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Contents: Urogynecology: Original Research

Postoperative Pain After Adjustable Single-Incision or Transobturator Sling for Incontinence

A Randomized Controlled Trial

Schweitzer, Karlijn J. MD; Milani, Alfredo L. MD, PhD; van Eijndhoven, Hugo W.F. MD, PhD; Gietelink, Dirk A. MD, PhD; Hallensleben, Eric MD; Cromheecke, Geert-Jan MD; van der Vaart, Carl H. MD, PhD

Author Information
doi: 10.1097/AOG.0000000000000604
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Stress urinary incontinence (SUI) is defined as involuntary loss of urine on effort or physical exertion (eg, sporting activities) or on sneezing or coughing.1 For many gynecologists, the surgical treatment of choice for SUI has become a synthetic midurethral sling. To minimize the risk of retropubic hematomas, bladder, or bowel injury, associated with retropubic midurethral sling placement, the transobturator approach was developed.2–4 One of the concerns regarding the transobturator approach is persistent groin and thigh pain, which can have a negative effect on women's quality of life.5

Since 2006, third-generation slings, often described as “single-incision” or “minislings,” became available. These slings avoid both the retropubic space and the adductor muscles of the thigh. A recent review on single-incision slings demonstrated, after exclusion of TVT-Secur results, no differences in objective and subjective cure between midurethral slings and single-incision slings.6 In addition, the single-incision sling was associated with lower postoperative pain scores than midurethral slings, although heterogeneity in data cautions interpretation. A blinded, randomized, controlled study with postoperative pain as the primary outcome measure was not available at the time the current study was designed and executed.

Since 2009, an adjustable single-incision sling has been available. This single-incision sling combines robust fixation with adjustability of tension of the tape during surgery (http://www.bardurological.com).

The primary aim of this multicenter randomized trial was to compare the adjustable single-incision sling with the transobturator sling (inside-out) in terms of surgery-related pain. Objective and subjective efficacy and complications and time of return to normal daily activities were secondary outcomes.

MATERIAL AND METHODS

In this single-blinded randomized trial, women aged between 35 and 80 years who had moderate to severe SUI, defined as a Sandvik score 3 or greater, and who had not experienced relief after pelvic floor muscle physiotherapy treatment, were included.7 The diagnosis of objective SUI was based on a positive cough stress test during examination showing urine leakage. Urodynamic evaluation was not considered mandatory for the diagnosis of SUI. Exclusion criteria were a history of anti incontinence surgery, a postvoiding residual volume of more than 100 mL, genital prolapse stage 2 or higher according to the Pelvic Organ Prolapse Quantification classification, desire for future pregnancy, or all of these.8

Women were recruited at the outpatient clinics of one university clinic and four large teaching hospitals. After having obtained written informed consent, they were randomized between the transobturator tension-free vaginal tape and the adjustable single-incision sling. Bard Company offered an unrestricted research grant.

The research nurse performed central telephone randomization with sequentially numbered, opaque, sealed envelopes. Randomization was performed in a two-to-one (adjustable single-incision sling:transobturator sling) design. The reason for this was twofold. First, the adjustable single-incision sling is a relatively new technique, which could have unknown complications that did not yet emerge from other observational studies. Second, every new technique has its own learning curve. Although each participating gynecologist inserted at least 10 adjustable single-incision slings before the first randomization, the two-to-one design also minimized the effect of a potentially longer learning curve and increased the opportunity to observe potential adverse effects. Each procedure was performed strictly according to the instructions of the manufacturers.

All women received perioperative antibiotic prophylaxis according to local protocols. Mode of anesthesia was per patient request and could either be general or locoregional (spinal analgesia).

Blinding of women was secured by not informing them on the randomization result before the procedure until 6 weeks postoperatively and by the additional use of two small (2-mm) sham “incisions” in the groin at the skin exit point, where a transobturator sling is expected to perforate the skin in case an adjustable single-incision sling procedure was done. This area was covered with a small plaster, comparable to that of the transobturator sling procedure. Immediately after the surgical procedure, all women received 1,000 mg acetaminophen. Subsequent pain medication was given depending on the visual analog scale and according to a strict protocol that is represented in Figure 1.

