Since it was introduced in 1996, the minimally invasive retropubic tension-free vaginal tape (TVT) procedure1–9 has become the surgery of choice for treating stress urinary incontinence (SUI). Concern about complications associated with TVT4–9 led in 2001 to the development of another minimally invasive procedure using the transobturator tape.10
Before introducing transobturator tape into clinical practice in Calgary, we conducted a trial of 52 transobturator tape procedures using the Obtape device (Mentor Corp., Santa Barbara, CA). At 12 months postoperatively, the vaginal erosion rate was found to be unacceptably high (15%).11 We believed that the high rate of erosion was associated with the polypropylene mesh (pore size 50 micrometers) used in the Obtape device,12 but we remained concerned that the transobturator approach itself could be at fault. We decided to undertake a randomized trial comparing transobturator tape with TVT using surgical devices from a single manufacturer that incorporated a polypropylene mesh that was completely macroporous (pore size more than 75 micrometers) to permit infiltration by macrophages, fibroblasts, and blood vessels.12 Thus, the trial was designed to compare the outcome of the different surgical approaches.
Our study was designed to answer the following primary question: How effective is transobturator tape compared with TVT in terms of objective cure at 12 months postoperatively? Secondary questions examined surgical complications and subjective effectiveness of transobturator tape compared with TVT at 12 months.
MATERIALS AND METHODS
The study was conducted by seven surgeons (urogynecologists, urologists, obstetrician–gynecologists) in a tertiary care hospital and two academic community hospitals in Calgary. All surgeons received training in both techniques and had carried out at least five of each procedure using Boston Scientific (Natick, MA) devices before recruiting patients to the trial. During the period of recruitment, transobturator tape was available only as a study intervention. The TVT was considered the standard of care. The study was approved by the University of Calgary Conjoint Health Research Ethics Board (Ethics ID 18421).
Women were eligible for inclusion if they 1) elected surgical management of SUI, 2) were visualized leaking urine from the urethra with cough,13,14 and 3) were suitable for either the transobturator tape or TVT sling procedure. Women were excluded if they had previous incontinence surgery; required any concurrent surgery; had an overactive bladder (urinary frequency and urgency with or without urge incontinence15); had more than 100 mL postvoid residual; intended to have more children; had Alzheimer’s or Parkinson’s disease, progressive neurological disease such as multiple sclerosis, or were immunocompromised; were unable to understand English; or would be unavailable for follow-up. Patients agreeing to join the study provided written informed consent.
Participants were asked to complete a questionnaire including incontinence-related quality of life questions (Urogenital Distress Inventory [UDI-6], a six-item measure of urogenital distress, and incontinence impact questionnaire [IIQ-7], a seven-item measure of incontinence effect16). Patient characteristics were abstracted from patient charts.
Consenting patients were randomly allocated to receive either a transobturator tape procedure or a TVT procedure. The randomization list was generated by the study statistician (using ralloc procedure in Stata [StataCorp LP, College Station, TX]) using permuted block randomization with block sizes varying from 2 to 8 and stratification by surgeon. Neither the surgical team nor the patient knew the next treatment allocation. Randomization was carried out a few days before surgery to ensure that the appropriate surgical device was available in the operating room.
Boston Scientific (Natick, MA) devices were used for all procedures: the outside-in Obtryx Halo midurethral sling system was used for transobturator tape procedures, and the Advantage retropubic midurethral sling system was used for TVT procedures. All procedures were carried out according to the usual practice of participating surgeons, consistent with the recommendations of Boston Scientific. Anesthesia was either general or local, depending on the clinical state and choice of the patient and according to the usual clinical practice of the anesthesiologist. Intraoperative cystoscopy was carried out for all patients. Where possible, operations were planned as outpatient procedures with postoperative home care (usual care in Calgary). If necessary for clinical or logistic reasons, women were admitted to the hospital. Surgical details were extracted from patient charts and verified by the surgeon if necessary.
