Inside-out versus outside-in transobturator tension-free vaginal tape: A 5-year prospective comparative study


  • Rachel Yau Kar Cheung,

    Corresponding author
    1. Department of Obstetrics and Gynaecology, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
    • Correspondence: Rachel Yau Kar Cheung M.B.Ch.B., M.R.C.O.G., F.H.K.A.M.(O&G), F.H.K.C.O.G., Department of Obstetrics and Gynaecology, Prince of Wales Hospital, 30-32 Ngan Shing Street, Shatin, New Territories, Hong Kong, China. Email:

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  • Symphorosa Shing Chee Chan,

    1. Department of Obstetrics and Gynaecology, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
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  • Ka Wah Yiu,

    1. Department of Obstetrics and Gynaecology, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
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  • Tony Kwok Hung Chung

    1. Department of Obstetrics and Gynaecology, Faculty of Medicine, The Chinese University of Hong Kong, Hong Kong, China
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To compare the 1-year and 5-year outcomes of transobturator tension-free vaginal tape with outside-in and inside-out approaches in women with urinary stress incontinence, and to identify risk factors for treatment failure at 5 years.


A prospective observational study was carried out for women with urinary stress incontinence who underwent transobturator tension-free vaginal tape from September 2004 to March 2008 in a tertiary urogynecology center. Women (n = 213) had either an outside-in (n = 124) or inside-out (n = 89) procedure. They were followed up annually until 5 years after the operation. Subjective cure was defined as women not experiencing any urine loss on physical activity. Objective cure was defined as no urine leak at cough during a standard urodynamic study.


At a mean follow up of 59.2 months, the subjective cure rates were 81.7% and 84.1%; the objective cure rate were 82.6% and 82.5% for the outside-in and inside-out approach, respectively. There was no statistically significant difference between the procedures. De novo overactive bladder syndrome (10.6% in outside-in and 14.6% in inside-out approach; P = 0.40) and de novo detrusor overactivity (5.8% in outside-in and 15% in inside-out approach; P = 0.11) was also comparable between the two groups. Complications at the fifth year were low and not significantly different among both methods.


The outside-in approach and inside-out approach are both safe and effective in treating women with urinary stress incontinence up to 5 years.

Abbreviations & Acronyms

body mass index


detrusor overactivity


maximum urine flow rate


overactive bladder

Pdetmax filling

maximum detrusor pressure at filling


randomized clinical trials


standard deviation


stress urinary incontinence


outside-in approach


transobturator tension-free vaginal tape


tension-free vaginal tape


inside-out approach


urinary stress incontinence


USI is a worldwide health problem that significantly affects the quality of life in women.[1, 2] Midurethral sling has been the most commonly carried out surgical treatment for USI in the past decade.[3] Retropubic TVT has proven to be safe, effective and with a sustainable treatment outcome for over 10 years.[4] TO-TVT was launched and gained its popularity because of the lower surgical risk, but comparable short- to medium-term outcome to TVT. Two types of TO-TVT have been introduced with “inside-out” and “outside-in” techniques. Although these two techniques share the same anatomical approach and use the same synthetic materials for the tape, the curve and shape of the introducer, the way to insert, and the passage are different.[5, 6] Comparisons of these two approaches have been limited to surgical safety and short- to medium-term outcome. Long-term outcome is still lacking.[7]

The present study was carried out to compare the long-term outcome, including subjective and objective cure rates of women with USI who had transobturator tape by two different approaches. The possible factors causing failure of surgery at the fifth year were also evaluated.


This is an analysis of a prospectively collected audit database involving all patients presenting to the outpatients department with urinary incontinence. This cohort now numbers over 7500 patients, accumulated since 1996. The database has been progressively enhanced and improved. The study period was from September 2004 to March 2008, and included all women who presented with predominant urodynamic stress incontinence and had transobturator tape surgery carried out during the aforementioned period. It is therefore a convenient sample. Women with predominant detrusor overactivity and who had previous continence procedures were excluded. Those were mental incapacity that would preclude completion of the questionnaires or refused to complete the questionnaire were excluded.

Ethical approval was obtained from the institutional review board to carry out a multifaceted analysis of this database (CRE-2009.080). No ethical issues were identified.

