Tissue Integration of Synthetic Grafts and the Impact of Soft-Tissue Infection – An Experimental Model

Objective: Starting with the ‘Vinyon-N-revolution’ of the 50’s, there has been a constant interest in understanting tissue integration, or the so-called graft healing process, as well as its relationship with infection. In this study we present an experimental animal model designed to assess tissue integration of different graft materials, and their reaction to the presence of infection. Methods: Synthetic grafts (knitted Dacron®, woven Dacron®, silver-impregnated Dacron® and Gore-Tex®) were implanted subfascially in the interscapular region of Wistar rats. Animals were divided into a control group and an infected group, with infection induced using bacterial suspensions of standard strains of Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli. Implants were retrieved at 2 and 4 weeks postoperatively in the control group and at 1, 2 and 3 weeks postoperatively in theinfected group. Retrieved grafts were assessed bacteriologically and morpho-pathologically. Results: All microorganisms produced clinically evident infections, with positive blood cultures in case of E. coli. Staphylococci produced more massive infections on Dacron® grafts, except for the silver-impregnated version, while E. coli produced more significant infections on Gore-Tex® grafts. Morpho-pathologically Dacron® grafts behaved poorly, with ocassional complete structural compromise, and no difference between the conventional and the silver-impregnated type. The Gore-Tex® graft showed a consistent structural resistance throughout the study period. Conclusions: Although the silver-impregnated graft inhibited bacterial growth, it was poorly tolerated by the host tissue. In contrast, Gore-Tex® grafts showed more massive infection, especially with E. coli, but kept their structural integrity surprisingly well.