Midurethral slings are largely considered the gold standard for treating stress urinary incontinence (SUI), with an estimated 250,000 midurethral sling procedures performed yearly in the United States.1 Stress urinary incontinence affects one in three women in their lifetimes,2 and once treated, patients often have a significant improvement in quality of life, including increased ability to exercise, laugh and engage in sexual activity.2,3 Given the minimally invasive nature and shorter operative time of midurethral slings, these procedures have largely replaced traditional, more invasive procedures, such as the autologous fascial sling and open retropubic urethropexy (Burch colposuspension), over the past decade.4–8
Overall, the midurethral sling has been extensively researched and found to be safe and effective in the short (less than 1 year) and medium term (1–5 years).2 Patients can experience complications which include pain, mesh exposure, as well as continued or recurrent SUI.9–11 Although complication and failure rates are well characterized in less than 5 years of follow-up, there is limited long-term (more than 5 years) evidence for safety (complications) and efficacy (success or failure).2,12
In 2011 the U.S. Food and Drug Administration (FDA) published a safety communication in response to concerns over surgical complications involving the use of transvaginal mesh for pelvic organ prolapse.13 This statement raised concerns about the efficacy and safety of transvaginal mesh for pelvic organ prolapse, and the FDA ultimately banned its production and sale on April 16, 2019.14 Despite explicit exclusion of mesh used for treatment of SUI in the FDA communications, litigation efforts have included both transvaginal mesh used for SUI and pelvic organ prolapse, and more than 50,000 women have joined class action lawsuits alleging mesh complications from both types of procedures.15 These financial and public concerns related to safety have increased awareness of all synthetic mesh use in pelvic floor disorders including SUI. Several countries (eg, Australia, New Zealand) have recently banned or paused the use of midurethral sling mesh, and many of the companies that supply midurethral slings have stopped producing them.15 The situation facing the midurethral sling is a challenging one. Although the advantages of midurethral slings include minimal invasive approach, shorter operative and recovery times, and high efficacy rates, there are increasing concerns from the public and medical community with mesh related adverse events.1,2 With this in mind, our objective was to measure the long-term (more than 5 years) reoperation risk for mesh revision or removal (safety) and recurrent SUI (efficacy) after midurethral sling surgery.
This retrospective cohort study was approved by the Kaiser Permanente Southern California Institutional Review Board (#11508). We evaluated all female patients who underwent a synthetic mesh midurethral sling surgery for SUI (2005–2016) at a large managed care organization of 4.5 million patients. Kaiser Permanente patients receive nearly all their health care within this system. Inclusion criteria included women older than 18 years of age whose index surgery for SUI was a synthetic mesh sling. Exclusion criteria included women who received a nonsynthetic midurethral sling, autologous fascial sling, needle urethropexy, or retropubic urethropexy. We linked each patient's electronic, surgical, and implant records to create a record of primary midurethral sling and reoperations. In addition, we used surgical implant logs containing the product name, product number, and manufacturer to identify the midurethral sling implants used and physicians' Current Procedural Terminology and International Classification of Diseases 9th or 10th Revision codes to identify perioperative and demographic data (Appendix 1, available online at http://links.lww.com/AOG/B597.). We performed an individual review of a sample of cases to confirm validity of the data collection strategy.
We evaluated the primary outcome (overall reoperation rate after midurethral sling) as well as secondary outcomes (specific reoperation rates for mesh revision or removal and recurrent SUI). The indication for reoperation for mesh revision or removal included urinary retention, mesh exposure, pain, bleeding, infection, nerve injury, retropubic hematoma, bladder or urethral injury, and bowel injury. We excluded intraoperative complications because these have been reported in prior large prospective randomized trials.15,16 The type of reoperation for recurrent SUI included repeat midurethral sling, bulking injection, laparoscopic or abdominal retropubic urethropexy, needle bladder neck suspension, Kelly plication, and cystourethroplasty. Additionally, we assessed postoperative complications including urinary tract infection (UTI), recurrent UTI (at least two culture-proven UTIs in 6 months or at least three in 12 months), de novo (occurring only after primary midurethral sling placement) urgency urinary incontinence, and urinary retention requiring prolonged catheterization.