Outcomes were measured at 12 months after surgery. All participating women were invited to the Pelvic Floor Clinic for follow-up. Data were collected by an independent research nurse. Women who were unable to attend the Pelvic Floor Clinic were asked to complete questionnaires, including subjective outcome and return to usual activities.
Objective evidence of SUI was obtained using a standardized pad test at 12 months after surgery. Women undertaking the test had retrograde bladder filling with 300 mL of sterile water and wore preweighed pads while they undertook the physical activities recommended by the International Continence Society.13 Women were considered “cured” if the pad weight gain was less than 1 g over the test period.2,17
Complications were identified from hospital and routine 6-week follow-up charts. At the 12-month follow-up, women undertook a urine-flow test to assess voiding dysfunction. A physician carried out standardized examinations of operative wounds and digital vaginal examinations to palpate for tape extrusion and pain. Women also were asked to recall any problems they had experienced after surgery.
Subjective symptom assessment by questionnaire took place 12 months after surgery. Subjective cure was defined as “no experience of lost or leaked urine when you coughed, laughed, sneezed, lifted, exercised, etc” or if urine loss had been “no problem at all” or a “small problem” over the previous 7 days.
All women were asked at 12 months to complete UDI-6 and IIQ-7.16 Each measure produces a single score of 0 (no distress for UDI-6, no impact for IIQ-7) to 100 (maximum distress or impact). Both measures were developed for use in incontinence trials, have been independently validated,18–20 and are widely used.21
At 12 months, women were asked whether they had returned to their usual sexual activity and when they had done so. They also were asked whether the outcome of surgery had met expectations and whether they would recommend the surgery to someone else.
At the start of our study, the baseline TVT cure rate was estimated to be 73%.2 The study clinicians decided that a 15% difference between groups (eg, 90% compared with 75%) would be necessary to change clinical practice. To detect a difference of that order, assuming 80% power and a two-sided significance level of 0.05, a sample of 100 patients per group with complete follow-up would be required (total 200).
Analyses were undertaken following the intention-to-treat principle: women were analyzed in the surgical group to which they were randomized. A single analysis was planned when all women had completed the 12 month follow-up.
Data entry and management were carried out using Access (Microsoft, Redmond, WA), and analyses were carried out using SAS 9.1 (SAS Institute, Inc., Cary, NC). Primary outcome data were verified visually for all records, and range and logic checks identified other data discrepancies. All complications were reviewed by a urogynecologist. Descriptive statistics (means, standard deviations, proportions) were calculated for baseline data. The primary analysis compared the proportion of patients who demonstrated cure on the 1-hour pad test at 12 months after surgery using the Fisher exact test; relative risk (RR) and 95% confidence interval (CI) also are reported. Analyses of secondary outcomes used the Fisher exact test to compare binomial outcomes for the two groups. Time differences were compared using the Mann-Whitney U-test. Changes in UDI-6 and IIQ-7 scores were compared using unpaired t tests. Imputation was not used for missing data except in sensitivity analyses for the primary outcome. Results are reported according to the CONSORT Statement extension for pragmatic trials.22
The study recruited 228 women between October 2005 and June 2007 (Fig. 1). Twenty-nine women, not included in the analysis, consented to join the study but were not selected because recruitment closed before their operations were scheduled. Of the 199 women randomly assigned, 94 were allocated to the transobturator tape group and 105 to the TVT group. A total of 182 (91%) women were followed up at 12 months.
Baseline data are presented in Table 1. Mean age was 50.1 years for the transobturator tape group and 51.8 for the TVT group. The majority of women were parous (89 [94.7%] in the transobturator tape group and 96 [91.4%] in the TVT group). Median UDI-6 scores were 39 for the transobturator tape group and 44 for the TVT group, and median IIQ-7 scores were 33 for both groups.
