Managing mesh exposure following vaginal prolapse repair: a decision analysis comparing conservative versus surgical treatment

Tissue response to collagen containing polypropylene meshes in an ovine vaginal repair model

Pelvic Organ Prolapse (POP) is the herniation of pelvic organs into the vagina. Despite broad acceptance of mesh use in POP surgical repair, the complication rate is unacceptable. We hypothesized that collagen-containing polypropylene (PP) mesh types could modulate mesh-tissue integration and reduce long-term inflammation, thereby reducing mesh-associated complications. This study compared the long-term tissue response to an unmodified PP mesh and two collagen containing meshes in an ovine model which has similar pelvic anatomy and vaginal size to human. Three commercially available macroporous PP meshes, uncoated PP mesh (Avaulta Solo) (PP), the same textile PP mesh layered with a sheet of cross-linked porcine acellular matrix (Avaulta Plus) (PP-ACM) and a different yet also macroporous PP (Sofradim) mesh coated with solubilized atelocollagen (Ugytex) (PP-sCOL) were implanted in the ovine vagina and tissue explanted after 60 and 180days. The macrophage phenotype and response to implanted meshes, and vascularity were quantified by immunostaining and morphometry. We quantified changes in extracellular matrix composition biochemically and collagen organisation and percentage area around the interface of the mesh implants by Sirius Red birefringence and morphometry. PP-ACM induced a more sustained inflammatory response, indicated by similar CD45(+) leukocytes but reduced CD163(+) M2 macrophages at 60days (P<0.05). PP-sCOL increased Von Willebrand Factor (vWF)-immunoreactive vessel profiles after 60days. At the micro-molecular level, collagen birefringence quantification revealed significantly fewer mature collagen fibrils (red, thick fibrils) at the mesh-tissue interface than control tissue for all mesh types (P<0.001) but still significantly greater than the proportion of immature (green thin fibrils) at 60days (P<0.05). The proportion of mature collagen fibrils increased with time around the mesh filaments, particularly those containing collagen. The total collagen percent area at the mesh interface was greatest around the PP-ACM mesh at 60days (P<0.05). By 180days the total mature and immature collagen fibres at the interface of the mesh filaments resembled that of native tissue. In particular, these results suggest that both meshes containing collagen evoke different types of tissue responses at different times during the healing response yet both ultimately lead to physiological tissue formation approaching that of normal tissue.

STATEMENT OF SIGNIFICANCE

Pelvic organ prolapse (POP) is the descent of the pelvic organs to the vagina. POP affects more than 25% of all women and the lifetime risk of undergoing POP surgery is 19%. Although synthetic polypropylene (PP) meshes have improved the outcome of the surgical treatment for POP, there was an unacceptable rate of adverse events including mesh exposure and contracture. It is hypothesized that coating the PP meshes with collagen would provide a protective effect by preventing severe mesh adhesions to the wound, resulting in a better controlled initial inflammatory response, and diminished risk of exposure. In this study we assessed the effect of two collagen-containing PP meshes on the long-term vaginal tissue response using new techniques to quantify these tissue responses.

In vivo response to polypropylene following implantation in animal models: a review of biocompatibility

INTRODUCTION AND HYPOTHESIS

Polypropylene is a material that is commonly used to treat pelvic floor conditions such as pelvic organ prolapse (POP) and stress urinary incontinence (SUI). Owing to the nature of complications experienced by some patients implanted with either incontinence or prolapse meshes, the biocompatibility of polypropylene has recently been questioned. This literature review considers the in vivo response to polypropylene following implantation in animal models. The specific areas explored in this review are material selection, impact of anatomical location, and the structure, weight and size of polypropylene mesh types.

METHODS

All relevant abstracts from original articles investigating the host response of mesh in vivo were reviewed. Papers were obtained and categorised into various mesh material types: polypropylene, polypropylene composites, and other synthetic and biologically derived mesh.

RESULTS

Polypropylene mesh fared well in comparison with other material types in terms of host response. It was found that a lightweight, large-pore mesh is the most appropriate structure.

CONCLUSION

The evidence reviewed shows that polypropylene evokes a less inflammatory or similar host response when compared with other materials used in mesh devices.

Vaginal native tissue repair versus transvaginal mesh repair for apical prolapse: how utilizing different methods of analysis affects the estimated trade-off between reoperation for mesh exposure/erosion and reoperation for recurrent prolapse

INTRODUCTION AND HYPOTHESIS

Informed decision-making about optimal surgical repair of apical prolapse with vaginal native tissue (NT) versus transvaginal mesh (TVM) requires understanding the balance between the potential "harm" of mesh-related complications and the potential "benefit" of reducing prolapse recurrence. Synthesis of data from observational studies is required and the current literature shows that the average follow-up for NT repair is significantly longer than for TVM repair. We examined this harm/benefit balance. We hypothesized that using different methods of analysis to incorporate follow-up time would affect the balance of outcomes.

METHODS

We used a Markov state transition model to estimate the cumulative 24-month probabilities of reoperation for mesh exposure/erosion or for recurrent prolapse after either NT or TVM repair. We used four different analytic approaches to estimate probability distributions ranging from simple pooled proportions to a random effects meta-analysis using study-specific events per patient-time.

RESULTS

As variability in follow-up time was accounted for better, the balance of outcomes became more uncertain. For TVM repair, the incremental ratio of number of operations for mesh exposure/erosion per single reoperation for recurrent prolapse prevented increased progressively from 1.4 to over 100 with more rigorous analysis methods. The most rigorous analysis showed a 70% probability that TVM would result in more operations for recurrent prolapse repair than NT.

CONCLUSIONS

Based on the best available evidence, there is considerable uncertainty about the harm/benefit trade-off between NT and TVM for apical prolapse repair. Future studies should incorporate time-to-event analyses, with greater standardization of reporting, in order to better inform decision-making.