Background
Biologic grafts used in ventral hernia repair are derived from various sources and undergo different post-tissue-harvesting processing, handling, and sterilization techniques. It is unclear how these various characteristics impact graft response in the setting of contamination. We evaluated four materials in an infected hernia repair animal model using fluorescence imaging and quantitative culture studies.
Methods
One hundred seven rats underwent creation of a chronic hernia. They were then repaired with one synthetic polyester control material (n = 12) and four different biologic grafts (n = 24 per material). Biologic grafts evaluated included Surgisis (porcine small intestinal submucosa), Permacol (crosslinked porcine dermis), Xenmatrix (noncrosslinked porcine dermis), and Strattice (noncrosslinked porcine dermis). Half of the repairs in each group were inoculated with Staphylococcus aureus at 104 CFU/ml and survived for 30 days without systemic antibiotics. Animals then underwent fluorescence imaging and quantitative bacterial studies.
Results
All clean repairs remained sterile. Rates of bacterial clearance were as follows: polyester synthetic 0%, Surgisis 58%, Permacol 67%, Xenmatrix 75%, and Strattice 92% (P = 0.003). Quantitative bacterial counts had a similar trend in bacterial clearance: polyester synthetic 1 × 106 CFU/g, Surgisis 4.3 × 105 CFU/g, Permacol 1.7 × 103 CFU/g, Xenmatrix 46 CFU/g, and Strattice 31 CFU/g (P = 0.001). Fluorescence imaging was unable to detect low bacterial fluorescence counts observed on bacterial studies.
Conclusion
Biologic grafts, in comparison to synthetic material, are able to clear a Staphylococcus aureus contamination; however, they are able to do so at different rates. Bacterial clearance correlated to the level of residual bacterial burden observed in our study. Post-tissue-harvesting processing, handling, and sterilization techniques may contribute to this observed difference in ability to clear bacteria.
The results support the use of this rating system as a tool for the objective evaluation of trainee operative skill. Instruction in the performance of segmental colectomy using deconstructed, step-by-step direction improved the ability of junior trainees to complete the operation. This evaluation system may be useful in the assessment, instruction and technical development of surgical trainees.
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