Objective
The objective of the study was to estimate the long-term risk of sling revision/removal after an initial sling and to assess indications (mesh erosion and urinary retention) and predictors of sling revision/removal.
Study Design
Using a population-based cohort of commercially insured individuals, we identified women 18 years old or older who underwent a sling (Current Procedural Terminology code 57288) between 2001 and 2010 and any subsequent sling revision/removal (Current Procedural Terminology code 57287). We estimated the cumulative risk of revision/removal annually and evaluated predictors of sling revision/removal using Kaplan-Meier survival curves and Cox proportional hazards models, respectively.
Results
We identified 188,454 eligible women who underwent an index sling. The 9 year cumulative risk of sling revision/removal was 3.7% (95% confidence interval [CI], 3.5–3.9). At 1 year, this risk was already 2.2% and then increased to 3.2% at 4 years before plateauing. With regard to the indication for the sling revision/removal, a greater proportion was due to mesh erosion compared with urinary retention, with a 9 year risk of 2.5% (95% CI, 2.3–2.6) for mesh erosion vs 1.3% (95% CI, 1.2–1.4) for urinary retention. Age had an effect on the revision/removal rates for both mesh erosion and urinary retention, with the higher risks among those aged 18-29 years. The risk of revision/removal for mesh erosion and urinary retention was also elevated among women who had a concomitant anterior or apical prolapse procedure.
Conclusion
In this population-based analysis, the 9 year risk of sling revision/removal was relatively low at 3.7%, with 60% of revisions/removals caused by mesh erosion.
Slings represent the most common surgery for stress urinary incontinence (SUI) and are now considered the gold standard procedure. Historically, the term slings referred to bladder neck slings, which remain an effective surgery for SUI. However, midurethral slings now dominate the surgical management of stress incontinence. The uptake of the midurethral synthetic mesh sling has increased dramatically since the introduction of the tension-free vaginal tape in the United States in 1998. Over the last decade, the retropubic midurethral sling has been modified, and the category of midurethral slings now includes transobturator slings as well as minislings.
For Editors’ Commentary, see Contents
The adoption of the midurethral sling was supported by level I evidence, which demonstrated similar 5 year effectiveness of retropubic midurethral slings and Burch colposuspensions, the prior gold standard SUI procedure. Furthermore, randomized trials have reported equivalence between retropubic and transobturator slings at 1 year. Although high-quality data from randomized trials exist regarding long-term effectiveness of midurethral slings, the long-term, population-based data are limited regarding the need for repeat surgery to manage complications such as mesh erosion or urinary retention. The best available data on complications suggest that the risk of sling revision/removal for either mesh erosion or retention is fairly low, ranging from approximately 1-3% 8,9 and 0.6-1.2%, respectively.
To date, the largest observational cohort reported on fewer than 4000 sling procedures followed up for a maximum of 21 months. Thus, long-term follow-up of patients treated in real-world clinical settings are needed to further characterize the rates of repeat surgery to manage complications such as mesh erosion or urinary retention.
The recent Food and Drug Administration (FDA) notification regarding vaginal mesh for prolapse has simultaneously increased the attention directed at midurethral slings because these procedures involve synthetic mesh placed vaginally. Although the FDA notification specifically addresses vaginal mesh prolapse procedures, an update on Jan. 4, 2012, stated that “the FDA continues to evaluate the effects of using surgical mesh for the treatment of urine leakage during moments of physical activity (stress urinary incontinence) and will provide updates on this web page at a later date.” Thus, the FDA verdict regarding mesh slings for SUI is pending.
For relatively new procedures, it is critical to conduct long-term outcome assessments. For the midurethral sling, an important outcome to assess is the risk of a sling revision or removal to manage complications such as a mesh erosion or urinary retention.
Given the FDA emphasis on evaluating medical devices involving vaginal mesh and the limited, long-term, population-based data regarding slings, the objective of this study was to estimate the long-term risk of sling revision/removal after an initial sling in a large, population-based cohort. Our secondary objective was to assess the indication for sling revision/removal (mesh erosion and urinary retention) as well as predictors of revision/removal.
Materials and Methods
Data source
We utilized the Thomson Reuters MarketScan Commercial Claims and Encounters and Medicare Supplemental Coordination of Benefits database from 2001 to 2010 (copyright 2011, Thomson Healthcare Inc, Montvale, NJ). This database contains deidentified, individual-level health care utilization and enrollment data for inpatient, outpatient, and pharmacy visits from approximately 100 employer-based plans in the United States. These deidentified data represent the medical experience of privately insured employees, retirees, covered spouses, and dependents. This database has been rigorously evaluated and is valid and reliable. Individuals can be followed up longitudinally using encrypted unique identification numbers, and enrollment data allowed us to determine which individuals have insurance coverage at any point in time. This database provided information on 44.8 million women aged 18 years and older between the years 2001 and 2010. This study was determined to be exempt from further review by the institutional review board at the University of North Carolina at Chapel Hill.
