Evaluation of silver-titanium implants activated by low intensity direct current for orthopedic infection control: An in vitro and in vivo study Daniel L. Cavanaugh,1 Zhuo (George) Tan,2 James P. Norris IV,1 Amelia Hardee,2 Paul S. Weinhold,1,3 Laurence E. Dahners,1 Paul E. Orndorff,4 Rohan A. Shirwaiker2,3 1
Department of Orthopaedics, University of North Carolina, Chapel-Hill, North Carolina Department of Industrial and Systems Engineering, North Carolina State University, Raleigh, North Carolina 3 Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Raleigh, North Carolina 4 Department of Population Health and Pathobiology, North Carolina State University, Raleigh, North Carolina 2
Received 1 November 2014; revised 15 March 2015; accepted 24 April 2015 Published online 21 May 2015 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/jbm.b.33451 Abstract: Silver is an alternative antimicrobial of interest for the prophylaxis of prosthetic infections and electrical activation is known to augment its oligodynamic efficacy. In this study, we evaluated the in vitro and in vivo efficacy of a silver (Ag)-titanium (Ti) implant activated by 30 mA direct current compared with three controls – passive Ag-Ti, active Ti-Ti, and passive Ti-Ti. We hypothesized that the experimental group would provide better resistance to pathogenic colonization on the implant. Modified Kirby-Bauer technique was used to evaluate in vitro efficacy of the four groups against five bacteria and one fungus. For in vivo evaluation, forty-eight rats were divided into four groups. The implant was secured in a wound cavity along the posterior margin of the femur. The wound was inoculated with 7.5 3 105 CFU of Staphylococcus aureus. Rats were euthanized 14 days postsurgery and quantitative
cultures were performed on the implant segments and the wound cavity tissue. In vitro tests showed that the growth of all six pathogens was inhibited around the active Ag anodes of the experimental group. In vivo, none of the four groups were able to prevent wound infection, but the experimental group resulted in reduced colonization. The mean bacterial loads on Ti segments were significantly lower in the implants which also had an Ag segment (p 5 0.0007), and this effect was more pronounced with electrical activation (p 5 0.0377). The results demonstrate the antimicrobial potential of LIDCC 2015 Wiley Periodicals, Inc. J Biomed activated Ag-Ti implants. V Mater Res Part B: Appl Biomater, 104B: 1023–1031, 2016.
Key Words: prosthetic infection, oligodynamic silver, antimicrobial implant, electrical activation
How to cite this article: Cavanaugh DL, Tan Z(G), Norris JP, Hardee A, Weinhold PS, Dahners LE, Orndorff PE, Shirwaiker RA. 2016. Evaluation of silver-titanium implants activated by low intensity direct current for orthopedic infection control: An in vitro and in vivo study. J Biomed Mater Res Part B 2016:104B:1023–1031.
INTRODUCTION
Pathogenic colonization and postoperative infection is a serious risk associated with the implantation of orthopedic implants. The incidence of infection after orthopedic procedures ranges broadly. Infection has been estimated to occur following 1 to 4% of all total joint arthroplasties (TJA)1,2 and 0.7 to 12% of adult spine procedures.3 The rate of postoperative infection after treatment of open fracture ranges from
Department of Orthopaedics, University of North Carolina, Chapel-Hill, North Carolina Department of Industrial and Systems Engineering, North Carolina State University, Raleigh, North Carolina 3 Joint Department of Biomedical Engineering, University of North Carolina and North Carolina State University, Raleigh, North Carolina 4 Department of Population Health and Pathobiology, North Carolina State University, Raleigh, North Carolina 2
Received 1 November 2014; revised 15 March 2015; accepted 24 April 2015 Published online 21 May 2015 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/jbm.b.33451 Abstract: Silver is an alternative antimicrobial of interest for the prophylaxis of prosthetic infections and electrical activation is known to augment its oligodynamic efficacy. In this study, we evaluated the in vitro and in vivo efficacy of a silver (Ag)-titanium (Ti) implant activated by 30 mA direct current compared with three controls – passive Ag-Ti, active Ti-Ti, and passive Ti-Ti. We hypothesized that the experimental group would provide better resistance to pathogenic colonization on the implant. Modified Kirby-Bauer technique was used to evaluate in vitro efficacy of the four groups against five bacteria and one fungus. For in vivo evaluation, forty-eight rats were divided into four groups. The implant was secured in a wound cavity along the posterior margin of the femur. The wound was inoculated with 7.5 3 105 CFU of Staphylococcus aureus. Rats were euthanized 14 days postsurgery and quantitative
cultures were performed on the implant segments and the wound cavity tissue. In vitro tests showed that the growth of all six pathogens was inhibited around the active Ag anodes of the experimental group. In vivo, none of the four groups were able to prevent wound infection, but the experimental group resulted in reduced colonization. The mean bacterial loads on Ti segments were significantly lower in the implants which also had an Ag segment (p 5 0.0007), and this effect was more pronounced with electrical activation (p 5 0.0377). The results demonstrate the antimicrobial potential of LIDCC 2015 Wiley Periodicals, Inc. J Biomed activated Ag-Ti implants. V Mater Res Part B: Appl Biomater, 104B: 1023–1031, 2016.
Key Words: prosthetic infection, oligodynamic silver, antimicrobial implant, electrical activation
How to cite this article: Cavanaugh DL, Tan Z(G), Norris JP, Hardee A, Weinhold PS, Dahners LE, Orndorff PE, Shirwaiker RA. 2016. Evaluation of silver-titanium implants activated by low intensity direct current for orthopedic infection control: An in vitro and in vivo study. J Biomed Mater Res Part B 2016:104B:1023–1031.
INTRODUCTION
Pathogenic colonization and postoperative infection is a serious risk associated with the implantation of orthopedic implants. The incidence of infection after orthopedic procedures ranges broadly. Infection has been estimated to occur following 1 to 4% of all total joint arthroplasties (TJA)1,2 and 0.7 to 12% of adult spine procedures.3 The rate of postoperative infection after treatment of open fracture ranges from
