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A Sling is Not Just a Backboard of Urethral Support

Petrou, Steven P. MD; Broderick, Gregory A. MD

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Suburethral sling surgery and urethropexy operations are established methods of treating stress urinary incontinence. 1,2 The goal of a surgical urethropexy is to restore the urethra to a high retropubic position. 3,4 In Burch’s description of the Cooper ligament urethrovesical suspension, he describes postoperative changes including a recession of the urethral meatus and an elevation of the bladder neck. 5

Conversely, sling procedures improve coaptation and compression of the urethra and better address urinary incontinence caused by intrinsic sphincter deficiency. 4,6 The sling provides a backboard of suburethral support that is accentuated with abdominal strain and minimal static tension. 7 Because of potential bladder outlet obstruction and secondary urinary retention from a suburethral sling, emphasis has been placed on tying the sling sutures very loosely. 8

This study reviewed the pre- and postoperative static urethral angles of a group of women with stress urinary incontinence who had undergone a pubovaginal sling with autologous rectus abdominis fascia. The objective was to determine whether a loosely tied suburethral sling, which provides a backboard of urethral support, would also mimic a urethropexy by placing the urethra and bladder neck in a higher retropubic position.

Materials and Methods

All women who underwent evaluation for urinary incontinence over a 12-month period were included in the initial study group and evaluated in the same fashion. Patients underwent a urologic-based history, physical examination, and laboratory testing. The physical examination included an assessment for pelvic prolapse and a resting urethral angle measurement. The urethral angle measurement was completed by placement of a sterile cotton swab per urethra to the bladder neck with the patient flat in the dorsal lithotomy position and with an empty bladder. 9 Urethral angle was measured with a goniometer quantifying the degree of deflection of the cotton swab from the horizontal plane. Measurements below the horizontal were referred to as negative and above the horizontal as positive. 10

A single physician performed all urethral angle measurements and physical examinations. Patients’ evaluations were completed with video urodynamics, the Valasalva maneuver leak point pressure determination, and cystourethroscopy when indicated. Fluoroscopic examination of the urethra identified hypermobility, intrinsic deficiency, or a combination of the two. The study group was limited to the women with video-urodynamically proven stress urinary incontinence from urethral hypermobility, intrinsic sphincter deficiency, or a combination of the two, and who were receiving therapy consisting of a suburethral sling operation without synchronous vaginal prolapse repair.

Surgical Technique

All patients who had a classic pubovaginal sling received the modified approach utilizing the Cobb-Ragde needle. 11

With this technique, a 2 × 10 cm rectus fascial strip is harvested from the anterior rectus sheath. Each end of the sling is oversewn with a number 1 polypropylene suture, which acts as the sling suspending suture. The harvest site is closed with a running number 1 polydioxanone suture. Appropriate transvaginal dissection is completed to gain access to the retropubic space. A Cobb-Ragde needle is passed from an intact region of the anterior rectus fascia, at least 2 to 3 cm inferior to the harvest site, under digital control through the retropubic space and out through the vaginal incision. The sling sutures are threaded and transferred suprapubically and then elevated to remove all slack. The sling is positioned just distal to the bladder neck and sutured in place to the periurethral fascia with the use of a small polyglactin suture. Indigo Carmine (Becton Dickinson & Co; Franklin Lakes, NJ) is administered intravenously, and cystourethroscopy is performed to ensure that no suture material has violated the bladder and to document bilateral blue-tinged ureteral efflux. 12 A suprapubic tube is place with standard technique.

After cystoscopy, a 16 French Foley catheter is reinserted. The weighted vaginal retractor is removed and a green surgical towel is placed over the vaginal introitus. The patient is then placed in 20 reverse Trendelenburg position. The ipsilateral sling suspending sutures are tied over an inverted Kelly clamp, yielding an approximately 1 cm air knot (Fig. 1). The bilateral sutures are tied to each other over the midline in a loose loop. The urethra is calibrated with a female urethral sound to assure no undue tethering, and surgical closure is completed.

Figure 1
Figure 1:
Sling sutures are tied with no tension, leaving an actual airknot. Figure reprinted by permission of Mayo Foundation.

After the Kelly clamp is removed, there is no tension on the suspending sutures with an actual air knot present. No attempt is made to suspend the urethra in the retropubic space or change the angulation of the urethra.

Approximately 1 and 3 months after the date of surgery, patients underwent repeat physical examination including pelvic examination, repeat resting urethral angle measurement, and postvoid residual determination. The same physician performed all postoperative examinations, including static urethral angle measurements, and was unaware of the preoperative static urethral angle measurement.


Twenty-nine patients qualified for the study. The patient’s ages ranged from 51 to 81 years (average, 69.5 years). Of the 29 women, 15 were diagnosed with urethral hypermobility, 7 with intrinsic sphincter deficiency, and 7 with a combination of the two. All of the women underwent a pubovaginal sling with autologous rectus abdominis fascia.

