Strength of Tissue Attachment to Composite and ePTFE Grafts After Ventral Hernia Repair

OBJECTIVES: We sought to measure the strength of tissue attachment to mesh after laparoscopic ventral hernia repair in a porcine model. METHODS: Twelve swine had two 10-cm × 16-cm sheets of ePTFE and polypropylene/ePTFE composite mesh fixated to the abdominal wall laparoscopically. Animals were euthanized at 2, 4, 6, and 12 weeks. The strength of tissue ingrowth was measured using a lap-shear method. Data are reported as mean force in pounds. RESULTS: Average surface area of adhesions to percentage of surface area was not statistically significant between the composite and ePTFE materials. For the composite material, there was a 98.7% posterior probability that the force required at 2 weeks was less than that required at 12 weeks. There was no difference in graft-abdominal wall interface strength between week 2 and week 12 for ePTFE material. Both prosthetics achieved the majority of their strength from tissue ingrowth by 2 weeks, but the composite prosthesis continued to gain strength while the strength of the ePTFE plateaued. Composite mesh demonstrated a statistically significant increase in strength between the lap-shear force, whereas no statistically significant difference occurred in the ePTFE graft. For the composite material, there was complete cellular infiltration through the entire thickness of polypropylene (approximately 500 μm) to the ePTFE layer at 2 weeks. At 2 weeks for ePTFE, the cells did not penetrate into the graft on the visceral side. On the abdominal wall side, the grooves filled with tissue, but no cellular penetration into the ePTFE occurred. No histological difference existed in cellularity. CONCLUSION: This study demonstrates that the strength of tissue ingrowth is significantly higher (P<0.05) for the composite grafts relative to the ePTFE grafts at each time point. Approximately 74% of tissue ingrowth and strength occurs by 2 weeks postoperatively for the composite pros-thesis. The ePTFE graft tissue strength peaked and plateaued by 2 weeks. This may have clinical implications for human ventral hernia repair by partly addressing the issue of graft fixation to the abdominal wall during laparoscopic ventral hernia repair.