QUEBEC CITY, Que: -- Knitted polypropylene appears to be the material of choice for sub-urethral implantation in the female patient with stress urinary incontinence (SUI).
Not only does it have properties that promote fibroplasia and macrophage infiltration to help prevent infection and erosion, but the way in which it is manufactured creates a large pore size without compromising strength, elasticity and durability.
Nevertheless, Dr. Jacques Corcos warned delegates to Urogynecology Quebec 2007 that many of the sub-urethral sling products currently on the market have not undergone adequate clinical testing. Dr. Corcos is director of the urology department at Jewish General Hospital, Montreal, and professor of urology at McGill University.
“Recent series have begun to investigate their individual properties and to undertake randomized comparisons, but many products currently on the market are still implanted without necessary pre-market testing, potentially placing the public at risk,” said Dr. Corcos.
He advised physicians to insist on results from randomized controlled trials and long-term followup trials before considering the use of any new sling product on the market. “Be very vigilant about what people are proposing,” he said.
Since 1995, the list of products offering a minimally-invasive means of surgically correcting SUI has increased dramatically. Since products for surgical interventions can be marketed directly to surgeons without the same kind of rigorous testing required for new medications, a lot of the evidence supporting their use is anecdotal.
The only way that the surgical and scientific communities can determine the durability and success of sub-urethral slings is through longitudinal, controlled studies, pointed out Dr. Corcos.
At present, there are fewer than 160 articles in peer-reviewed journals that document experience with sub-urethral tape insertions using both retropubic and trans-obturator approaches. TVT is the most-studied method to date and the method of choice for SUI in many centers, noted Dr. Corcos.
Several retrospective analyses have compared the trans-obturator approach of Monarc tape, a relatively new addition to the market, to TOT products or to retropubic TVT. These show that the Monarc is associated with lower rates of bladder injury as well as a reduced need for urethrolysis and less use of anti-cholinergic medication. Whether or not Monarc can be associated with post-operative voiding dysfunction compared to other trans-obturator tapes, however, has not yet been evaluated, said Dr. Corcos.
Rigorous prospective safety and efficacy analysis of the Sparc suprapubic sling is also lacking, said Dr. Corcos. Several small retrospective studies, in Australia and elsewhere, have indicated that Sparc performs equally well as Monarc for the treatment of SUI. However, a recent trial (Lord HE et al, BJU Int2006; 98(2):367-376) comparing TVT and Sparc disputes this claim, demonstrating statistically significant operative difficulties as well as post-operative complications, including mesh erosion and a lower overall cure rate. “This trial highlighted differences between two devices,” noted Dr. Corcos, “both with untested features in need of further investigation.”
Although several small French observational studies have documented the biomechanical properties of Uretex compared to other tapes, “…this product has not been examined in a randomized, controlled trial,” said Dr. Corcos.
Similarly, there have been no published randomized, controlled trials of Safyre TOT, although there have been reports in the literature demonstrating equivalent cure rates for Safyre and TVT, with lower complication rates and reduced transient, irritative voiding symptomatology.
Obtape, which initially showed promised as an effective treatment alternative to TVT, was pulled from the market following reports of significantly higher rates of erosion compared to other trans-obturator tapes. Dr. Corcose noted that tapes such as Obtryx and Arix, which are distributed to urologists worldwide, have not been formally studied and don’t appear to have been investigated for safety and efficacy.
Dr. Corcos urged colleagues to carefully assess how easily any bio-prosthetic material can be removed. “This is a basic surgical principle,” he noted, that must be observed given “…the significant difficulty of surgical removal in the setting of deep space infections.”
Although partial resection is the recommended surgical approach for vaginal erosions, “the possibility of leaving behind infected portions of mesh is real,” said Dr. Corcos. As a result, many women may present with late-onset deep space infections that ultimately require radical debridement.
This is in marked contrast to TVT and the retropubic approach, he pointed out, where the tape can be completely removed if necessary. “It is thus incumbent on surgeons, their patients and ultimately industry partners to continue efforts to optimize the biocompatibility, construction process and implantation procedure of sling products to derive the benefits of TOT, while minimizing important potential complications.”