Follow-up was concluded 3 months after the operative date. None of the patients had postoperative urinary retention (inability to void or postvoid residual greater than 100 mL). Surgical success was defined by complete subjective urinary continence, with no pad use, and a negative Marshall test during postoperative follow-up examination. The Marshall test was completed with 200 mL in the bladder, with the patient flat and with her legs in the dorsolithotomy position. Twenty-seven of the women were surgical successes and 2 were operative failures secondary to continued stress urinary incontinence.

The overall change in urethral angle at 1 month postoperatively was −15.0 degrees whereas at 3 months it was −14.3 degrees (Table 1). Using the Wilcoxon signed rank test, the change between the 1 month and baseline values and between the 3 month and baseline values was statistically significant (P < 0.001) whereas the difference between the 1 and 3 month angle changes was not (P = 0.909).

Table 1
Table 1:
Urethral Angle Before and After Surgery

Patients were subdivided into three groups based on their incontinence diagnosis (urethral hypermobility (n = 15), intrinsic sphincter deficiency (n = 7), and a combination of the two (n = 7). The data were reanalyzed to see if the angle change with surgery varied depending on the preoperative classification of incontinence (Table 2). Using the Wilcoxon rank sum test there were no statistically significant differences in the value changes among the three groups at 1 month (P = 0.850), 3 months (P = 0.070), or between the 1 and 3 month values (P = 0.310). Meaningful statistical comparisons utilizing the two failures could not be made because of the small numbers.

Table 2
Table 2:
Urethral Angle Before and After Surgery


Static urethral axis position has not been found to differ between continent and incontinent women. 10,13 Urethral position may indicate the degree of urethral support by periurethral tissues but does not in itself determine urethral function. 10 The cotton-swab test has been described as a simple test that establishes the presence or absence of an anatomic defect of the support for the urethra and bladder neck. 9

The pubovaginal sling and the urethropexy are viewed as two different operations. The former provides a backboard of support for the urethra with coaptation and compression of the urethra and the latter maximizes retropubic fixation of the bladder neck. 14,15 Earlier authors have expressed that sling success is based on replacement of the proximal urethra inside the pressure chamber of the abdomen and restoration and support of the urethrovesical angle, but these authors did not stress the importance of loose placement of the sling sutures. 16,17

The current emphasis of sling placement is to not tie the suspension sutures too tightly, which could cause outflow obstruction. 18 However, given the urethral angle changes, even a loosely tied pubovaginal sling may alter postoperative urethral position. If a loosely tied suburethral sling only provided a passive backboard of support and exerted its influence at the time of increases in abdominal pressure, then the static urethral angle would not significantly change after surgery. The change in the straining urethral angle after a suburethral sling has been noted previously. Ogundipe et al volitionally attempted to alter the urethral angle to 0 degrees at the time of surgery. 19 In this study group, no attempt was made to alter the urethral angle, but the average change in the urethral angle was −15.0 degrees.

With a standard pubovaginal sling, access is gained to the retropubic space, which potentiates retropubic fibrosis and supportive scar tissue. The formation of scar tissue may help to fix the urethra in a higher retropubic position. The reported long-term durability of the pubovaginal sling may be secondary to the incorporation of the sling into retropubic scar tissue. 2 This tissue reaction, as has been discussed previously, is necessary for the success of a retropubic urethropexy. 1

Other than reinforced urethral support, the suburethral sling may be similar to a retropubic urethropexy in that it restores the angle to a more retropubic position and is a fibrous-scar based operation. Anatomically, a Burch colposuspension or a Marshall-Marchetti-Krantz operation may be similar to a vaginal patch sling except that the former operations may stimulate a higher measure of retropubic fibrosis by their dissection and the latter is potentially a more suture-based operation. 20 In Burch’s description of the Cooper ligament urethropexy, he states that the bladder neck seems to be suspended in the upper portion of the pelvis by a broad sling. 5 This has also been noted by Korda et al. 21

Because urethral axis does change with a sling, no matter how loosely it is tied, careful preoperative vaginal examination should be performed so as to avoid prolapse by the new vaginal tilt. 6,22 Special emphasis should be placed on identification of a significant cystocele because presence of a large cystocele before colposuspension has been noted in women who required genital prolapse surgery after colposuspension. 23 In contrast, others have doubted the presence of any prolapse induced by vaginal axis change after placement of a pubovaginal sling. 5

The excellent results noted with the suburethral sling in the treatment of incontinence may be secondary to an increase in urethral support and to the more retropubic positioning of the urethra. This combination effect would occur even if the sutures were tied with no tension.


Even when loosely tied, slings change the static urethral axis. This change in urethral angle effectively restores the urethra to a more retropubic position while the suburethral sling provides a backboard of urethral support. This may inadvertently potentiate future vaginal prolapse. Although the suburethral sling has been viewed as different from a urethropexy, it may be similar with regard to alteration of vesico-urethral anatomy.


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