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Background: Midline laparotomy wound failure like burst abdomen remains one of the major complications after abdominal surgery. The use of sutures with a closer resemblance to abdominal wall physiology, like elastic threads, could decrease the risk of these complications occurring. Thus, we evaluated the possibility of using a new elastic thread composed of thermoplastic polyurethane (TPU) as a suture for the closure of midline laparotomies compared to conventionally used polypropylene (PP) in a rabbit model. Methods: The elastic TPU thread was processed and tensile tests were performed. Twenty female chinchilla rabbits underwent midline laparotomy. They were randomized to a TPU and a PP group depending on the suture used for fascia closure. After 7 or 21 days, the abdominal walls were assessed macroscopically for wound healing complications and were explanted for histopathological investigation. Results: Tensile tests showed a mean elastic elongation of 55.5% and a sufficient material strength of the TPU thread. In animal experiments, there was no difference between the groups at 7 days; however, the TPU suture showed significantly less CD68 positive cells ( p < 0.001) and a higher collagen I/III ratio ( p = 0.011) than PP did after 21 days. The amount of apoptotic cells was significantly elevated in the TPU group ( p = 0.007) after 21 days. No differences were found concerning granuloma size and number of Ki67-positive cells. Conclusions: The newly developed TPU thread shows promising tensile characteristics. Midline laparotomy closure is feasible and safe in a rabbit model. Immunohistochemistry indicates similar biocompatibility and wound healing after implantation compared to PP after 21 days. To confirm these findings and to proof long-term capability further studies need to be conducted. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 103B: 417-423, 2015. [ABSTRACT FROM AUTHOR]

Background: Abdominal hernia repair is the most frequently performed operation in surgery. Mesh repair in hernia surgery has become an integral component. Although meshes made of PVDF are already in clinical use, so far no data of long-term biocompability are available. Methods: In this study a PVDF mesh was compared to a polypropylene mesh with regard to its long-term biocompatibility. A total of 28 rats were randomized to two groups. Mesh material was implanted subcutaneously; animals were euthanized seven days and six months postoperatively. The quantity of inflammatory tissue response was characterized by measuring the diameter of the foreign body granuloma. Furthermore quality of cellular immune response (T-lymphocytes, macrophages, and neutrophils), and inflammation (COX-2) was analyzed by immunohistochemistry. Furthermore the collagen type I/III ratio was determined. Results: Macrophages, T-lymphocytes, neutrophiles, and COX-2 declined significantly up to six months postoperatively in comparison to day 7 for both PVDF and PP meshes, and in both groups the collagen ratio increased significantly in the course of time. PVDF meshes showed a foreign body granuloma size significantly reduced compared to PP (7 days: 20 ± 2 μm vs. 27 ± 2 μm; 6 months 15 ± 2 μm vs. 22 ± 3 μm; p < .001). However no significant differences were found analyzing cellular response six months postoperatively. Conclusions: Our current data suggest that even in the long-term course after six months and despite a higher effective surface of the PVDF samples it showed a smaller foreign body granuloma than with PP whereas the cellular response was similar. [ABSTRACT FROM AUTHOR]

Incisional hernia remains as one of the most common surgical complications. Different mesh techniques are used in 75–80% of hernia repair. The aim of this study was to evaluate the dependence of mesh positioning and the type of mesh implanted on foreign body reaction and collagenous ingrowth. In 24 male Chinchilla rabbits, an incisional hernia repair was performed with mesh reinforcement either by sublay ( n = 12) or by onlay technique ( n = 12). In each group, two different types of mesh prosthesis were investigated: polypropylene (PP, Prolene®) and polypropylene-polyglecaprone 25 composite (PP-PG, UltraPro®). On postoperative day 60, the inflammatory and connective tissue formation was characterised by measuring the diameter of inner cellular infiltrate and outer fibrous capsule of the foreign body granuloma, and by verifying the collagen type I/III ratio. Furthermore, the expression of matrix metalloproteinase-2 (MMP-2) was analysed. Microscopic investigation of the mesh/host-tissue interface showed typical formation of foreign body granuloma. The diameters of the inner part of the foreign body granuloma representing the amount of inflammatory cell infiltrate were significantly increased in the PP mesh compared to the PP-PG mesh, both in the sublay group (PP 13.1 ± 1.21 μm vs. PP-PG 11.7 ± 0.34 μm; P = 0.026) and in the onlay group (PP 13.1 ± 1.24 μm vs. PP-PG 11.2 ± 0.55 μm; P = 0.009). The diameter of the fibrous capsule as the outer ring of the granuloma was significantly increased when investigating the PP mesh in sublay position (29.5 ± 1.12 μm) compared to the PP mesh in onlay position (27.9 ± 0.73 μm) ( P = 0.026). Investigating the quality of perifilamentary collagen deposition expressed as collagen type I/III ratio, the sublay group showed significantly elevated values compared to the onlay group (PP sublay 3.1 ± 0.18 vs. PP onlay 2.4 ± 0.41; P = 0.004) (PP-PG sublay 3.5 ± 0.34 vs. PP-PG onlay 2.6 ± 0.13; P = 0.002). The analysis of MMP-2 expression revealed no significant differences. The beneficial results of mesh reinforcement in the sublay technique might be due to a superior quality of postoperative connective tissue formation. Mesh incorporation, irrespective of positioning, is favourable in low-weight, large, porous mesh material represented by a reduced inflammatory part of the foreign body granuloma. [ABSTRACT FROM AUTHOR]