This comparative observational study was carried out on 213 women who had either TOT (outside-in techniques, MONARC subfascial hammock; American Medical Systems, Minnetonka, MN, USA) or TVT-O (inside-out technique, TVT obturator system; Ethicon, Bridgewater, NJ, USA) carried out in a urogynecology center from September 2004 to March 2008. A total of 124 women who underwent TOT and 89 women who underwent TVT-O were included.

All women who presented with urinary incontinence were assessed in the clinic by a trained gynecologist. Their urinary symptoms and voiding problems were assessed. Demographic information, and medical and obstetrical history were obtained, followed by a physical examination. All women underwent a standard urodynamic investigation, including uroflowmetry, and filling and voiding cystometry with a Dantec Menuet (from 2004 to 2009; Dantec Medical, Skovlunde, Denmark) or MAQUET RADIUS (from 2009–2012; MAQUET GmbH&Co. KG, Rastatt, Germany) multichannel urodynamic machine. The urodynamic procedure and diagnoses were in accordance with standards published by the International Continence Society.[8] During the urodynamic study, the peak flow rate, voiding pattern and residual urine volume were observed from the uroflowmetry. During filling cystometry, the voiding sensations, detrusor pressure and any urine leak were observed at cough or valsalva. Severity of USI was classified according to urine leakage in the cough stress test: mild (following a series of coughs), moderate (with a few coughs) and marked (with a single cough). DO is defined as the occurrence of involuntary detrusor contractions >15 cmH2O during filling cystometry with variable duration, either spontaneous or provoked. All definitions were adopted from the latest version of the International Continence Society standardization of terminology.[8] Only those women with confirmed USI and failed pelvic floor exercise were offered TO-TVT. However, if women had any voiding problem shown in the urodynamic study, including slow flow rate of <15 mL/s, obstructive pattern on uroflowmetry and residual urine >100 mL, they were not offered a continence procedure.

All TOT and TVT-O procedures were carried out in the same unit. From September 2004 to June 2006, TOT was carried out; and from July 2006 to March 2008, TVT-O was carried out. The change from TOT to TVT-O was due to the availability of TVT-O. All procedures were carried out or supervised by a urogynecologist according to the original techniques.[3, 4] Regional or general anesthesia was carried out according to the anesthetists' recommendation and patients' preference. Cystoscopy was carried out after the procedure to rule out bladder injury. A Foley catheter was kept for 1 day.

Women were followed up 2 months after the operation, and then annually up to 5 years to review their urinary symptoms. A physical examination was carried out to look for stress incontinence or vaginal tape erosion. Women were asked whether their USI symptoms were “better”, “the same” or “worsened”. A urodynamic study was repeated at the first and fifth year. Subjective cure was defined as not experiencing any urine loss on physical exercise, whereas objective cure was defined as no urine leak at cough or valsalva during the urodynamic study. Women were discharged from the clinic after the fifth year visit if they had no or minimal symptoms.

Women who did not attend the follow-up visit at the first year were contacted and another follow up was arranged within 2 months. Those who did not come back at the fifth year were contacted and offered another appointment. If they defaulted again, they would have a phone interview using the same set of questions.

Categorical variables were compared using the χ2-test or Fisher's exact test, and independent sample t-test was used for continuous variables. A univariate analysis was used to assess risk factors associated with failure at the fifth year. Statistically significant factors were included for a multivariable logistic regression model to identify independent risk factors. Statistical Package for the Social Sciences for Windows (version 17; SPSS, Chicago, IL, USA) was used. A P-value of <0.05 was considered statistically significant.


