Midurethral sling position and surgical outcome: A meta-analysis

Abstract

There is still ongoing debate as to whether the outcome of the sling is determined by the position of the midurethral sling. In order to evaluate the potential impact of sling position on the outcomes of retropubic and transobturator sling procedures for stress urinary incontinence, it is necessary to conduct further investigations. We conducted a comprehensive search across various electronic databases such as PubMed, EMBASE, MEDLINE. Relevant data were extracted, organized in a table format, and analyzed using RevMan software for further analysis. This review comprised a total of 9 studies. The findings indicate that patients with TVT tape placement in the midurethra exhibited a slightly higher cure rate compared to those with proximal placement. Conversely, tape placement in the midurethra was associated with a significantly higher cure rate compared to distal placement [RR = 0.84, 95% CI (0.74–0.95), P < .05]. In the case of transobturator slings, tape positioning beneath the midurethra or distal urethra yielded better outcomes compared to placement near the bladder neck [RR = 0.74, 95% CI (0.57–0.94), P = .02; RR = 0.61, 95% CI (0.39–0.96), P = .03]. Based on 2D and 3D ultrasound imaging, differences in TVT placement appear to have minimal impact on the cure rate. However, the highest rate of failure after transobturator sling surgery is closely linked to the positioning.

1. Introduction

Midurethral slings have emerged as the important surgical technique for managing urethral disease.^[1,2] Building upon this foundation, Ulmsten developed the minimally invasive TVT procedure, which aims to bolster the midurethra and achieve urinary continence.^[3–5] Despite the advancements, approximately 10% to 20% of patients may still experience treatment resistance.^[6–8] Among the factors investigated, sling position has garnered significant attention due to its potential impact on the surgical outcome of suburethral tape procedures. Several studies have supported the notion that placing the sling under the 40th to 70th percentile of the urethra could enhance its effectiveness.^[9–11] Nevertheless, there have been conflicting findings in certain studies regarding the association between tape position and treatment outcomes.^[12,13] It is important to acknowledge that these controversies may arise from limitations such as small sample sizes and the influence of various factors. To address this, our manuscript aims to systematically assess the available data on the impact of suburethral tape location (retropubic and transobturator) on surgical outcomes, providing reliable evidence on this matter.

2. Methods

2.1. Literature search

We conducted a systematic search for relevant studies published up until May 2020, utilizing databases such as PubMed, EMBASE, MEDLINE, and Web of Science. The search incorporated various combinations of keywords, including stress urinary incontinence, midurethral sling, midurethral tape, TVT, TVT-O, and TOT. Furthermore, we obtained additional pertinent literature from the reference lists of the included manuscripts. The study was approved by the hospital ethics committee.

2.2. Data collection

Two independent investigators (N.H. and P.Q.) extracted relevant data from each study, with any discrepancies resolved through discussion. The inclusion criteria for this review were as follows: 1. Studies focused on evaluating the effectiveness and complications of midurethral sling for female stress urinary incontinence. 2. Clinical trials exploring the relationship between sling position and treatment outcomes for stress urinary incontinence using midurethral sling. 3. Studies that utilized ultrasound for visualizing the midurethral sling. 4. Observed indicators included the cure rate and complications. Conversely, the exclusion criteria were as follows: 1. Studies employing inappropriate statistical methods. 2. Studies with a follow-up loss rate exceeding 20%. We collected the following data from each study that met the inclusion criteria: first author’s name, publication year, country.^[14] Studies with a score of > 6 were considered high-quality, while those with a score of < 6 were classified as low-quality.

Patients were deemed to have achieved complete cure if they exhibited no subjective symptoms of urethral disease. Additionally, diagnosis of stress urinary incontinence was based on International Continence Society recommendations, considering symptoms such as pollakisuria, nocturia, and urgency. Moreover, patients with residual urine volumes exceeding 100 mL were diagnosed with voiding dysfunction.

2.3. Statistical analysis

The included manuscripts were subjected to meta-analysis using RevMan v.5.3 (Cochrane Collaboration, Oxford, UK). The analysis was conducted using the Mantel-Haenszel method. In cases where no heterogeneity was observed, the fixed-effect model was employed. Conversely, if heterogeneity was present, the random-effects model was utilized.

The findings were presented as relative risks along with corresponding 95% confidence bounds was determined. Statistical inconsistency was evaluated by χ² test, and the degree of heterogeneity was expressed by Higgins’ I².

3. Results

3.1. Characteristics of the included studies

After a thorough and rigorous research process, a total of 9 studies were ultimately included in the analysis. These studies consisted of 7 prospective cohort studies and 2 retrospective studies. The extracted information from these studies, as well as the results of their quality assessment, are presented in Table 1. The excluded papers and the corresponding reasons for their exclusion are provided in Table 2. It is worth noting that the definitions of outcomes varied among the included studies, while others employed a two-category system (success, improvement). Due to the inability to standardize the outcome criteria across all studies, modifications were made to accommodate the original criteria used in each study. For the purpose of this study, a two-category system was adopted, merging patients with improvement and success. In all of the included studies, the urethra was classified into three sections: proximal (<40th percentile), middle (40th–70th percentile), and distal (>70th percentile). The postoperative continence status was compared using the suburethral sling position in 9 studies,^{[15–17,19–24]} while postoperative lower urinary tract symptoms were assessed in 6 studies.^{[15–17,20,23,24,25]}

Table 1.