Fig. 1
Fig. 1:
Pain medication protocol.Schweitzer. Single-Incision Compared With Transobturator Sling for Stress Incontinence. Obstet Gynecol 2015.

The primary outcome was postoperative pain. This was assessed with a 100-mm visual analog scale at 1 and 2 hours after awakening from general anesthesia or after vanishing of the analgesic effect of spinal anesthesia and thereafter subsequently daily for the first 3 days and weekly for 6 weeks.

Secondary outcomes were objective cure, defined as a negative stress cough test at a bladder volume of at least 300 mL; subjective cure, defined as a negative answer to the Urogenital Distress Inventory question “Do you experience urine leakage related to physical activity, coughing or sneezing?”9; subjective improvement, defined as a “(very) much better” answer on the Patient Global Impression of Improvement scale10–12; and de novo urge urinary incontinence, defined as a positive answer to the Urogenital Distress Inventory question “do you experience urine leakage related to a feeling of urgency.” Bother scores, effect on quality of life, and symptom severity were recorded with the Urogenital Distress Inventory, the Incontinence Impact Questionnaire, and the Patient Global Impression of Severity scale, respectively. To assess sexual functioning, the short form of the Prolapse and Incontinence Sexual Questionnaire was used.13 An independent research nurse or physician performed all trial assessments before surgery at 6 weeks and at 6 and 12 months after surgery.

Sample size calculation was based on expected differences in pain scores between interventions at 24 hours postsurgery. Based on data we collected over a period of 6 years, the 24-hour pain score of the transobturator sling has a mean value of 30 (standard deviation 21), which is close to 40 that is reported in literature.14 To detect a difference with a minimal effect size of 0.5, a reduction in pain score of 11 points to a mean value of 19 was necessary. This change of 11 points can be detected at an α of 0.05 with a power of 80% at an allocation ratio of two to one with 88 women in the adjustable single-incision sling group and 44 women in the transobturator sling group. With an anticipated loss of follow-up of 10%, 145 women were needed for inclusion.

Analysis was performed on an intention-to-treat basis. All data were analyzed with the use of SPSS Statistics for Windows 20.0. Continuous variables were checked for normality of distribution and reported as means (±standard deviation) for the parametric variables or median (interquartile range) for nonparametric variables. Unpaired t test and the Mann-Whitney U test were used to detect statistically significant differences for parametric variables and nonparametric variables, respectively.

χ2 tests were used for categorical variables. Changes in continuous variables over time were analyzed with the use of paired-sample Student's t tests or Wilcoxon signed rank test. Bonferroni correction was used to correct overestimation in multiple testing.

The study was approved by the ethics committee of the University Medical Center Utrecht and each of the participating hospitals and was registered in the Dutch trial register (http://www.trialregister.nl NTR: 2558). All women provided written informed consent.

RESULTS

Between September 2010 and August 2011, a total of 292 women underwent surgery for SUI in the four participating clinics. A total of 156 women (53.4%) fulfilled the in- and exclusion criteria and agreed to participate and were randomized (100 for an adjustable single-incision sling and 56 for a transobturator sling). Early in the study, eight women, four in the adjustable single-incision sling group and four in the transobturator sling group, refrained from surgery shortly after randomization. One woman in the transobturator sling group erroneously received two randomization numbers and was excluded. As a result of this unexpected pretreatment dropout early in the inclusion phase, we decided to expand our inclusion to 156 women to assure a final adequate sample size to answer our research question. Three women, originally assigned to an adjustable single-incision sling, mistakenly received a transobturator sling but were analyzed according to the intention-to-treat principle.