A total of 213 women had TO-TVT carried out in this period; 124 had TOT and 89 had TVT-O. All medical records were available for the study. The mean age at the time of surgery was 60.4 years (SD 12.7), and the mean parity was 3.4 (SD 1.8), and none of the women were on hormone replacement therapy (Table 1). Nine women who died from non-surgery related illnesses were excluded; seven had TOT and two had TVT-O. The rest had follow up, and 192 (94.1%) out of 204 women were reviewed and 182 (89.2%) had a urodynamic study carried out 1 year later. At the fifth year, 186 (91.2%) of 204 women were available for evaluation (166 attended the clinic and 20 were reached by phone) with 109 (53.4%) having a urodynamic study carried out. The mean follow-up duration was 59.9 months (SD 7.0 months) for the TOT group and 58.2 months (SD 8.1 months) for the TVT-O group (P = 0.15). There was no statistical difference in the follow-up rate and follow-up method in both groups. There was no significant difference in demographic data, past obstetric history, previous pelvic floor surgery, previous overactive bladder syndrome or detrusor overactivity and concomitant pelvic floor repair surgery between the two groups (Table 1). If concomitant pelvic floor repair surgery was required, the majority had a vaginal hysterectomy and anterior colporrhaphy. They all had urodynamic stress incontinence, and not occult USI. Preoperatively, the numbers of women who had mild, moderate and severe USI shown in the urodynamic study were: five (4.3%), 66 (56.4%) and 46 (39.3%), and three (3.5%), 48 (55.8%) and 35 (40.7%) in the TOT and TVT-O group, respectively. There were six (5.1%) and four (4.6%) cases of pre-existing DO in the TOT and TVT-O groups, respectively, and no woman had a voiding problem. There was no statistically significant difference of pre-existing DO in the TOT and TVT-O groups.

Table 1. Demographics of women with different approaches of transobturator tape
 All (n = 204)TOT group (n = 117)TVT-O group (n = 87)P-value*
  1. *Statistics were carried out to compare the TOT and TVT-O groups. Data presented in mean (standard deviation) or number (percentage).
Age (years)60.4 (12.7)60.9 (12.3)59.6 (13.2)0.48
BMI (kg/m2)25.3 (4.0)25.3 (5.0)24.9 (3.2)0.58
Menopause132 (64.7%)83 (70.9%)49 (56.3%)0.08
Hypertension53 (24.9%)36 (29%)17 (19.1%)0.10
Diabetic mellitus28 (13.1%)18 (14.5%)10 (11.2%)0.55
Chronic respiratory disease6 (2.8%)4 (3.2%)2 (2.2%)0.67
No. vaginal births3.4 (1.8)3.4 (1.7)3.3 (1.9)0.81
Biggest birth weight (kg)3.4 (0.7)3.3 (0.7)3.4 (0.7)0.34
Previous prolapse surgery4 (2.0%)3 (2.6%)1 (1.1%)0.49
Previous hysterectomy9 (4.4%)6 (5.1%)3 (3.4%)0.60
Preoperative OAB syndrome71 (34.8%)46 (39.3%)25 (28.7%)0.18
Preoperative DO10 (4.9%)6 (5.1%)4 (4.6%)0.74
Concomitant pelvic floor surgery118 (57.8%)73 (62.4%)45 (51.7%)0.23

The first and fifth year outcomes are shown in Table 2. At the fifth year, the subjective cure rate was 81.7% and 84.1% in the TOT and TVT-O group, respectively, whereas the objective cure was 82.6% and 82.5%, respectively. Sensitivity analysis was carried out to explore different assumptions for women who were lost to follow up (Table 3). The urodynamic parameters in women with TOT or TVT-O carried out is shown in Table 4. There was no significant difference in any of the parameters among the TOT and TVT-O groups. The maximum urine flow rate and maximum detrusor pressure at filling showed no significant difference in both groups before and 5 years after TOT and TVT-O.

