoulder and the marked suprapubic exit site. The endopelvic fascia is perforated and the trocar is directed along the back of the pubic symphysis—with great care to hug the posterior aspect of the bone—to exit at the previously marked abdominal incisions. In a modification of the TVT using a top-to-bottom approach, the two needle trocars are inserted through the suprapubic incisions, passed through the retropubic space behind the pubic bone on top of the operator’s finger and exit through a vaginal incision.

After each trocar placement—although it can be performed after passage of both trocars—the Foley catheter is removed, and the bladder is inspected with a 70-degree cystoscope. It is important that the bladder is filled to capacity during cystoscopy so that a bladder perforation is not missed behind a mucosal fold. The area at highest risk for bladder perforation is the anterolateral portion of the bladder dome.

After bladder integrity is confirmed, the handle is detached from the trocar and the trocar is pulled through the abdominal incision. The encased mesh is clamped just below the trocar and cut so that the trocar can be removed from the operative field. The second trocar is then placed on the opposite side using the same technique. Should bladder perforation occur, the trocar is withdrawn, the bladder is drained, the appropriate landmarks are reviewed, and a second attempt at trocar placement is made, taking care to stay as close as possible to the posterior surface of the pubic bone. As the typical TVT bladder injury is small (less than 1 cm), extraperitoneal, and in the bladder dome, it is usually unnecessary to perform any type of repair. Although some surgeons prefer short-term catheterization after such an injury, findings from a retrospective case series found the majority of subjects experiencing a cystotomy during MUS were successfully discharged home the day of surgery without catheter drainage.30

The tension of the TVT sling is adjusted to allow for dynamic urethral kinking while avoiding compression of the urethra at rest. The original technique specified the sling to be “loosely placed—without elevation—around the urethra” and it was intended for an intraoperative cough stress testing to determine the tension.17 If the procedure is performed using local anesthesia as initially described, the patient may be asked to cough repeatedly with a bladder volume of 250 to 300 mL. The sling is tightened so that a few drops of urine are present at the external meatus during coughing. This ensures that the sling is not too tight and minimizes the risk of urinary retention. If general anesthesia is used, the sling is tightened empirically without the benefit of the cough test. Some surgeons use a spacer between the urethra and the sling such as a blunt scissor, Hegar dilator, or Babcock clamp to ensure a tension-free application.31,32,33 Others use a Credé maneuver with a full bladder to simulate a Valsalva.34 In patients who receive regional anesthesia, any of the above techniques may be used, depending on the patient’s level of consciousness and ability to perform forceful cough or Valsalva. The use of the cough test to guide TVT tensioning was originally thought to be an important component of the TVT procedure; however, numerous authors have reported high cure rates with a low incidence of voiding dysfunction in patients who received general anesthesia or when the cough test was otherwise omitted.35,36,37,38,39,40 Some authors have found that when compared with general anesthesia, the use of local anesthesia with a cough test improved continence rates, whereas others have found no relationship between anesthesia type and TVT efficacy.41,42 Adamiak et al. randomized 103 women with SUI to undergo a TVT with either local anesthetic or spinal anesthesia and found no difference in efficacy or safety between the two types of anesthesia.37 One randomized, double-blind, multicenter trial compared tensioning with scissors or Babcock clamp and found high rates of objective and subjective cure in both groups; however, women in the Babcock group experienced higher vaginal mesh erosion rates (5.3% vs. 0.7%) and women in the scissor group were more likely to have uroflowmetry suggestive of urinary obstruction (26% vs. 15%).33

Once the desired tension is achieved, the sheath encasing the sling is removed while stabilizing the sling below the urethra. The abdominal ends of the sling are cut below the skin surface and the incisions are closed with absorbable suture, Steri-strips, or skin adhesive. The vaginal incision is closed with 2-0 or 3-0 absorbable suture in a running fashion. A voiding trial is typically performed in the recovery room. A commonly described technique is the backfill-assisted voiding trial wherein the bladder is retrograde filled with 300 mL of sterile fluid, the catheter removed, and the patient allowed to void. If the patient voids at least two-thirds of the instilled volume, she is discharged without a catheter. This technique has been found to be more efficient than a simple voiding trial wherein the catheter is removed and a postvoid residual measured after spontaneous void.43 In a randomized, double-blinded trial of backfill standard voiding trial compared to patients’ subjective evaluation based on the assessment of force of stream after MUS, there were no differences in rates of catheterization up to 6 weeks postoperatively.44