To calculate the cumulative incidence function and reoperation risk as a function of time, we considered leaving the medical system and death as competing events and the end of the study period as a censoring event using SAS 9.4 and R studio 0.98.1080. We compared demographics, characteristics, and reoperation of patients using χ2 for categorical variables and Wilcoxon rank sum for continuous variables. We estimated the adjusted hazard ratio (HR) and the 95% CI of reoperation using a Cox proportional hazards model. The reoperation counts compared with time did confirm the model's assumption of proportional hazards. Covariates included age, body mass index (BMI, calculated as weight in kilograms divided by height in meters squared), marital status, race, parity, vaginal estrogen use, sling type, smoking, diabetes, and menopausal status. Although our primary analysis considered the first reoperation, we performed a subanalysis of the risk of multiple reoperations for patients after mesh revision or removal.
From 2005 to 2016, 17,030 patients with SUI who met inclusion and exclusion criteria were treated with a synthetic mesh midurethral sling (Fig. 1). Median follow-up was 4.4 years, 7,534 patients had at least long-term (more than 5 years) follow-up, and there were no differences in patient characteristics when comparing length of follow-up. Of the midurethral sling surgeries, 10,750 (63%) were retropubic, followed by 4,554 (27%) transobturator, and 1,726 (10%) single incision. Demographics are presented in Table 1. The patients had a mean age of 54.8 (SD 11.9) years old and a mean BMI of 29.5 (SD 5.5); 10,039 (58.7%) of the patients were nonwhite (49.8% Hispanic, 4.4% Asian or Pacific Islander, and 3.4% black) and 11,345 (66%) were married. The median parity of patients was three; 790 (4.9%) of the patients were active smokers, 2,233 (13.1%) had diabetes, 3,539 (20.5%) were on vaginal estrogen, and 10,498 (61.6%) were postmenopausal.
Patients had an all-cause reoperation rate of 2.1% (95% CI 1.9–2.4%) at 1 year, 4.5% (95% CI 4.1–4.8%) at 5 years, and 6.0% (95% CI 5.5–6.5%) at 9 years (Fig. 2). Risk of reoperation was not associated with demographic or perioperative factors (Table 1), other than Asian or Pacific Islander compared with white ethnicity (adjusted HR 0.41 [95% CI 0.2–0.84]).
Reoperation rate for mesh revision or removal was 0.7% (95% CI 0.6–0.8%) at 1 year, 1.0% (95% CI 0.8–1.1%) at 5 years, and 1.1% (95% CI 0.9–1.3%) at 9 years. The primary indication for revision or removal was urinary retention (n=114, 0.7%), followed by mesh exposure (n=37, 0.2%), pain (n=18, 0.1%), bleeding (n=9, 0.1%), and infection (n=5, 0.03%). There were no cases of midurethral mesh sling revision or removal for nerve injury, retropubic hematoma, bladder, urethral, or bowel injury. When considering potential demographic and perioperative characteristics, adjusted HRs revealed no statistically significant differences (Table 2).
Reoperation for recurrent SUI was 1.6% (95% CI 1.4–1.8%) at 1 year, 3.9% (95% CI 3.5–4.2%) at 5 years, and 5.2% (95% CI 4.7–5.7%) at 9 years. The most common reoperation type was synthetic midurethral sling (n=425, 2.5%), followed by bulking injection (n=164, 1.0%), laparoscopic retropubic urethropexy (n=36, 0.2%), abdominal retropubic urethropexy (n=32, 0.2%), needle bladder neck suspension (n=3), Kelly plication (n=1), cystourethroplasty (n=1). Risk of reoperation for recurrent SUI was associated with sling type (P=.03), with patients having a single incision sling having a greater risk when compared with retropubic midurethral sling (adjusted HR 1.5 [95% CI 1.06–2.11]) (Table 3). At 9 years, the rate of reoperation for recurrent SUI was 9.8% (95% CI 3.2–20.9) in patients with single incision sling, compared with 3.7% (95% CI 3.1–4.4) in patients with retropubic midurethral sling, and 4.6% (95% CI 3.7–5.8) in patients with transobturator midurethral sling.
