Contasure-needleless single incision slings versus transobturator slings (TOT/TVT-O) for female patients with stress urinary incontinence: a systematic review and meta-analysis

Stress urinary incontinence (SUI) is a common disease among middle-aged and elderly women. It is a widespread, global disease that affects 50% of women [1]. Symptoms of SUI are manifested as the involuntary flow of urine from the urethra when the patient coughs, sneezes or runs, all of which elevate abdominal pressure [2]. It is generally recognized that urethral closure pressure is the key factor maintaining continence [3]. When exertion raises the intra-abdominal pressure, an insufficient pressure of urethral closure will cause leakage. The lack of urethral closure pressure is associated with anatomic changes in the bladder and urethra [4, 5]. Surgical treatment is now prioritized because of its efficacy when conservative therapy fails [6]. The purpose of surgical treatment is to reconstruct the anatomy and function through surgery and to restore normal urine control. However, for patients with intrinsic sphincter deficiency (ISD) or urgency urinary incontinence, a high failure rate of anti-incontinence surgeries has been reported [7, 8]. Surgical treatment of SUI has been developed for more than a century, and up to 200 surgical procedures are documented in the existing literature. The Burch retropubic urethropexy or Marshall-Marchetti-Krantz (MMK) procedure through the retropubic routine was the gold-standard surgical treatment of SUI before the introduction of MUS [9]. Recently, the frequency of similar surgical approaches has decreased significantly. DeLancey proposed the hammock hypothesis in 1994 [10], which provided theoretical support for subsequent minimally invasive surgery, bringing revolutionary changes to surgery. Since the introduction of tension-free vaginal tape (TVT), similar surgical approaches have made great progress. At present, standard midurethral slings (SMUS) have become the first-line surgical treatment [6]. Among them, the transobturator sling (TOT/TVT-O) is widely used because of its high cure rate and lower number of complications [11‐13]. However, persistent groin and thigh pain after surgery is the main complication affecting patient satisfaction [14].

Single incision mini-slings (SIMSs) were introduced in 2006 to make use of a shorter sling and a single vaginal incision [15]. The short- and medium-term efficacy of SIMS are still controversial due to its recent introduction. Currently, as a new category of SIMS, Contasure-Needleless (C-NDL) slings have a non-inferior cure rate and fewer complications than transobturator slings [16, 17]. To the best of our knowledge, there are no systematic reviews and meta-analyses of C-NDL slings. To better evaluate clinical efficacy and safety, we systematically assessed data about C-NDL and transobturator slings (TOT/TVT-O) to provide a reference for the surgical choice of SUI.

With a grade A commendation according to the European Association of Urology (EAU) guidelines, SMUS is widely used to treat SUI [29]. The midurethral slings can be classified into 3 generations throughout their development history. As the first generation, TVT was introduced in 1995 [30] and became the best choice for the surgical treatment of SUI due to its minimal invasiveness and high cure rate. However, as a retropubic sling, the main complications include voiding dysfunction and bladder injuries, which decrease its safety [31, 32]. To avoid potential complications associated with retropubic placement, a mesh inserted through the obturator foramen was created. Delorme introduced the “outside-in” technique (TOT), placing the suburethral tape via a transobturator route in 2001 [33]. Subsequently, the “inside-out” technique (TVT-O) was modified by De Leval [34]. As the second generation, transobturator slings (TOT/TVT-O) achieve similar efficacy and fewer complications, especially regarding the risk of visceral injury [35]. Some studies mainly focused on primary SUI in females without ISD and mixed incontinence were performed to compare the efficacy of the two sling surgeries. The results from a five-year term showed that the subjective and objective cure rates were not significantly different between TVT and TVT-O, and there appeared to be very few complications during follow-up [12]. The meta-analysis performed by Huang et al. [36] showed that TOT can achieve a similar success rate as TVT and requires less operative time and a shorter hospital stay. Few studies reported outcomes with longer term follow-up for more than 5 years. According to the guide for stress urinary incontinence treatment, compared to transobturator slings, slings inserted by the retropubic routes have higher objective patient-reported cure rates at 8 years and lower re-operation rates [37]. In addition, when the tape is placed, the introducer needle passes through the obturator foramen blindly. The obturator nerve and blood vessel will likely be injured during the procedure, which may cause postoperative groin pain and haematoma. According to the existing literature focused on primary SUI in females, transient groin pain occurs in 0.8–7.5% of patients after the placement of transobturator slings [38, 39]. It is worth mentioning that shorter than traditional transobturator slings, TVT-Abbrevo is only 12 cm long, achieves similar efficacy and reduces post-operative groin pain [40, 41]. However, further long-term data and prospective studies are required to clarify its efficacy and safety. To simplify the surgical procedure and decrease the relative complication rate, the third-generation SIMS was introduced. With a shorter mesh and insertion into a single incision, SIMS provides a shorter operative time and fewer adverse effects, particularly regarding postoperative groin pain, vessel and bladder injury [1]. In contrast to other SIMSs, C-NDL has a unique shape. It is made of a polypropylene monofilament mesh with no guide needle and is apparently widened at both ends, which is called the T-pocket. This device aids surrounding tissue ingrowth to provide sufficient support for the urethra [42]. Surgical forceps are placed inside the T-pocket to fold the mesh by opening and closing the forceps. The forceps with the folded mesh are introduced into the paraurethral space and penetrate the internal obturator muscle by controlling the pushing force. The forceps are then opened to extend the T-pocket pocket inside the internal obturator muscles for fixation, closed, and pulled out of the vagina. The same manoeuvre is performed on the contralateral side to complete the sling insertion without twisting the tape. The surgeon can decrease the support by pulling on the two sutures in the middle of the mesh, leaving a space between the mesh and the urethra and allowing a surgical forceps to be interposed between them, thus avoiding any tension on the mesh [24, 25].

