Effects of Electrically-Stimulated Silver-Coated Implants and Bacterial Contamination in a Canine Radius Fracture Gap Model

Abstract

The purpose of this project was to study the effects of anodic electrically stimulated silver-coated stainless steel implants and bacterial contamination in a canine radius fracture gap model. Twelve skeletally mature canines weighing 19.2-23.2 kg were used. Dogs were randomly assigned to into control and contaminated groups. A 5 mm ostectomy gap was made in both radii of each dog. One radius of each dog was stabilized with a silver-coated stainless steel bone plate and the other with an uncoated stainless steel bone plate. The ostectomy sites were inoculated with sterile PBS in 6 dogs and S. intermedius in the other 6 dogs. Each implant set was electrically stimulated with direct current for 20 minutes daily, for 10 days. Animals were treated with Cephalexin orally for 10 days. Radiographs were obtained at two week intervals. Animals were euthanized at 12 weeks and each plate was cultured. Radiographic, histologic and bacteriologic evaluations of each radius were performed. The difference in bone healing between silver-coated and stainless steel treated radii was determined for each dog by subjective radiographic evaluation and quantitative analysis of radiographic density using commercial software. At week 12, a significant decrease in bone healing was found on radiographic evaluations and quantitative bone area analysis of contaminated radii that were treated with electrically stimulated silver-coated implants (p-value 0.025 and 0.018 respectively). Inoculum or implant treatment type showed no significant difference on radiographic evaluations or quantitative bone area analysis. No significant differences were detected in radiographic evaluations of osteomyelitis or histologic evaluations of bone healing, inflammation and peri-implant resorption. Culture results were not indicative of S. intermedius inoculated osteomyelitis. The use of a bilateral radial ostectomy model allowed comparison of electrically stimulated silver-coated and uncoated implants within each dog. Bone healing in the stable 5 mm fracture gap radial ostectomy model, was progressive in both contaminated and non-contaminated situations. Our study found a negative effect on bone healing when electrically-stimulated silver stearate coated implant were used in S. intermedius contaminated radius ostectomies. This trend became apparent at 6 weeks post-operatively, but was not statistically evident until 12 weeks. Further studies are warranted to evaluate the appropriate protocol, the effects of, and indicated use of this treatment modality in contaminated fractures and clinical osteomyelitis situations.