Within 1 year after placement of midurethral sling, 23.1% of patients developed at least one UTI, and 3.7% of patients developed a de novo diagnosis of recurrent UTI. Postoperatively, 5.6% of patients receiving a midurethral sling developed de novo urgency urinary incontinence, and 1.1% developed de novo urgency urinary incontinence with continued or recurrent SUI. Prolonged catheterization (beyond the first postop void trial visit, two to four days postop) secondary to urinary retention after their midurethral sling procedure was uncommon (5.6%). Of those patients with a reoperation for mesh revision or removal, 11.5% went on to have at least one reoperation for recurrent SUI (2% had more than one reoperation). Of these reoperations, 8.9% had another midurethral sling surgery, 3.2% had a bulking injection, and 1.3% had a laparoscopic retropubic urethropexy.
In this large long-term retrospective cohort study of women undergoing primary synthetic mesh midurethral sling for SUI, we found a low rate of reoperation. At 9 years the overall rate of reoperation was 6%. This rate was lower in Asian or Pacific Islanders when compared with white patients and risk of reoperation for recurrent SUI was more common after single incision when compared with retropubic midurethral sling; however, demographic and perioperative factors otherwise had no effect on rate of reoperation in our adjusted model. The long-term rates of reoperation for mesh revision or removal were similarly low at 1.1% by 9 years, with urinary retention the most common indication. Reoperation for mesh exposure and pain was uncommon. Patients rarely had a reoperation for recurrent SUI (5.2% at 9 years), with repeat synthetic midurethral sling being the most likely surgical approach.
As midurethral sling as a treatment option for surgical management of SUI continues to be scrutinized in the media,17 some surgeons and patients may feel compelled to undergo more invasive procedures, such as retropubic urethropexy (Burch colposuspension) or autologous fascial sling, under the belief that these procedures are safer options. Systematic reviews have found that these procedures, which involve an abdominal incision, have longer operative and hospitalization time, an increased risk of perioperative complications, and an increased risk of reoperation compared with midurethral sling.5–8,18 One randomized controlled trial (RCT) found a 2-year risk of reoperation for urinary retention of 4% and 0%, after Burch colposuspension and midurethral sling, respectively.4 Another RCT19 found a higher risk of reoperation for urinary retention (odds ratio 13) and intermittent self-catheterization after autologous fascial sling compared with midurethral sling. Similar to synthetic midurethral sling procedures, long-term rates of adverse events related to these traditional incontinence procedures are also lacking in the scientific literature.
In addition to a higher risk of complications, the Burch colposuspension and autologous fascial sling procedures have a higher risk of reoperation for recurrent SUI. A secondary analysis20 of the Urinary Incontinence Treatment Network Stress Incontinence Surgical Treatment Efficacy Trial and Trial of Midurethral Sling found that retreatment for recurrent SUI was more common after Burch colposuspension and autologous fascial slings compared with midurethral sling. Traditional Burch colposuspension and autologous fascial sling procedures appear to have a higher risk of complications and a higher risk of recurrent SUI compared with midurethral sling.
A 2017 Cochrane systematic review2 found 81 RCTs including 12,113 women with SUI undergoing midurethral sling surgery concluded that the midurethral sling has been extensively researched and has a good safety profile with short (less than 1 year) and medium term (less than 5 years) efficacy. Many of these studies allow for detailed subjective, objective and intra-operative and short-term safety outcomes. However, the authors determined that there is a significant need for long-term (more than 5 years) outcome data to support safety and efficacy. Compared with the existing database studies with long-term outcome data, our study has enhanced internal validity, which is evidenced by our review of individual patient records, linkage of patient to implant, and reporting of details of comorbidities, procedures, reoperations and outcomes. In addition, our results are generalizable with a diverse cohort of patients, surgeons and implants. Furthermore, we studied a current cohort, reflective of modern improvements in technique, trocars, and surgeon training.
