Immediate postoperative changes in synthetic meshes – In vivo measurements

Laparoscopic sacrocolpopexy comparing polypropylene mesh with polyvinylidene fluoride mesh for pelvic organ prolapse: Technique description and long term outcomes

AIM

Our aim was to evaluate the feasibility and safety of laparoscopic sacrocolpopexy (LSCP) and compare the long-term outcomes and complication rates of polypropelene (PP) and polyvinylidene fluoride (PVDF), following up within a minimum of 12 months.

METHODS

This was a retrospective cohort study using patients who underwent LSCP for POP involving either PP or PVDF mesh between January 2011 and January 2018.

RESULTS

Our study focused on 172 women who underwent LSCP with mesh between January 2011 and January 2018. All procedures were successfully completed laparoscopically, and patients' baseline characteristics were not statistically different in the two groups. Between January 2011 and December 2014, we performed 82 cases of LSC, mainly using PP mesh. Over the last 5 years, since January 2015, we have used PVDF mesh for POP.

CONCLUSIONS

LSCP using PVDF mesh was found to provide excellent anatomical and functional outcomes after a median follow-up duration of 41 months, compared with the PP group, which had a median follow-up duration of 54 months. Mesh infection and erosion rates in the PP group were significantly higher than those in the PVDF group. Additionally, rates of vaginal pain and discomfort were significantly lower in the PVDF group when compared with the PP group.

The importance of developing relevant animal models to assess existing and new materials

PURPOSE OF REVIEW

We summarize the recent literature on the use of different animal models for testing existing and new materials for treatment of pelvic organ prolapse.

RECENT FINDINGS

A wide spectrum of animal models is being used in urogynecology, both for the study of physiologic and pathophysiologic processes, training in surgical procedures, yet mainly to study the host response to implant materials. The quality of studies is variable, and procedures, read-outs, and reporting are not standardized. This makes comparison very difficult. The research community is experimenting with different knitting patterns, novel polymers, bioactivation, as well as resorbable rather than durable implants. Outcomes of the experiments are dependent on the location of implantation. Lighter polypropylene constructs seem to induce a less vigorous host response than elder heavier products. Modification of the surface yields contradictory findings. Resorbable acellular collagen matrices may be reintroduced as prophylactically inserted support structures.

SUMMARY

Although animal experimentation with novel candidate implants is advocated, there is a lack of standardization in reporting. The concept of resorbable construct is being revived, as durable materials have caused clinical graft-related complications. Large animal experiments seem to provide interesting and more comprehensive information, yet their use may be contested.

Medium-term outcome of laparoscopic sacrocolpopexy using polivinylidene fluoride as compared to a hybrid polyglecaprone and polypropylene mesh: A matched control study

AIM

To compare 2-year outcomes of laparoscopic sacrocolpopexy (LSCP) either with polyvinylidene fluoride (PVDF) or hybrid polypropylene containing a resorbable polyglecaprone (PP+ PG) mesh.

MATERIALS AND METHODS

Retrospective audit on 105 consecutive patients undergoing LSCP a with PVDF-mesh (DynaMesh, FEG Textiltechniken), matched by prolapse stage and cervicopexy or vault suspension to 105 controls undergoing LSCP with a hybrid PP + PG-mesh (Ultrapro, Ethicon). Patients are part of an ongoing prospective study. The primary outcome measure was the Patient Global Impression of Change score (PGIC), the coprimary variable was failure rate at the vault (≤1 cm). Other outcomes were intraoperative and postoperative complications within 3 months categorized by the Clavien-Dindo classification, reinterventions, graft-related complications (GRCs) and functional outcomes. All assessments were performed by an independent assessor. Data are reported as median (interquartile range) number and percent as appropriate, the Mann-Whitney U, χ² , or Fisher exact were used for comparison.

RESULTS

Patient satisfaction in the PVDF group, as measured with the PGIC, was high (90.9% PGIC, ≥4) as well as was the anatomical success (97.3%) at a follow-up of 26 months. These outcomes were comparable to those of PP + PG-patients (84.8% PGIC, ≥4; 94.9% anatomical success). There were five patients (2.4%) with Dindo-III or higher complications and three patients had GRCs (1.5%), without differences between mesh type. Level-II posterior defects (Bp ≥ -1) were less likely in PVDF patients (34.1% vs 50% for PP + PG-patients; P = .003). Women in the PVDF group also were less bothered by prolapse (7.5% vs 26.4%; P = .001), yet they complained more of constipation (15.0% vs 9.0%; P = .01).

CONCLUSION

There were no differences in patient satisfaction and anatomical outcomes after LSCP either with PVDF or PP + PG mesh.

Ultrasound visualization of sacrocolpopexy polyvinylidene fluoride meshes containing paramagnetic Fe particles compared with polypropylene mesh

INTRODUCTION AND HYPOTHESIS

Paramagnetic Fe particles can be added during synthetic mesh production to allow visibility on magnetic resonance imaging. Our aim was to evaluate whether transperineal ultrasound (TPUS) allows visualization, measurement, and characterization of polyvinylidene fluoride (PVDF mesh) containing Fe particles compared with regular polypropylene (PP) meshes used for sacrocolpopexy.

METHODS

Women up to 1.5 years after laparoscopic sacrocolpopexy who were implanted with a PP or PVDF mesh underwent clinical examination and 2D, 3D, and 4D TPUS. Acquired volumes were analyzed offline for mesh position at rest and maximal Valsalva and for mesh dimensions and characteristics, with the operator blinded to group assignment. The two groups were compared.