The most important indicators for evaluating efficacy are the subjective and objective cure rates. The tension provided by the tape support plays a significant role in efficacy and is associated with the cure rate and necessity for re-surgery. Some studies of SIMS have been performed previously to evaluate the efficacy. One meta-analysis compared the TVT-Secure, Mini-Arc and Ophira together with standard midurethral slings, and the result showed an inferior cure rate for these SIMSs [15]. An animal trial reported that with the highest surface area to counteract extraction, the anchor of the C-NDL has the highest mean immediate extraction forces compared with other SIMSs [43]. Additionally, the surface area in the pelvic floor is almost the same as for the TVT-O, which ensures sufficient firmness [17]. Our meta-analysis, found no significant differences in the comparison of subjective and objective cure rates. However, Fernandez et al. (2017) reported that C-NDL was inferior in a comparison of negative stress test results and patient satisfaction [24]. In contrast to other included studies, they used a non-inferiority test for analysis. However, differences in the statistical tools used could have resulted in bias. In addition, there are no standardized assessment tools to evaluate the success rate. Patients may have different expectations regarding treatment after surgery for SUI, and some postoperative complications may also affect the subjective cure rate. Notably, four studies [17, 24, 25, 27] included patients with pelvic organ prolapse (POP). Because of the pelvic structure, SUI and POP are often comorbid diseases. For these patients, anti-incontinence surgery simultaneous with POP repair was undertaken. There is strong evidence that prolapse surgery combined with incontinence surgery reduces the risk of postoperative SUI [44]. Therefore, it is doubtless that many factors influence the cure rate. Regarding these aspects, more strict inclusion and exclusion criteria and standardized assessment tools are recommended to make the results more comparable. Apart from the investigations of Dogan in 2018 [23] and Franco in 2014 [17], the follow-up time of the included studies was only 1 year. Due to the limitations in follow-up time, only one study [23] (Dogan 2018) with a 2 year follow-up reported the incidence of repeated SUI surgery and revealed no significant differences between groups [C-NDL (1/89): TOT (0/89) p > 0.05]. However, longer follow-up is required to determine re-operation rates. Our outcome can only indicate that C-NDL slings have similar short-term efficacy to transobturator slings. Due to the short period of C-NDL use, determination of long-term efficacy will require high quality-RCTs.