Our overall reoperation risk and risk of reoperation for recurrent SUI findings are similar to previous studies. A U.K. study21 of 95,057 patients within the UK National Health Service explored all cause reoperation, as well as reoperation for sling revision or removal and SUI using a database of all surgeries conducted within this system. The study found that all-cause reoperation was 2.6% at 1 year, 5.5% at 5 years, and 6.9% at 9 years and reoperation for mesh revision or removal was 1.4% at 1 year, 2.7% at 5 years, and 3.5% at 9 years. A Canadian study22 of 59,887 women that used linked databases of all patients undergoing midurethral sling surgery in Ontario, Canada found a 10-year cumulative incidence of mesh revision or removal of 3.29%. A U.S. study23 of 188,454 women who received a midurethral sling and had reoperations captured by their enrollment in employer-based health plans found a 9-year cumulative risk of sling revision or removal of 3.7%. Only one22 study reported the indication for mesh revision or removal, with mesh erosion (2.5%) as the most common indication followed by urinary retention (1.3%), rates higher than those found in our study (urinary retention [0.7%], mesh exposure [0.2%]). Overall, our cohort had a lower risk of reoperation for mesh revision or removal compared with these studies.
Although it is difficult to speculate, the lower rates of reoperation for mesh revision or removal in our study compared with these other cohort studies may be secondary to our integrated health care model that commonly refer pelvic floor patients to specialty clinics. The potential reason behind higher mesh revision or removal in that study21 may be the climate of surgeon and patient awareness of and restrictions to synthetic mesh midurethral sling in that country. Within our system, most midurethral sling surgeries are performed by experienced, higher-volume surgeons, which may further explain the lower reoperation for mesh revision or removal rate.21,24
This study has several limitations related to its retrospective design and other factors. Patients within Kaiser Permanente obtain virtually all care within our system and have high year-to-year retention rates; however patients may have had a primary procedure or reoperation outside the Kaiser system, making their outcomes not capturable. Likewise, some patients, after receiving their primary sling, may have relocated from the area, changed health plans, or chosen not to report complications. We focused on reporting reoperation as our outcome, therefore we were unable to detect complications (such as mesh exposure managed with vaginal estrogen) or recurrent SUI (such as pelvic floor physical therapy, office bulking or incontinence pessaries) managed nonoperatively. This approach limited coding inaccuracy that can lead to overestimation of complications. Other potential sources of miscoding could have occurred because data may have been entered incorrectly or data could have been omitted. To limit this, the research team confirmed data with quality checks by reviewing the electronic medical record in a sample of cases. The quality checks confirmed a high internal validity. Secondary to the limitations of coding, we were unable to report on the extent of mesh removed in cases of mesh revision or removal. Adjusted HRs were calculated to account for potential confounders; however it is possible there was residual confounding. The Cox proportional hazard only accounted for the first reoperation, and, thus, cannot account for the burden of reoperation in patients that received multiple reoperations.
The study has several strengths. We examined women who received a wide range of midurethral sling synthetic mesh implants and midurethral sling approaches (Appendix 2, available online at http://links.lww.com/AOG/B597). In addition, the women were racially diverse and of a range of ages. These features enhance generalizability by mirroring typical practice patterns and patient factors. We collected potential comorbidities and incorporated them in our analysis. By linking patient to implant we enhanced construct validity. Additionally, by reporting on the type of reoperation for recurrent SUI and indication for mesh revision or removal we add to the literature and provide a high level of detail on important indicators of efficacy and safety.
This study has several important implications for patient care and safety. Our study shows that long-term risk of reoperation after synthetic mesh midurethral sling is low. Furthermore, patients rarely had a reoperation for mesh revision or removal or recurrent SUI, which adds to evidence supporting long-term safety and efficacy. When adverse events occur, they can be significant for some women, demonstrating the importance of preoperative counseling including discussion of nonsurgical treatment options, condition specific bother, and individual surgeon's procedure specific outcomes. In the current polarized environment of mesh litigation, removal by several manufacturers of midurethral sling products from the market, and prohibition of midurethral sling use in other countries, our study offers information on long-term safety and efficacy data that will help guide surgeons and patients in making informed, evidence-based decisions regarding care for women with SUI.
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