Table 2. Comparison of subjective and objective outcome at 1 year and 5 years after TOT and TVT-O
  First year follow upP-valueFifth year follow upP-value
n = 192/204 (94.1%)n = 107/117 (91.5%)n = 85/87 (97.7%)0.06n = 186/204 (91.2%)n = 104/117 (88.9%)n = 82/87 (94.3%)0.18
SICure158 (82.3%)93 (86.9%)65 (76.5%)0.06154 (82.8%)85 (81.7%)69 (84.1%)0.67
Better32 (16.7%)13 (12.2%)19 (22.4%)0.0622 (11.8%)13 (12.5%)9 (11.0%)0.82
Same2 (1.0%)1 (0.9%)1 (1.1%)0.8710 (5.4%)6 (5.8%)4 (4.9%)0.79
De novo OAB 10 (5.2%)4 (3.7%)6 (7.1%)0.3023 (12.4%)11 (10.6%)12 (14.6%)0.40
  n = 182/204 (89.2%)n = 103/117 (88.0%)n = 79/87 (89.7%)0.53n = 109/204 (53.4%)n = 69/117 (58.1%)n = 40/87 (46.0%)0.06
USINo USI153 (84.1%)86 (83.5%)67 (84.8%)0.8190 (82.6%)57 (82.6%)33 (82.5%)0.38
Mild USI10 (5.5%)9 (8.7%)1 (1.3%)0.035 (4.6%)2 (2.9%)3 (7.5%)0.43
Moderate USI10 (5.5%)3 (2.9%)7 (8.8%)0.085 (4.6%)4 (5.8%)1 (2.5%)0.57
Severe USI9 (4.9%)5 (4.9%)4 (5.1%)0.949 (8.2%)6 (8.7%)3 (7.5%)0.67
De novo DO 10 (5.5%)4 (3.1%)6 (6.9%)0.3410 (9.2%)4 (5.8%)6 (15.0%)0.43
Table 3. Sensitivity analysis of different assumptions of success for women lost to follow up at the fifth year
 Subjective cureObjective cure
TOT, n (%)TVT-O, n (%)Odds ratio (95% CI)P-valueTOT, n (%)TVT-O, n (%)Odds ratio (95% CI)P-value
Only data from interview follow up76/94 (80.9%)60/72 (83.3%)0.844 (0.35–2.02)0.6857/69 (82.6%)33/40 (82.5%)0.932 (0.33–0.61)0.89
Missing data not analyzed85/104 (81.7%)69/82 (84.1%)1.075 (0.37–3.17)0.9057/69 (82.6%)33/40 (82.5%)0.932 (0.33–0.61)0.89
Assume missing data as failure85/117 (72.6%)69/87 (79.3%)1.235 (0.65–2.33)0.5257/117 (48.7%)33/87 (37.9%)0.583 (0.33–1.03)0.13
Assume missing data as success97/117 (82.9%)71/87 (81.6%)0.915 (0.44–1.89)0.81105/117 (89.7%)80/87 (92.0%)1.306 (0.49–3.47)0.59
Table 4. Urodynamic parameters in women before, 1 year and 5 years after TOT and TVT-O operations
 PreoperativePostoperative 1 yearPostoperative 5 years
  1. Data presented in mean (SD).
First sensation of bladder (mL)163 (65)155 (72)0.41172 (69)187 (66)0.14211 (60)196 (70)0.24
Normal desire to void (mL)210 (65)200 (79)0.32257 (320)237 (65)0.59239 (56)251 (64)0.31
Cystometric capacity (mL)354 (79)349 (70)0.71302 (95)292 (47)0.39309 (19)309 (11)1.0
Pdetmax filling (cmH2O)7 (5)7.5 (5.1)0.489.8 (9.9)11.4 (11.1)0.319.2 (15.2)8.8 (9.2)0.88
MUFR (mL/s)21 (12)21 (11)1.016.3 (8.8)17.1 (9.0)0.5519.5 (8.7)20.1 (7.0)0.71
Residual volume (mL)35 (61)39 (68)0.6621 (53)12 (29)0.189.2 (26.5)5.4 (18.4)0.42

De novo OAB syndrome was found in 10 and 23 women at the first and fifth year follow up, respectively. There was no significant difference among the TOT and TVT-O groups. De novo DO was diagnosed in 10 women at the first year and fifth year. Again, there was no significant difference in both groups (P = 0.34). At the first year, four (2.1%) women required medication for their de novo OAB syndrome, with one (0.9%) in the TOT group and three (3.5%) in the TVT-O group (P = 0.21). At the fifth year, six (3.2%) women required medical treatment for their de novo OAB syndrome, with three (2.9%) in the TOT group and three (3.7%) in the TVT-O group (P = 0.77). Two women out of six in the TOT group with pre-existing DO had their symptoms resolved after surgery, but the symptoms of four women in the TVT-O group persisted (P = 0.33).

