Pin tract infections: silver vs uncoated pins

To test the hypothesis that coating external fixation pins with a silver-containing compound (Spi-Argent, Spire Corp, Bedford, Mass) will reduce bacterial colonization and/or pin tract infection, 36 silver-coated and 12 conventional stainless steel pins were placed in the iliac crest of six sheep and inoculated with Staphylococcus aureus. After 2 1/2 weeks the pin sites were examined for motion and inflammation, and the pin tips were quantitatively cultured and examined with scanning electron microscopy (SEM). We found that 84% of the uncoated pins were infected, while 62% of the silver-coated pins were infected. Silver-coated pins were less frequently infected than uncoated pins (confidence interval [CI] > 85%). Also, silver-coated pins were loose less frequently than uncoated pins. Pin motion was closely correlated with infection: 28 of 32 infected pins (88%) had motion, while only 9 of 16 uninfected pins (56%) had motion (CI > 80%). SEM study of the pin tips showed a decreased level of glycocalyx-protected colonization on the surface of the silver-coated pins. Clinically, these results suggest that silver-coated pins will result in less infection and motion at the pin site, the most significant problems in external fixation.