A review article published last June in the Current Urology Reports Journal assesses the outcomes and complications of using synthetic mesh materials in pelvic organ prolapse (POP) repair procedures, as well as the public health notification released by the FDA about these procedures. The present article summarizes the information presented in the review.
Pelvic organs, including bladder, urethra, uterus and vagina, are held in place by bones, muscles and connective tissue. Pelvic organ prolapse takes place when there is a downward displacement of those organs resulting in a protuberance within the vagina. Those anatomical defects can be classified according to their location, anterior (cystocele), posterior (rectocele) and apical (enterocele).
Traditionally, POP repairs were done by plicating or “folding” native tissue (colporrhaphy) or by anchoring those tissues to other structures. These repair techniques present a 17% risk of the patient needing reoperation, either at the same or at a different anatomical site. New technologies that use grafts to supplement plication-type techniques by helping to strengthen weak tissues and therefore decreasing chances of recurrence were developed to increase surgery outcomes. Using grafts, the surgeon can also repair multiple sites simultaneously. Biologic grafts, which include autograft (graft tissue from same individual), allograft (tissue from another human being), xenografts (non-human organism tissue), present several limitations, including but not limited to, high costs, limited availability and risk of disease transmission. More predictable synthetic grafts were then developed and first approved by the U.S. Food and Drug Administration (FDA) in 2001.
According to the authors, it is difficult to manufacture an ideal graft that has all the desired characteristics; consequently, there are different categories of grafts, each presenting diverse characteristics. Meshes can be classified according to their filament number and pore size (Types 1-4), different characteristics are also observed within each type, like variations in weight or flexibility. Type 1 meshes (Marlex, Atrium, Prolene, Gynemesh, Pelvitex) are composed of monofilament macroporous polypropylene and are reported to present the highest success rates by allowing collagen growth, and, thanks to the bigger pore size, immune system cells migration through the membrane, offering better defense against infections. Regardless of their success, these meshes can provoke persistent mast cell (defense cells) response and formation of granulomas (groups of immune cells, macrophages). Commercial POP repair kits were developed thanks to success rates and advances in synthetic mesh technology as well as implementation techniques. All available commercial mesh kits are made of monofilament, macroporous polypropylene.
Success rates vary according to the techniques used: traditional plication-type (colporrhaphy) versus augmented (graft implementation), and the compartment that was repaired (anterior, posterior or apical). With respect to anterior compartment repairs, based on the data presented in this review, mesh augmentation was proved to decrease the recurrence rates, although complications were also higher with this procedure. Similarly, better outcomes were observed when using synthetic meshes for apical compartment repairs. No significant differences were observed between colporrhaphy and augmented techniques when repairing the posterior compartment.
The complications associated with synthetic meshes and kits can be classified based on the affected compartment and can be subdivided based on the time of occurrence: immediate (visceral injury caused by the physician), short-term (mesh erosion, bleeding, urination dysfunction) and long-term (mesh extrusion, pain, painful sexual intercourse). Data presented in this article shows that occurrence of mesh erosion and extrusion oscillate between 5 and 19%, de novo stress incontinence was higher in patients that received synthetic meshes when compared to colporrhaphy procedures. Dyspareunia (painful sexual intercourse) presented similar rates in both groups, although there was higher incidence in the posterior compartment repaired through colporrhaphy. Another study presented in this review shows that polypropylene meshes can retract as much as 66% after surgery, which leads to vaginal shortening and narrowing.
In 2006, the French Health Authorities stated that transvaginal POP repairs using synthetic mesh should be restricted to research. Subsequently, in 2008, the FDA released a public health notification about the use of synthetic mesh in POP repairs and suggested that physicians followed these recommendations: obtain training for all the different mesh implementation techniques; consider that most cases can be repaired without mesh and therefore only perform mesh surgery after weighting all the different alternatives; inform patients about potential complications and the fact that mesh implantation is permanent; provide patients with kit information from manufacturers; monitor patients and watch for complications. In July 2011, the FDA released an update to the 2008 notification and stated that complications resulting from mesh placements are not rare and that it was not clear if these procedures are more effective than the traditional ones. However, literature reviewed in this article concludes that the FDA presented a biased view on POP repair and further research would be necessary to compare colporrhaphy to the different synthetic mesh kits, including second generation kits.
Reference
Evaluation of Current Synthetic Mesh Materials in Pelvic Organ Prolapse Repair. Prashanth Kanagarajah; Rajinikanth Ayyathurai and Christopher Gomez. Current Urology Reports. 2012. 13:240-246