Metallic implants are used frequently in the operative repair of joints and fractures in orthopaedic surgery. Metal infection is a catastrophic complication of the surgery with patients loosing their newfound mobility and independence, associated morbidity and mortality is high. Orthopaedic implant infection is chronic and biofilm based. Present treatment focuses on removing the infective substratum and implant surgically as well as prolonged anti-microbial therapy. Biofilms are 500 times more resistant than planktonic strains of bacterial flora to antibiotics, and with evolving resistant strains this form of therapy is loosing ground. Silver coatings on polymers and nylon (catheters, heart valve cuffs, burn dressings) have shown inhibition of this biofilm formation in its adhesion stage. Our aim was to deposit effective, minute, biocompatible, anti-bacterial layers of silver on orthopaedic stainless steel K-wires. Combining magnetron sputtering with a neutral atom beam (Saddle Field) plasma source at 10−4 mbar in argon gas at temperatures of 60°C, a silver coating of 99.9% purity was deposited onto stainless steel orthopaedic K-wires. Coating thickness measurements were obtained using glancing angle x-ray diffraction of glass slides coated adjacent to wires. Magnetron parameters were modified to produce varying thickness of silver. Adhesiveness was examined using Rockwell punch tests and tape tests. Silver leaching experiments were carried out in phosphate buffered saline at 37°C for 48hrs and using inductive coupled plasma spectrometry to assess leached silver ions. Surface microscopy visualised physical changes in the coatings. Biofilm adhesion was determined by exposing wires to K-wires were coated with 5 to 50 nm of silver by running the magnetron sputtering at low currents. These coatings showed excellent adhesive properties within the 48hr exposed with only 5% of silver leaching in buffered saline. The silver coated wires showed a log 3–4 fold reduction in biofilm formation as compared to control wires. The coatings showed no cytotoxic effects. Silver coating of medical implants has been shown in urological catheters to reduce biofilm infection. We have perfected a method of depositing thin layers of anti-bacterial silver onto stainless steel, which is both anti-infective and biocompatible. This coating could potentially add to the armourary of anti-infective agents in the elimination of infection related orthopaedic implant failure.
Infection around implanted biomaterials in humans is a major healthcare issue and current ability to effectively prevent and treat such infections using antibiotics is limited. The hypothesis of the study was that surface charge could be manipulated to a positive state and thus moderate bacterial adhesion to the implant. The surface charge was manipulated by creating a galvanic cell using a zinc strip in a standard suction drain. Adhesion of In this experiment we have shown that alteration of the electrochemical environment around an implant influences bacterial adhesion. While our technique is not therapeutically viable, further manipulation of surface charge of an implant is possible using other electroactive materials. This may be explored in the prophylactic treatment of implant infection