Of the women in the study who received surgery 95.8% (92/96) of the adjustable single-incision sling group and 94.1% (48/51) of the transobturator sling group attended the 12-month follow-up visit, as is presented in our flowchart of the study (Fig. 2). Total short form of the Prolapse and Incontinence Sexual Questionnaire score could only be calculated for women who were sexually active and answered at least 10 of 12 questions, leaving 60 in the adjustable single-incision sling group and 35 in the transobturator sling group for analysis.

Fig. 2
Fig. 2:
Flowchart of study participants.Schweitzer. Single-Incision Compared With Transobturator Sling for Stress Incontinence. Obstet Gynecol 2015.

In Table 1 baseline characteristics of both groups are shown. No statistically significant differences in baseline characteristics between groups were found. Table 2 shows the median postoperative pain scores on a visual analog scale after surgery up to 6 weeks of follow-up. The score on a visual analog scale in the adjustable single-incision sling group was significantly lower immediately postsurgery and was sustained up to the end of the first week postsurgery. There were no significant differences in the use of acetaminophen (P=.088 and P=.310) or ibuprofen (P=.595 and P=.655) in the first 3 days or first 6 weeks, respectively.

Table 1
Table 1:
Baseline Characteristics
Table 2
Table 2:
Pain Scores on a Visual Analog Scale (Range 0–10)

All women had their surgery under general or spinal anesthesia, and this was not significantly different between procedures (P=.09) The adjustable single-incision sling procedure was associated with a statistically significantly shorter operating time when compared with the transobturator sling. The average blood loss was comparable between procedures (Table 3).

Table 3
Table 3:
Postoperative Characteristics

At 6 weeks of follow-up, 87.5% in the transobturator group had complete resumed work as compared with 93.7% in the adjustable sling group; this was not significantly different between the groups (P=.252).

At 12 months, the reported objective cure was 90.8% (79/87) in the adjustable single-incision sling group and 88.6% (39/44) in the transobturator sling group (P=.760). Subjective cure was reported by 77.2% (71/92) in the adjustable single-incision sling group and 72.9% (35/48) in the transobturator sling group (P=.577). Much or very much improvement on the Patient Global Impression of Improvement scale was reported by 90.0% (81/90) in the adjustable single-incision sling group and 87.0% (40/44) in the transobturator sling group (P=.592).

Table 4 shows the changes in preoperative and postoperative symptom bother, quality of life, and sexual function scores. After Bonferroni correction, there was no statistically significant difference in total short form of the Prolapse and Incontinence Sexual Questionnaire scores at 12 months follow-up. De novo dyspareunia was reported by 38.5% (10/26) in the adjustable single-incision sling group and by 25% (4/16) in the transobturator sling group; this was not significantly different (P=.369).

Table 4
Table 4:
Effect of Surgery on Urogenital Symptoms

Major intraoperative complications did not occur in either group. In two women assigned to the adjustable single-incision sling group, the surgeon encountered technical difficulties with the insertion of the sling. During one procedure, the surgeon was unable to introduce the anchor on the left side of the patient with the first adjustable single-incision sling. He decided to remove that sling completely and inserted a second one without technical difficulties. In the other procedure, the surgeon was unable to perforate the obturator membrane on the left side of the patient but could not remove the adjustable single-incision sling anchor from the right side either. The surgeon removed the sling material but left the anchor in situ. Subsequently he inserted a second tape without technical difficulties. In two women in the adjustable single-incision sling group, a vaginal lateral fornix perforation was identified during surgery and repaired immediately. We did not experience any technical difficulties in the transobturator sling group.

Postoperative complication rates were comparable in both groups (Table 3). Thirteen women, eight in the adjustable single-incision sling and five in the transobturator sling group (P=.772) experienced temporary voiding difficulties that required intermittent catheterization (with a maximum duration of 14 days). Seven women in the adjustable single-incision sling and four women in the transobturator sling group (P=.75) developed new-onset urge urinary incontinence symptoms. In the adjustable single-incision sling group, two women received a retropubic tension vaginal tape as a result of failure of the initial procedure. One woman with a transobturator sling underwent tape removal because of persistent thigh pain and later received a retropubic tension vaginal tape. Four women in the adjustable single-incision sling group and none in the transobturator sling group had vaginal exposure of the tape in the lateral vaginal fornix. All exposures were successfully surgically treated.