The intermediate and late complications are listed in Table 5. Three women (2 with TOT and 1 with TVT-O) were complicated with tape erosion and required excision of the exposed tape. One woman with TOT presented with persistent vaginal pain 6 months after the operation, and was found to have 1 cm of tape erosion on the right side of the vagina. Another woman with TOT presented with severe dyspareunia 1 year after the operation, and was found to have 1.5 cm of tape erosion on the left side of the vagina. One woman with TVT-O had progressive vaginal pain 6 months after the operation and 5 mm of tape erosion was noted on the left side of the vagina. All of them had excision of the exposed tape and repair of vaginal skin under either local or regional anesthesia. They remained continent up to 5 years with no voiding problems after tape excision.

Table 5. Complications of transobturator tape at 5 years after surgery
  1. *Statistics were carried out to compare the TOT and TVT-O groups.
De novo OAB23/186 (12.4%)11/104 (10.6%)12/82 (14.6%)0.40
De novo DO10/109 (9.2%)4/69 (5.8%)6/40 (15%)0.11
Tape erosion3/166 (1.8%)2/92 (2.2%)1/74 (1.4%)0.59
Voiding problem2/186 (1.1%)2/104 (1.9%)00.31
Groin pain1/186 (0.5%)1/104 (1.0(%)00.56

Two women who received TOT surgery suffered from voiding difficulty with slow urine stream and a sense of incomplete emptying. They experienced worsening of OAB symptoms, and one had the tape released 4 months later and the other had the tape cut 18 months later. Both operations were under regional anesthesia. Their voiding problems were resolved and they remained continent for up to 5 years. There was no voiding difficulty in the TVT-O group. One woman with TOT had persistent mild left groin pain 4 years after the operation. There was no tape erosion on physical examination and her symptoms were relieved by an oral analgesic. No woman in either group required second continence surgery during the follow-up period.

In women with concomitant pelvic floor surgery, the 5-year subjective cure was 93.1%; whereas the transobturator tape only group was 70.5% (P < 0.01). The objective cure rates were 85.0% and 80.0% (P = 0.48), respectively. Further analysis for women with or without concomitant pelvic floor surgery was carried out and listed in Table 6. In women with or without concomitant pelvic surgery, the subjective and objective cure rates were not significantly different in TOT or TVT-O at the first and fifth year.

Table 6. Cure rates at the first and fifth year in women with or without concomitant pelvic floor surgery
  First year follow upFifth year follow up
Subjective cure n = 158/192P-valueObjective cure n = 153/182P-valueSubjective cure n = 154/186P-valueObjective cure n = 90/109P-value
Concomitant surgery (n = 109)


n = 66

54/60 (90%)0.1054/60 (90%)0.3757/59 (96.6%)0.1731/37 (83.8%)0.67


n = 43

32/41 (78.5%)31/37 (83.8%)35/39 (89.7%)15/17 (88.2%)
TO-TVT only (n = 95)


n = 51

39/47 (88.6%)0.3533/43 (76.7%)0.4528/45 (80%)0.0826/32 (81.3%)0.79


n = 44

33/44 (75%)35/42 (83.3%)34/43 (79.1%)18/23 (78.3%)

Univariate analysis was carried out for the possible factors predicting persistence or recurrence of USI symptoms 5 years after the surgery (Table 7). Factors analyzed are listed in Table 7. The only significant factor is concomitant pelvic floor surgery, which showed a significant improvement in the subjective outcome at the fifth year (P < 0.01).

