Women with stress urinary incontinence (SUI) are recognized to have a spectrum of urethral characteristics ranging from a highly mobile urethra with good intrinsic function to an immobile urethra with poor intrinsic function.1 In intrinsic sphincter deficiency, the urethral closure mechanism is considered to function poorly, possibly due to aging, previous surgery, or a neurological etiology. Clinically, women with intrinsic sphincter deficiency have more severe incontinence and a lower surgical success rate than women with stress incontinence and normal urethral function. Before the introduction of tension-free vaginal tape (TVT), the pubovaginal sling was considered the procedure of choice for women with intrinsic sphincter deficiency and bulking agents a less morbid but less successful second choice.2
Minimally invasive midurethral synthetic slings have largely replaced both the pubovaginal fascial sling and Burch colposuspension and are currently the most common procedures performed for SUI. The first of these to be introduced, TVT has been assessed prospectively and has a long-term success rate of more than 77% in the cure of SUI.3 The TVT procedure has been shown to have efficacy equivalent to Burch colposuspension with fewer adverse effects and a faster recovery.4,5 A cure rate of 74% and improvement of 12% was described with TVT in women with intrinsic sphincter deficiency, defined as maximum urethral closure pressure less than 20 cm H2O.6 The intraoperative morbidities described with TVT are bladder perforation and, rarely, vascular and bowel injury.
Transobturator tape was introduced to avoid the retropubic space and to minimize the risk of viscus or vascular injury. Transobturator tape has been shown to have similar efficacy and safety to TVT in retrospective series and meta-analyses.7 However, the number of women with stress incontinence and intrinsic sphincter deficiency was small and not analyzed separately; indeed, intrinsic sphincter deficiency was frequently an exclusion criterion.8,9
Based on a systematic search of the literature from 1996 to the present using PubMed (search terms: TVT, transobturator tape, intrinsic sphincter deficiency, randomized controlled trial, RCT). There is no prospective, randomized controlled study of TVT compared with transobturator tape in women with intrinsic sphincter deficiency published in the literature. The purpose of this study was to compare the efficacy of the TVT retropubic approach with transobturator tape in women with SUI and intrinsic sphincter deficiency.
MATERIALS AND METHODS
This study was approved by the ethics committees of the two participating hospitals. All women with SUI who had unsuccessful conservative therapy and, on urodynamic assessment, had a diagnosis of intrinsic sphincter deficiency were invited to participate in this trial to compare the efficacy of TVT and transobturator tape. Written informed consent was obtained.
All methods and definitions conform to the standards recommended by the International Continence Society (Herrmann V, Herrmann V, Palma PCR, Riccetto CLZ, Cruz J, Fraga R, et al. Minimally invasive surgical treatment for stress urinary incontinence: preliminary results with Monarc [abstract]. Int Urogynecol J 2003;14(suppl 1): S30].1 The surgeons were experienced in the TVT and transobturator tape procedures, having performed at least 15 of each independently before the study.
The diagnosis of intrinsic sphincter deficiency was based on the measurements of the resting maximum urethral pressure profile and/or the abdominal leak point pressure with valsalva maneuver and/or cough. Intrinsic sphincter deficiency was defined as either a maximum urethral closure pressure (measured both with the bladder empty and at capacity) of 20 cm H2O or less10 and/or a pressure rise from baseline required to cause incontinence (Δ valsalva or cough leak point pressure) of 60 cm H2O or less.11 In our institutions, these measurements normally are taken at 500 mL bladder fill or at maximum bladder capacity if less than 500 mL.
Exclusion criteria were the presence of pelvic infection, a persistent postvoid residual volume greater than 100 mL, malignancy, fistula, congenital or neurogenic bladder disorder, and inability to give informed consent. Women requiring concomitant pelvic organ prolapse surgery or with coexisting detrusor overactivity were included.