Inclusion criteria and index sling
The population of interest included all women aged 18 years and older from 2001 to 2010. The first, or index, sling was identified for each woman, based on current procedural terminology (CPT) code 57288. We included women with at least 90 days of continuous enrollment prior to the procedure. Those with a diagnosis of a urethral diverticulum ( International Classification of Diseases , 9th revision, clinical modification [ICD-9-CM] code 619.0) or any urinary-genital tract fistula (codes 599.1 and 599.2) in the 90 days prior to the index surgery were excluded. If an additional SUI procedure (ie, a different type of SUI surgery such as a Burch colposuspension) was coded on the same date as the sling, these individuals were excluded. The location for the procedure was also assessed, whether inpatient or outpatient. If both an inpatient and outpatient procedure claim occurred on the same service date, we preferentially included the inpatient procedure.
Sling revision/removal
After the index sling, the first subsequent sling revision/removal was identified using CPT code 57287. If another SUI surgery was performed after the index sling (ie, another sling, Burch colposuspension, bulking agent, etc), the outcomes of these individuals were censored at that surgery date because we were unable to determine whether any subsequent revision/removal was secondary to the index sling or the repeat SUI procedure. Otherwise, individuals were censored at the earliest disenrollment or on Dec. 31, 2010.
In addition to identifying sling revision/removals, we assessed the indication for this procedure based on ICD-9-CM codes for mesh erosion (996.30, 996.39, 996.59, 996.60, 996.65, 996.69, 996.70, 996.76, 996.79, 939.0, 939.2, and 939.9) and urinary retention (596.0, 598.1, 598.2, 598.8, 598.9, 599.6, 599.69, 788.2, 788.21, 788.29, 788.61, 788.62, and 788.65). We did not utilize 629.3 (complication of implanted vaginal mesh and other prosthetic materials), 629.31 (erosion of implanted vaginal mesh), or 629.32 (exposure of implanted vaginal mesh) because these ICD-9 codes were not released until 2011, and thus were not applicable during our study period.
It is important to note that the diagnoses of mesh erosion and/or urinary retention were not mutually exclusive; thus, both mesh erosion and urinary retention could be associated with a single sling revision/removal procedure. For the indication-specific outcome definitions, individuals were censored if they had a revision/removal for another indication.
Statistical analysis
Descriptive statistics were used to characterize the population of women who underwent an index sling procedure. Kaplan-Meier survival curves were used to estimate the cumulative incidence (with 95% confidence intervals [CIs]) of sling revision/removal at 3 months, 6 months, and annually through 9 years of follow-up. We also estimated the cumulative incidence of sling revision/removal for mesh erosion and urinary retention separately. To explore the potential for differences in the risk of these outcomes because of the year when the index sling was placed, we also compared the cumulative risk at 1 year after the index sling, stratified by calendar year in which the index sling was performed.
We used Cox proportional hazards models to estimate the adjusted hazard ratio (adjHR) of the following: (1) sling revision/removal separately by decade of age (18-29, 30-39, 40-49, 50-59, 60-69 years) at the time of the index surgery compared with those 70 years of age and older; (2) inpatient vs outpatient procedures; (3) concomitant hysterectomy; and (4) concomitant prolapse procedures.
To further examine the possibility of different effects of these risk factors on revision/removal for mesh erosion and urinary retention, we also estimated the adjHRs separately for each of these outcomes. We estimated 95% confidence intervals on all effect estimates. Statistical analyses were performed using SAS, version 9.2 (SAS Institute, Cary, NC).
Results
Of the 44.8 million women aged 18 years or older from 2001 to 2010, there were 188,454 index sling procedures. The median age of women undergoing surgery was 53 years (interquartile range, 45–61), and approximately 60% of these procedures were performed in women aged 40-59 years of age ( Table 1 ). Table 1 also depicts the year in which the index sling was performed and illustrates that a higher proportion of surgeries were done in the latter years reflecting an increase in the database’s enrolled population. Because the majority of procedures were performed in the latter portion of the decade, there are relatively more procedures with shorter time intervals of follow-up ( Table 1 ). Nonetheless, we have 4 or more years of follow-up on 25,219 individuals and more than 8 years on 1864 individuals. A majority of the procedures (67%) was performed on an outpatient basis, and the South had the largest proportion of sling procedures (49%). Concomitant hysterectomy and concurrent prolapse procedures were also common ( Table 1 ).