Our meta-analysis showed that the patients who underwent C-NDL had a shorter operative time (by 7 min), confirming previously published outcomes [1, 45]. Due to its unique T-pocket, the mesh implant is simpler and more convenient. However, this shorter operative time may not contribute to improving the safety of the operation. Although the pooled results showed a statistically significant reduction in blood loss of 8 ml in the C-NDL group, this difference is not clinically significant. In addition, the pooled results showed that patients receiving C-NDL presented improved postoperative pain and postoperative VAS scores (24 h after operation). In particular, groin pain was greatly improved. These results are consistent with those of Kim’s study [45], which reported that SIMSs are superior with respect to immediate postoperative pain. The difference may be explained by the surgical procedure. Similar to other SIMSs, the C-NDL is inserted through a single vaginal incision and blindly avoids the retropubic space and obturator foramen. The reduction in pain occurrence with C-NDL is related to the fact that there is no incision in the groin area, the sling does not reach the groin, and there is no foreign body sensation. The surgical routine also decreases the risk of blood vessel and nerve injury, consistent with our present analysis. In Baya’s study, after three-year follow-up, there were no cases of groin pain, and only one patient had a mild haematoma [46]. In addition to the cure rate, postoperative pain also plays an important role in patient satisfaction. In a study by Schellart et al., patients with SUI were willing to accept a relatively lower cure rate with a less invasive procedure to avoid postoperative pain [47]. Although these outcomes from our study demonstrated that C-NDL slings cause less pain, some factors should be taken into consideration. Regarding the important outcome of groin pain, only three studies reported the outcome independently; some studies included it in the postoperative pain outcome. The postoperative VAS scores compared the feeling of postoperative pain, which may be influenced by incisions and individual differences. The different anaesthesia protocols among the studies may also contribute heterogeneity to the postoperative VAS results. In addition, the pain evaluation for this surgery is short-term. Lv et al. reported no significant difference between the two groups in VAS at 6 months after surgery, which was associated with the postoperative time [26]. Further studies should pay more attention to groin pain and consider its relative influence. With respect to the length of hospital stay, a previous meta-analysis showed that SIMSs involve a shorter hospitalization time than transobturator slings [48]. However, our results showed no significant differences in hospital stay between the two groups. According to our clinical experience, the length of hospital stay might be associated with the patients’ baseline basic characteristics and with hospital conditions, which are affected by human factors. However, after excluding the study by Fernandez et al., the difference was significant; that study included patients with POP, which may influence the results. In addition, the inpatient stay was fixed at 1 to 2 days, which also indicates that C-NDL slings involve a fast recovery time.

The results of the present meta-analysis, revealed no remarkable difference between the two types of slings with respect to vaginal tape erosion. Some SIMS, such as TVT-Secure and Mini-Arc, have been withdrawn from clinical use due to their nonideal efficacy and high risk of mesh exposure [49, 50]. The C-NDL sling is shorter than the standard sling and thus introduces, less foreign material. Due to the use of monofilament knotless weaving technology, the C-NDL sling is macroporous, with a porosity of 55%; thus, the risk of bacterial retention and reproduction resulting from the dead space caused by knotting after implantation in the human body is reduced [51, 52]. The C-NDL sling also contributes to the reduction in possible complications. In addition, the incidence of urinary retention, de novo urgency and/or worsening of pre-existing urgency, difficulty urinating, urinary tract infection, bladder injury, and haematoma were not significantly different between the groups. Some complications, such as vaginal tape erosion and urinary tract infection, will appear over time. Due to the limitations in follow-up time, long-term safety is still worth observing. Based on the simple operation required, the C-NDL procedure is more suitable for local anaesthesia [42]. Additionally, compared to the traditional sling, the mini-sling is considered lower cost [53, 54]. ElSheemy et al. reported they reduced the cost from US$500 to US$10 by using a surgeon-tailored ordinary polypropylene mesh through the needle-less single-incision technique [55]. More studies are required to verify the cost-effectiveness of the C-NDL procedure in the management of SUI.

There were several limitations to our study. First, the included RCTs did not describe the blinding procedures clearly and in detail, which might have led to conclusion bias. Some potential biases caused by CCTs are inevitable. Moreover, the heterogeneity among these trials was found to be high in terms of several parameters, including operative time, hospital stay, blood loss, and postoperative VAS. The heterogeneity in these parameters can be explained by the differences in outcome definitions, measurements, and standards, such as the time from incision to closure and the overall time spent in the operating room. Haemoglobin levels or gauze was used to estimate blood loss. In addition, the availability of technical equipment and surgical experience also play critical roles in evaluating the effectiveness of the two techniques and could not be assessed in the present review. Another limitation of this study is that some included studies included unselected populations (patients with POP and different severity of SUI), and some patients included in two studies [17, 27] may have come from the same group. Finally, the follow-up times in these included studies were different and not sufficiently long, and the sample sizes and numbers of included studies were small; thus, more high-quality RCTs with long follow-up times are needed to further evaluate the effectiveness and safety of C-NDL. The results of this meta-analysis should be interpreted with caution due to these limitations.

In summary, C-NDL slings have similar short-term efficacy as TOT/TVT-O slings in curing pure SUI patients without evidence of ISD. Compared with TOT/TVT-O, C-NDL is associated with a shorter operative time (by 7 min) and less blood loss (by 8 ml). In addition, C-NDL is associated with lower postoperative pain compared to TOT/TVT-O. The limitations identified should be taken into consideration when interpreting these results. Further large-volume, well-designed prospective RCTs with extensive follow-up are required to confirm long-term efficacy and safety.