The preoperative and postoperative protocol was a comprehensive urogynecologic history and examination, a 24-hour pad test, a 3-day urinary diary, and multichannel urodynamic testing. This included uroflowmetry, resting urethral pressure profilometry before and after cystometry to a capacity up to 500 mL if tolerated, estimation of valsalva and cough leak point pressure in the semi-recumbent and standing position by direct visualization, and a voiding pressure study. The short forms of the Urogenital Distress Inventory (UDI6) and the Incontinence Impact Questionnaire (IIQ7) were used for subjective assessment of quality of life (QOL), and patients self-evaluated the success of their sling procedures with a numerical success score ranging from 0 to 100 (0 corresponding with complete failure and 100 with complete cure).
Women were randomized to TVT or transobturator tape using a computer-generated random allocation.
All women received prophylactic antibiotic treatment at the beginning of the surgery. The anesthesia was local anesthesia and sedation, spinal, or general anesthesia, depending on patient and surgeon preference. The TVT procedure (Gynecare, Ethicon, Inc., Somerville, NJ) was performed as previously described by Ulmsten.12 The transobturator tape procedure was performed with the Monarc subfascial hammock system (American Medical Systems, Inc., Minnetonka, MN) using the technique described by the manufacturer. Cystoscopy was used routinely to verify the absence of bladder and urethral injury after both procedures (TVT and transobturator tape). Sling tensioning was by a tension-free placement of fine dissecting scissors between urethra and tape with or without the aid of a cough test.
The postoperative catheter management for women who had a sling alone was removal of the catheter at the end of the procedure followed by a trial of void. Those patients with concomitant prolapse surgery often had a catheter and vaginal pack left in for 24 to 48 hours. In all patients, a successful trial of void was defined by two postvoid residual urine volumes less than 150 mL on ultrasound examination. Short-term urinary retention was managed by intermittent or continuous catheter drainage.
Postoperatively, all women were reviewed at 6 weeks, 6 and 12 months, and annually thereafter. At 6 months, the urodynamic assessment and 24-hour pad weight test were repeated in addition to the QOL questionnaires and numerical success score.
The primary endpoint for this study was the objective failure of tape surgery assessed at 6 months on urodynamic testing. Failure was defined as urodynamic stress incontinence. The secondary outcomes that were evaluated included subjective failure rate with symptoms requiring further surgery, intraoperative and postoperative complications, voiding function, urgency or urge incontinence symptoms, and change in QOL as assessed by the Short Urinary Distress Inventory and Short Incontinence Impact Questionnaire.
The sample size calculation was performed assuming an 80% success rate in the TVT group and a chosen effect size of 20%. At a power of 80% and a significance level of .05, the sample size estimate was 91 patients per group. Recruitment began in February 2004, and, by February 2007, the accrual rate was falling and the trial was ceased. The demographic data are tabulated, but no hypothesis testing is used to compare demographic data groups. Data are presented as mean (standard deviation), median [25th–75th percentile] depending on distribution or count (%). Hypothesis testing based on postoperative–preoperative difference scores used the Wilcoxon signed rank test for within-group change and the Wilcoxon rank sum test for between-group analysis for continuous data. Count data used McNemar’s test for within-group change and the Fisher exact test for between-group comparisons. Significance level was set at .05. Significance level within domains was adjusted for multiple comparisons using the Bonferroni correction. Stata 10 statistical software was used in all analyses (Stata Corp., College Station, TX).
A total of 180 women were assessed for eligibility. Sixteen women declined participation, and 164 women who met the inclusion criteria and consented to participate were randomly assigned to either TVT (n=82) or transobturator tape sling (n=82) and underwent surgery. Three women were lost to follow-up in each group, and a further three overall (two TVT and one transobturator tape) requested withdrawal from the trial. All randomized patients received their allocated treatment except one patient, randomized to TVT; the TVT was abandoned because of repeated bladder perforation, and a transobturator tape sling was performed. Analysis was by intention to treat; therefore, this patient continued as a participant in the TVT group (Fig. 1).
Table 1 shows no clinically significant difference in demographic characteristics such as age, parity, menopausal status, use of hormone replacement, and type of anesthesia between the two groups. In one third of both groups, concomitant prolapse surgery was performed.