Main characteristics of all eligible studies in the meta-analysis.

Author	Publication year	Country	Type of UI	Tape type	Ultrasound	Sample size	Follow-up	Nos score
Christopher C. M.	2005	Singapore	SUI	TVT, Ethicon	Transperineal 3D	31	6 mo	7
F. Flock	2010	Germany	SUI	TVT, Ethicon	Introital 2D	308	3 yr	6
J. Kociszewski	2012	Germany	SUI	TVT, Ethicon	Introital 2D	102	6 mo	6
J. Kociszewski	2008	Germany	SUI	TVT, Ethicon	Introital 2D	72	3 mo	5
Yuan-Hong Jiang	2013	China	SUI	TVT, Ethicon	transrectal 2D	153	3 yr	8
Foulot	2007	France	SUI	TOT, Monarc	Vaginal 2D	54	5 mo	6
Bogusiewicz	2014	Poland	SUI	TOT CovidienR	Vaginal 2D	141	24 mo	6
Aparna Hegde	2016	USA	SUI	TOT Monarc	Transperineal2d/3D	100	1–2 yr	7
Ayman Tamma	2019	Germany	SUI	TVT-O Ethicon	Transperineal2d	124	10 yr	6

SUI = stress urinary incontinence.

Table 2.

The excluded studies and the reason.

Kociszewski J 2010[18]	The same study as Kociszewski J 2012[19]
Kociszewski J 2017[21]	The patients had different types of tapes

3.1.1. Sling position and cure rate (retropubic approach).

Among the 6 included studies, The prevailing number of women (74.2%, 477 women) possessed the TVT ribbon positioned within the intermediate section of the urethra. Additionally, 13.8% (89 women) and 12.0% (77 women) possessed the TVT ribbon located in the near and far segments of the urethra.

In the studies that were included, the overall cure rate was 88.9%. Specifically, among women who had the middle urethral sling, approximately 92.2%. For women with the proximal urethral sling, the cure rate was 80.9%, while for women with the distal urethral sling, the cure rate was 77.9%.

It was concluded that the heterogeneity met the acceptable criteria (I² = 5%, P = .37). Patients with demonstrated a slightly higher cure rate compared to those with placement in the proximal urethra (Fig. 1), although this difference had no statistical significance [RR = 0.95, 95% CI (0.80–1.13), P > .05]. On the other hand, tape placement within the urethral midpoint was significantly associated accompanied by a higher cure in contrast to when placed in the distal urethra [RR = 0.84, 95% CI (0.74–0.95), P < .05] (Fig. 2). Interestingly, patients with the tape located in the proximal urethra exhibited a similar cure rate to those with placement in the distal urethra [RR = 1.08, 95% CI (0.74–1.58), P > .05] (Fig. 3).

Figure 1.

Meta-analysis of cure rate: proximal vs middle of the urethra (proximal = sling located in the proximal of the urethra; midurethral = sling located in the middle of the urethra).

Figure 2.

Meta-analysis of cure rate: distal vs middle of the urethra (distal = sling located in the distal of the urethra; midurethral = sling located in the middle of the urethra).

Figure 3.

Meta-analysis of cure rate: proximal vs distal of the urethra (proximal = sling located in the proximal of the urethra; distal = sling located in the distal of the urethra).

3.1.2. Sling position and postoperative lower urinary tract symptoms (retropubic approach).

The heterogeneity was determined to be acceptable (I² = 0%, P = .57). There was no significant difference observed in the statistics regarding postoperative de novo urgency among the groups [RR = 0.93, 95% CI (0.48–1.82), P > .05; RR = 1.54, 95% CI (0.82–2.90), P > .05] (Figs. 4 and 5).

Figure 4.

Meta-analysis of postoperative de novo urgency (distal = sling located in the distal of the urethra; mid = sling located in the middle of the urethra).

Figure 5.

Meta-analysis of postoperative de novo urgency (proximal = sling located in the proximal of the urethra; mid = sling located in the middle of the urethra).

3.1.3. Sling position and cure rate (transobturator approach).

After excluding the study conducted by Aparna Hegde,^[22] It was concluded that the heterogeneity met the acceptable criteria (I² = 21%, P = .28). Tape placement within the urethral midpoint was significantly associated with a higher cure rate compared to placement in the proximal urethra [RR = 0.74, 95% CI (0.57–0.94), P = .02] (Fig. 1). Interestingly, patients accompanied by the ribbon located within the urethral midpoint exhibited a similar cure rate to those with placement in the distal urethra [RR = 1.03, 95% CI (0.78–1.35), P = .85] (Fig. 2). Furthermore, tape placement in the distal urethra was also associated with a higher cure rate compared to placement in the proximal urethra [RR = 0.61, 95% CI (0.39–0.96), P = .03] (Fig. 3).

