The use of porcine dermal implant in a minimally invasive pubovaginal sling procedure for genuine stress incontinence
Objective To assess the outcome of a suburethral sling using a porcine dermal implant (Pelvicol™, Bard Urology, UK) in the surgical management of urinary stress incontinence.
Patients and methods Forty women with urodynamically confirmed genuine stress incontinence were recruited into the study and followed up at 6 weeks and at least 6 months (mean 12 months, range 6–18). The sling was inserted using a minimal-access technique, which allowed 23 women to be operated as day-cases. Outcome measures included continence rates, voiding dysfunction, satisfaction scores and whether the patients would recommend the operation to a friend or relative.
Results The cure rate was 85%, with sustained benefit; a further 10% of the women were improved by surgery. Voiding dysfunction rates were low and satisfaction scores high. Most women would undergo the procedure again if they became incontinent in the future and would recommend the procedure to a friend or relative.
Conclusion A minimal access pubovaginal sling using Pelvicol™ is effective in treating stress incontinence. The complication rate is low and the procedure can be performed as a day-case with no loss of efficacy.
Sling procedures are currently experiencing a revival in the surgical management of genuine stress incontinence. First described at the beginning of the century, early studies reported the use of autologous fascia, usually pyrimidalis muscle . However, it was following the description by Aldridge in 1942  that rectus sheath gained popularity and the sling procedure became recognized as the current operation. The results of incontinence surgery using rectus sheath are good, with a success rate of >90% . However, the rectus sheath procedure carries some surgical morbidity because of the need to harvest a strip of fascia through a large abdominal incision. In addition, the quality of the connective tissue may be weak and is therefore a possible cause for the development of stress incontinence.
In recent years synthetic sling materials have been introduced to reduce these complications. There is no doubt that the tension-free vaginal tape (TVT) procedure has increased the popularity of sling procedures . However, there are concerns about the long-term safety of TVT, particularly for urethral erosion, which is a potential risk whenever synthetic materials are used for this purpose .
Porcine dermis has been previously described as an allogenic graft material [6,7] and Oliver et al. showed that cell-free porcine autografts resisted biodegradation for 35 days. Subsequently it was shown that cross-linking protected the autografts from degradation, which prolonged their survival and permanence after implantation . The initial porcine grafts were cross-linked using aldehyde but a potential problem is that the grafts may develop foci of mineralization, which can extend into extensive calcification of the graft . Aldehydes are also cytotoxic at higher levels  and therefore a search for a different cross-linking compound led to the use of diisocyanate; this is not toxic, causes no mineralization and gives permanence to the graft . Pelvicol™ (Bard Urology, UK) is a porcine dermal implant which is cross-linked with diisocyanate and has been extensively used throughout the human body . The present study was therefore carried out to investigate the use of Pelvicol in the surgical treatment of urinary stress incontinence.
Patients and methods
Forty women (mean age 56 years, range 42–79) were recruited into the study over a year (38 parous women, mean two children, and 2 nulliparous). The mean (range) duration of incontinence was 33 (6–216) months. The operation was a primary procedure in 36 women and a secondary procedure in four. Previous surgery included one periurethral collagen injection, one Marshall-Marchetti-Kranz and two Stamey procedures. All the women had previously undergone urodynamic studies that had confirmed genuine stress incontinence.
Wherever possible (in 23 women) the procedure was carried out in the day-surgery unit (DSU). The remaining 17 patients were not considered candidates for the DSU for either medical reasons or a lack of support at home; the procedures were carried out in the main theatre complex with a planned overnight stay. The DSU patients were all given a total intravenous anaesthetic using propofol with additional local anaesthetic (20 mL of 1% bupivacaine) to the suprapubic skin area. Most of the patients (nine) operated in the main theatre were given a spinal anaesthetic for medical reasons. Spinal anaesthesia was not considered suitable for day surgery because of its variable length of action and possible interference with pelvic floor function during the cough-stress test. Once the women were suitably anaesthetized they were placed in the lithotomy position and the skin and vagina cleaned with aqueous iodine. An 18 G Foley catheter was inserted and the mid-urethral point identified; this was marked by a pair of forceps, over which a midline vaginal incision ≈2.5 cm long was made. A suburethral tunnel was made with scissors until the pubic ramus was reached and the endopelvic fascia was then perforated using a pair of Roberts forceps. The procedure was then repeated on the other side. A catheter guide was inserted down the Foley catheter and used to deviate the bladder and urethra to the opposite side to the insertion of the sling, to reduce the risk of bladder trauma. A full-length #1 polyglactin suture was sutured to each end of a 10–12 cm×2 cm strip of Pelvicol, leaving the free ends of equal length. Polyglactin was chosen to avoid the risk of suture migration into the bladder, as seen with needle suspension procedures. By the time the polyglactin sutures dissolved it is likely that the Pelvicol implant would have already been integrated into the host tissues. A 1-cm incision was then made immediately above the pubic ramus and ≈3 cm from the mid line. A 15° Stamey needle was passed down the medial side of each incision and guided digitally behind the pubic ramus and through the defect in the endopelvic fascia into the vagina. One end of the polyglactin suture was passed through the eyelet in the Stamey needle, which was withdrawn upwards. The needle was passed down a second time but on this occasion the needle was inserted at the lateral margin of the incision, leaving a bridge of rectus sheath over which the suture could be tied. The procedure was then repeated on the opposite side, after which the catheter was removed and the sling pulled upwards to lie under the mid-urethra with minimal tension. Cystoscopy was then carried out; no bladder perforations were identified in this study, but if so the perforating sutures would have been removed and the procedure repeated, taking care to insert the needle more lateral. The bladder was filled to the volume at which urinary leakage was seen on urodynamic testing. If a general anaesthetic had been used, the patient was then woken and asked to cough. The sutures were then elevated, thereby pulling up the sling until no further leakage was seen with cough provocation. Although there is some evidence to suggest a cough-stress test is not always useful, it was thought necessary in this study to compare with the description of other commonly performed sling procedures, e.g. TVT. The sutures were then tied loosely over the rectus sheath and the skin incisions closed using dissolvable sutures. The bladder was then emptied and the patient returned to the recovery bay. Once the patient was able to void leaving residuals of <100 mL, or the voided volume was repeatedly in excess of twice the residual volume, the patient was discharged. Patients were evaluated for follow-up at 6 weeks and at least 6 months after surgery (mean 12 months, range 6–18).