| Characteristic | n = 188,454 | % |
|---|---|---|
| Age at index sling, y | ||
| Median (IQR) | 53 (45–61) | — |
| Mean (SD) | 53.7 (11.9) | — |
| 18-29 | 1314 | 0.7 |
| 30-39 | 18,429 | 9.8 |
| 40-49 | 55,248 | 29.3 |
| 50-59 | 57,208 | 30.4 |
| 60-69 | 35,150 | 18.6 |
| 70-79 | 16,183 | 8.6 |
| ≥80 | 4942 | 2.6 |
| Year when index surgery performed | ||
| 2001 | 2322 | 1.2 |
| 2002 | 5026 | 2.7 |
| 2003 | 8835 | 4.7 |
| 2004 | 13,350 | 7.1 |
| 2005 | 17,445 | 9.3 |
| 2006 | 20,437 | 10.8 |
| 2007 | 23.066 | 12.2 |
| 2008 | 30,155 | 16.0 |
| 2009 | 33,654 | 17.9 |
| 2010 | 34,164 | 18.1 |
| Time intervals of follow-up, y | ||
| 0 to <2 | 122,213 | 64.9 |
| 2 to <4 | 41,022 | 21.8 |
| 4 to <6 | 16,827 | 8.9 |
| 6 to <8 | 6528 | 3.5 |
| ≥8 | 1864 | 1.0 |
| Outpatient index slings | 126,443 | 67.1 |
| Region | ||
| Northeast | 13,724 | 7.3 |
| Midwest | 52,035 | 27.6 |
| South | 92,145 | 48.9 |
| West | 29,624 | 15.7 |
| Unknown | 924 | 0.5 |
| Concomitant surgery | ||
| Hysterectomy | 47,065 | 25.0 |
| Anterior prolapse procedures | 62,469 | 33.2 |
| Apical prolapse procedures | 22,743 | 12.1 |
| Posterior prolapse procedures | 13,198 | 7.0 |
The cumulative incidence of sling revision/removal for any indication was 3.7% (95% CI, 3.5–3.9) at 9 years of follow-up ( Table 2 ). At 1 year of follow-up, this risk was 2.2% and then increased to 3.2% at 4 years before plateauing. Thus, a majority of sling revision/removals occurred within the first few years after the index surgery. With regard to the indication for the sling revision/removal, a greater proportion was due to mesh erosion compared with urinary retention, with a 9 year risk of 2.5% (95% CI, 2.3–2.6) for mesh erosion vs 1.3% (95% CI, 1.2–1.4) for urinary retention. Focusing on mesh erosion, the risk of revision/removal increased from 1.3% at 1 year to 2.1% at 4 years before leveling off. For urinary retention, the risk was 0.9% at 1 year and then remained fairly stable afterward.
| Follow-up after index sling, y | Cumulative risk of revision/removal for urinary retention | Cumulative risk of revision/removal for mesh erosion | Cumulative risk of sling revision/removal for any indication |
|---|---|---|---|
| 0.25 | 0.6 (0.5, 0.6) | 0.5 (0.5, 0.5) | 1.0 (1.0, 1.1) |
| 0.5 | 0.8 (0.7, 0.8) | 0.9 (0.8, 0.9) | 1.6 (1.5, 1.6) |
| 1 | 0.9 (0.9, 1.0) | 1.3 (1.2, 1.3) | 2.2 (2.1, 2.2) |
| 2 | 1.1 (1.0, 1.1) | 1.6 (1.6, 1.7) | 2.6 (2.5, 2.7) |
| 3 | 1.2 (1.1, 1.2) | 1.9 (1.8, 2.0) | 3.0 (2.9, 3.1) |
| 4 | 1.2 (1.1, 1.3) | 2.1 (2.0, 2.2) | 3.2 (3.1, 3.4) |
| 5 | 1.2 (1.2, 1.3) | 2.2 (2.1, 2.3) | 3.4 (3.3, 3.5) |
| 6 | 1.3 (1.2, 1.4) | 2.3 (2.2, 2.4) | 3.6 (3.5, 3.7) |
| 7 | 1.3 (1.2, 1.4) | 2.5 (2.3, 2.6) | 3.7 (3.5, 3.9) |
| 8 | 1.3 (1.2, 1.4) | 2.5 (2.3, 2.6) | 3.7 (3.5, 3.9) |
| 9 | 1.3 (1.2, 1.4) | 2.5 (2.3, 2.6) | 3.7 (3.5, 3.9) |
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