MRI Evaluation of an Elastic TPU Mesh under Pneumoperitoneum in IPOM Position in a Porcine Model.

BACKGROUND: The frequency of laparoscopic approaches increased in hernia surgery over the past years. After mesh placement in IPOM position, the real extent of the meshes configurational changes after termination of pneumoperitoneum is still largely unknown. To prevent a later mesh folding it might be useful to place the mesh while it is kept under tension. Conventionally used meshes may lose their Effective Porosity under these conditions due to poor elastic properties. The aim of this study was to evaluate a newly developed elastic thermoplastic polyurethane (TPU) containing mesh that retains its Effective Porosity under mechanical strain in IPOM position in a porcine model. It was visualized under pneumoperitoneum using MRI in comparison to polyvinylidenefluoride (PVDF) meshes with similar structure. METHODS: In each of ten minipigs, a mesh (TPU containing or native PVDF, 10 × 20 cm) was randomly placed in IPOM position at the center of the abdominal wall. After 8 weeks, six pigs underwent MRI evaluation with and without pneumoperitoneum to assess the visibility and elasticity of the mesh. Finally, pigs were euthanized and abdominal walls were explanted for histological and immunohistochemical assessment. The degree of adhesion formation was documented. RESULTS: Laparoscopic implantation of elastic TPU meshes in IPOM position was feasible and safe in a minipig model. Mesh position could be precisely visualized and assessed with and without pneumoperitoneum using MRI after 8 weeks. Elastic TPU meshes showed a significantly higher surface increase under pneumoperitoneum in comparison to PVDF. Immunohistochemically, the amount of CD45-positive cells was significantly lower and the Collagen I/III ratio was significantly higher in TPU meshes after 8 weeks. There were no differences regarding adhesion formation between study groups. CONCLUSIONS: The TPU mesh preserves its elastic properties in IPOM position in a porcine model after 8 weeks. Immunohistochemistry indicates superior biocompatibility regarding CD45-positive cells and Collagen I/III ratio in comparison to PVDF meshes with a similar structure.

In vivo MRI visualization of parastomal mesh in a porcine model.

INTRODUCTION: After two-dimensional plane MRI-visible mesh implants could be successfully visualized in phantom and small animal model, the aim of the underlying study was to explore the feasibility of an MRI visualization of complex three-dimensional mesh geometry in close contact to the intestine. We therefore used a MR-visible three-dimensional intra-peritoneal stoma (IPST) mesh in a porcine model. MATERIALS AND METHODS: Laparoscopic terminal sigmoid colostomy has been done with implantation of a prophylactic MRI-visible IPST mesh in two animals. MRI investigations were done after 1 week, 6 months and in case of clinical impairment. These findings were compared to endoscopy and makroscopical and histological investigation of the preparation. RESULTS: The first animal has to be killed because of an ileus 4 weeks after operation. The second animal has to be killed after 7 weeks because of recurrent obstipation. In all cases MRI investigation could identify the IPST mesh and could clearly separate between mesh and intestine. MRI revealed a big bowl ileus due to a funnel dislocation in the first animal. In the second animal, MR diagnostic explored a functional stenosis because of a too small diameter of the central funnel in combination with sticky feces and distension of the terminal sigmoid before discharging into the funnel. Endoscopy, makroscopical and histological investigation of the preparation supported MRI findings. CONCLUSION: Although complicate clinical course was a diagnostic challenge exploring 3D implants such as IPST, visualization of this new MRI-visible IPST mesh could be proved and turned out as an effective diagnostic possibility. Further studies are necessary to analyze long-time effects such as shrinkage, mesh migration and tissue integration using MRI scanning.