Table 7. Risk factors for failure of transobturator tape at 5-year follow up
 Subjective cure at 5th year (n = 186)Objective cure at 5th year (n = 109)
Univariate analysisUnivariate analysis
Success n = 154Failure n = 32P-valueOdd ratio (95% CI)Success n = 90Failure n = 19P-valueOdd ratio (95% CI)
  1. Data presented in n (%).
Age at surgery ≥65 years55 (35.7)11(34.4)0.891.061 (0.476–2.362)28 (31.1)7 (36.8)0.670.774 (0.275–2.176)
History of smoking5 (3.2)3 (9.4)0.110.324 (0.073–1.433)2 (2.2)2 (10.5)0.110.193 (0.025–1.468)
Menopausal92 (59.7)18 (56.2)0.791.154 (0.535–2.490)49 (54.4)14 (73.7)0.140.427 (0.142–1.29)
BMI ≥25 kg/m267 (43.5)20 (62.5)0.070.462 (0.211–1.012)39 (43.3)12 (63.2)0.230.446 (0.161–1.239)
Vaginal delivery ≥3 times86 (55.8)17 (53.1)0.821.116 (0.520–2.395)44 (48.9)10 (52.6)0.660.861 (0.320–2.319)
Delivered birth weight ≥3 kg45 (29.2)14 (43.8)0.170.531 (0.243–1.158)29 (32.2)7 (36.8)0.790.815 (0.291–2.287)
Previous continent surgery4 (2.6)00.36NA4 (4.4)00.34NA
Previous pelvic floor surgery3 (1.9)1 (3.1)0.680.616 (0.062–6.118)2 (2.2)1 (5.3)0.470.409 (0.035–4.76)
Previous hysterectomy7 (100)00.22NA3 (3.3)2 (10.5)0.180.293 (0.046–1.89)
Preoperative OAB syndrome49(31.8)13 (40.6)0.320.682 (0.312–1.492)30 (33.3)5 (26.3)0.451.4 (0.461–4.253)
MUFR ≤25 mL/s63 (40.9)18 (56.2)0.050.539 (0.250–1.162)32 (35.6)9 (47.4)0.490.613 (0.226–1.66)
First sensation ≤200 mL41 (26.6)6 (18.8)0.371.572 (0.604–4.094)8 (8.9)3 (15.8)0.410.520 (0.124–2.176)
Pdetmax filling ≥10 cmH2O27 (17.5)6 (18.8)0.730.921 (0.346–2.455)16 (17.8)5 (26.3)0.530.605 (0.191–1.922)
Pre-existing DO4 (2.6)3 (9.4)0.060.258 (0.0548–1.2133)2 (2.2)2 (10.5)0.980.193 (0.025–1.468)
Concomitant prolapse surgery92 (59.7)6 (18.75)<0.016.43 (2.338–18.6)46 (51.1)8 (42.1)0.4761.438 (0.478–4.378)


Current reports suggest a similar efficacy in inside-out and outside-in techniques in short- and medium-term outcome, and mainly focused on patient-reported results. According to a recent meta-analysis,[7] four RCT showed similar subjective and objective outcomes at 3–12 months.[9-12] Two RCT compared the subjective outcome up to 3 years.[13, 14] Only one prospective cohort study reported the subjective outcome up to 2–4 years.[15] Our study provides evidence with adequate samples in long-term subjective and objective outcomes in TOT and TVT-O up to 5 years.

The subjective success rate of transobturator tape was shown to be 82.8% in the present study at the fifth year (81.7% for TOT and 84.1% for TVT-O). This is consistent with published data that there was no significant difference among TOT and TVT-O[15] during medium-term follow up. The subjective cure rate remained similar from 1 year after surgery to 5 years. The overall subjective cure rate of 82.8% for all women in the present study was slightly higher than those reported in previous studies. The subjective cure rate of 70.5% for those with transobturator tape alone was also comparable to previous studies. Angioli reported 62% satisfaction in 37 patients after TVT-O at 5 years,[16] Lipais reported 79.1% in 115 patients after TVT-O at the fourth year,[17] and Houwert reported 72% in 93 patients after TVT-O and 69% after TOT at 2–4 years.[15]

The overall objective cure rate was 84.1% at 1 year and 82.6% at the fifth year postoperatively. The 5-year cure rate for the TOT and TVT-O group were 82.6% and 82.5%, respectively. There was no significant difference among the two groups, and the decrease from the first to fifth year after the surgery was statistically insignificant. Up to our current knowledge, there is no long-term objective comparison using urodynamic studies on the surgical outcome of these two approaches of transobturator tape. The objective cure rate reported by Angioli was 72.9% 5 years after TVT-O,[16] as defined by a cough stress test, whereas Liapis reported 82.4% in 115 patients at 4 years after TVT-O,[17] as defined by a pad test. Lipias compared the 1-year objective cure rate of 87% for the TVT-O group and 90% for the TOT group,[11] and Lee et al. also reported 86% for the TVT-O group and 92% for the TOT group at 1-year follow up.[10] Both concluded the short-term objective cure rate was not significantly different in both transobturator tapes. Our data can further demonstrate the similar objective cure rates for TOT and TVT-O as a long-term outcome.

