Ultrastructural alterations of polytetrafluoroethylene prostheses implanted in abdominal wall provoked by infection: clinical and experimental study.

Infection of an expanded polytetrafluoroethylene (ePTFE) prosthesis after implant is a major drawback of its use in current clinical practice. The aim of the present study was to compare the behavior of such prostheses implanted into New Zealand rabbits with that of prostheses infected after clinical implant. Experimental implants of ePTFE Soft Tissue Patch were performed to repair defects (7 x 5 cm) created in the abdominal wall of 10 rabbits. Prior to implant the prostheses were contaminated with Staphylococcus aureus. Five animals implanted with noncontaminated ePTFE prostheses served as controls. All the animals were sacrificed at 30 days after implant. For the clinical study, specimens were taken from three ePTFE implants that had been found to be infected after intervention. The clinical and experimental implant specimens were processed for light microscopy and scanning electron microscopy. Macroscopic and microscopic examination of experimental and clinical implants revealed alterations to the ePTFE structure, such as areas of fragmentation, fracture lines, and detachment of fine layers of ePTFE that harbored numerous Staphylococcus colonies. Neoformed tissue around contaminated implants was arranged more loosely, and on occasion large spaces between fibers gave rise to an "unknitted" appearance with respect to the control implants. It may be concluded that microporous ePTFE prostheses show similar behavior following experimental or clinical implant in the presence of infection. Irreversible changes to the structure of the prosthesis are produced owing to colonization of the biomaterial by microorganisms, which in most cases necessitates total replacement of the prosthesis.