Operating time, estimated blood loss, duration of catheterization, and length of hospital stay were similar between the two groups (Table 2). The most common tape-related intraoperative complications were bladder perforation (7.3% with TVT compared with 0% with transobturator tape) and vaginal perforation (4.9% with transobturator tape compared with 0% with TVT). The incidence of bladder perforation in TVT performed by a consultant urogynecologist was 0 in 46 cases compared with 6 in 36 cases performed by gynecologists in fellowship training (Fisher exact test, P=.006). When bladder perforation was recognized, the trochar was reintroduced, cystoscopy repeated, and indwelling urethral catheter left overnight. Four vaginal perforations were recognized and repaired intraoperatively. There were no longer-term sequelae of bladder or vaginal perforation. There was no difference in the number of patients with total blood loss greater than 200 mL; in the majority, the blood loss was due to concomitant prolapse surgery. None of the patients required blood transfusions or surgical exploration and drainage. One patient required surgical exploration and drainage of an abscess at the left groin site 6 months postoperatively in the transobturator tape group. Division of the tape was performed in three patients (two with TVT and one with transobturator tape); loosening of the tape within the first 2 weeks was performed once in each group (Table 2).
Urodynamic assessment was repeated 6 months after surgery in 138 of the participants (67 TVT and 71 transobturator tape). Seventeen patients (10 TVT and seven transobturator tape) declined the repeat assessment because they were “cured” on subjective assessment and did not feel that further testing was needed. Analysis of baseline characteristics of women who did not have urodynamics at 6 months has been performed, and there is no difference between the groups. Of the 138 patients tested, 14 of 67 (21%) in the TVT group had stress incontinence demonstrated during repeat urodynamic assessment compared with 32 of 71 (45%) in the transobturator tape group (Fisher exact test, P=.004). Excluding women symptomatically cured declining urodynamics in the TVT group, 19 of 72 (26%) had urodynamic stress incontinence compared with 36 of 75 (48%) in the transobturator tape group (Fisher exact test, P=.01). Of these, 13 of 72 in the TVT group compared with 19 of 75 in the transobturator tape group reported no symptoms of incontinence. A small number reported leakage that was “not bothersome” (one TVT compared with four transobturator tape). Nine of 67 women (13%) in the transobturator tape group did request further surgical treatment to correct SUI compared with 0 of 71 (0%) in the TVT group. In the intention-to-treat analysis, 13 of 82 (19.9%) patients in the transobturator tape group compared with 5 of 82 (6.1%) in the TVT group (Fisher exact test, P=.08) would have requested repeat surgery. The incident rate difference was 9.7% (95% confidence interval 0–19.9); repeat surgery would be requested in one of every six transobturator tape procedures compared with 1 in every 16 TVT procedures. The risk ratio of repeat surgery was 2.6 (95% confidence interval 0.9–9.3) times higher in the transobturator tape group.
Repeat surgery with TVT was performed in all women except for one in the transobturator tape group who developed a groin infection requiring partial sling removal, drainage, and antibiotic treatment; subsequently, she had a pubovaginal sling. Of the nine women who received further surgery, six were cured and three reported persistent SUI, including one with minimal leakage.
Prior continence surgery had occurred in six women in the TVT group and in 10 women in the transobturator tape group. In the TVT group, four of the six women were continent and had a normal 6-month urodynamic assessment, one had urodynamic stress incontinence but was asymptomatic, and one was lost to follow-up. In the transobturator tape group, 4 of the 10 women with previous SUI surgery had normal 6-month urodynamic results, five had urodynamic stress incontinence (three asymptomatic, one coital incontinence, one symptomatic and received a repeat sling), and one declined urodynamic assessment because she was asymptomatic.
The repeat urodynamic assessment at 6 months showed a statistically significant decrease in the maximum flow rate from baseline in both the TVT and transobturator tape groups. There was no significant difference between groups in maximal flow rate; however, postvoid residual urine volume was significantly increased postoperatively in the TVT group only (Table 3).