In 2001, Delorme45 described the transobturator suburethral sling. Similar to the TVT, this is a minimally invasive synthetic MUS; however, it is placed using a transobturator rather than retropubic approach. Transobturator slings are positioned under the midurethra and brought laterally through the obturator membrane in either an inside-out or outside-in approach. The inside-out technique involves the blind passage of a curved trocar from the periurethral incision through the
obturator internus muscle, obturator membrane, and obturator externus muscle to an incision in the groin.46 The outside-in approach involves the reverse blind passage of the trocar from the groin incision around the ischiopubic ramus and out the vaginal incision at the level of the midurethra.45,47 The anatomic approach of the TOT differs from other sling procedures because the retropubic space is not entered. Additionally, the relationship between the sling and the urethra is different for the TOT than for other slings. In other sling techniques, including the TVT, the sling axis is roughly vertical, or U-shape, in relation to the urethral axis.47 In contrast, the axis of the TOT is more horizontal in relation to the urethral axis. As such, the TOT potentially provides less circumferential compression of the urethra than do traditional or retropubic slings.

Obturator Anatomy

Because of the popularity of the TOT technique, pelvic surgeons should have an intimate knowledge of obturator compartment and medial thigh anatomy in order to properly perform this procedure and manage its complications (Fig. 29.1). The obturator membrane is a fibrous sheath that spans the obturator foramen, through which the obturator neurovascular bundle penetrates via the obturator canal. The obturator internus muscle lies on the superior (intrapelvic) side of the obturator membrane. The obturator internus origin is on the inferior margin of the superior pubic ramus and the pelvic surface of the obturator membrane. Its tendon passes through the lesser sciatic foramen to insert onto the greater trochanter of the femur to externally rotate the thigh. The obturator artery and vein originate as branches of the internal iliac vessels. As they emerge from the cranial side of the obturator membrane via the obturator canal and enter the obturator space, they divide into many small branches supplying the muscles of the adductor compartment of the thigh (Fig. 29.2). Cadaveric study by Whiteside and Walters47 has contradicted previous reports of the obturator vessels bifurcating into medial and lateral branches. Rather, the vessels are predominantly small
(less than 5 mm in diameter) and splinter into variable courses. The muscles of the medial thigh and adductor compartment are, from superficial to deep, the gracilis, adductors longus, adductors brevis, adductors magnus, and obturator externus muscles.

In contrast to the vessels, the obturator nerve emerges from the obturator canal and bifurcates into anterior and posterior divisions traveling distally down the thigh to supply the adductor muscles.47 In a recent cadaveric study by Shah et al.,48 the anterior nerve divided into smaller branches that perforated the adductor brevis and adductor longus muscles. The posterior nerve divided into smaller branches that perforated the gracilis, adductor brevis, adductor magnus, and obturator externus muscles.48 With the patient in the dorsal lithotomy position, the nerves and vessels follow the thigh and course laterally away from the ischiopubic ramus.


The TOT may be performed under general, regional, or local anesthesia with sedation. The patient is placed in dorsal lithotomy position in high stirrups. The vagina, lower abdomen, and inner thighs are prepped and draped, and a Foley catheter is placed to dependent drainage. Important landmarks in the obturator compartment are identified, including the ischiopubic ramus and the adductor longus tendon. When using an outside-in approach, the location of the inner thigh incisions is identified by palpating the notch below the adductor longus tendon just lateral to the labia majora. A pen is used to mark the location of the incisions on each side within this notch at the level of the clitoris. The location of these incision sites is approximately 2.5 cm medial to the obturator neurovascular bundle as it exits the obturator canal.47 If the procedure is being performed using local anesthetic, 10 to 60 mL of local anesthetic with dilute epinephrine is injected into the incision site and carried down through underlying muscle to the level of the obturator membrane just lateral to the ischiopubic ramus on each side. A 1-cm stab incision is made at the marked sites.

A weighted speculum is placed in the vagina for exposure. Using the marking pen, the site for the 2-cm midurethral incision is marked vertically beginning at least 1 cm from the external urethral meatus. Local anesthetic with dilute epinephrine or vasopressin is
infiltrated in the anterior vaginal wall at the location of the urethral incision site and laterally to the inferior pubic rami for hydrodissection and hemostasis. The vaginal epithelium at the midurethra is incised, and the dissection is carried laterally with Metzenbaum scissors to create a tunnel, large enough to allow an index finger, to the inferior pubic ramus on each side of the urethra.