No patients were lost to follow-up. The mean (range) duration of surgery was 35 (20–80) min. There were no major intraoperative complications and no bladder perforations. Seventeen of the DSU patients were discharged on the same day; the remainder were admitted for various reasons, including voiding problems (one), bleeding (two) and migraine/pain (one), and all were discharged on the following day. In those women with a planned inpatient stay, the mean (range) duration of stay was 3.5 (1–12) days. Longer term voiding problems occurred in five women; this was temporary in two but in three these symptoms persisted, requiring incision of the sling through a vaginal incision at 4–6 weeks after surgery, when the sling had fibrosed adequately under the urethra. The overall cure rate (defined as an improvement rate of >90%, as described by Ulmsten et al.) at the 6-week follow-up was 88% (35 women): four further women (10%) were significantly improved (defined as an improvement rate of 70–89%) and the procedure considered a failure in one. Three of the women who had had previous surgery were cured and one (previous collagen injection) was improved by the Pelvicol sling operation. Release of the sling to aid voiding did not affect the outcome of the operation and only one woman requires self-catheterization to empty her bladder. One woman who had a primary procedure and was dry at 6 weeks became incontinent again by the 6-month follow-up, giving an 85% sustained cure rate. The expectation is that this cure rate would be sustained, as it appears that sling operations that are successful after 6 months are likely to remain successful for several years . One of the women in whom the procedure failed was later successfully treated by colposuspension; the other woman in whom the sling failed has chosen a repeat sling procedure. The mean (median, range) number of incontinence pads used for protection decreased from 4.2 (3, 1–10) pads before surgery to 2.2 (1, 1–10) pads afterwards. The mean (median, range) satisfaction score was 7.88 (9, 0–10). Thirty-one (78%) women would have the sling procedure again if they became incontinent, six would not and three were uncertain. Twenty-nine (73%) would recommend the operation to a friend, three would not and eight were uncertain.
This study showed that a minimal-access pubovaginal sling procedure using Pelvicol is effective for the surgical management of urinary stress incontinence. The cure rate is comparable with that after colposuspension and the TVT technique [15,16]. The choice of sling material probably affects the outcome , provided that excess sling tension is avoided. Urethral obstruction is unnecessary for a successful result and a relatively loose sling that provides support to the urethra appears to be the aim. The technique described is suitable for day-case surgery with no loss of efficacy. The dissection is slightly greater than for minimally invasive sling procedures but this is offset by the reduced risk to viscera, as the needle is smaller and guided digitally throughout.
We have altered our management of patients with short-term voiding difficulty in the DSU since this study; women who cannot void adequately by the time the DSU closes at 18.00 hours are discharged home with a urethral catheter in situ and return to the DSU 3 days later for a trial of without catheter, which is almost always successful. The long-term voiding dysfunction rate is comparable with sling procedures using autologous fascia . The urethrolysis rate is slightly higher that cited for TVT [18,19] and this might be related to the characteristics of porcine fascia. As the sling is incorporated into the host tissue it could possibly contract and obstruct the urethra. We have recently been placing the Pelvicol implant more loosely, and the voiding dysfunction rate and subsequent urethrolysis rate has been lower. There was also a reluctance amongst the patients to learn to self-catheterize and it is possible that given time these voiding problems may have resolved.
There were too few patients in the present study to investigate urethral erosion, but it would not be expected given the excellent biocompatability of porcine dermis with human tissue. Further research using this technique and material is urgently required; the present series is currently being expanded to include more patients, a longer follow-up and to directly compare Pelvicol with TVT in a randomized trial.
J.W. Barrington, Department of Obstetrics & Gynaecology, Torbay Hospital, Torquay, Devon TQ2 7AA, UK.