3.1.4. Sling position and postoperative lower urinary tract symptoms (transobturator approach).

In the study conducted by Michał Bogusiewicz, it was observed that 11 women experienced de novo urgency after the surgery. However, there was no significant relationship found between ultrasonographic parameters of tape location and this condition. Similarly, Chantarasorn et al^[26] also reported that the ultrasonographic parameters of tape location or function were not associated with symptoms of urgency or voiding dysfunction in the postoperative period.

The heterogeneity was deemed acceptable (I² = 0%; P = .77). The analysis of postoperative de novo urgency revealed no significant difference among the groups [RR = 1.19, 95% CI (0.73–1.92), P > .05; RR = 0.43, 95% CI (0.07–2.76), P > .05; RR = 0.93, 95% CI (0.48–1.82), P > .05] (Figs. 4, 5).

3.2. Publication bias

Due to the inclusion of a limited number of studies (less than 10), funnel plot analysis was not conducted to assess the possible presence of publication bias in this study.

3.3. Sensitivity analysis

In the sensitivity analysis, we systematically excluded individual studies to evaluate the impact of each study on the combined relative risks (RRs). For the majority of outcomes, the exclusion of any single study did not substantially alter the overall results. However, when the study conducted by Hegde et al^[22] was removed, a statistically significant difference in cure rate between proximal and midurethral groups was observed after pooling the remaining three studies. Furthermore, the heterogeneity decreased significantly from 73% to 21%.

4. Discussion

The findings of the current study suggest that the significance of positioning the TVT tape in the mid urethral area for achieving continence may not be essential. Although placing the tape in the middle of the urethra resulted in a higher rate of successful treatment compared to the exclusion of the urethra, the relative risk (RR) was close to 1 and considering potential bias, the results may lack meaningfulness, with a 95% confidence interval (CI) ranging from 0.74 to 0.95. We hypothesize that the TVT sling procedure, due to its retropubic placement, could contribute to increased tension of the tape and compression of the urethra, potentially compensating for any incorrect sling positioning while still ensuring continence.

During ultrasound examination, the transobturator sling’s effectiveness in preventing incontinence is observed as the tape protrudes into the posterior wall of the urethra, causing temporary narrowing of its lumen when pressure is applied.^[27] Therefore, if the tape is positioned near the bladder neck, these mechanisms may not function properly.

Postoperative development of urge symptoms is a potential complication of anti-incontinence surgery.^[28,29] The underlying causes of de novo urge symptoms may include bladder outlet obstruction and disruption of bladder autonomic innervation caused by the sling procedure.^[30]

To the best of our knowledge, this meta-analysis represents the first systematic analysis of the relationship between the position of midurethral slings and surgical outcomes. However, it is vital to acknowledge several limitations in our study. Firstly, all the studies included in our analysis were non-randomized, which introduces potential biases such as selective reporting, attrition, and publication bias. Secondly, the follow-up periods in these studies were limited to months, and it is possible that the position of the sling may change over time, potentially impacting surgical outcomes. Therefore, the findings of our review primarily reflect short-term and mid-term surgical outcomes. Third, some observation indicators and assessment methods of studies are different, which resulted in the loss of some study data. Fourth, we could not take into consideration other factors such as sling tension that might have influenced the sling outcomes because of insufficient data and different assessment standard among the studies.

5. Conclusion

Assessment of sling location can be achieved using ultrasound, However, standard ultrasound evaluation of the midurethral sling should be unified and established in the future studies. Based on the aforementioned evidence, our conclusion is that placing the midurethral sling closer is better. On the other hand, variations in placement of the TVT procedure seem to have minimal impact on the cure rate. Additionally, there is no direct association between sling position beneath the urethra and the development of de novo urge symptoms.

Author contributions

Conceptualization: Peng Qu.

Data curation: Peng Qu.

Formal analysis: Peng Qu, Jingdong Yang.

Funding acquisition: Ning Hai.

Investigation: Peng Qu, Ning Hai, Zhaoyang Lv.

Methodology: Peng Qu, Jingdong Yang.

Project administration: Ning Hai.

Resources: Ning Hai, Zhaoyang Lv.

Software: Peng Qu, Ning Hai, Zhaoyang Lv.

Supervision: Ning Hai, Jingdong Yang.

Validation: Peng Qu, Ning Hai, Zhaoyang Lv.

Visualization: Peng Qu, Ning Hai, Zhaoyang Lv, Jingdong Yang.

Writing – original draft: Peng Qu.

Writing – review & editing: Peng Qu, Ning Hai, Zhaoyang Lv, Jingdong Yang.