Decreasing Bacterial Colonization of External Fixation Pins Through Nitric Oxide Release Coatings

Objective: Bacterial infection of the pin tract represents the most common complication associated with external fixation. This study was designed to evaluate the antibacterial activity of nitric oxide (NO)-releasing xerogel films applied to commercially pure titanium pins in a rat model. Methods: Pins were coated with xerogel solution through a dip-coating procedure. Half of the xerogel-coated implant pins were modified into NO donors and served as the NO-releasing group, whereas the remaining pins were left unmodified to serve as non-NO-releasing xerogel-coated controls. Acid-etched pins served as uncoated controls. Animal selection was randomized and every rat had one pin from each of the three groups randomly allocated to the third, fourth, or fifth tail vertebrae. Quantification of bacterial infection was performed 48 days postoperatively and the tissue-implant interface was inspected for clinical signs of infection on Days 14 and 28 postimplantation. Results: Pin tract bacterial colony counts of the NO-releasing group (170,000 +/- 181,000) were significantly lower than both the xerogel-coated group (677,000 +/- 675,000) and the control group (1,181,000 +/- 2,717,000) 48 days postoperatively (P < 0.05). No significant difference in colony counts was observed between the xerogel-coated group and the control group. The NO-releasing group also had significantly fewer clinical signs of infection than both the coated and the control groups on postoperative Day 28 (P < 0.05). Conclusion: The application of NO-releasing xerogel coatings can inhibit bacterial colonization of external fixation pins both during the initial postsurgical period and up to 48 days postimplantation.