Factors Influencing the Incidence of Mesh Erosion After Transobturator Sling Placement for Stress Urinary Incontinence

Abstract

Objective: The objective of this study was to identify factors associated with mesh erosion after placement of a transobturator sling for correction of stress urinary incontinence (SUI). Design: Between 2006 and 2008, a consecutive series of patients underwent surgery for SUI. A retrospective analysis was performed and included baseline, surgical, postoperative, and complication data. Materials and Methods: A total of 69 patients underwent surgery for SUI by placement of a polypropylene mesh sling using the transobturator approach. Demographic and medical history data were collected by interview at baseline, 1 month, 6 months, and 1 year after the procedure. A speculum examination to screen for mesh erosion and infection was performed at each postoperative visit. Comparisons between groups were performed using a χ² and unpaired Student's t-test. The level of significance was set at p<0.05. Results: There were 5 (7.2%) mesh erosions reported within 1 year of surgery. Forty-two (60.9%) patients had concomitant surgeries. Age, parity, menopause status, hormonal therapy, body mass index, diabetes mellitus, vaginal trophism, previous and concomitant surgery, and perioperative complications were not associated with mesh erosion. Univariate analysis only identified previous surgery for SUI (3.6 versus 33.3%; p=0.002) and perioperative inadvertent vaginal transfixation (4.5 versus 66.7%; p<0.001) as significant factors associated with vaginal erosion. Conclusions: Previous surgery for SUI, and perioperative inadvertent vaginal transfixation, are risk factors for vaginal mesh erosion after transobturator sling placement. (J GYNECOL SURG 29:231)

Introduction

As the utility of the pubovaginal sling procedure for all types of stress urinary incontinence (SUI) became evident, the autologous fascial sling began to be widely used. In an attempt to decrease the morbidity of these procedures, graft substitution was adopted.¹ Synthetic slings include nonabsorbable materials, which are stronger than native tissue, available in any size, and free of any potentially infectious agents. When considering the principles of infection prevention and host tissue integration, it seems clear that one would theoretically favor implantation of a type I (macroporous and monofilament) synthetic mesh. These meshes promote the most rapid host tissue infiltration and host defense mechanisms, and the large pore size reduces the stiffness of the material and allows easier incorporation during reconstructive procedures. At present, the mesh material most commonly used for sling surgery is polypropylene.²

In 1996, Ulmsten et al. were the first to report the use of polypropylene mesh around the mid-urethra.³ Petros and Ulmsten described the tension-free vaginal tape (TVT) procedure based on the integral theory.⁴ These procedures facilitated the use of permanent graft materials as a result of the principles of tension-free graft placement and small incisions. In 2001, the preliminary work of Delorme on the use of the transobturator route for suburethral tape implantation opened up an interesting perspective, which simplified the surgical procedure and made it more innocuous.⁵ Recent case series have documented not only the success of the transobturator route for the treatment of stress incontinence, but also the low rates of associated complications. Moore et al. reported no procedure-related complications after transobturator sling placement in 47 women.⁶ However, a recent European trial by Jacquetin et al. reported a 13.7% complication rate in 146 patients, including 2 cases of vaginal erosion (1.4%).⁷ Wang et al. found that 2.1% of patients developed tape erosion when an inside-out transobturator tape was used.⁸

The pathophysiology of these complications is not known, and not implied by the word “erosion,” which is used here to indicate an unplanned exposure of surgical material. Erosion may result from an inflammatory reaction because of infection of a foreign body or, possibly. because of an immunologic response to the graft or suture material. Alternatively, the mesh or sutures may be exposed without an obvious inflammatory reaction and can be relatively asymptomatic. Nevertheless, the development of erosions is a significant and major complication.⁹

The objective of this study was to identify risk factors for mesh erosion using an inside-out transobturator procedure for the correction of SUI.

Materials and Methods

Between 2006 and 2008, a consecutive series of 69 patients underwent surgery for stress urinary incontinence by tension-free placement of a polypropylene mesh sling using the transobturator approach (Polyform® Synthetic Mesh, Boston Scientific).

The patients were recruited from the Urogynecology Ambulatory Clinic of the Minas Gerais Federal University. All of them had the diagnosis of SUI confirmed by history, physical examination, and urodynamic studies. The hospital ethics committee approved the study protocol, and all the women gave their written consent after receiving full information about the study.

This retrospective analysis included baseline, surgical, postoperative, and complication data. Demographic and medical history data were collected by interview at baseline, 1 month, 6 months, and 1 year after the procedure. The patients answered questions about their obstetric history, infant birth weight, age of menopause, use of hormone therapy, and length of time with SUI. All women were examined by a physician, and the clinical data were registered. Patient weight and height were taken, and body mass index was calculated. The severity of preoperative pelvic organ prolapse was assessed in all patients using the Pelvic Organ Prolapse Quantification (POP-Q) system.¹⁰ Each patient underwent preoperative urodynamic testing and completed a 24-hour pad test. A speculum examination to screen for mesh erosion and infection was performed at each postoperative visit. Mesh erosion was defined as any visible mesh exposure identified on vaginal examination. Immediate vaginal erosion of the mesh was considered when the erosion occurred in the first 12 weeks postoperatively. Erosions after that time were considered late erosions.

