This study was aimed at evaluating the in vitro degradation, the in vivo biocompatibility and at comparing the effects of two methods of sterilization on poly(L-lactic acid) (PLA(94)) resorbable mesh. The mesh was manufactured to be used as surgical soft tissue reinforcement in the vaginal area. Samples of 100 mg of PLA(94) mesh (10 x 10 mm(2)) were immersed in isoosmolar 0.13M, pH 7.4 phosphate buffer solution at 37 degrees C, during 12 months. The hydrolytic degradation up to 12 months after immersion was monitored by measuring weight loss, mesh area changes, and by various analytical techniques namely Differential scanning calorimetry (DSC), capillary zone electrophoresis (CZE), size exclusion chromatography (SEC), and environmental scanning electron microscopy (ESEM). Specimens of nonsterilized, ethylene-oxide (ETO) sterilized, and gamma-ray sterilized PLA(94) mesh were compared. Fifteen samples were implanted in an incisional hernia Wistar rat model. Histopathology was performed up to 90 days after implantation to evaluate the inflammatory response and the collagen deposition. Although the decrease of molecular weight due to polymer chain scissions started 6 weeks after in vitro immersion, water-soluble degradation products and decrease of tensile strength appeared after 8 months only. Analyses showed also that ETO sterilization did not affect the degradation of the PLA(94) mesh. In contrast, gamma-ray sterilization increased very much the sensitivity of the mesh to the hydrolytic degradation. In vivo, the PLA(94) mesh exhibited good biocompatibility over the investigated time period.

The purpose of this study was to evaluate host response and soft-tissue regeneration after poly(lactic acid) (PLA) mesh implantation in a rat model, in comparison with light-weight polypropylene (PPL) and poly(glycolic acid) (PGA) meshes. Full-thickness abdominal wall defects were created in 45 Wistar rats and reconstructed with 15 PLA(94), 15 PPL and 15 PGA meshes. Animals were killed on days 7, 30 and 90 to evaluate the presence of adhesions and changes in tensile strength of the implants. Histopathology and immunohistochemistry were performed to evaluate the collagen deposition and the inflammatory response. Statistics were done using unpaired Student's t-test, Mann-Whitney rank sum test, Student-Newman-Keuls test and Bonferroni (Dunn) t-test. The inflammatory response induced by the PLA mesh implantation was significantly milder than after PPL mesh. In PLA, vascularity and collagen organization was significantly higher than in PPL and PGA at 30 and 90 days, and collagen composition score was significantly higher than in PPL at 7 and 30 days. In PLA, shrinkage was significantly lower than in PPL and PGA at 7 and 30 days. Elongation at break and tensile strength were comparable between PLA and PPL over the 90-day period. The PLA mesh induces a milder inflammatory response, more orderly collagen deposition than PPL, and preserved comparable tensile strength after 90 days.

Aim: The purpose was to evaluate soft-tissue healing after poly(lactic acid) (PLA₉₄) mesh implantation in a rat model. Methods: Full-thickness abdominal wall defects were created in 108 Wistar rats, and reconstructed with 83 PLA₉₄ and 25 lightweight polypropylene (PPL) meshes. The meshes were previously γ-ray sterilised with 25, 75 or 125 kGy to accelerate PLA₉₄ degradation. Results: The inflammatory response in PLA₉₄ was significantly less pronounced and collagen organisation significantly better than in PPL. The higher the level of γ-radiation, the higher the incidence of abdominal wall herniation (22.2, 31.3 and 52.6% with 25, 75 and 125 kGy, respectively). No herniation occurred in the PPL group. Tensile strength was dramatically reduced after γ-ray-sterilised PLA₉₄ mesh implantation. Conclusion: The γ-ray-sterilised PLA₉₄ mesh was poor in preventing abdominal wall hernia recurrences in a rat model.

No abstract