Vaginal angle injuries were reported to be significantly higher in the TOT group, whereas groin and thigh pain was higher in the TVT-O group, but was statistically insignificant in published reports.[7] However, overall, the pain was reported to resolve in 1–4 months. In the present study, there was only one TOT patient who reported groin pain 4 years after the operation. There were other late complications of tape erosion and voiding problem that required attention. Those who had TOT appeared to have a higher risk of tape erosion and voiding problems, although this did not reach statistical significance. This was consistent with reports by Houwert.[15] Further studies are required to clarify this finding.

There is comparatively scant data on de novo OAB syndrome and de novo DO in relation to TOT and TVT-O. The de novo OAB syndrome increased from 5.2% to 12.4% 1–5 years after surgery. Aging might contribute to this increase. The same might be true for de novo DO, the prevalence of which increased from 4.9% to 9.2%. However, the data at the fifth year might be overestimated, as most of the women remained well at five years and did not want a further urodynamic test. These results were comparable with a previously reported 8.1% de novo urge incontinence and 10.8% urgency by Liapis in women 4 years after TVT-O,[17] and Waltergny reported 11% de novo urgency and 5% de novo urge incontinence 3 years after TVT-O.[18] Among the TOT and TVT-O group, the prevalence of de novo OAB syndrome and DO was similar, and with no significant difference at both 1 year and 5 years after the operation. This was consistent with previous observational studies for the short-term OAB syndrome,[9, 10, 19] and provide additional information that over the longer term, the de novo OAB syndrome and DO will remain similar in both groups.

We have analyzed some demographic risk factors associated with objective and subjective stress incontinence 5 years after transobturator tape. Obesity (BMI >30 kg/m2) was identified by Serati[20] as a risk factor for objective recurrence of SI 10 years after TVT. However, BMI ≥25 kg/m2 was not shown to be a risk factor in our group of women. This might due to the low mean BMI (25 kg/m2) in Chinese, and only a few of our participants having a BMI >30 kg/m2. There were no women who required further continence surgery in either group.

The present study had several strengths, including an adequate sample size in each approach of transobturator tapes, the availability of preoperative details, strict outcome parameters, postoperative subjective and objective assessment at the first and fifth years, and also standardized postoperative urodynamic study. We obtained a high follow-up rate up to 5 years.

We acknowledge this was not a randomized trial, although the groups of women were comparable. However, given the similarity in outcomes, a RCT might not be justified, because the differences being looked for are likely to be small and a large trial is required. We had to contact 12% of patients by phone interview at the fifth year, and just 52% of them completed the 5-year urodynamic study. This was because some of the asymptomatic women declined further follow up or refused to repeat a urodynamic study at the fifth year. Besides, there was no evaluation on quality of life, as validated instruments were available only after the study period;[2, 21] although improvement of quality of life in women at a mean of 9 months after receiving TVT-O has been confirmed.[22]

Approximately half of the women had received concomitant pelvic floor surgery, although the number was not significant different between the two groups. Some urodynamic measurements including urethral mobility, Valsalva leak point pressure or maximum urethral closure pressure were not available to the women being studied before 2006. On subgroup analysis of women with or without concomitant pelvic floor surgery, the subjective and objective cure rates at the fifth year were not statistically different in the TOT or TVT-O groups. The concomitant pelvic surgery was shown to not have an effect on the outcome of the transobturator tape.[23-26] However, from some of the published data,[23-25] the continence rates in women with concomitant prolapse surgery tended to be higher than in the TVT only group, whereas some data did not show this,[27] and all of them were not statistical significant. In the present study, the subjective cure rate was statistically higher, whereas the objective cure rate was not significant at the fifth year. As most of our women who had concomitant prolapse surgery would have anterior colporraphy for anterior compartment prolapse, this could have an additional anti-incontinence effect by anterior colporraphy.[28] Besides, women with prolapse surgery might experience recurrence prolapse at long-term follow up, with pelvic organ prolapse possibly masking the effect of their SI symptoms. However, further study might be required to confirm this finding.

The present study did not show any significant difference in subjective and objective cure rates, and the occurrence of de novo OAB syndrome and DO 5 years after TOT or TVT-O. The late complication risk was low in both methods.

Conflict of interest

None declared.