Statistical analysis

Statistical analyses were conducted using a statistical analysis package (SPSS 16.0 Inc., Chicago, IL). Comparisons between groups were performed using a χ² and an unpaired Student's t test. The level of significance was set at p<0.05. Subsequently, using linear regression, a model to predict the factors that influenced the risk of mesh erosion in women who underwent transobturator sling placement for SUI was created.

Results

The mean age was 52.8 years (range 33–79), and the mean parity was 3.6 (range 0–13). The basic characteristics, demographic data, and POP-Q stages of all patients are presented in Table 1.

Table 1.

Demographics, Clinical Characteristics, and POP-Q Stage of the Study Group

Variables	Numbers
Age (years)	52.8±1.3 (33–79)
Length of time with SUI (years)	4.5 (1–20)
Parity	3.6 (0–13)
Birth weight (g)	3207.8
BMI (kg/m²)	28.6 (18.9–59.4)
Pad test (g)	79.5
VLPP (cm H₂O)	98.4
Previous urinary incontinence surgery	9 (13%)
Menopausal status	32 (46.4%)
Clinical signs of hypoestrogenism	22 (31.9%)
Hormone therapy	2 (97.1%)
Diabetes mellitus	3 (4.3%)
Stage 0 (POP-Q)	2 (2.9%)
Stage I (POP-Q)	7 (10.1%)
Stage II (POP-Q)	24 (34.8%)
Stage III (POP-Q)	35 (50.7%)
Stage IV (POP-Q)	1 (1.5%)

Data are expressed as the mean±standard error of the mean (range) or n (%).

POP-Q, Pelvic Organ Prolapse Quantification; SUI, stress urinary incontinence; BMI, body mass index; VLPP, valsalva leak point pressure.

Forty-two (60.9%) patients had concomitant surgeries. The concomitant surgeries consisted of anterior or posterior colpoperineoplasty, vaginal hysterectomy, and abdominal total hysterectomy. There were five (7.2%) mesh erosions reported within 1 year of surgery. There were no cases of urethral or bladder erosion in this series. The intraoperative complications included one bladder perforation (1.4%), two bleeding events (2.9%), and three (4.3%) inadvertent transfixations of the vaginal mucosa. Four patients with mesh erosion had concomitant anterior and posterior colpoperineoplasty and 1 patient underwent concomitant total abdominal hysterectomy. Four patients (80%) complained of odorless vaginal discharge that necessitated a partial excision of the mesh. The 1 remaining patient was treated with administration of intravaginal estrogen. Four mesh erosions (80%) were diagnosed within 12 weeks. One late erosion occurred 8 months postoperatively.

A univariate analysis of the factors that possibly influenced mesh extrusion in women who underwent transobturator sling placement for SUI was performed (Table 2). Variables considered were age ≥50, parity ≥3, menopause, hormonal therapy, body mass index ≥30 kg/m², diabetes mellitus, vaginal trophism, previous and concomitant surgery, and perioperative complications. The perioperative complications studied were bladder lesions, bleeding, and perioperative inadvertent vaginal transfixation. Univariate analysis only identified previous surgery for SUI (p=0.002) and perioperative inadvertent vaginal transfixation (p<0.001) as significant factors associated with the probability of vaginal erosion (Table 2). None of the patients had signs of vaginal infection associated with mesh erosion.

Table 2.

Univariate Analysis of the Factors Influencing Mesh Erosion in Women Who Underwent Transobturator Sling Placement for SUI

Variable	Mesh extrusion	p
Age		0.190
<50 years	4 (12.5%)
≥50 years	1 (2.9%)
Parity		1.00
<3	2 (9.1%)
≥3	3 (7%)
BMI (kg/m²)		1.00
<30 (kg/m²)	3 (6.8%)
≥30 (kg/m²)	2 (9.1%)
Menopause		0.672
No	2 (6.1%)
Yes	3 (9.4%)
Hormone therapy		1.00
No	5 (8.3%)
Yes	0
Diabetes mellitus		1.00
No	3 (8.8%)
Yes	2 (6.5%)
Vaginal trophism		0.652
Normal	4 (9.5%)
Hypotrophic	1 (4.5%)
Previous surgery		0.002
No	2 (3.6%)
Yes	3 (33.3%)
Concomitant surgery		0.641
No	1 (3.7%)
Yes	4 (9.5%)
Perioperative complications		0.885
No	5 (7.6%)
Bladder injury	0
Excessive bleeding	0
Perioperative inadvertent vaginal transfixation		<0.001
No	3 (4.5%)
Yes	2 (66.7%)

Data are expressed as n (%). Differences between groups were assessed by χ² test.

SUI, stress urinary incontinence; BMI, body mass index.

The linear regression analysis revealed that previous surgery for SUI (p=0.002) and perioperative vaginal transfixation (p<0.001) were associated with the occurrence of mesh erosion in women who underwent transobturator sling placement for SUI (Table 3).

Table 3.