The incidence of urinary frequency (more than seven voids per day) and nocturia (more than two voids per night) did not change between preoperative and postoperative assessments and showed no difference between the two slings. The prevalence of urgency did not differ preoperatively and postoperatively or between TVT and transobturator tape sling and resolved in 14 of 28 (50%) women and 15 of 34 (44%) women, respectively. There was no statistical difference in the incidence of de novo urgency between the two groups (21% in the TVT group and 10% in the transobturator tape group). Urge incontinence increased in both sling groups after surgery but did not reach statistical significance. The resolution of urge incontinence was 4 of 10 (40%) women in the TVT group and 4 of 11 (36%) women in the transobturator tape group. In addition, the incidence of de novo urge incontinence was similar in both groups (13%).
In both groups, the 24-hour pad weight test showed a large baseline variation but confirmed severe incontinence with median loss of 25 g for the TVT group and 45 g for the transobturator tape group. There was marked improvement after surgery in both the TVT and transobturator tape groups to a median of 0 g (Wilcoxon signed rank test, P<.001 in both groups) and no statistically significant difference between the two groups (Wilcoxon rank sum test, P=.53) (Table 3).
The baseline QOL assessment (UDI6, IIQ7) did not differ between the two groups. In both the TVT and transobturator tape groups, there was an overall marked improvement postoperatively in UDI6 and IIQ7 scores to a median score of 3 and 0, respectively (Wilcoxon signed rank test, P<.001). There was no difference in improvement between groups. In the group of women requiring repeat surgery, the mean score for UDI6 was similar preoperatively and 6 months postoperatively (preoperative score 12, postoperative score 11) and significantly improved after repeat surgery (mean score 5). The mean score of the IIQ7 also was similar preoperatively and postoperatively (preoperative score 12, postoperative score 11) and improved after repeat surgery (mean score 3.5).
Since its advent in 2001, transobturator tape has been increasingly used in preference to the retropubic sling to correct urinary stress incontinence. One meta-analysis has suggested that transobturator tape is as effective as a retropubic sling but has less risk of serious vascular or visceral injuries and possibly less postoperative voiding dysfunction.13 The subgroup of stress-incontinent women with intrinsic sphincter deficiency represents a more severe form of stress incontinence that has a poorer surgical outcome. Pubovaginal and retropubic sling surgery has been recommended as primary surgical treatment for all women with intrinsic sphincter deficiency.6,14
Despite the popularity of transobturator tape, few studies have prospectively evaluated its efficacy compared with TVT in women with intrinsic sphincter deficiency stress incontinence.
Goktolga et al found that TVT had an initial success rate of 87% at 6 months, which reduced to 74% at 5-year follow-up in women with intrinsic sphincter deficiency.15 In a series of 20 women with intrinsic sphincter deficiency who underwent the transobturator tape procedure (Monarc), the cure rate was 95% at 4-month follow-up.16 However, two retrospective studies have reported that TVT is less effective in women with urodynamic stress incontinence and intrinsic sphincter deficiency than urodynamic stress incontinence alone.17,18 In retrospective studies in women with intrinsic sphincter deficiency, Jeon and colleagues found a significantly lower success rate after transobturator tape compared with pubovaginal sling and TVT.19 Miller et al20 reported a six times higher failure rate in transobturator tape compared with TVT in women with borderline-low maximum urethral closure pressure (less than 40 cm H2O); this was confirmed by Guerette et al.21 Popovic et al reported only a slight reduction in success after transobturator tape.22 In our series, patients with urodynamic stress incontinence and intrinsic sphincter deficiency fared significantly worse with the transobturator tape compared with TVT, with further surgery after 6 months required in 13% of the transobturator tape group compared with 0% in the TVT group. One possible explanation for this may be the difference in sling axis of these two approaches. The sling axis of the TVT is more perpendicular to the urethral axis, creating more circumferential compression of the urethra. The less-acute axis of the transobturator tape mimics the subfascial hammock support of the urethra,23 and, therefore, it may not provide adequate support in the intrinsic sphincter deficiency group suffering from more severe compromise of the urethral closure and support mechanism.20,24
On ultrasound assessment, Long et al compared TVT and transobturator tape (TVT-Obturator), showing that, at rest or during valsalva, the middle of the TVT-Obturator tape localized more distally than the TVT (P<.01). A higher rate of urethral kinking during straining was observed in the TVT group compared with the TVT-Obturator group after surgery (86.9% compared with 23.9%, P<.01). This difference also may contribute to reduced success of transobturator tape in the subgroup of intrinsic sphincter deficiency.25
Sling tension did not appear to be a significant factor because clinicians sought to achieve tension-free placement of slings in both procedures. Similar to Barry et al,26 we found that a reduction in the maximum urine flow rate was measured after both procedures, but no difference between the two slings was observed. The increased postvoid residual volume in the TVT group from 5 to 19 mL postoperatively was statistically significant but probably not clinically significant. Furthermore, the rate of voiding difficulty and need for tape loosening/division was similar in both groups. In his meta-analysis, Latthe et al found that voiding difficulty was significantly less with transobturator tape than with the retropubic TVT-type tapes.9 However, in another recent prospective randomized trial,26 no significant difference was found in the incidence of postoperative voiding difficulties between the TVT and transobturator tape groups, similar to our results.
