Comparison of Two Single Incision Slings on the Vagina in an Ovine Model.

Abstract Background Stress Urinary Incontinence carries a significant healthcare burden for women worldwide. Single incision slings are minimally invasive mesh devices designed to treat stress urinary incontinence. For prolapse repair, meshes with higher porosity and lower structural stiffness have been associated with improved outcomes. Objective We compared the higher stiffness, lower porosity Altis sling (SIS-B; Coloplast, Humlebaek, Denmark) to the lower stiffness, higher porosity Solyx sling (SIS-A; Boston Scientific ,Marlborough, MA) in an ovine model. We hypothesized that SIS-B would have a negative impact on the host response. Study Design 13 SIS-A and 11 SIS-B were implanted sub-urethrally into sheep according to the manufacturer’s instructions on minimal tension. The mesh-urethral-vaginal complex and adjacent ungrafted vagina (no mesh control) were harvested en bloc at 3 months. Masson’s trichrome and picrosirius staining of 6μm thin sections was performed to measure inter-fiber distance and tissue integration. Smooth muscle contractility to a 120mM KCl stimulus was performed in an organ bath to measure myofiber driven contractions. Standard biochemical assays were used to quantify glycosamingoglycan, total collagen and elastin content, and collagen subtypes. Bending stiffness was performed in response to a uniaxial force to define susceptibility to folding/buckling. Statistical analysis was performed using Mann-Whitney, Gabriels’ pairwise post-hoc, Wilcoxon matched pairs and Chi-Square tests. Results Animals had similar age (3-5 years), parity (multiparous) and weight (45-72 kg). Trichrome cross sections showed that the SIS-B buckled in a “C” or “S” shape in most samples (8/11), while buckling following SIS-A implantation was observed in only a single sample (1/13, P = 0.004). Tissue integration, as measured by the presence of collagen or smooth muscle between mesh fibers on Trichrome 4x imaging, was increased in SIS-A implanted samples as compared to SIS-B (P Conclusions The structurally stiffer SIS-B had decreased tissue integration and increased propensity to buckle after implantation. Increased collagen I and III following implantation of this device suggests that these changes may be associated with a fibrotic response. In contrast, SIS-A largely maintained a flat configuration and had improved tissue integration. The deformation of SIS-B is not an intended effect and is likely caused by its lower bending stiffness. Both meshes induced a decrease in collagen content and smooth muscle contractility similar to previous findings for prolapse meshes and consistent with stress shielding. The long term impact of buckling warrants further investigation.