Operative details and hospital stay are presented in Table 2. All women had the allocated surgery, except one woman in the transobturator tape group whose surgeon initiated a transobturator tape procedure but converted to the TVT procedure at the same surgery after urethral muscles were torn. Other operative complications were as follows: one transobturator tape patient required two passes of the transobturator tape needles on the left side, three TVT patients had bladder perforations, and three TVT patients had a 200-mL or larger blood loss. Duration of operation was similar for both groups (median 19 minutes for transobturator tape compared with 18 minutes for TVT). The majority of women in each group had their operations as outpatient procedures and were not admitted to the hospital (87 [92.5%] in the transobturator tape group and 88 [83.8%] in the TVT group). Women who were admitted to the hospital stayed a median of 1 day.
The primary outcome, objective cure at 12 months postoperatively, was measured using a pad test in 84 women in the transobturator tape group and 87 women in the TVT group (Table 3). Of the women in the transobturator tape group, 68 (81.0%) were cured, compared with 67 (77.0%) in the TVT group (not statistically different). Sensitivity analyses were performed to estimate whether the incomplete cases affected the results. Neither assuming all nonresponders failed (RR 1.13, 95% CI 0.94–1.37) nor that all nonresponders were cured (RR 1.03, 95% CI 0.90–1.17) changed the conclusion in a meaningful way.
Additional pelvic procedures since the index surgery were reported for seven women (8.2%) in the transobturator tape group and five women (5.6%) in the TVT group, mainly associated with release of tape or surgery for mesh extrusion (Table 3). At follow-up, other complications during the 12-month postoperative period were reported by 19 women (22.4%) in the transobturator tape group and 20 women (22.2%) in the TVT group, most of which were minor and did not require treatment. Palpation of the external wound sites was normal for 82 women (96.5%) in the transobturator tape group and 89 women (98.9%) in the TVT group (P>.999). However, on vaginal examination, the tape was palpable for 68 women (80.0%) in the transobturator tape group and for 24 women (26.7%) in the TVT group (P<.001); more women in the transobturator tape group experienced groin pain during vaginal palpation (13 [15.3%] in the transobturator tape group and five [5.6%] in the TVT group, P=.044). Among the women with abnormal palpation in the transobturator tape group, five were found to have small vaginal extrusions, which were treated successfully with Premarin cream.
Questionnaires were completed at 12 months by 86 of 94 women (91.5%) in the transobturator tape group and by 95 of 105 women (90.5%) in the TVT group (Table 4). Incontinence symptoms did not differ between groups: subjective cure (no or little problem with stress incontinence symptoms) was reported by 85 women (98.8%) in the transobturator tape group and 88 women (92.6%) in the TVT group. Quality of life had improved for both groups as reported using UDI-6 and IIQ-7 (median UDI-6 scores: 3 for the transobturator tape group, 11 for the TVT group; median IIQ-7 scores: 0 for both groups) but did not differ between groups. The majority of women in both groups (58 [67.4%] in the transobturator tape group and 54 [56.8%] in the TVT group, P=.766) had returned to usual sexual activities by a median of 6 weeks (interquartile range 6 to 8). The majority of women reported that the surgery met their expectations (78 [90.7%] in the transobturator tape group compared with 80 [84.2%] in the TVT group, P=.133) and would recommend the surgery to someone else with similar symptoms (82 [95.4%] compared with 88 [92.6%], P=.622).
Our randomized trial compared the effectiveness of transobturator tape with TVT in terms of objective and subjective cure at 12 months postoperatively, finding that the majority of women were cured, with no statistically significant difference between groups. Despite the lack of difference in cure rate between groups, it was found on digital vaginal examination that more women in the transobturator tape group had tape that was palpable and experienced groin pain compared with women in the TVT group.
Two systematic reviews have examined the evidence on effectiveness of transobturator tape compared with TVT, without finding clear differences in outcome.23,24 Objective cure after transobturator tape ranged from 84% to 98%; for TVT it ranged from 86% to 99%.23,24 The objective cure rates in our study (81.0% for transobturator tape, 77.0% for TVT) appear lower than those previously reported, but the difference is likely because our follow-up and definition of objective cure was very rigorous.