DISCUSSION

This randomized trial was performed to evaluate the pain profile of a relatively new adjustable single-incision sling compared with an established transobturator technique. The adjustable single-incision sling is associated with statistically significant less pain in the first week after surgery and demonstrates comparable functional outcome at 12 months follow-up when compared with the transobturator sling for the treatment of female urinary stress incontinence. However, pain scores in both groups were relatively low, and the difference in pain score did not lead to a statistically significant difference in postoperative use of pain medication. The significantly shorter operating time in the adjustable single-incision sling group (86 seconds) was not considered to be of clinical relevance.

One of the concerns with the traditional transobturator techniques is pain caused by perforating several adductor muscles. The intent of this new single-incision sling is a decrease in postoperative pain with comparable surgical effectiveness. Although postoperative pain scores were significantly lower in the adjustable single-incision sling group, the mean score on a visual analog scale in the transobturator sling group was still less than 40, which is generally regarded as “bearable” pain.15 We used a strict a strict pain protocol after surgery; this also could be an explanation for the low pain scores in both groups. Although the clinical significance of the differences in pain is uncertain, our findings are consistent with those by Mostafa et al who also reported significantly lower postoperative pain scores in favor of the adjustable single-incision sling.16,17

The very low pain scores of the adjustable single-incision sling and the significantly shorter operating time might be a possibility to confirm the potential of this procedure as a surgical procedure under local anesthesia.

The most important outcome measure from patients' perspectives is a decrease of incontinence symptoms. Our data on the Patient Global Impression of Improvement scale are consistent with the literature with (very) much improvement reported at 12 months follow-up by 81–84% of women.17–20 Despite differences in the way cure is defined, comparative studies consistently show that outcomes between the transobturator and adjustable single-incision sling are comparable.

With validated instruments we demonstrated that urogenital symptoms, quality of life, and sexual functioning scores all significantly improved both after the adjustable single-incision and the transobturator sling with no differences between procedures. It is noteworthy that bother scores in the overactive bladder domain, which were present alongside the predominant stress incontinence in either group, were significantly reduced in both groups.

A point of concern is that we did experience some technical difficulties with the adjustable sling, although the study was not designed to compare safety; the learning curve of this new technique was probably longer than the 10 procedures we had chosen in this study. Although 12-month results are considered short term, they are generally long enough to detect mesh exposures.

To appreciate our findings, some possible limitations need to be acknowledged. First, not all eligible women in the participating centers entered into the study. In part, this is related to exclusion criteria, but personal preferences of the physician and the woman may have played a role. This may have introduced some selection bias. Second, we only compared two inside-out obturator procedures. On one hand, this reduced variation in techniques; on the other hand, our results cannot be translated to other midurethral sling procedures. Third, the timing at which the first score on a visual analog scale was obtained after surgery with spinal analgesia was somewhat subjective. This may have affected the proper timing to perform the 1- and 2-hour postsurgery scores on a visual analog scale. However, there is no reason to assume that this possible timing effect was different between groups, because the distribution of spinal and general anesthesia was not significantly different between groups. Later measurements showed persistent significantly less pain scores in the adjustable single-incision sling group that continued up to 1 week. Finally, some may feel that urodynamic evaluation is mandatory to objectify stress incontinence before surgery and this may have introduced an indication bias. Because two recent studies have shown that the role of urodynamics before surgery for uncomplicated stress incontinence is limited, we do not consider this as a limitation.12,21

The strengths of this study are its randomized, single-blinded multicenter design, the use validated outcome measurements, the independent data assessment, and the two-to-one design in which complications can be detected more easily.

In conclusion, the adjustable single-incision sling is associated with significantly less postoperative pain; maximum difference in pain score was reported on the evening of the day of surgery.

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© 2015 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.