The total number of reported intraoperative and early postoperative complications was similar in both groups. Bladder perforation was the most common complication in the TVT group but appears not to cause any long-term sequelae. In our study, surgical experience with TVT was an important factor in the incidence of bladder perforation, confirming a longer learning curve for insertion of TVT.27
The subjective outcome measures in QOL questionnaires did show a significant improvement postoperatively within each group, and there was no significant difference between the two groups. The discrepancy between subjective and objective results may be due to the high overall satisfaction scores in both treatment groups and the low number of patients being symptomatic enough to require further treatment (nine in the transobturator tape group). Secondly, the questionnaires also capture aspects of urogenital well-being other than stress incontinence and, therefore, may not be specific enough to reflect on stress incontinence in the setting of our trial.
The number of patients recruited fell short of that determined by sample size calculation because of both falling recruitment numbers and limitations of resources. We found a difference of 9.7% in the rate of repeat surgery between the TVT and transobturator tape sling procedures, and, although this was not found to be statistically significant at the .05 level, the smaller sample size may have led to a type II error. With 164 patients, this study had a power of 0.75 to detect a 20% difference or 80% power to detect a 22% difference in cure rates. We considered participants with subjective cure who declined invasive repeat urodynamic testing at 6 months as treatment successes, whereas patients who withdrew or who were lost to follow-up were regarded as treatment failures. A further limitation of this study is the nonblinded study design of surgeon and patient to the treatment assignment; however, because efficacy at 6 months was the primary outcome, blinding of the patient to the type of sling was of little relevance. Six-month follow-up is relatively short, but this article concerns itself with the primary short-term surgical failures that are well known to the clinician who treats patients with intrinsic sphincter deficiency.
One third of the patients in both groups had concomitant pelvic reconstructive surgery. Therefore, blood loss, voiding times, and length of hospital stay in this study are likely to be overestimated compared with sling-only surgery. Concomitant pelvic reconstructive surgery did not affect treatment efficacy of TVT or transobturator tape slings in intrinsic sphincter deficiency. This trial population also represents our usual patient population of multiple pelvic floor defects.
In conclusion, women with SUI associated with intrinsic sphincter deficiency are significantly less likely to have recurrent urodynamic stress incontinence or require further SUI surgery after insertion of retropubic TVT than the transobturator sling in the short term. On the basis of the findings of our study, we conclude that, in the treatment of urodynamic stress incontinence with intrinsic sphincter deficiency, the insertion of TVT is the preferable surgical option. We chose to study women with intrinsic sphincter deficiency because they are the most severely affected in the spectrum of female SUI and have worse outcomes; if there was a difference in effectiveness, it would show first in this group. It remains to be seen whether the increased failure of transobturator tape compared with TVT found at 6 months in women with intrinsic sphincter deficiency continues into the long term.
Prospective randomized trials of TVT and transobturator tape with longer follow-up are necessary in women with good and poor intrinsic function to determine the efficacy and safety of these procedures and their place in the treatment of female stress urinary incontinence.
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