In our study, the most common perioperative complications associated with TVT were bladder perforation and bleeding. Bladder perforation also was found to be the most commonly reported complication for TVT in studies of transobturator tape compared with TVT.9,24–27 One review suggests that bladder perforation may be related to surgeon inexperience.9 Our study involved only experienced surgeons, perhaps leading to our lower than usual perforation rate (2.9%) but also suggesting that even surgeons experienced in the use of TVT may encounter this complication.
Authors have discussed whether transobturator tape may be associated with more vaginal mesh extrusions or erosions compared with TVT, finding insufficient evidence to support this possible association,9,25,26 except in the instance of Obtape (Mentor Corp., Santa Barbara, CA).9 Our previous research found a high vaginal erosion rate of 15% among women who had transobturator tape procedures using Obtape,11 and we were concerned that this may be a problem with the obturator approach more generally. Our current randomized controlled trial therefore included a systematic vaginal examination of women at 12 months postoperatively. One patient in each group required surgery for mesh extrusion, a much lower rate than that found in our previous research,11 which we believe is because of the more favorable characteristics of the Boston Scientific (Natick, MA) surgical tape (woven tape with pore size more than 75 micrometers). Postoperative vaginal examination found a high proportion of patients with palpable tape in the transobturator tape group compared with the TVT group (80.0% compared with 26.7%). Of particular concern, some of these women also experienced tenderness and groin pain on vaginal examination. These are unexpected findings, and we are unable to say what will be the longer-term consequences. Possible options are that no further deterioration will occur or that the tape will be incorporated deeper into the tissues. Another more troubling option is that some women will go on to develop tape extrusion over time. To determine the longer-term consequences of palpable tape, we intend to seek funding for follow-up of the trial patients at 5 years postoperatively.
Our study was designed as a pragmatic, randomized trial to reflect usual clinical practice and to maximize the applicability of the results.22 It was undertaken in academic and community academic settings, involving a variety of surgeons and ensuring that the study findings are generalizable. Our study did not include patients requiring concomitant procedures, allowing us to be confident that the outcomes measured were related to the stress incontinence surgery, unlike Barber’s recent trial, in which 62% of patients had concomitant surgery such as hysterectomy or prolapse repair.25 Our standardized 12-month follow-up ensures that our follow-up rate and comparisons between groups are easy to interpret, in contrast to Barber’s variable follow-up (mean 18 months).25 Outcome measurement was not carried out blindly but was conducted by a research nurse who was independent of clinical care. The vaginal examinations were carried out by a clinician (M.R.) who had recruited 24 of the study patients. Although not informed of the patient’s group of allocation at the time of vaginal examination, it became apparent that palpable tapes tended to be associated with transobturator tape, and it was therefore not possible to maintain examiner blinding.
A further difference between our trial and Barber’s is that we designed a conventional trial, whereas Barber’s was a noninferiority trial28 in which a noninferiority margin of 15% would be required before rejecting transobturator tape as being inferior to TVT.25 We did not consider a noninferiority design given the lack of long-term outcome data available for transobturator tape and concerns about vaginal erosion.11 In these circumstances, where there is the potential for long-term adverse effects of a procedure, we believe that benefit should be demonstrated before adopting a newer procedure into clinical practice.29
Our trial did not demonstrate significant differences in objective or subjective outcome between women who had transobturator tape procedures and those who had TVT procedures. At 12 months, the majority of women had minimal urine leakage and their incontinence-specific quality of life had improved significantly, but differences were not observed between groups. Compared with the TVT group, more women in the transobturator tape group had tape that was palpable and groin pain on vaginal examination. The presence of palpable tape is concerning; longer follow-up is needed to determine whether this outcome leads to extrusion or resolves over time. Until long-term follow-up is available from this and other trials, TVT should remain the midurethral sling procedure of choice.
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