Chitosan-coated stainless steel screws for fixation in contaminated fractures

Stainless steel screws and other internal fixation devices are used routinely to stabilize bacteria-contaminated bone fractures from multiple injury mechanisms. In this preliminary study, we hypothesize that a chitosan coating either unloaded or loaded with an antibiotic, gentamicin, could lessen or prevent these devices from becoming an initial nidus for infection. The questions investigated for this hypothesis were: (1) how much of the sterilized coating remains on the screw with simulated functional use; (2) is the unloaded or loaded chitosan coating bacteriostatic and biocompatible; and (3) what amount and rate does an antibiotic elute from the coating? In this study, the gentamicin eluted from the coating at a detectable level during 72 to 96 hours. The coating was retained at the 90% level in simulated bone screw fixation and the unloaded and loaded chitosan coatings had encouraging in vitro biocompatibility with fibroblasts and stem cells and were bacteriostatic against at least one strain of Staphylococcus aureus. The use of an antibiotic-loaded chitosan coating on stainless steel bone screws and internal fixation devices in contaminated bone fracture fixation may be considered after optimization of antibiotic loading and elution and more expanded in vitro and in vivo investigations with other organisms and antibiotics.