[Temporary arthrodesis of the knee in two-stage septic prosthesis exchange : In vitro analysis of adhesion of Staphylococcus aureus on steel and carbon fiber rods].

BACKGROUND

In two-stage septic revision arthroplasty of the knee, a temporary intramedullary fixation with an antibiotic-containing polymethyl methacrylate (PMMA) spacer is often performed in cases of extensive bone defects after endoprosthesis explantation. A common method is the use of conventional steel or carbon fiber rods, which are connected via a tube-to-tube connector and finally reinforced near the joint with bone cement.

OBJECTIVE

As the surface of foreign materials plays a critical role in the colonization and biofilm formation in the treatment of periprosthetic joint infections (PJI), the steel and carbon fiber rods were examined and compared with respect to bacterial surface adhesions.

MATERIAL AND METHODS

Carbon fiber and steel rods of external fixator systems were used for this experimental study. The sample material was placed in a substrate enriched with S. aureus. The adherent bacteria were examined both by fluorescence microscopy and quantitatively after ultrasonic detachment (sonication) in a smear preparation. In addition, scanning electron micrograph (SEM) images were taken to analyze the topography of bacterial adhesions.

RESULTS

The fluorescence microscopy revealed a uniform surface distribution for both materials. The observation of the SEM images showed that for carbon fiber rods the growth of bacteria ran in unison with the direction of the fiber, while for the steel rods an arbitrary arrangement was found. With the help of sonication a significant difference in the number of adherent micro-organisms between the two materials could not be determined using the Wilcoxon test (significance level p < 0.05).

CONCLUSION

Both materials can be used to perform PMMA-reinforced intramedullary fixation without fear of sacrificing therapeutic success. From an economic point of view, the use of steel rods seems reasonable as the material costs are significantly lower.