Several different transobturator slings have been marketed, with some using helical trocars and others using curved trocars. The surgeon should follow the manufacturer’s recommendations for each sling. The angle of trocar passage from the thigh incision to the periurethral incision is approximately 30 to 40 degrees. The trocar is oriented appropriately and held with the ipsilateral hand. The surgeon’s contralateral index finger is inserted into the periurethral tunnel to the medial edge of the ramus. The trocar passes through the following layers as it is passed around the ischiopubic ramus: skin, subcutaneous fat, gracilis muscle, adductor brevis, obturator externus muscle, obturator membrane, obturator internus muscle, and periurethral endopelvic fascia (Fig. 29.3).47 If passed properly, the trocar tip will meet the surgeon’s finger as it passes around the ramus so that it can be guided out the periurethral tunnel lateral to the urethra. The sling is connected to the trocar and pulled through the periurethral tunnel, around the ischiopubic ramus and out the inner thigh incision (Fig. 29.4). The sling is clamped and cut just below the trocar, and the trocar is removed from the operative field. This procedure is repeated on the opposite side (Fig. 29.5). Although some have suggested that intraoperative cystoscopy may be unnecessary with the TOT, bladder injuries have been reported.49,50 Routine cystoscopy is recommended because of the significant adverse consequences that can occur with an unrecognized bladder injury involving an exposed foreign body within the bladder.

The sling is adjusted in a tension-free application beneath the midurethra. Tensioning techniques are similar to those described for the TVT. Some authors have suggested that TOT slings should be tensioned somewhat tighter than a TVT; however, there are no randomized trials evaluating different TOT tensioning techniques. Once the desired tension is achieved, the sheath encasing the sling is removed while stabilizing the sling below the urethra. The outer ends of the sling are cut below the skin surface and the incisions are closed with 4-0 absorbable suture or skin adhesive. The vaginal incision is closed with 2-0 or 3-0 absorbable suture in a running fashion. A voiding trial is typically performed in the recovery room.

Unlike other TOT kits, the TVT Obturator (TVT-O) system (Ethicon, Somerville, New Jersey) uses an inside-out approach. Like the TOT procedure, a 2-cm midurethral incision is made, and the periurethral tunnels are developed bilaterally. Unlike the TOT,

where the dissection stops at the ischiopubic ramus, the obturator membrane is perforated with the tip of the scissors in this approach. Included within the TVT-O kit is a winged metal trocar guide whose purpose is to help guide the helical TVT-O trocars around the ischiopubic ramus. The winged guide is inserted into the periurethral tunnels, and the tip is pushed just beyond the perforated obturator membrane. The tip of the helical trocar is passed into the periurethral tunnel just inside the metal guide (Fig. 29.6). The trocar is then rotated around the ischiopubic ramus to exit the skin through stab incisions (Fig. 29.7). The groin incisions of the TVT-O are somewhat lateral to those of the outside-in technique, located 2 cm above a horizontal line at the level of the urethral meatus and 2 cm outside the thigh folds. The sling is then pulled through the thigh incision and held. The same procedure is repeated on the opposite side. The sling is tensioned and the procedure completed similar to technique described earlier.

Retropubic Midurethral Sling Complications

One of the aspects of the TVT procedure that differentiates it from more traditional continence procedures is the blind trocar passage through the retropubic space. This blind trocar passage has been the source of some concern, particularly regarding perioperative complications. Generally, the complication rate with the TVT procedure is low; however, in meta-analysis of comparative data, bladder perforations were more common after MUS compared to Burch colposuspensions, and lower urinary tract symptoms and reoperation were more common after traditional sling procedures.3,51,52 Long-term outcomes following surgical treatment for SUI have been evaluated in several population-based datasets. Muller et al.53 used National Health Service administrative data to compare the risk of reoperation up to 10 years after retropubic colposuspension, mesh sling insertion, and autologous sling in 96,020 women. They found retropubic colposuspension was associated with a higher risk of reoperation in the first 10 years after SUI surgery compared with mesh sling insertion or autologous sling procedures (21.3% compared to 10.9% and 12%, respectively).53

The complication rates noted in early nationwide registries from Finland and Austria are shown in Table 29.2. The one complication that occurs more frequently with TVT than with other procedures is bladder injury, ranging from 2.9% to 9% in the literature.54,55,56,57 Fortunately, the long-term sequelae from these bladder perforations appear to be minimal, assuming

they are identified intraoperatively. Trocar injuries to the bladder are typically small and extraperitoneal, requiring no intervention other than replacement of the trocar in the proper location. Trocar injuries of the bowel and major blood vessels have been reported but are exceedingly rare.54,55,57

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May 1, 2023 | Posted by in GYNECOLOGY | Comments Off on Midurethral Slings

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