RESULTS

There were 17 women in the PP and 25 in the PVDF mesh group, without differences in baseline demographics. None had significant prolapse, recurrence, symptoms, or complications. On TPUS, mesh was visible in all patients both caudally (perineal) and cranially but was more echogenic in the PVDF mesh group. Mesh length from distal to proximal that was visible on TPUS was longer for PVDF mesh, for both anterior and posterior vaginal arms (all P < 0.05), and for mesh above the vaginal apex (P = 0.002). The inferior aspects of the mesh showed areas of double mesh layers, suggesting folding in 80% of women in both groups, without symptoms.

CONCLUSIONS

PVDF mesh permits clearer visualization and is seen over a longer stretch on TPUS, with longer visible mesh arms. The latter can be due to differences in operative technique, presence of microparticles, implant textile structure, or patient characteristics.

Short term post-operative morphing of sacrocolpopexy mesh measured by magnetic resonance imaging

BACKGROUND

Sacrocolpopexy (SC) involves suspension of the vaginal vault or cervix to the sacrum using a mesh. Following insertion, the meshes have been observed to have undergone dimensional changes.

OBJECTIVE

To quantify dimensional changes of meshes following implantation and characterize their morphology in-vivo.

DESIGN SETTING AND PARTICIPANTS

24 patients underwent SC using PolyVinyliDeneFluoride mesh loaded with Fe₃O₄ particles. Tailored anterior and posterior mesh flaps were sutured to the respective vaginal walls, uniting at the apex. The posterior flap continued to the sacrum and was attached there. Meshes were visualized on magnetic resonance (MR) imaging at 12 [3-12] (median [range]) months postoperatively and 3D models of the mesh were generated. Dynamic MR sequences were acquired during valsalva to record mesh mobility.

OUTCOME MEASURES

The area of the vagina effectively supported by the mesh (Effective Support Area (ESA)) was calculated. The 3D models' wall thickness map was analyzed to identify the locations of mesh folding. Intraclass correlation (ICC) was calculated to test the reliability of the methods. To measure the laxity and flatness of the mesh, the curvature and the ellipticity of the sacral flap were calculated.

RESULTS

The ESA calculation methodology had ICC = 0.97. A reduction of 75.49 [61.55-78.67] % (median [IQR]) in area, 47.64 [38.07-59.81] % in anterior flap, and of 23.95 [10.96-27.21] % in the posterior flap was measured. The mesh appeared thicker near its attachment at the sacral promontory (n = 19) and near the vaginal apex (n = 22). The laxity of the mesh was 1.13 [1.10-1.16] and 60.55 [49.76-76.25] % of the sacral flap was flat. We could not reliably measure mesh mobility (ICC = 0.16).

CONCLUSION

A methodology for complete 3D characterization of SC meshes using MR images was presented. After implantation, the supported area is much lower than what is prepared prior to implantation. We propose this happened during the surgery itself.

In vitro study of the mechanical performance of hernia mesh under cyclic loading

The use of prostheses for hernia surgery, made from synthetic polymers may lead to development of postoperative complications. The reason for this can be the mismatch of the mechanical properties of meshes and the loads acting on them. The aim of this work was to investigate the behavior of 3 different hernia meshes under in vitro simulated physiological conditions followed by cyclic loadings. Meshes, Ultrapro (poliglecaprone and polypropylene), Dynamesh (polyvinylidenefluoride) and Surgipro (polypropylene) were selected. For in vitro degradation test, samples were kept in alkaline and acid mediums at 37 °C during 42 and 90 days and analyzed in terms of their weight loss and thickness changes. This was followed by cyclic loading in three increasing load stages. The greatest weight loss and thickness reduction were suffered by Ultrapro mesh. The mesh showed pH independent characteristics. Surgipro mesh had pH independent behavior due to the degradation process, with slight weight loss and thickness reduction. The degradation mechanism of Dynamesh is highly dependent on the pH, with acid surrounding medium acting as a degradation catalyst. Mechanical hysteresis was observed in all three meshes. The larger deformations occurred in Surgipro (25%); necking phenomenon was also observed. The deformation of Dynamesh was 22%, the mesh unweaves under applied load and was unable to withstand the third period of cyclic loads. Ultrapro mesh exhibits the lowest level of deformation (10%). Despite the different compositions and architectures of the meshes, all three underwent permanent plastic deformation, which will induce decreased mesh flexibility over time.

Structural differences and architectural features of two different polypropylene slings (TVT-O and I-STOP) have no impact on biocompatibility and tissue reactions

Introduction

To evaluate the impact of design features of the synthetic mid-urethral slings on tissue integrity and inflammatory responses.

Material and methods

In total 30 female Sprague-Dawley rats were implanted with type I monofilamentous, macroporous polypropylene meshes: Gynecare TVT-Obturator tape^® (Ethicon Inc., Johnson & Johnson, Somerville, NJ, USA) and I-STOP^® (CL Medical Inc., Lyon, France). All animal groups were sacrificed at set time intervals – 6 weeks, 3 months, 6 months, 9 months and 12 months – and the abdominal wall was harvested with mesh strips for histological evaluation.

Results

All mesh strips appeared to be well incorporated into the abdominal wall, and no signs of shrinkage was noticed. All specimens showed a thin/delicate, loose, fibrous interface between the synthetic graft plate and abdominal wall, along with mild inflammatory reactions from 6 weeks to 12 months.

Conclusions

Both mesh brands induced comparable, minimal foreign body reactions and integrated well into the host tissues despite differences in architectural features. TVT-O^® and I-STOP^® evoked similar low-grade inflammatory responses up to 12 months in this animal model.

Structural differences and architectural features of polypropylene slings used in this study have had no impact on tissue integrity and inflammatory responses.