Linear Regression Analysis of the Factors that Influence Mesh Erosion in Women Who Underwent Transobturator Sling Placement for SUI

	Unstandardized coefficients		Standardized coefficient
Variable	B	Std. Error	Beta	t	Sig.	95% CI for B
Previous surgery	0.193	0.088	0.250	2.207	0.002	0.018–0.368
Perioperative inadvertent vaginal transfixation	0.511	0.144	0.403	3.550	<0.001	0.223–0.799

SUI, stress urinary incontinence, Std., standard; Sig., significance, CI, confidence interval.

Discussion

The main goal of surgical treatment for SUI is to render patients completely continent without generating significant morbidity. Despite the recognition of the risk of erosion, synthetic graft materials have been preferred over autologous grafts because they are durable, avoid the morbidity and operative time of harvesting fascia, are readily available, and are relatively inexpensive. The ideal material should be inert, sterile, durable, and non-carcinogenic, and should not cause an inflammatory or immune reaction. In addition, it should be inexpensive, readily available, and easy to use. None of the graft materials available for use today fulfill these “ideal” criteria. Current evidence would suggest that monofilament polypropylene (type I) has the lowest incidence of infection and erosion compared with other non-reabsorbable meshes.¹¹

The current authors used a type I polypropylene tape as a sling and placed it at the mid-portion of the urethra. Numerous researchers have reported erosion rates of ≤1% with type I polypropylene mesh using a variety of techniques.^12–14 In this prospective study with standardized follow-up, 5 of 69 (7.2%) patients had mesh erosion. Although the exact etiology of vaginal erosion is not known, placement of the sling in a plane too close to the urethra, inadequate vaginal tissue dissection, inadequate coverage, excessive tension applied to the sling, and infection are the proposed putative factors. When dissection is too superficial, the chance of subsequent vaginal erosion increases.¹⁵ Achtari et al. found that surgeon experience was associated with mesh erosion.¹⁶ Surgeries in this study were performed in a university hospital with a residency program, which can partially explain the high rates of erosion. Surgeon experience may be related to another finding from the study: Perioperative inadvertent vaginal transfixation is a risk factor for mesh erosion. Inadvertent vaginal transfixation using mesh proved to be a significant factor associated with erosion. This information is important, because inadvertent transfixation is a modifiable situation. Surgeons have to pay more attention and be more careful when they pass needles through the peri-urethral space. After the inadvertent transfixation, it is necessary to remove the needle, suture the vaginal mucosa with 2-0 Vicryl, and then pass the needle through again.

With regard to the new reconstructive pelvic surgical techniques used in prolapse correction, two principal risk factors for mesh erosion have been highlighted. These risk factors are concomitant hysterectomy and anterior inverted T colpotomy.¹⁷ In the present study, erosion was not associated with concomitant surgeries. This finding may be expected because the transobturator sling used much less mesh and had a smaller dissection area when compared with prolapse correction surgery.

Some researchers found an association between mesh erosion and age.^16,17 Achtari et al. have reported that patient age, urethral atrophy, and estrogen deficiency were found to be risks factors for mesh erosion.¹⁶ The present study did not find an association between erosion and age, vaginal hypotrophism, menopause, and the use of hormone therapy, which makes the treatment of erosion with estrogen questionable. There is minimal literature evaluating this approach, although the available evidence only reports a 14% cure rate.¹⁸

Immunologic reactions to a foreign body and infection are suspected to cause mesh erosion.¹⁹ Boulanger et al. examined the role of bacterial infection in complications following the surgical management of urinary incontinence and genital prolapse using meshes. The most frequent cause for removal of the mesh was symptomatic vaginal erosion. Bacterial contamination was found in all meshes, but quantification was often low; therefore, its exact role was not clear.²⁰ In the present study, none of the 5 patients with mesh erosion had signs of vaginal infection.

In addition, local tissue factors, including scarring from previous surgery and radiation-induced ischemia, influence vaginal erosion rates. Obese, diabetic, and immunocompromised patients have a higher risk of vaginal erosion.¹⁶ In the present study, none of these factors, except previous surgeries, were associated with erosion. The scarring caused by previous surgery completely changes the characteristics of the tissue, which becomes fibrotic and less vascularized. Therefore, wound healing may be impaired.

The time course of mesh erosion can be associated with the etiology. Late erosion is possibly associated with progressive erosion of the vaginal wall. On the other hand, erosion after a vaginal procedure could be the result of defective healing of the wound, because the erosion is usually found on the incision line. In the present study, four mesh erosions (80%) were diagnosed within 12 weeks. This is in accordance with the factors associated with mesh erosion in this study. Inadvertent transfixation and previous surgery can affect the healing process, which leads to more immediate erosions.

One limitation of this study was the relatively small sample size. Mesh erosion after transobturator sling placement for SUI is associated with reoperations and with perioperative inadvertent transfixation of the vaginal mucosa, which is an important and modifiable risk factor.

Conclusions

Previous surgery for SUI and perioperative inadvertent vaginal transfixation are risk factors for vaginal mesh erosion after transobturator sling placement.

Disclosure Statement

No competing financial interests exist.

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